Seminars in Cardiothoracic and Vascular Anesthesia http://scv.sagepub.com/
Pulmonary Endarterectomy: Part II. Operation, Anesthetic Management, and Postoperative Care Dalia A. Banks, Gert Victor D. Pretorius, Kim M. Kerr and Gerard R. Manecke SEMIN CARDIOTHORAC VASC ANESTH published online 7 July 2014 DOI: 10.1177/1089253214537688 The online version of this article can be found at: http://scv.sagepub.com/content/early/2014/07/22/1089253214537688
Published by: http://www.sagepublications.com
Additional services and information for Seminars in Cardiothoracic and Vascular Anesthesia can be found at: Email Alerts: http://scv.sagepub.com/cgi/alerts Subscriptions: http://scv.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav Citations: http://scv.sagepub.com/content/early/2014/07/22/1089253214537688.refs.html
>> OnlineFirst Version of Record - Jul 22, 2014 OnlineFirst Version of Record - Jul 16, 2014 OnlineFirst Version of Record - Jul 13, 2014 OnlineFirst Version of Record - Jul 7, 2014 What is This?
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
537688 research-article2014
SCVXXX10.1177/1089253214537688Seminars in Cardiothoracic and Vascular AnesthesiaBanks et al
Article
Pulmonary Endarterectomy: Part II. Operation, Anesthetic Management, and Postoperative Care
Seminars in Cardiothoracic and Vascular Anesthesia 1–10 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1089253214537688 scv.sagepub.com
Dalia A. Banks, MD, FASE1, Gert Victor D. Pretorius, MBChB1, Kim M. Kerr, MD1, and Gerard R. Manecke, MD1
Abstract Chronic thromboembolic pulmonary hypertension (CTEPH) results from recurrent or incomplete resolution of pulmonary embolism. CTEPH is much more common than generally appreciated. Although pulmonary embolism (PE) affects a large number of Americans, chronic pulmonary thromboembolic hypertension remains underdiagnosed. It is imperative that all patients with pulmonary hypertension (PH) be screened for the presence of CTEPH since this form of PH is potentially curable with pulmonary endarterectomy (PEA) surgery. The success of this procedure depends greatly on the collaboration of a multidisciplinary team approach that includes pulmonary medicine, cardiothoracic surgery, and cardiac anesthesiology. This review, based on the experience of more than 3000 pulmonary endarterectomy surgeries, is divided into 2 parts. Part I focuses on the clinical history and pathophysiology, diagnostic workup, and intraoperative echocardiography. Part II focuses on the surgical approach, anesthetic management, postoperative care, and complications. Keywords pulmonary endarterectomy, pulmonary thromboendarterectomy, sickle cell disease, heparin-induced thrombocytopenia (HIT), transesophageal echocardiography in CTEPH, deep hypothermic circulatory arrest, pulmonary hemorrhage in PEA, reperfusion lung injury
Introduction The University of California, San Diego, has reported most of the world experience in pulmonary endarterectomy (PEA), having performed >3000 cases. The operation, using deep hypothermia and circulatory arrest, has evolved over the past 3 decades. Chronic thromboembolic pulmonary hypertension (CTEPH) is the only type of pulmonary hypertension amenable to surgical treatment, and PEA is its definitive treatment. Success depends on the close collaboration of a multidisciplinary team including pulmonologists, cardiothoracic surgeons, and cardiac anesthesiologists. In this review, anesthetic and surgical considerations are presented, as are approaches to 2 challenging conditions: sickle cell disease and heparin-induced thrombocytopenia.
The Operation There are 3 reasons to perform PEA on patients with CTEPH: hemodynamic compromise, respiratory dysfunction, and the prevention of disease progression (prophylaxis).1,2 The hemodynamic goal is to ameliorate right ventricular (RV) compromise caused by high pulmonary
vascular resistance (PVR). The respiratory objectives are to improve ventilation-perfusion (V/Q) matching and to treat dyspnea. The prophylactic goals are to prevent progressive RV dysfunction, and secondary arteriopathy in the remaining patent vessels. Most patients present with PVR in the range of 800 dynes-sec-cm–5 and pulmonary artery (PA) pressures less than systemic, although disease progression and hypertrophy of the right ventricle can cause suprasystemic PA pressure. Good outcomes can be achieved in patients with PVR in excess of 1000 dynessec-cm–5 and suprasystemic PA pressures, so there are no upper limits of PVR, PA pressure, or the degree of RV dysfunction that contraindicate PEA. Most patients presenting for PEA are in New York Heart Association class III or IV heart failure. Occasionally, PEA is indicated even with normal resting PVR such as in symptomatic patients with significant vascular obstruction. 1
University of California, San Diego, San Diego, CA, USA
Corresponding Author: Dalia A. Banks, MD, FASE, University of California, San Diego, 9300 Campus Point Drive, #7651, La Jolla, CA 92037, USA Email: [email protected]
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
2
Seminars in Cardiothoracic and Vascular Anesthesia Guiding principles for the operation are as follows: 1. The endarterectomy should be bilateral, via median sternotomy. Historically, there were reports of unilateral PEA. At some centers, this ill-advised operation is still performed, via thoracotomy. This approach has significant disadvantages: it leaves untreated disease on the contralateral side, subjects the patient to hemodynamic jeopardy during PA clamping, does not allow good surgical exposure because of the continued presence of bronchial blood flow, and usually exposes the patient to a second operation on the contralateral side. Also, thoracotomy for PEA may be very bloody because of prominent collateral vessels present in CTEPH (diaphragmatic, intercostal, and pleural). 2. Cardiopulmonary bypass (CPB) is used. 3. A true endarterectomy in the plane of the media, extending to the distal vessels, must be accomplished. The mere removal of visible acute thrombus is ineffective.3 4. A bloodless field is required to extend the endarterectomy deep into the subsegmental vessels. Because of the copious bronchial flow in CTEPH, periods of circulatory arrest are necessary.
Figure 1. Surgical field with standard cannulation strategy for cardiopulmonary bypass includes aortic and bicaval cannulation with vent cannulas in the pulmonary artery and left atrium.
Surgical Technique After median sternotomy, one generally finds an enlarged right heart with a tense right atrium. These patients may become unstable with the manipulation of the heart. CPB is instituted after an activated clotting time > 450 seconds is achieved. A temporary PA vent is placed in the midline of the main PA (Figure 1). In addition to cooling the blood via the pump oxygenator, surface cooling with both a head jacket and a cooling blanket is begun. Cooling to 20°C must be gradual to ensure uniform cooling, generally taking 60 to 90 minutes.4 A left ventricular (LV) vent is placed to prevent overdistension, which can be particularly hazardous upon fibrillation. At a core temperature of 20°C, the aorta is cross-clamped and a single dose (1 L) of coldblood cardioplegia is administered. A cooling jacket wrapped around the heart offers additional myocardial protection. The primary surgeon stands on the patient’s left side. The approach to the right PA is made medial to the superior vena cava (Figure 2). All dissection of the pulmonary arteries is carried out intrapericardially, avoiding entering the pleural cavity. An incision is then made in the right PA from beneath the ascending aorta under the superior vena cava, entering the lower lobe branch of the PA. It is important that the incision stay in the center of the vessel. When blood obscures direct vision, circulatory arrest is initiated, and the patient undergoes exsanguination. Although continuous selective cerebral perfusion has been advocated during circulatory arrest in other procedures, it
Figure 2. Access to the right pulmonary artery is enhanced by complete mobilization of the superior vena cava (SVC) and spreading the aorta and SVC apart with a self-retaining retractor.
is not used in this operation, because it does not allow a completely bloodless field. Furthermore, the circulatory arrest times are relatively short in PEA, obviating the need for continuous cerebral perfusion.5 Endarterectomy in the correct dissection plane is critical. If the plane is too deep, the PA may be perforated, and if it is too shallow, inadequate amounts of thromboembolic material will be removed. The ideal layer is a pearly white plane that strips easily. Once the plane is correctly developed, the endarterectomy is performed with an eversion technique. It is important that each subsegmental branch be followed and freed individually until it ends in a “tail,”
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
3
Banks et al
Figure 3. Type I disease with clot in the main pulmonary arteries.
Figure 5. Type III disease with dissection plane raised in the segmental branches to remove clot as far out as the subsegmental level.
repaired. To perform the left endarterectomy, the surgeon moves to the patient’s right side. Once endarterectomies are completed on both sides, CPB is reinstituted and warming is commenced. Methylprednisolone (500 mg) and mannitol (12.5 g) are administered; this is in addition to methylprednisolone present in the pump prime (see the following discussion). If a patent foramen ovale (PFO) is present, it is repaired, and other indicated cardiac procedures, such as coronary artery bypass and mitral or aortic valve surgery, are performed during the rewarming period. Wound closure is routine, with hemostasis being important because the patient will receive anticoagulation treatment within hours of reaching the intensive care unit (ICU).3 Figure 4. Type II disease with clot in the lobar arteries where the dissection plane was raised.
Anesthetic Management Preoperative Preparation
beyond which there is no further obstruction. Residual material should never be cut free; the entire specimen should “tail off” and come free spontaneously. Jamieson5,6 classified pulmonary occlusive disease into 4 types. Type I disease (approximately 12%; Figure 3) involves a major vessel clot that is present and readily visible on opening the pulmonary arteries. In type II disease (approximately 38%; Figure 4), only thickened intima can be seen, and the endarterectomy plane is initially raised in the main, lobar. In type III disease (approximately 39%; Figure 5), the disease is distal, confined to the segmental and subsegmental branches. Type IV disease represents intrinsic small-vessel disease and is inoperable, although secondary thrombi may occur from stasis. Once the right-sided endarterectomy is completed, circulation is restarted and the arteriotomy is
Patients with CTEPH typically present with varying degrees of right heart failure, paradoxical interventricular septal motion, tricuspid regurgitation, hepatic congestion, and decreased cardiac indices.7,8 Much of the preoperative preparation is common to other open-heart procedures, although the workup is usually more extensive. Right heart catheterization provides important information prior to surgery. RV diastolic pressure > 14 mm Hg together with elevated right atrial pressure suggests RV failure. Mean PA pressure > 50 mm Hg and PVR > 600 dynes-sec-cm–5 signify severe pulmonary hypertension. Cardiac output and cardiac index also provide important information about RV function as well as other cardiac problems. On the day of surgery a large-bore peripheral intravenous catheter and radial arterial catheter are placed preoperatively.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
4
Seminars in Cardiothoracic and Vascular Anesthesia
Benzodiazepines may be administered preoperatively, but with extreme caution, with full monitoring, and preferably in the operating room. Opiates are generally avoided preoperatively because of their respiratory-depressant effects. Preoperative sedation should be individualized, with the understanding that anxiety and pain can increase PVR, while excessive sedation can itself cause hypercarbia and hypoxia, resulting in increased PVR. Standard monitoring together with transesophageal echocardiography (TEE), PA catheterization (PAC), cerebral function monitoring, and a cooling head device are planned. An internal jugular introducer and PA catheter are placed after induction rather than before, because patients with severe pulmonary hypertension may not tolerate lying flat. Preoperative hemodynamic data from recent right heart catheterization are usually known before surgery, thus making placement of a PA catheter before induction unnecessary. Intraoperative PAC is integral to assess RV function, PVR, and the (hopefully favorable) impact of the endarterectomy.
Hemodynamic Considerations and Induction Most patients with CTEPH presenting for PEA have isolated right heart dysfunction, without LV pathology. Induction choice and hemodynamic management are thus centered around RV function. The right ventricle is typically hypertrophied and dilated, and the right atrium is dilated. PEA patients have relatively fixed PVR, so attempts to reduce PVR pharmacologically using vasodilators such as nitroglycerin or nitroprusside will have little if any benefit. Such vasodilators should be avoided because they cause a decrease in systemic vascular resistance, compromising RV coronary perfusion and leading to hypotension and cardiovascular collapse. Inhaled nitric oxide (NO) is generally safe in this population, but most patients with CTEPH are not very responsive to NO. Maintenance of adequate systemic vascular resistance is paramount, because RV blood and oxygen supply is directly proportional to systemic pressure and inversely proportional to RV pressure. Vasopressors such as phenylephrine and vasopressin are useful to maintain systemic vascular resistance and RV perfusion. In addition, any further increase in PVR should be avoided and treated aggressively by preventing hypoxia, hypercarbia, and acidosis. The choice of anesthetic induction agents depends on disease severity and the degree of hemodynamic instability. Most induction agents can be used provided sympatholysis and myocardial depression are minimized. Likewise, most muscle relaxants can be used, targeting hemodynamic stability and quick, optimal intubating conditions. Titration of narcotics should take place after control of ventilation and administration of muscle relaxant to avoid hypoventilation and chest rigidity. RV end-diastolic pressure > 15 mm Hg,
severe tricuspid regurgitation, PVR > 1000 dynes-sec-cm–5, and cardiac index < 1.5 L/min/m2 are signs of impending cardiovascular collapse, and it is recommended that an inotrope be infused on induction. TEE is performed after induction but before line placement to guide PA catheter advancement, monitor hemodynamics, and detect right atrial or proximal PA thrombus. If proximal thrombus is present, the PA catheter is advanced only to the superior vena cava (about 20 cm), to avoid dislodging the thrombus. Later, after the endarterectomies and thrombectomies are complete, the PA catheter is advanced into the PA. A femoral arterial catheter is placed after induction to monitor arterial pressure, as after prolonged periods of hypothermic bypass and circulatory arrest, a radial artery catheter significantly underestimates systemic arterial pressure. A central-peripheral gradient of as much as 20 mm Hg is not uncommon in the postbypass period.9 Mohr et al10 and Baba et al11 described the redistribution of blood flow away from the extremity as a potential mechanism for this phenomenon. Brain function monitoring (SEDLine; Hospira, Lake Forest, Illinois) is used to ensure electroencephalographic isoelectricity and thus minimal brain oxygen use prior to circulatory arrest. It also serves to monitor the level of consciousness. In addition to the SEDLine monitor, cerebral oximetry is used to detect ischemic events during CPB. It is a noninvasive, near-infrared spectroscopic technology that measures frontal cortex blood hemoglobin-oxygen saturation continuously.12 Cerebral oximetry is promising in terms of monitoring the brain as the index organ for systemic perfusion.13 A retrospective study of >2000 patients by Goldman et al14 confirmed that use of cerebral oximetry was associated with a decreased stroke rate in cardiac surgical patients at their institution. Yao et al15 observed an association between cerebral desaturation and neurocognitive dysfunction in 101 patients undergoing cardiac surgery. He found that patients with cerebral oxygen saturation < 40% for >10 minutes had an increased incidence of neurocognitive dysfunction. Several methods of temperature monitoring are used in PEA to allow accurate quantification of thermal gradients and to ensure even cooling and warming. Bladder and rectal temperature probes provide core temperature estimation. A tympanic membrane probe is used to estimate brain temperature,16 and the PA catheter measures blood temperature. For head cooling during circulatory arrest, a circulating cold water head wrap (Polar Care; Breg, Inc, Vista, California) (Figure 6) is used. Most patients presenting for PEA have polycythemia from chronic hypoxemia. For these patients, 1 to 2 U of blood is harvested before heparinization, to be reinfused after protamine administration. Moderate hemodilution has benefits for patients undergoing deep hypothermic circulatory arrest (DHCA), decreasing blood viscosity (which
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
5
Banks et al
case of sparse electroencephalographic activity, propofol will abolish any residual activity.21 Sodium thiopental provides similar cerebral protection but is no longer available commercially.22,23 At circulatory arrest, the electroencephalographic waveform must be isoelectric, the tympanic membrane temperature must be ≤ 18°C, and the bladder or rectal temperature must be ≤ 20°C. The duration of DHCA never exceeds 20 minutes at a time, and if extra time is needed on either side, circulation is resumed for 10 minutes, followed by another period of DHCA.
Rewarming and Separation From Bypass
Figure 6. Head wrap system (Polar Care; Breg, Inc, Vista, California).
tends to increase with hypothermia) and promoting uniform cooling.17 Moreover, the autologous whole blood is rich in factors and platelets, replacing factors diluted and lost during bypass. Antifibrinolytic agents are not used, because these patients are inherently hypercoagulable. Complete TEE is performed in all patients undergoing PEA, with emphasis on RV and LV function. PFOs are present in 25% to 35% of PEA patients.18 All patients are evaluated with color flow Doppler, and if the results are inconclusive, a contrast echocardiographic study is performed: positive end-expiratory pressure (30 cm H2O) is applied for 10 seconds, and with release of positive endexpiratory pressure, echocardiographic contrast agent (agitated blood or 5% albumin, without adding air) is injected. The study is performed only after the patient is prepared and draped, because instances of hemodynamic collapse have been associated with this maneuver. Most PFOs are repaired intraoperatively. In the rare instance when the results of the operation are unfavorable, with severe residual pulmonary hypertension anticipated, the PFO is left open as a “pop-off” to improve cardiac output at the expense of some hypoxemia.19
CPB and DHCA The prebypass time is typically short. The bypass pump is primed in the same manner as for other procedures, with the exception of the addition of methylprednisolone 30 mg/kg (maximum, 3 g). Methylprednisolone is a cell membrane stabilizer and anti-inflammatory agent.20 For postoperative seizure prophylaxis, phenytoin (15 mg/kg) is administered after the initiation of bypass. Immediately prior to the initiation of DHCA, propofol 2.5 mg/kg is administered to ensure complete cerebral isoelectricity; in
The temperature of the infusate during rewarming should not exceed 37.5°C, and rewarming should be slow, so as to be even and complete. This approach promotes temperature maintenance without “after-drop” after bypass. Communication with the surgeon is important, because surgical classification of the disease and how much clot was successfully removed will dictate how much inotropic and vasopressor support will be needed. Improved hemodynamics are expected, with substantial reduction in PVR and improved RV function. These favorable changes are revealed immediately after bypass with TEE.24 Types III and IV present the most challenging situations. Type III disease is distal, confined to the segmental and subsegmental branches. The majority of patients with type III disease, however, experience clinical improvement. If residual pulmonary hypertension is observed, aggressive inotropic support (eg, dopamine, epinephrine), together with a pulmonary vasodilator such as milrinone, inhaled prostacyclin, or NO, may be required. Inhaled NO is preferable to other vasodilators because it exerts its effect on the pulmonary vasculature with minimal systemic effects. The right atrium is paced at 90 to 100 beats/min with temporary epicardial pacing electrodes. The brisk heart rate promotes reduced RV filling and reduced wall tension. Ventricular epicardial electrodes are placed as well but used only if atrioventricular conduction is impaired. Endtidal carbon dioxide is a poor measure of ventilation in these patients, both before and after CPB, because deadspace ventilation, causing an increased end-tidal carbon dioxide/partial pressure of carbon dioxide gradient, is an integral part of the disease. This gradient will improve after successful surgery, but the response varies; therefore, higher minute ventilation is often continued after bypass. With successful PEA, immediate improvements in RV function with less distortion and flattening of the interventricular septum are seen on TEE. Severe preoperative tricuspid regurgitation rarely requires repair or replacement unless there is a structural abnormality of the leaflets, as tricuspid annular geometry is restored with remodeling after PEA.25
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
6
Seminars in Cardiothoracic and Vascular Anesthesia
Two of the most dreaded complications of PEA are airway bleeding and reperfusion pulmonary edema (RPE).26 Checking the endotracheal tube before separation from bypass for the presence of frothy sputum or bleeding is thus very important. If blood is seen in the endotracheal tube, 2 major causes are considered: (1) dark blood seen after separation from CPB usually indicates disruption of the bloodairway barrier in 1 of the PA branches, and (2) pink frothy blood usually indicates early and severe reperfusion injury from increased capillary permeability. Unfortunately, the integrity of the PA can be tested only during weaning from CPB, because PA bleeding will manifest only when cardiac ejection and PA pressure are generated. Anesthesiologists must be prepared to provide diagnostic and therapeutic maneuvers for this rare complication.
Management of Airway Bleeding The 2 main goals in the management of airway bleeding are the prevention of exsanguination and the maintenance of adequate gas exchange. Management depends on the severity of the bleeding. Conservative management, consisting of positive end-expiratory pressure, lung isolation of the segment bleeding with a bronchial blockade, reversal of heparin, a topical vasoconstrictor such as vasopressin or epinephrine, and correction of coagulopathies, will often reduce small bleeds and reperfusion injuries.26 If bleeding is recognized before separation from bypass, allowing the heart to briefly eject with the bleeding area under direct visualization with fiber-optic bronchoscopy will establish the location. An attempt is made to isolate the affected segment to prevent spilling of blood into other segments, which will cause further impairment of ventilation and gas exchange. A bronchial blocker placed through the endotracheal tube is the preferred method for lung or segment isolation. A double-lumen endobronchial tube is also an option but has the disadvantages of not allowing a large bronchoscope to be placed, possible difficulty in placement in the setting of the bleeding airway, and safety concerns about exchanging it with a single-lumen tube at the conclusion of the procedure. Airway bleeding and RPE can both cause inadequate oxygenation, ventilation problems, and/or hemodynamic instability. In biventricular dysfunction, venoarterial extracorporeal membrane oxygenation (ECMO) should be considered. In the case of RV dysfunction with preserved LV function, ECMO with right atrial inflow and PA outflow cannulas can be used. In the case of preserved RV and LV function, venovenous ECMO, using a heparin-bonded circuit, without systemic anticoagulation is an attractive alternative. Advantages of this approach include avoidance of anticoagulants, rapid placement of cannulas, maintenance of gas exchange, and preservation of pulsatile pulmonary and systemic flow, while allowing natural hemostatic processes to repair the affected PA or capillary bed. This natural repair is usually complete after 24 to 48
hours, allowing weaning from ECMO. The technique requires preserved RV and LV function, because venovenous ECMO does not provide ventricular support. Massive pulmonary hemorrhage after PEA, although a very rare event, is the third most common cause for perioperative mortality in the PEA population, with residual pulmonary hypertension and RPE being the leading 2 causes. All PEA patients are transported to the ICU with transport ventilators to standardize and maintain proper ventilation. In the absence of complications, most patients are extubated the day after surgery, discharged from the ICU on the second or third postoperative day, and discharged from the hospital 1 to 2 weeks postoperatively.
Postoperative Care Patients undergoing PEA are subject to many of the same postoperative complications as those undergoing other cardiothoracic surgical procedures such as delirium, atelectasis, pleural effusion, pericardial effusion, diaphragmatic dysfunction, and dysrhythmias. These complications are typically managed in the same manner as other for cardiothoracic procedures, but some differences exist. All patients are mechanically ventilated, at least overnight, to observe for RPE. Pneumatic compression devices are used for venous thrombosis prophylaxis, and the use of subcutaneous heparin is begun on the evening of surgery. Anticoagulation with warfarin is begun as soon as the pacing wires are removed (usually on postoperative day 1), with a target international normalized ratio of 2.5 to 3.5. Hypoxemia is common postoperatively in the PEA population for a number of reasons. In addition to the atelectasis, postoperative pain, and respiratory muscle dysfunction commonly seen in cardiothoracic surgery patients, V/Q mismatch is more pronounced in the PEA patient population because of loss of hypoxic vasoconstriction. This results from a disproportionate increase in blood flow to endarterectomized regions of lung and decreased blood flow to regions that were previously normal. This results in a “steal” phenomenon, which is commonly documented on postoperative perfusion scintigraphy.27 This creates regions of high and low V/Q, with low-V/Q regions representing newly reperfused lung regions, contributing to hypoxemia. This steal phenomenon can be dramatic, resulting in high oxygen requirements. This maldistribution of flow resolves over weeks to months, resulting in more homogenous perfusion of the lung by 1 year.28 RPE occurs in 10% to 40% of patients, depending on the definition used. Reperfusion injury is a localized form of high-permeability edema defined as a radiologic opacity seen in the areas of the lungs that have been endarterectomized and reperfused.29,30 In its most severe forms, it can present as severe alveolar hemorrhage with profound hypoxemia, and it is associated with high mortality.26 RPE is an early postoperative complication, with 60% of cases
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
7
Banks et al presenting immediately following surgery, 30% developing within the first 48 hours, and a minority (10%) occurring later during the hospitalization (>48 hours). The incidence of RPE has decreased over time for unclear reasons. Two studies using the same definition of RPE (partial pressure of oxygen/fraction of inspired oxygen < 300, opacity on a chest radiograph in a region reperfused following PEA, and no other reason for the previous 2 criteria such as pneumonia or atelectasis) showed that the incidence of RPE had decreased from 60% to 41% in patients treated similarly at the same institution.31,32 A more recent study demonstrated a 28% incidence of this condition. The severity of preoperative pulmonary hypertension and the presence of residual pulmonary hypertension are associated with an increased risk for RPE.31 RPE is associated with significant increases in the duration of mechanical ventilation and length of ICU stay32 and in its most severe form may result in death. Several interventions have been attempted to reduce reperfusion lung injury. A small, 2-center clinical trial demonstrated that a strategy of minimizing inotropes and using low tidal ventilation following PEA could reduce the incidence of RPE in PEA patients and reduce mortality.33 However, limitations of this study included its small number of patients, lack of a clear definition of RPE, 2 simultaneous interventions, and treatment group allocation by institution rather than randomization of patients at each institution. In addition to elevated protein levels, increased neutrophils have been found in the bronchial alveolar lavage of patients with lung injury compared with those without lung injury, suggesting that the injury is a consequence of inflammation.30,34 A trial using a selectin analogue to reduce neutrophil rolling and theoretically reduce neutrophil-mediated inflammation in the lung showed promise by reducing the incidence of lung injury from 60% to 30% in a small, single-institution study, supporting the concept that RPE is at least in part mediated by neutrophils.30 However, a more recent and larger study showed no benefit of high-dose methylprednisolone in preventing RPE.31 Treatment of RPE is primarily supportive. Diuresis to reduce lung water and avoidance of high cardiac output are typically used, along with minimizing oxygen consumption. In contrast to acute respiratory distress syndrome, RPE is often asymmetric, and patients may oxygenate better in one lateral decubitus position than the other. Inhaled NO may improve oxygenation, and ECMO support can be lifesaving in severe cases.35 Residual pulmonary hypertension remains a significant problem in 5% to 35%8,36,37 of patients undergoing PEA and is the most common cause of perioperative mortality.8,36,38 Operative mortality increases with increasing preoperative PVR,8,38 but an even greater predictor of postoperative mortality is residual pulmonary hypertension following PEA.8,36 Residual pulmonary hypertension is the
result of distal chronic thromboembolic disease or superimposed small-vessel vasculopathy that is not cured by endarterectomy. Hence, removal of chronic thromboembolic material from the proximal pulmonary arterial bed may still allow significant residual pulmonary hypertension due to distal small vessel vasculopathy. Microscopically, these changes resemble those of idiopathic pulmonary hypertension.39 Determining the presence of small-vessel arteriopathy prior to surgery remains problematic and is of great interest.40,41 Treatment of severe residual pulmonary hypertension and right heart failure in the immediate postoperative period is challenging. Inotropic support is required, and careful attention to optimizing RV preload is important. Attempts to reduce PA pressure with systemic vasodilators are often unsuccessful and carry the risk for systemic vasodilatation with associated poor coronary perfusion. Reductions in PVR can be accomplished in some patients with inhaled NO or inhaled iloprost, without an associated reduction in systemic blood pressure.42-44 Patients treated preoperatively with pulmonary antihypertensive agents (prostacyclin analogues, phosphodiesterase-5 inhibitors, endothelin receptor antagonists) can usually have these medications discontinued at the time of operation if PEA has resulted in significant reductions in PVR. However, if patients have significant residual pulmonary hypertension, continuation of these medications postoperatively should be considered. Postoperative pericardial effusions are not uncommon and should be considered when patients exhibit worsening edema, chest pain, and dyspnea. Echocardiography should be performed immediately to confirm the diagnosis, and significant effusions should be drained. Atrial dysrhythmias are treated as they are in other patients with atrial flutter or fibrillation following cardiac surgery, with the caveat that β-blockers are tolerated poorly in patients with residual pulmonary hypertension. Anticoagulation is begun the night of surgery if there are no bleeding complications. Lifelong anticoagulation is recommended for all patients, to avoid recurrent thrombosis.
PEA in Patients With Sickle Cell Disease The prevalence of pulmonary hypertension in sickle cell disease was reported by Sutton et al,45 Simmons et al,46 Moser and Shea,47 and Collins and Orringer.48 All confirmed the relationship among pulmonary infarction, cor pulmonale, and sickle cell disease. While many sickle cell patients have ulmonary hypertension due to small vessel disease some present with CTEPH. Patients with sickle cell disease undergoing PEA present a unique challenge because prolonged CPB, deep hypothermia, and circulatory arrest all tend to promote sickling. Sickling and hemolysis during or after CPB is a known concern.49,50 Stagnation of blood,
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
8
Seminars in Cardiothoracic and Vascular Anesthesia
deep hypothermia, anemia, and acidosis encountered during circulatory arrest increase the likelihood of sickling, with cellular acidosis and hypoxia likely more important factors than hypothermia per se.51,52 Patients with sickle cell disease presenting for PEA should undergo thorough preoperative evaluation, with particular attention to correction of anemia, early screening for antibodies in blood typing, preoperative and intraoperative exchange transfusion, and avoidance of hypoxemia and acidosis during and after surgery. Particular attention should be paid to hypoxic complications such as atelectasis and RPE during the postoperative period. These conditions must be treated aggressively, with the goal of maintaining adequate peripheral perfusion and arterial oxygen saturation ≥95%.53
PEA in Patients With Heparininduced Thrombocytopenia Patients with heparin-induced thrombocytopenia present unique challenges, because for these patients, alternative means of anticoagulation during bypass must be used. There are reports of the successful use of recombinant hirudin.54 Systemic anticoagulation in patients with suspected type II heparin-induced thrombocytopenia using the glycoprotein IIb/IIIa inhibitor tirofiban and unfractionated heparin has also been successful. Tirofiban binds competitively to platelet glycoprotein IIb/IIIa receptors and has a half-life of approximately 2 hours.55-57 With >80% blockade of glycoprotein IIb/IIIa receptors, systemic heparinization can be performed safely. A loading dose of 10 µg/kg is given 10 minutes before CPB, followed by a continuous infusion at 0.15 µg/kg/min.56,57 Platelet activation is measured using the Ultegra rapid platelet function assay (Accumetrics Inc, San Diego, California). Once platelet inhibition is >80%, full heparinization (400 IU/kg) can be performed. Systemic anticoagulation is monitored with automated heparin concentration using the Hepcon Hemostasis Management System (Medtronic Inc, Minneapolis, Minnesota), with the goal of maintaining clotting time > 480 seconds. Heparin concentration and clotting time are monitored every 30 minutes, as is platelet inhibition. Tirofiban infusion is discontinued 1 hour prior to the cessation of CPB. In patients with compromised renal function, ultrafiltration is used to decrease the tirofiban plasma concentration. Heparin is neutralized with protamine as usual, and donor platelets are transfused if necessary.57 It is critical to avoid exposure to heparin before and after bypass, including heparin-treated CPB components and monitoring lines.
The Future PEA is now recognized as the definitive treatment of CTEPH. With increased awareness of the disease and referral of patients early in the disease process, PEA will
become an increasingly common operation. However, because morbidity and mortality rates are still significant, continued research into etiology, diagnosis, medical management, and surgical treatment are necessary. Residual pulmonary hypertension, RPE, vascular steal, RV failure, and cerebral protection remain areas of research that will likely result in improved outcomes. Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.
References 1. Moser KM, Houk VN, Jones RC, et al. Chronic, massive thrombotic obstruction of the pulmonary arteries. Analysis of four operated cases. Circulation. 1965;32(3):377-385. 2. Fedullo P, Kerr KM, Kim NH, Auger WR. Chronic thromboembolic pulmonary hypertension. Am J Respir Crit Care Med. 2011;183(12):1605-1613. 3. Madani MM, Jamieson SW. Technical advances of pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension. Semin Thorac Cardiovasc Surg. 2006;18(3):243-249. 4. Winkler MH, Rohrer CH, Ratty SC, et al. Perfusion techniques of profound hypothermia and circulatory arrest for pulmonary thromboendarterectomy. J Extra Corp Technol. 1990;22(57):35799. 5. Jamieson SW, Kapelanski DP. Pulmonary endarterectomy. Curr Probl Surg. 2000;37(3):165-252. 6. Jamieson SW. Pulmonary thromboendarterectomy. In Franco KL, Putnam JB, eds. Advanced Therapy in Thoracic Surgery. Hamilton, ON, Canada: BC Decker; 1998: 310-318. 7. Thistlethwaite PA, Kemp A, Du L, Madani MM, Jamieson SW. Outcomes of pulmonary endarterectomy for treatment of extreme thromboembolic pulmonary hypertension. J Thorac Cardiovasc Surg. 2006;131:307-313. 8. Madani MM, Auger WR, Pretorius V, et al. Pulmonary endarterectomy: recent changes in a single institution’s experience of more than 2,700 patients. Ann Thorac Surg. 2012;94:97-103. 9. Manecke GR Jr, Parimucha M, Stratmann G, et al. Deep hypothermic circulatory arrest and the femoral-to-radial arterial pressure gradient. J Cardiothorac Vasc Anesth. 2004;18(2):175-179. 10. Mohr R, Lavee J, Goor DA. Inaccuracy of radial artery pressure measurement after cardiac operations. J Thorac Cardiovasc Surg. 1987;94(2):286-290. 11. Baba T, Goto T, Yoshitake A, et al. Radial artery diameter decreases with increased femoral to radial arterial pressure gradient during cardiopulmonary bypass. Anesth Analg. 1997;85:252-258.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
9
Banks et al 12. Edmonds HL Jr, Ganzel BL, Austin EH III. Cerebral oximetry for cardiac and vascular surgery. Semin Cardiothorac Vasc Anesth. 2004;8:147-166. 13. Hong SW, Shim JK, Choi YS, Kim DH, et al. Prediction of cognitive dysfunction and the role of cerebral oximetry. Eur J Cardiothorac Surg. 2008;33:560-565. 14. Goldman S, Sutter F, Ferdinand F, Trace C. Optimizing intraoperative cerebral oxygen delivery using noninvasive cerebral oximetry decreases the incidence of stroke for cardiac surgical patients. Heart Surg Forum. 2004;7:E376-E381. 15. Yao FSF, Tseng C-C, Ho CYA, et al. Cerebral oxygen desaturation is associated with early postoperative neuropsychological dysfunction in patients undergoing cardiac surgery. J Cardiothorac Vasc Anesth. 2004;18(5):552-558. 16. Schuhmann MU, Suhr DF, van Gosseln HH, et al. Local brain surface temperature compared to temperatures measured at standard extracranial monitoring sites during posterior fossa surgery. J Neurosurg Anesthesiol. 1999;11(2):90-95. 17. Svyatets M, Tolani K, Zhang M, et al. Perioperative management of deep hypothermic circulatory arrest. J Cardiothorac Vasc Anesth. 2010;24(4):644-655. 18. Dittrich HC, McCann HA, Wilson WC. Identification of interatrial communication in patients with elevated right atrial pressure using surface and transesophageal contrast echocardiography. J Am Coll Cardiol. 1993;21(Suppl):135A. 19. Amsel BJ, Rodrigus I, De Paep R, et al. Right-to-left flow through a patent foramen ovale in acute right ventricular infarction. Two case reports and a proposal for management. Chest. 1995;108(5):1468-1471. 20. Langley SM, Chai PJ, Jaggers JJ, et al. Preoperative high dose methylprednisolone attenuates the cerebral response to deep hypothermic circulatory arrest. Eur J Cardiothorac Surg. 2000;17(3):279-286. 21. Newman MF, Mm-kin JM, Roach G, et al. Cerebral physiologic effects of burst suppression doses of propofol during nonpulsatile cardiopulmonary bypass. Anesth Analg. 1995;81:452-457. 22. Nussmeier NA, Arlund C, Slogoff S. Neuropsychiatric complications after cardiopulmonary bypass: cerebral protection by a barbiturate. Anesthesiology. 1986;64(2):165-170. 23. Nehls DG, Todd MM, Spetzler RF, et al. A comparison of the cerebral protective effects of isoflurane and barbiturates during temporary focal ischemia in primates. Anesthesiology. 1987;66(4):453-464. 24. Dittrich HC, Nicod PH, Chow LC, et al. Early changes of right heart geometry after pulmonary thromboendarterectomy. J Am Coll Cardiol. 1988;11(5):937-943. 25. Menzel T, Kramm T, Wagner S, et al. Improvement of tricuspid regurgitation after pulmonary thromboendarterectomy. Ann Thorac Surg. 2002;73(3):756-761. 26. Manecke GR Jr, Kotzur A, Atkins G, et al. Massive pulmonary hemorrhage after pulmonary thromboendarterectomy. Anesth Analg. 2004;99(3):672-675. 27. Olman MA, Auger WR, Fedullo PF, et al. Pulmonary vascular steal in chronic thromboembolic pulmonary hypertension. Chest. 1990;98:1430-1434. 28. Moser KM, Metersky ML, Auger WR, et al. Resolution of vascular steal after pulmonary thromboendarterectomy. Chest. 1993;104:1441-1444.
29. Levinson RM, Shure D, Moser KM. Reperfusion pulmonary edema after pulmonary artery thromboendarterectomy. Am Rev Respir Dis. 1986;134:1241-1245. 30. Kerr KM, Auger WR, Marsh JJ, et al. The use of cylexin (CY-1503) in prevention of reperfusion lung injury in patients undergoing pulmonary endarterectomy. Am J Respir Crit Care Med. 2000;162:14-20. 31. Kerr KM, Auger SR, Marsh JJ, et al. Efficacy of methylprednisolone in preventing lung injury following pulmonary thromboendarterectomy. Chest. 2012;141(1):27-35. 32. Duwe BV, Kerr KM, Fedullo PF, Kim NH, Test VJ, Auger WR. Clinical impact of reperfusion lung injury on patients undergoing pulmonary thromboendarterectomy. Am J Respir Crit Care Med. 2009;179:A4628. 33. Mares P, Gilbert TB, Tschernko EM, et al. Pulmonary artery thromboendarterectomy: a comparison of two different postoperative treatment strategies. Anesth Analg. 2000;90(2):267-273. 34. Auger WR, Moser KM, Comito RM, Kerr KM, et al. Efficacy of intravenous ICI 200,880 in the prevention of adult respiratory distress syndrome in patients undergoing pulmonary endarterectomy. Am J Respir Crit Care Med. 1994;149:A1032. 35. Berman M, Tsui S, Vuylsteke A, et al. Successful extracorporeal membrane oxygenation support after pulmonary thromboendarterectomy. Ann Thorac Surg. 2008;86: 1261-1267. 36. Mayer E, Jenkins D, Lindner J, et al. Surgical management and outcome of patients with chronic thromboembolic pulmonary hypertension: results from an international prospective registry. J Thorac Cardiovasc Surg. 2011;141(3):702-710. 37. Bondermann D, Skoro-Sager N, Jakowitsch J, et al. Predictors of outcome in chronic thromboembolic disease. Circulation. 2007;115:2153-2158. 38. Dartevelle P, Fadel E, Mussot S, et al. Chronic thromboembolic pulmonary hypertension. Eur Respir J. 2004;23(4): 637-648. 39. Moser KM, Bloor CM. Pulmonary vascular lesions occurring in patients with chronic major vessel thromboembolic pulmonary hypertension. Chest. 1993;103:685-692. 40. Kim NH, Fessler P, Channick RN, et al. Preoperative partitioning of pulmonary vascular resistance correlates with early outcome after thromboendarterectomy for chronic thromboembolic pulmonary hypertension. Circulation. 2004;109:18-22. 41. Hardziyenka M, Reesink HJ, Bouma BJ, et al. A novel echocardiographic predictor of in-hospital mortality and mid-term haemodynamic improvement after pulmonary endarterectomy for chronic thrombo-embolic pulmonary hypertension. Eur Heart J. 2007;28(7):842-849. 42. Kramm T, Eberle B, Guth S, Mayer E. Inhaled iloprost to control residual pulmonary hypertension following pulmonary endarterectomy. Eur J Cardiothorac Surg. 2005;28:882-888. 43. Flonder M, Merkel M, Hofsteter C, et al. The effect of inhaled nitric oxide and inhaled iloprost on hypoxaemia in a patient with pulmonary hypertension after pulmonary thromboendarterectomy. Anaesthesia. 2006;61: 1200-1203.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
10
Seminars in Cardiothoracic and Vascular Anesthesia
44. Imanaka H, Miyano H, Takeuchi M, et al. Effects of nitric oxide inhalation after pulmonary thromboendarterectomy for chronic thromboembolism. Chest. 2000;118:39-46. 45. Sutton LL, Castro O, Cross DJ, Spencer JE, et al. Pulmonary hypertension in sickle cell disease. Am J Cardiol. 1994;74:626-628. 46. Simmons BE, Santhanam V, Castaner A, et al. Sickle cell disease: two-dimensional echo and Doppler ultrasonographic findings in hearts of adult patients with sickle anemia. Arch Intern Med. 1988;148:1526. 47. Moser KM, Shea JG. The relationship between pulmonary infarction, cor pulmonale, and the sickle cell states. Am J Med. 1957;27:561. 48. Collins FS, Orringer E. Pulmonary hypertension and cor pulmonale in the sickle hemoglobinopathies. Am J Med. 1982;73(6):814-821. 49. Balasundaram S, Duran CG, al-Halees Z, Kassay M. Cardiopulmonary bypass in sickle cell anaemia. Report of five cases. J Cardiovasc Surg. 1991;32(2):271-274. 50. Hockmuth D, Mills N. Management of unusual problems encountered in initiating and maintaining cardiopulmonary bypass. In: Cardiopulmonary Bypass: Principles and Practice. Baltimore, MD: Williams & Wilkins; 1993: 750-751. 51. Deleval M, Taswell HF, Bowie EJW, et al. Open heart surgery in patients with inherited hemoglobinopathies, red
cell dyscrasias and coagulopathies. Arch Surg. 1974;109(5): 618-622. 52. Vichinsky EP, Haberkern CM, Neumayr L. A compari son of conservative and aggressive transfusion regimens in the perioperative management of sickle cell disease: the Perioperative Transfusion in Sickle Cell Disease Study Group. N Engl J Med. 1995;333(4):206-213. 53. Aldrich TK, Dhuper SK, Patwa NS, et al. Pulmonary entrapment of sickle cells: the role of regional alveolar hypoxia. J Appl Physiol. 1996;80(2):531-539. 54. Rubens FD, Sabloff M, Wells PS. Use of recombinant hirudin in pulmonary thromboendarterectomy. Ann Thorac Surg. 2000;69(6):1942-1943. 55. Koster A, Meyer O, Fischer T, et al. One-year experience with the platelet glycoprotein IIb/IIIa antagonist tirofiban, and heparin during cardiopulmonary bypass in patients with heparin-induced thrombocytopenia type II. J Thorac Cardiovasc Surg. 2001;122(6):1254-1255. 56. Warkentin TE, Greinacher A. Heparin-induced throm bocytopenia and cardiac surgery. Ann Thorac Surg. 2003;76(6):2121-2131. 57. Warkentin TE, Greinacher A, Koster A. Treatment and prevention of heparin-induced thrombocytopenia: American College of Chest Physicians evidence-based clinical practice guidelines (8th edition). Chest. 2008;133(6 Suppl): 340S-380S.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
Pulmonary Endarterectomy: Part II. Operation, Anesthetic Management, and Postoperative Care Dalia A. Banks, Gert Victor D. Pretorius, Kim M. Kerr and Gerard R. Manecke SEMIN CARDIOTHORAC VASC ANESTH published online 7 July 2014 DOI: 10.1177/1089253214537688 The online version of this article can be found at: http://scv.sagepub.com/content/early/2014/07/22/1089253214537688
Published by: http://www.sagepublications.com
Additional services and information for Seminars in Cardiothoracic and Vascular Anesthesia can be found at: Email Alerts: http://scv.sagepub.com/cgi/alerts Subscriptions: http://scv.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav Citations: http://scv.sagepub.com/content/early/2014/07/22/1089253214537688.refs.html
>> OnlineFirst Version of Record - Jul 22, 2014 OnlineFirst Version of Record - Jul 16, 2014 OnlineFirst Version of Record - Jul 13, 2014 OnlineFirst Version of Record - Jul 7, 2014 What is This?
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
537688 research-article2014
SCVXXX10.1177/1089253214537688Seminars in Cardiothoracic and Vascular AnesthesiaBanks et al
Article
Pulmonary Endarterectomy: Part II. Operation, Anesthetic Management, and Postoperative Care
Seminars in Cardiothoracic and Vascular Anesthesia 1–10 © The Author(s) 2014 Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1089253214537688 scv.sagepub.com
Dalia A. Banks, MD, FASE1, Gert Victor D. Pretorius, MBChB1, Kim M. Kerr, MD1, and Gerard R. Manecke, MD1
Abstract Chronic thromboembolic pulmonary hypertension (CTEPH) results from recurrent or incomplete resolution of pulmonary embolism. CTEPH is much more common than generally appreciated. Although pulmonary embolism (PE) affects a large number of Americans, chronic pulmonary thromboembolic hypertension remains underdiagnosed. It is imperative that all patients with pulmonary hypertension (PH) be screened for the presence of CTEPH since this form of PH is potentially curable with pulmonary endarterectomy (PEA) surgery. The success of this procedure depends greatly on the collaboration of a multidisciplinary team approach that includes pulmonary medicine, cardiothoracic surgery, and cardiac anesthesiology. This review, based on the experience of more than 3000 pulmonary endarterectomy surgeries, is divided into 2 parts. Part I focuses on the clinical history and pathophysiology, diagnostic workup, and intraoperative echocardiography. Part II focuses on the surgical approach, anesthetic management, postoperative care, and complications. Keywords pulmonary endarterectomy, pulmonary thromboendarterectomy, sickle cell disease, heparin-induced thrombocytopenia (HIT), transesophageal echocardiography in CTEPH, deep hypothermic circulatory arrest, pulmonary hemorrhage in PEA, reperfusion lung injury
Introduction The University of California, San Diego, has reported most of the world experience in pulmonary endarterectomy (PEA), having performed >3000 cases. The operation, using deep hypothermia and circulatory arrest, has evolved over the past 3 decades. Chronic thromboembolic pulmonary hypertension (CTEPH) is the only type of pulmonary hypertension amenable to surgical treatment, and PEA is its definitive treatment. Success depends on the close collaboration of a multidisciplinary team including pulmonologists, cardiothoracic surgeons, and cardiac anesthesiologists. In this review, anesthetic and surgical considerations are presented, as are approaches to 2 challenging conditions: sickle cell disease and heparin-induced thrombocytopenia.
The Operation There are 3 reasons to perform PEA on patients with CTEPH: hemodynamic compromise, respiratory dysfunction, and the prevention of disease progression (prophylaxis).1,2 The hemodynamic goal is to ameliorate right ventricular (RV) compromise caused by high pulmonary
vascular resistance (PVR). The respiratory objectives are to improve ventilation-perfusion (V/Q) matching and to treat dyspnea. The prophylactic goals are to prevent progressive RV dysfunction, and secondary arteriopathy in the remaining patent vessels. Most patients present with PVR in the range of 800 dynes-sec-cm–5 and pulmonary artery (PA) pressures less than systemic, although disease progression and hypertrophy of the right ventricle can cause suprasystemic PA pressure. Good outcomes can be achieved in patients with PVR in excess of 1000 dynessec-cm–5 and suprasystemic PA pressures, so there are no upper limits of PVR, PA pressure, or the degree of RV dysfunction that contraindicate PEA. Most patients presenting for PEA are in New York Heart Association class III or IV heart failure. Occasionally, PEA is indicated even with normal resting PVR such as in symptomatic patients with significant vascular obstruction. 1
University of California, San Diego, San Diego, CA, USA
Corresponding Author: Dalia A. Banks, MD, FASE, University of California, San Diego, 9300 Campus Point Drive, #7651, La Jolla, CA 92037, USA Email: [email protected]
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
2
Seminars in Cardiothoracic and Vascular Anesthesia Guiding principles for the operation are as follows: 1. The endarterectomy should be bilateral, via median sternotomy. Historically, there were reports of unilateral PEA. At some centers, this ill-advised operation is still performed, via thoracotomy. This approach has significant disadvantages: it leaves untreated disease on the contralateral side, subjects the patient to hemodynamic jeopardy during PA clamping, does not allow good surgical exposure because of the continued presence of bronchial blood flow, and usually exposes the patient to a second operation on the contralateral side. Also, thoracotomy for PEA may be very bloody because of prominent collateral vessels present in CTEPH (diaphragmatic, intercostal, and pleural). 2. Cardiopulmonary bypass (CPB) is used. 3. A true endarterectomy in the plane of the media, extending to the distal vessels, must be accomplished. The mere removal of visible acute thrombus is ineffective.3 4. A bloodless field is required to extend the endarterectomy deep into the subsegmental vessels. Because of the copious bronchial flow in CTEPH, periods of circulatory arrest are necessary.
Figure 1. Surgical field with standard cannulation strategy for cardiopulmonary bypass includes aortic and bicaval cannulation with vent cannulas in the pulmonary artery and left atrium.
Surgical Technique After median sternotomy, one generally finds an enlarged right heart with a tense right atrium. These patients may become unstable with the manipulation of the heart. CPB is instituted after an activated clotting time > 450 seconds is achieved. A temporary PA vent is placed in the midline of the main PA (Figure 1). In addition to cooling the blood via the pump oxygenator, surface cooling with both a head jacket and a cooling blanket is begun. Cooling to 20°C must be gradual to ensure uniform cooling, generally taking 60 to 90 minutes.4 A left ventricular (LV) vent is placed to prevent overdistension, which can be particularly hazardous upon fibrillation. At a core temperature of 20°C, the aorta is cross-clamped and a single dose (1 L) of coldblood cardioplegia is administered. A cooling jacket wrapped around the heart offers additional myocardial protection. The primary surgeon stands on the patient’s left side. The approach to the right PA is made medial to the superior vena cava (Figure 2). All dissection of the pulmonary arteries is carried out intrapericardially, avoiding entering the pleural cavity. An incision is then made in the right PA from beneath the ascending aorta under the superior vena cava, entering the lower lobe branch of the PA. It is important that the incision stay in the center of the vessel. When blood obscures direct vision, circulatory arrest is initiated, and the patient undergoes exsanguination. Although continuous selective cerebral perfusion has been advocated during circulatory arrest in other procedures, it
Figure 2. Access to the right pulmonary artery is enhanced by complete mobilization of the superior vena cava (SVC) and spreading the aorta and SVC apart with a self-retaining retractor.
is not used in this operation, because it does not allow a completely bloodless field. Furthermore, the circulatory arrest times are relatively short in PEA, obviating the need for continuous cerebral perfusion.5 Endarterectomy in the correct dissection plane is critical. If the plane is too deep, the PA may be perforated, and if it is too shallow, inadequate amounts of thromboembolic material will be removed. The ideal layer is a pearly white plane that strips easily. Once the plane is correctly developed, the endarterectomy is performed with an eversion technique. It is important that each subsegmental branch be followed and freed individually until it ends in a “tail,”
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
3
Banks et al
Figure 3. Type I disease with clot in the main pulmonary arteries.
Figure 5. Type III disease with dissection plane raised in the segmental branches to remove clot as far out as the subsegmental level.
repaired. To perform the left endarterectomy, the surgeon moves to the patient’s right side. Once endarterectomies are completed on both sides, CPB is reinstituted and warming is commenced. Methylprednisolone (500 mg) and mannitol (12.5 g) are administered; this is in addition to methylprednisolone present in the pump prime (see the following discussion). If a patent foramen ovale (PFO) is present, it is repaired, and other indicated cardiac procedures, such as coronary artery bypass and mitral or aortic valve surgery, are performed during the rewarming period. Wound closure is routine, with hemostasis being important because the patient will receive anticoagulation treatment within hours of reaching the intensive care unit (ICU).3 Figure 4. Type II disease with clot in the lobar arteries where the dissection plane was raised.
Anesthetic Management Preoperative Preparation
beyond which there is no further obstruction. Residual material should never be cut free; the entire specimen should “tail off” and come free spontaneously. Jamieson5,6 classified pulmonary occlusive disease into 4 types. Type I disease (approximately 12%; Figure 3) involves a major vessel clot that is present and readily visible on opening the pulmonary arteries. In type II disease (approximately 38%; Figure 4), only thickened intima can be seen, and the endarterectomy plane is initially raised in the main, lobar. In type III disease (approximately 39%; Figure 5), the disease is distal, confined to the segmental and subsegmental branches. Type IV disease represents intrinsic small-vessel disease and is inoperable, although secondary thrombi may occur from stasis. Once the right-sided endarterectomy is completed, circulation is restarted and the arteriotomy is
Patients with CTEPH typically present with varying degrees of right heart failure, paradoxical interventricular septal motion, tricuspid regurgitation, hepatic congestion, and decreased cardiac indices.7,8 Much of the preoperative preparation is common to other open-heart procedures, although the workup is usually more extensive. Right heart catheterization provides important information prior to surgery. RV diastolic pressure > 14 mm Hg together with elevated right atrial pressure suggests RV failure. Mean PA pressure > 50 mm Hg and PVR > 600 dynes-sec-cm–5 signify severe pulmonary hypertension. Cardiac output and cardiac index also provide important information about RV function as well as other cardiac problems. On the day of surgery a large-bore peripheral intravenous catheter and radial arterial catheter are placed preoperatively.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
4
Seminars in Cardiothoracic and Vascular Anesthesia
Benzodiazepines may be administered preoperatively, but with extreme caution, with full monitoring, and preferably in the operating room. Opiates are generally avoided preoperatively because of their respiratory-depressant effects. Preoperative sedation should be individualized, with the understanding that anxiety and pain can increase PVR, while excessive sedation can itself cause hypercarbia and hypoxia, resulting in increased PVR. Standard monitoring together with transesophageal echocardiography (TEE), PA catheterization (PAC), cerebral function monitoring, and a cooling head device are planned. An internal jugular introducer and PA catheter are placed after induction rather than before, because patients with severe pulmonary hypertension may not tolerate lying flat. Preoperative hemodynamic data from recent right heart catheterization are usually known before surgery, thus making placement of a PA catheter before induction unnecessary. Intraoperative PAC is integral to assess RV function, PVR, and the (hopefully favorable) impact of the endarterectomy.
Hemodynamic Considerations and Induction Most patients with CTEPH presenting for PEA have isolated right heart dysfunction, without LV pathology. Induction choice and hemodynamic management are thus centered around RV function. The right ventricle is typically hypertrophied and dilated, and the right atrium is dilated. PEA patients have relatively fixed PVR, so attempts to reduce PVR pharmacologically using vasodilators such as nitroglycerin or nitroprusside will have little if any benefit. Such vasodilators should be avoided because they cause a decrease in systemic vascular resistance, compromising RV coronary perfusion and leading to hypotension and cardiovascular collapse. Inhaled nitric oxide (NO) is generally safe in this population, but most patients with CTEPH are not very responsive to NO. Maintenance of adequate systemic vascular resistance is paramount, because RV blood and oxygen supply is directly proportional to systemic pressure and inversely proportional to RV pressure. Vasopressors such as phenylephrine and vasopressin are useful to maintain systemic vascular resistance and RV perfusion. In addition, any further increase in PVR should be avoided and treated aggressively by preventing hypoxia, hypercarbia, and acidosis. The choice of anesthetic induction agents depends on disease severity and the degree of hemodynamic instability. Most induction agents can be used provided sympatholysis and myocardial depression are minimized. Likewise, most muscle relaxants can be used, targeting hemodynamic stability and quick, optimal intubating conditions. Titration of narcotics should take place after control of ventilation and administration of muscle relaxant to avoid hypoventilation and chest rigidity. RV end-diastolic pressure > 15 mm Hg,
severe tricuspid regurgitation, PVR > 1000 dynes-sec-cm–5, and cardiac index < 1.5 L/min/m2 are signs of impending cardiovascular collapse, and it is recommended that an inotrope be infused on induction. TEE is performed after induction but before line placement to guide PA catheter advancement, monitor hemodynamics, and detect right atrial or proximal PA thrombus. If proximal thrombus is present, the PA catheter is advanced only to the superior vena cava (about 20 cm), to avoid dislodging the thrombus. Later, after the endarterectomies and thrombectomies are complete, the PA catheter is advanced into the PA. A femoral arterial catheter is placed after induction to monitor arterial pressure, as after prolonged periods of hypothermic bypass and circulatory arrest, a radial artery catheter significantly underestimates systemic arterial pressure. A central-peripheral gradient of as much as 20 mm Hg is not uncommon in the postbypass period.9 Mohr et al10 and Baba et al11 described the redistribution of blood flow away from the extremity as a potential mechanism for this phenomenon. Brain function monitoring (SEDLine; Hospira, Lake Forest, Illinois) is used to ensure electroencephalographic isoelectricity and thus minimal brain oxygen use prior to circulatory arrest. It also serves to monitor the level of consciousness. In addition to the SEDLine monitor, cerebral oximetry is used to detect ischemic events during CPB. It is a noninvasive, near-infrared spectroscopic technology that measures frontal cortex blood hemoglobin-oxygen saturation continuously.12 Cerebral oximetry is promising in terms of monitoring the brain as the index organ for systemic perfusion.13 A retrospective study of >2000 patients by Goldman et al14 confirmed that use of cerebral oximetry was associated with a decreased stroke rate in cardiac surgical patients at their institution. Yao et al15 observed an association between cerebral desaturation and neurocognitive dysfunction in 101 patients undergoing cardiac surgery. He found that patients with cerebral oxygen saturation < 40% for >10 minutes had an increased incidence of neurocognitive dysfunction. Several methods of temperature monitoring are used in PEA to allow accurate quantification of thermal gradients and to ensure even cooling and warming. Bladder and rectal temperature probes provide core temperature estimation. A tympanic membrane probe is used to estimate brain temperature,16 and the PA catheter measures blood temperature. For head cooling during circulatory arrest, a circulating cold water head wrap (Polar Care; Breg, Inc, Vista, California) (Figure 6) is used. Most patients presenting for PEA have polycythemia from chronic hypoxemia. For these patients, 1 to 2 U of blood is harvested before heparinization, to be reinfused after protamine administration. Moderate hemodilution has benefits for patients undergoing deep hypothermic circulatory arrest (DHCA), decreasing blood viscosity (which
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
5
Banks et al
case of sparse electroencephalographic activity, propofol will abolish any residual activity.21 Sodium thiopental provides similar cerebral protection but is no longer available commercially.22,23 At circulatory arrest, the electroencephalographic waveform must be isoelectric, the tympanic membrane temperature must be ≤ 18°C, and the bladder or rectal temperature must be ≤ 20°C. The duration of DHCA never exceeds 20 minutes at a time, and if extra time is needed on either side, circulation is resumed for 10 minutes, followed by another period of DHCA.
Rewarming and Separation From Bypass
Figure 6. Head wrap system (Polar Care; Breg, Inc, Vista, California).
tends to increase with hypothermia) and promoting uniform cooling.17 Moreover, the autologous whole blood is rich in factors and platelets, replacing factors diluted and lost during bypass. Antifibrinolytic agents are not used, because these patients are inherently hypercoagulable. Complete TEE is performed in all patients undergoing PEA, with emphasis on RV and LV function. PFOs are present in 25% to 35% of PEA patients.18 All patients are evaluated with color flow Doppler, and if the results are inconclusive, a contrast echocardiographic study is performed: positive end-expiratory pressure (30 cm H2O) is applied for 10 seconds, and with release of positive endexpiratory pressure, echocardiographic contrast agent (agitated blood or 5% albumin, without adding air) is injected. The study is performed only after the patient is prepared and draped, because instances of hemodynamic collapse have been associated with this maneuver. Most PFOs are repaired intraoperatively. In the rare instance when the results of the operation are unfavorable, with severe residual pulmonary hypertension anticipated, the PFO is left open as a “pop-off” to improve cardiac output at the expense of some hypoxemia.19
CPB and DHCA The prebypass time is typically short. The bypass pump is primed in the same manner as for other procedures, with the exception of the addition of methylprednisolone 30 mg/kg (maximum, 3 g). Methylprednisolone is a cell membrane stabilizer and anti-inflammatory agent.20 For postoperative seizure prophylaxis, phenytoin (15 mg/kg) is administered after the initiation of bypass. Immediately prior to the initiation of DHCA, propofol 2.5 mg/kg is administered to ensure complete cerebral isoelectricity; in
The temperature of the infusate during rewarming should not exceed 37.5°C, and rewarming should be slow, so as to be even and complete. This approach promotes temperature maintenance without “after-drop” after bypass. Communication with the surgeon is important, because surgical classification of the disease and how much clot was successfully removed will dictate how much inotropic and vasopressor support will be needed. Improved hemodynamics are expected, with substantial reduction in PVR and improved RV function. These favorable changes are revealed immediately after bypass with TEE.24 Types III and IV present the most challenging situations. Type III disease is distal, confined to the segmental and subsegmental branches. The majority of patients with type III disease, however, experience clinical improvement. If residual pulmonary hypertension is observed, aggressive inotropic support (eg, dopamine, epinephrine), together with a pulmonary vasodilator such as milrinone, inhaled prostacyclin, or NO, may be required. Inhaled NO is preferable to other vasodilators because it exerts its effect on the pulmonary vasculature with minimal systemic effects. The right atrium is paced at 90 to 100 beats/min with temporary epicardial pacing electrodes. The brisk heart rate promotes reduced RV filling and reduced wall tension. Ventricular epicardial electrodes are placed as well but used only if atrioventricular conduction is impaired. Endtidal carbon dioxide is a poor measure of ventilation in these patients, both before and after CPB, because deadspace ventilation, causing an increased end-tidal carbon dioxide/partial pressure of carbon dioxide gradient, is an integral part of the disease. This gradient will improve after successful surgery, but the response varies; therefore, higher minute ventilation is often continued after bypass. With successful PEA, immediate improvements in RV function with less distortion and flattening of the interventricular septum are seen on TEE. Severe preoperative tricuspid regurgitation rarely requires repair or replacement unless there is a structural abnormality of the leaflets, as tricuspid annular geometry is restored with remodeling after PEA.25
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
6
Seminars in Cardiothoracic and Vascular Anesthesia
Two of the most dreaded complications of PEA are airway bleeding and reperfusion pulmonary edema (RPE).26 Checking the endotracheal tube before separation from bypass for the presence of frothy sputum or bleeding is thus very important. If blood is seen in the endotracheal tube, 2 major causes are considered: (1) dark blood seen after separation from CPB usually indicates disruption of the bloodairway barrier in 1 of the PA branches, and (2) pink frothy blood usually indicates early and severe reperfusion injury from increased capillary permeability. Unfortunately, the integrity of the PA can be tested only during weaning from CPB, because PA bleeding will manifest only when cardiac ejection and PA pressure are generated. Anesthesiologists must be prepared to provide diagnostic and therapeutic maneuvers for this rare complication.
Management of Airway Bleeding The 2 main goals in the management of airway bleeding are the prevention of exsanguination and the maintenance of adequate gas exchange. Management depends on the severity of the bleeding. Conservative management, consisting of positive end-expiratory pressure, lung isolation of the segment bleeding with a bronchial blockade, reversal of heparin, a topical vasoconstrictor such as vasopressin or epinephrine, and correction of coagulopathies, will often reduce small bleeds and reperfusion injuries.26 If bleeding is recognized before separation from bypass, allowing the heart to briefly eject with the bleeding area under direct visualization with fiber-optic bronchoscopy will establish the location. An attempt is made to isolate the affected segment to prevent spilling of blood into other segments, which will cause further impairment of ventilation and gas exchange. A bronchial blocker placed through the endotracheal tube is the preferred method for lung or segment isolation. A double-lumen endobronchial tube is also an option but has the disadvantages of not allowing a large bronchoscope to be placed, possible difficulty in placement in the setting of the bleeding airway, and safety concerns about exchanging it with a single-lumen tube at the conclusion of the procedure. Airway bleeding and RPE can both cause inadequate oxygenation, ventilation problems, and/or hemodynamic instability. In biventricular dysfunction, venoarterial extracorporeal membrane oxygenation (ECMO) should be considered. In the case of RV dysfunction with preserved LV function, ECMO with right atrial inflow and PA outflow cannulas can be used. In the case of preserved RV and LV function, venovenous ECMO, using a heparin-bonded circuit, without systemic anticoagulation is an attractive alternative. Advantages of this approach include avoidance of anticoagulants, rapid placement of cannulas, maintenance of gas exchange, and preservation of pulsatile pulmonary and systemic flow, while allowing natural hemostatic processes to repair the affected PA or capillary bed. This natural repair is usually complete after 24 to 48
hours, allowing weaning from ECMO. The technique requires preserved RV and LV function, because venovenous ECMO does not provide ventricular support. Massive pulmonary hemorrhage after PEA, although a very rare event, is the third most common cause for perioperative mortality in the PEA population, with residual pulmonary hypertension and RPE being the leading 2 causes. All PEA patients are transported to the ICU with transport ventilators to standardize and maintain proper ventilation. In the absence of complications, most patients are extubated the day after surgery, discharged from the ICU on the second or third postoperative day, and discharged from the hospital 1 to 2 weeks postoperatively.
Postoperative Care Patients undergoing PEA are subject to many of the same postoperative complications as those undergoing other cardiothoracic surgical procedures such as delirium, atelectasis, pleural effusion, pericardial effusion, diaphragmatic dysfunction, and dysrhythmias. These complications are typically managed in the same manner as other for cardiothoracic procedures, but some differences exist. All patients are mechanically ventilated, at least overnight, to observe for RPE. Pneumatic compression devices are used for venous thrombosis prophylaxis, and the use of subcutaneous heparin is begun on the evening of surgery. Anticoagulation with warfarin is begun as soon as the pacing wires are removed (usually on postoperative day 1), with a target international normalized ratio of 2.5 to 3.5. Hypoxemia is common postoperatively in the PEA population for a number of reasons. In addition to the atelectasis, postoperative pain, and respiratory muscle dysfunction commonly seen in cardiothoracic surgery patients, V/Q mismatch is more pronounced in the PEA patient population because of loss of hypoxic vasoconstriction. This results from a disproportionate increase in blood flow to endarterectomized regions of lung and decreased blood flow to regions that were previously normal. This results in a “steal” phenomenon, which is commonly documented on postoperative perfusion scintigraphy.27 This creates regions of high and low V/Q, with low-V/Q regions representing newly reperfused lung regions, contributing to hypoxemia. This steal phenomenon can be dramatic, resulting in high oxygen requirements. This maldistribution of flow resolves over weeks to months, resulting in more homogenous perfusion of the lung by 1 year.28 RPE occurs in 10% to 40% of patients, depending on the definition used. Reperfusion injury is a localized form of high-permeability edema defined as a radiologic opacity seen in the areas of the lungs that have been endarterectomized and reperfused.29,30 In its most severe forms, it can present as severe alveolar hemorrhage with profound hypoxemia, and it is associated with high mortality.26 RPE is an early postoperative complication, with 60% of cases
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
7
Banks et al presenting immediately following surgery, 30% developing within the first 48 hours, and a minority (10%) occurring later during the hospitalization (>48 hours). The incidence of RPE has decreased over time for unclear reasons. Two studies using the same definition of RPE (partial pressure of oxygen/fraction of inspired oxygen < 300, opacity on a chest radiograph in a region reperfused following PEA, and no other reason for the previous 2 criteria such as pneumonia or atelectasis) showed that the incidence of RPE had decreased from 60% to 41% in patients treated similarly at the same institution.31,32 A more recent study demonstrated a 28% incidence of this condition. The severity of preoperative pulmonary hypertension and the presence of residual pulmonary hypertension are associated with an increased risk for RPE.31 RPE is associated with significant increases in the duration of mechanical ventilation and length of ICU stay32 and in its most severe form may result in death. Several interventions have been attempted to reduce reperfusion lung injury. A small, 2-center clinical trial demonstrated that a strategy of minimizing inotropes and using low tidal ventilation following PEA could reduce the incidence of RPE in PEA patients and reduce mortality.33 However, limitations of this study included its small number of patients, lack of a clear definition of RPE, 2 simultaneous interventions, and treatment group allocation by institution rather than randomization of patients at each institution. In addition to elevated protein levels, increased neutrophils have been found in the bronchial alveolar lavage of patients with lung injury compared with those without lung injury, suggesting that the injury is a consequence of inflammation.30,34 A trial using a selectin analogue to reduce neutrophil rolling and theoretically reduce neutrophil-mediated inflammation in the lung showed promise by reducing the incidence of lung injury from 60% to 30% in a small, single-institution study, supporting the concept that RPE is at least in part mediated by neutrophils.30 However, a more recent and larger study showed no benefit of high-dose methylprednisolone in preventing RPE.31 Treatment of RPE is primarily supportive. Diuresis to reduce lung water and avoidance of high cardiac output are typically used, along with minimizing oxygen consumption. In contrast to acute respiratory distress syndrome, RPE is often asymmetric, and patients may oxygenate better in one lateral decubitus position than the other. Inhaled NO may improve oxygenation, and ECMO support can be lifesaving in severe cases.35 Residual pulmonary hypertension remains a significant problem in 5% to 35%8,36,37 of patients undergoing PEA and is the most common cause of perioperative mortality.8,36,38 Operative mortality increases with increasing preoperative PVR,8,38 but an even greater predictor of postoperative mortality is residual pulmonary hypertension following PEA.8,36 Residual pulmonary hypertension is the
result of distal chronic thromboembolic disease or superimposed small-vessel vasculopathy that is not cured by endarterectomy. Hence, removal of chronic thromboembolic material from the proximal pulmonary arterial bed may still allow significant residual pulmonary hypertension due to distal small vessel vasculopathy. Microscopically, these changes resemble those of idiopathic pulmonary hypertension.39 Determining the presence of small-vessel arteriopathy prior to surgery remains problematic and is of great interest.40,41 Treatment of severe residual pulmonary hypertension and right heart failure in the immediate postoperative period is challenging. Inotropic support is required, and careful attention to optimizing RV preload is important. Attempts to reduce PA pressure with systemic vasodilators are often unsuccessful and carry the risk for systemic vasodilatation with associated poor coronary perfusion. Reductions in PVR can be accomplished in some patients with inhaled NO or inhaled iloprost, without an associated reduction in systemic blood pressure.42-44 Patients treated preoperatively with pulmonary antihypertensive agents (prostacyclin analogues, phosphodiesterase-5 inhibitors, endothelin receptor antagonists) can usually have these medications discontinued at the time of operation if PEA has resulted in significant reductions in PVR. However, if patients have significant residual pulmonary hypertension, continuation of these medications postoperatively should be considered. Postoperative pericardial effusions are not uncommon and should be considered when patients exhibit worsening edema, chest pain, and dyspnea. Echocardiography should be performed immediately to confirm the diagnosis, and significant effusions should be drained. Atrial dysrhythmias are treated as they are in other patients with atrial flutter or fibrillation following cardiac surgery, with the caveat that β-blockers are tolerated poorly in patients with residual pulmonary hypertension. Anticoagulation is begun the night of surgery if there are no bleeding complications. Lifelong anticoagulation is recommended for all patients, to avoid recurrent thrombosis.
PEA in Patients With Sickle Cell Disease The prevalence of pulmonary hypertension in sickle cell disease was reported by Sutton et al,45 Simmons et al,46 Moser and Shea,47 and Collins and Orringer.48 All confirmed the relationship among pulmonary infarction, cor pulmonale, and sickle cell disease. While many sickle cell patients have ulmonary hypertension due to small vessel disease some present with CTEPH. Patients with sickle cell disease undergoing PEA present a unique challenge because prolonged CPB, deep hypothermia, and circulatory arrest all tend to promote sickling. Sickling and hemolysis during or after CPB is a known concern.49,50 Stagnation of blood,
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
8
Seminars in Cardiothoracic and Vascular Anesthesia
deep hypothermia, anemia, and acidosis encountered during circulatory arrest increase the likelihood of sickling, with cellular acidosis and hypoxia likely more important factors than hypothermia per se.51,52 Patients with sickle cell disease presenting for PEA should undergo thorough preoperative evaluation, with particular attention to correction of anemia, early screening for antibodies in blood typing, preoperative and intraoperative exchange transfusion, and avoidance of hypoxemia and acidosis during and after surgery. Particular attention should be paid to hypoxic complications such as atelectasis and RPE during the postoperative period. These conditions must be treated aggressively, with the goal of maintaining adequate peripheral perfusion and arterial oxygen saturation ≥95%.53
PEA in Patients With Heparininduced Thrombocytopenia Patients with heparin-induced thrombocytopenia present unique challenges, because for these patients, alternative means of anticoagulation during bypass must be used. There are reports of the successful use of recombinant hirudin.54 Systemic anticoagulation in patients with suspected type II heparin-induced thrombocytopenia using the glycoprotein IIb/IIIa inhibitor tirofiban and unfractionated heparin has also been successful. Tirofiban binds competitively to platelet glycoprotein IIb/IIIa receptors and has a half-life of approximately 2 hours.55-57 With >80% blockade of glycoprotein IIb/IIIa receptors, systemic heparinization can be performed safely. A loading dose of 10 µg/kg is given 10 minutes before CPB, followed by a continuous infusion at 0.15 µg/kg/min.56,57 Platelet activation is measured using the Ultegra rapid platelet function assay (Accumetrics Inc, San Diego, California). Once platelet inhibition is >80%, full heparinization (400 IU/kg) can be performed. Systemic anticoagulation is monitored with automated heparin concentration using the Hepcon Hemostasis Management System (Medtronic Inc, Minneapolis, Minnesota), with the goal of maintaining clotting time > 480 seconds. Heparin concentration and clotting time are monitored every 30 minutes, as is platelet inhibition. Tirofiban infusion is discontinued 1 hour prior to the cessation of CPB. In patients with compromised renal function, ultrafiltration is used to decrease the tirofiban plasma concentration. Heparin is neutralized with protamine as usual, and donor platelets are transfused if necessary.57 It is critical to avoid exposure to heparin before and after bypass, including heparin-treated CPB components and monitoring lines.
The Future PEA is now recognized as the definitive treatment of CTEPH. With increased awareness of the disease and referral of patients early in the disease process, PEA will
become an increasingly common operation. However, because morbidity and mortality rates are still significant, continued research into etiology, diagnosis, medical management, and surgical treatment are necessary. Residual pulmonary hypertension, RPE, vascular steal, RV failure, and cerebral protection remain areas of research that will likely result in improved outcomes. Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.
References 1. Moser KM, Houk VN, Jones RC, et al. Chronic, massive thrombotic obstruction of the pulmonary arteries. Analysis of four operated cases. Circulation. 1965;32(3):377-385. 2. Fedullo P, Kerr KM, Kim NH, Auger WR. Chronic thromboembolic pulmonary hypertension. Am J Respir Crit Care Med. 2011;183(12):1605-1613. 3. Madani MM, Jamieson SW. Technical advances of pulmonary endarterectomy for chronic thromboembolic pulmonary hypertension. Semin Thorac Cardiovasc Surg. 2006;18(3):243-249. 4. Winkler MH, Rohrer CH, Ratty SC, et al. Perfusion techniques of profound hypothermia and circulatory arrest for pulmonary thromboendarterectomy. J Extra Corp Technol. 1990;22(57):35799. 5. Jamieson SW, Kapelanski DP. Pulmonary endarterectomy. Curr Probl Surg. 2000;37(3):165-252. 6. Jamieson SW. Pulmonary thromboendarterectomy. In Franco KL, Putnam JB, eds. Advanced Therapy in Thoracic Surgery. Hamilton, ON, Canada: BC Decker; 1998: 310-318. 7. Thistlethwaite PA, Kemp A, Du L, Madani MM, Jamieson SW. Outcomes of pulmonary endarterectomy for treatment of extreme thromboembolic pulmonary hypertension. J Thorac Cardiovasc Surg. 2006;131:307-313. 8. Madani MM, Auger WR, Pretorius V, et al. Pulmonary endarterectomy: recent changes in a single institution’s experience of more than 2,700 patients. Ann Thorac Surg. 2012;94:97-103. 9. Manecke GR Jr, Parimucha M, Stratmann G, et al. Deep hypothermic circulatory arrest and the femoral-to-radial arterial pressure gradient. J Cardiothorac Vasc Anesth. 2004;18(2):175-179. 10. Mohr R, Lavee J, Goor DA. Inaccuracy of radial artery pressure measurement after cardiac operations. J Thorac Cardiovasc Surg. 1987;94(2):286-290. 11. Baba T, Goto T, Yoshitake A, et al. Radial artery diameter decreases with increased femoral to radial arterial pressure gradient during cardiopulmonary bypass. Anesth Analg. 1997;85:252-258.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
9
Banks et al 12. Edmonds HL Jr, Ganzel BL, Austin EH III. Cerebral oximetry for cardiac and vascular surgery. Semin Cardiothorac Vasc Anesth. 2004;8:147-166. 13. Hong SW, Shim JK, Choi YS, Kim DH, et al. Prediction of cognitive dysfunction and the role of cerebral oximetry. Eur J Cardiothorac Surg. 2008;33:560-565. 14. Goldman S, Sutter F, Ferdinand F, Trace C. Optimizing intraoperative cerebral oxygen delivery using noninvasive cerebral oximetry decreases the incidence of stroke for cardiac surgical patients. Heart Surg Forum. 2004;7:E376-E381. 15. Yao FSF, Tseng C-C, Ho CYA, et al. Cerebral oxygen desaturation is associated with early postoperative neuropsychological dysfunction in patients undergoing cardiac surgery. J Cardiothorac Vasc Anesth. 2004;18(5):552-558. 16. Schuhmann MU, Suhr DF, van Gosseln HH, et al. Local brain surface temperature compared to temperatures measured at standard extracranial monitoring sites during posterior fossa surgery. J Neurosurg Anesthesiol. 1999;11(2):90-95. 17. Svyatets M, Tolani K, Zhang M, et al. Perioperative management of deep hypothermic circulatory arrest. J Cardiothorac Vasc Anesth. 2010;24(4):644-655. 18. Dittrich HC, McCann HA, Wilson WC. Identification of interatrial communication in patients with elevated right atrial pressure using surface and transesophageal contrast echocardiography. J Am Coll Cardiol. 1993;21(Suppl):135A. 19. Amsel BJ, Rodrigus I, De Paep R, et al. Right-to-left flow through a patent foramen ovale in acute right ventricular infarction. Two case reports and a proposal for management. Chest. 1995;108(5):1468-1471. 20. Langley SM, Chai PJ, Jaggers JJ, et al. Preoperative high dose methylprednisolone attenuates the cerebral response to deep hypothermic circulatory arrest. Eur J Cardiothorac Surg. 2000;17(3):279-286. 21. Newman MF, Mm-kin JM, Roach G, et al. Cerebral physiologic effects of burst suppression doses of propofol during nonpulsatile cardiopulmonary bypass. Anesth Analg. 1995;81:452-457. 22. Nussmeier NA, Arlund C, Slogoff S. Neuropsychiatric complications after cardiopulmonary bypass: cerebral protection by a barbiturate. Anesthesiology. 1986;64(2):165-170. 23. Nehls DG, Todd MM, Spetzler RF, et al. A comparison of the cerebral protective effects of isoflurane and barbiturates during temporary focal ischemia in primates. Anesthesiology. 1987;66(4):453-464. 24. Dittrich HC, Nicod PH, Chow LC, et al. Early changes of right heart geometry after pulmonary thromboendarterectomy. J Am Coll Cardiol. 1988;11(5):937-943. 25. Menzel T, Kramm T, Wagner S, et al. Improvement of tricuspid regurgitation after pulmonary thromboendarterectomy. Ann Thorac Surg. 2002;73(3):756-761. 26. Manecke GR Jr, Kotzur A, Atkins G, et al. Massive pulmonary hemorrhage after pulmonary thromboendarterectomy. Anesth Analg. 2004;99(3):672-675. 27. Olman MA, Auger WR, Fedullo PF, et al. Pulmonary vascular steal in chronic thromboembolic pulmonary hypertension. Chest. 1990;98:1430-1434. 28. Moser KM, Metersky ML, Auger WR, et al. Resolution of vascular steal after pulmonary thromboendarterectomy. Chest. 1993;104:1441-1444.
29. Levinson RM, Shure D, Moser KM. Reperfusion pulmonary edema after pulmonary artery thromboendarterectomy. Am Rev Respir Dis. 1986;134:1241-1245. 30. Kerr KM, Auger WR, Marsh JJ, et al. The use of cylexin (CY-1503) in prevention of reperfusion lung injury in patients undergoing pulmonary endarterectomy. Am J Respir Crit Care Med. 2000;162:14-20. 31. Kerr KM, Auger SR, Marsh JJ, et al. Efficacy of methylprednisolone in preventing lung injury following pulmonary thromboendarterectomy. Chest. 2012;141(1):27-35. 32. Duwe BV, Kerr KM, Fedullo PF, Kim NH, Test VJ, Auger WR. Clinical impact of reperfusion lung injury on patients undergoing pulmonary thromboendarterectomy. Am J Respir Crit Care Med. 2009;179:A4628. 33. Mares P, Gilbert TB, Tschernko EM, et al. Pulmonary artery thromboendarterectomy: a comparison of two different postoperative treatment strategies. Anesth Analg. 2000;90(2):267-273. 34. Auger WR, Moser KM, Comito RM, Kerr KM, et al. Efficacy of intravenous ICI 200,880 in the prevention of adult respiratory distress syndrome in patients undergoing pulmonary endarterectomy. Am J Respir Crit Care Med. 1994;149:A1032. 35. Berman M, Tsui S, Vuylsteke A, et al. Successful extracorporeal membrane oxygenation support after pulmonary thromboendarterectomy. Ann Thorac Surg. 2008;86: 1261-1267. 36. Mayer E, Jenkins D, Lindner J, et al. Surgical management and outcome of patients with chronic thromboembolic pulmonary hypertension: results from an international prospective registry. J Thorac Cardiovasc Surg. 2011;141(3):702-710. 37. Bondermann D, Skoro-Sager N, Jakowitsch J, et al. Predictors of outcome in chronic thromboembolic disease. Circulation. 2007;115:2153-2158. 38. Dartevelle P, Fadel E, Mussot S, et al. Chronic thromboembolic pulmonary hypertension. Eur Respir J. 2004;23(4): 637-648. 39. Moser KM, Bloor CM. Pulmonary vascular lesions occurring in patients with chronic major vessel thromboembolic pulmonary hypertension. Chest. 1993;103:685-692. 40. Kim NH, Fessler P, Channick RN, et al. Preoperative partitioning of pulmonary vascular resistance correlates with early outcome after thromboendarterectomy for chronic thromboembolic pulmonary hypertension. Circulation. 2004;109:18-22. 41. Hardziyenka M, Reesink HJ, Bouma BJ, et al. A novel echocardiographic predictor of in-hospital mortality and mid-term haemodynamic improvement after pulmonary endarterectomy for chronic thrombo-embolic pulmonary hypertension. Eur Heart J. 2007;28(7):842-849. 42. Kramm T, Eberle B, Guth S, Mayer E. Inhaled iloprost to control residual pulmonary hypertension following pulmonary endarterectomy. Eur J Cardiothorac Surg. 2005;28:882-888. 43. Flonder M, Merkel M, Hofsteter C, et al. The effect of inhaled nitric oxide and inhaled iloprost on hypoxaemia in a patient with pulmonary hypertension after pulmonary thromboendarterectomy. Anaesthesia. 2006;61: 1200-1203.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
10
Seminars in Cardiothoracic and Vascular Anesthesia
44. Imanaka H, Miyano H, Takeuchi M, et al. Effects of nitric oxide inhalation after pulmonary thromboendarterectomy for chronic thromboembolism. Chest. 2000;118:39-46. 45. Sutton LL, Castro O, Cross DJ, Spencer JE, et al. Pulmonary hypertension in sickle cell disease. Am J Cardiol. 1994;74:626-628. 46. Simmons BE, Santhanam V, Castaner A, et al. Sickle cell disease: two-dimensional echo and Doppler ultrasonographic findings in hearts of adult patients with sickle anemia. Arch Intern Med. 1988;148:1526. 47. Moser KM, Shea JG. The relationship between pulmonary infarction, cor pulmonale, and the sickle cell states. Am J Med. 1957;27:561. 48. Collins FS, Orringer E. Pulmonary hypertension and cor pulmonale in the sickle hemoglobinopathies. Am J Med. 1982;73(6):814-821. 49. Balasundaram S, Duran CG, al-Halees Z, Kassay M. Cardiopulmonary bypass in sickle cell anaemia. Report of five cases. J Cardiovasc Surg. 1991;32(2):271-274. 50. Hockmuth D, Mills N. Management of unusual problems encountered in initiating and maintaining cardiopulmonary bypass. In: Cardiopulmonary Bypass: Principles and Practice. Baltimore, MD: Williams & Wilkins; 1993: 750-751. 51. Deleval M, Taswell HF, Bowie EJW, et al. Open heart surgery in patients with inherited hemoglobinopathies, red
cell dyscrasias and coagulopathies. Arch Surg. 1974;109(5): 618-622. 52. Vichinsky EP, Haberkern CM, Neumayr L. A compari son of conservative and aggressive transfusion regimens in the perioperative management of sickle cell disease: the Perioperative Transfusion in Sickle Cell Disease Study Group. N Engl J Med. 1995;333(4):206-213. 53. Aldrich TK, Dhuper SK, Patwa NS, et al. Pulmonary entrapment of sickle cells: the role of regional alveolar hypoxia. J Appl Physiol. 1996;80(2):531-539. 54. Rubens FD, Sabloff M, Wells PS. Use of recombinant hirudin in pulmonary thromboendarterectomy. Ann Thorac Surg. 2000;69(6):1942-1943. 55. Koster A, Meyer O, Fischer T, et al. One-year experience with the platelet glycoprotein IIb/IIIa antagonist tirofiban, and heparin during cardiopulmonary bypass in patients with heparin-induced thrombocytopenia type II. J Thorac Cardiovasc Surg. 2001;122(6):1254-1255. 56. Warkentin TE, Greinacher A. Heparin-induced throm bocytopenia and cardiac surgery. Ann Thorac Surg. 2003;76(6):2121-2131. 57. Warkentin TE, Greinacher A, Koster A. Treatment and prevention of heparin-induced thrombocytopenia: American College of Chest Physicians evidence-based clinical practice guidelines (8th edition). Chest. 2008;133(6 Suppl): 340S-380S.
Downloaded from scv.sagepub.com at TEXAS SOUTHERN UNIVERSITY on October 13, 2014
