REVIEW URRENT C OPINION

Preventing and managing perioperative pulmonary complications following cardiac surgery Manuel Garcı´a-Delgado a, Ine´s Navarrete-Sa´nchez a, and Manuel Colmenero b

Purpose of review To provide an update of research findings on the mechanisms underlying respiratory complications after cardiac surgery, especially acute respiratory distress syndrome, transfusion-related lung injury and ventilation-associated pneumonia. The article will review some of the preventive and therapeutic measures that can be implemented to reduce these complications, focusing on the use of protective invasive ventilation and postextubation noninvasive ventilation. Recent findings The development of postoperative pulmonary complications is related to various perioperative factors. The most effective preventive measures are a correct preoperative preparation and an uneventful surgery. The implementation of nosocomial pneumonia prevention bundles, or early extubation in a fast-track program, has proven to be effective in reducing the complication rate. The application of protective invasive ventilation, with low tidal volumes, has been found to reduce lung injury and mortality in patients with lung injury or healthy lungs. The use of noninvasive ventilation as a preventive postextubation approach in patients at risk and rescue noninvasive ventilation in those developing respiratory failure remains under debate and is subject to ongoing research. Summary Postoperative pulmonary complications are common, but severe complications are infrequent. Their reduction requires measures to prevent infection and mechanical ventilation-associated lung injury through the use of low tidal volumes and early extubation. Noninvasive ventilation after extubation can be utilized to avoid reintubation and the associated increased morbidity and mortality. However, noninvasive ventilation should be done under rigorous conditions and by following strict criteria. Keywords cardiac surgery, mechanical ventilation, noninvasive mechanical ventilation, postoperative pulmonary complications

INTRODUCTION Postoperative pulmonary complications (PPCs) are a major cause of morbidity and mortality in cardiac surgery patients, and are responsible for high healthcare costs and resource utilization. Almost all patients undergoing cardiac surgery develop some degree of postoperative pulmonary dysfunction, ranging from a mild hypoxemia to severe acute respiratory distress syndrome (ARDS). Apart from gas exchange alterations, other mechanisms specific to cardiac surgery have been implicated in the pathogenesis of postoperative pulmonary dysfunction [1], including the effects of median sternotomy, the use of cardiopulmonary bypass (CPB), frequent transfusion of blood product, local cooling procedures for myocardial protection, and dissection of the internal mammary artery. It is important to distinguish a true PPC from a www.co-anesthesiology.com

postoperative pulmonary dysfunction, which is a frequent event resulting from an increase in respiratory work, superficial breathing, ineffective cough, and hypoxemia [2]. The diagnosis of PPC is defined by the presence of pulmonary dysfunction with associated clinical findings, such as atelectasis, pneumonia, or other entities that adversely affect the clinical outcome. The physician responsible for these patients needs to possess a thorough a

Intensive Care Unit, Hospital Universitario Virgen de las Nieves and Intensive Care Unit, Hospital Universitario San Cecilio, Granada, Spain

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Correspondence to Dr Manuel Garcı´a-Delgado, Intensive Care Unit, Hospital Universitario Virgen de las Nieves, Avda. Fuerzas Armadas, 2. 18014 Granada, Spain. Tel: +34 958 020125; fax: +34 958 020174; e-mail: [email protected] Curr Opin Anesthesiol 2014, 27:146–152 DOI:10.1097/ACO.0000000000000059 Volume 27  Number 2  April 2014

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Respiratory complications after cardiac surgery Garcı´a-Delgado et al.

KEY POINTS  Postoperative pulmonary complications are a major cause of poor outcomes in cardiac surgery patients, and they must be identified and treated promptly.  A ventilatory strategy with low tidal volumes (6–8 ml/kg IBW) and PEEP is considered suitable in cardiac surgery patients, both during and after surgery.  The application of ‘ventilator care bundles’, including hand washing and cleansing of the oral cavity with chlorhexidine, is recommended to reduce the incidence of VAP.  Early extubation is considered a well tolerated and cost-effective practice for the nonhigh-risk patients and is associated with a reduction in hospital stay.  In selected patients, noninvasive ventilation can be instituted early after extubation to avoid postextubation respiratory failure and reduce the need of reintubation.

knowledge of the pathophysiological factors implicated in PPCs. Caregivers should be capable of identifying patients at greater risk of these complications and detecting their onset at an early stage. Early application of the appropriate preventive and/or evidence-based therapeutic measures may prevent PPC (Table 1).

ACUTE RESPIRATORY DISTRESS SYNDROME AND TRANSFUSION-RELATED ACUTE LUNG INJURY &&

The recent ‘Berlin definition’ [3 ] describes ARDS as a syndrome that appears within the first week of

exposure to a known risk factor and is characterized by hypoxemia and bilateral radiological infiltrates that cannot be wholly explained by the presence of atelectasis, fluid overload, heart failure, or pleural effusion, among others. ARDS is classified as a function of oxygenation impairment as mild (PaO2/FiO2 ratio between 200 and 300), moderate (PaO2/FiO2 between 100 and 200), or severe (PaO2/FiO2 below 100), always in the context of a positive end-expiratory pressure (PEEP) of at least 5 cmH2O. Many risk factors for ARDS have been identified. Cardiac surgery is a known risk factor for ARDS. It is a severe complication in these patients and is associated with a high mortality (above 50%) by some authors [4,5]. CPB has long been considered a relevant factor, being capable of triggering an intense systemic inflammatory syndrome that can produce diffuse lung injury with increased lung capillary permeability. Lung ischemia–reperfusion is also considered to favor ARDS by promoting the generation of injurious reactive oxygen species. Nevertheless, the true relevance of CPB as a risk factor for ARDS remains unclear, especially given the similarity between the lung injury observed in CPB and in off-pump operations, which may be influenced by transfusion-related lung injury (TRALI) or pharmacological toxicity [6], among others. At any rate, strategies that are recommended to minimize the effect of CPB on lung injury include reduction in the CPB duration or the use of off-pump coronary artery bypass grafting, heparincoated circuits, leukocyte depletion, or intraoperative ultrafiltration. Patient characteristics that increase the risk of ARDS include advanced age, arterial hypertension, tobacco smoking, previous cardiac surgery, high New York Heart Association (NYHA) functional

Table 1. Preventive measures and management of respiratory complications after cardiac surgery Prevention ARDS

Management

Reduction of CPB times

Protective MV: low tidal volume, optimal PEEP

Reduction of the CPB inflammatory response

Alveolar recruitment maneuvers

Tidal volumes between 6 and 8 ml/kg TRALI

Intraoperative hemostasis

As for ARDS

Restrictive transfusion strategies MV-associated pneumonia

Cleansing with chlorhexidine

Rational and early use of antibiotics

Ventilator care bundles Early extubation Perioperative physiotherapy Atelectasis

NIV in selected high-risk patients

Early NIV in nonsevere respiratory failure

Peri-operative physiotherapy

Early reintubation if NIV is ineffective

ARDS, acute respiratory distress syndrome; CPB, cardiopulmonary bypass; MV, mechanical ventilation; NIV, noninvasive ventilation; PEEP, positive end-expiratory pressure; TRALI, transfusion-related acute lung injury.

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Intensive care and resuscitation

grade, and the presence of shock [4,5,7,8]. The risk can be higher in certain types of cardiac surgery, including aortic or complex surgery, lung transplant, the use of left-ventricular assist devices, and emergency surgery [4,5,7,9]. The ventilatory management of ARDS patients is based on a lung protection strategy and ‘open lung’ approach, as described below. Transfusion-related lung injury is characterized by the onset of hypoxemia and diffuse lung infiltrates in the first 6 h after a blood transfusion. It is an immunological and inflammatory condition in which the lung endothelium is damaged and high-permeability lung edema is produced. Cardiac patients are at risk of developing TRALI in the postoperative period, and the risk is higher with the transfusion of frozen fresh plasma and platelets than of red blood cells. Vlaar et al. [10 ] recently reported an influx of neutrophils into the lung in TRALI, an elevation of intrapulmonary levels of proinflammatory cytokines, coagulation disorders and fibrinolysis at systemic and pulmonary level. These features can also be observed in transfused patients who do not develop TRALI. The transfusion of red blood cells can increase lung permeability in a dosedependent manner [11 ]. The prevalence of TRALI is only around 2.5% in cardiac surgery patients [12,13], but is associated with a higher mortality rate, and a longer mechanical ventilation time and ICU stay. Restrictive transfusion procedures that maintain postoperative hemoglobin between 7 and 8 g/dl or a hematocrit concentration of 24% appear to represent a safe approach that is superior to more liberal transfusion strategies [14,15]. &

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VENTILATION-ASSOCIATED PNEUMONIA Ventilation-associated pneumonia (VAP) is one of the most important risk factors for hospital mortality in cardiac surgery patients [16]. Oronasopharyngeal decontamination with chlorhexidine has proven to be an effective method to reduce the VAP rate in these patients [17] and should be a routine measure. Aspiration of subglottic secretions appears to be a well tolerated procedure and can also reduce the risk of VAP [18]. The application of ‘ventilator care bundles’ has been recommended over the past few years, including hand washing, cleansing of the oral cavity with chlorhexidine, semi-recumbent posture (minimum of 308), monitoring of endotracheal cuff pressure, and optimization of the sedative therapy; these measures have reduced the incidence of VAP and shortened the time on ventilator and ICU stay [19 ]. Although the early use of antibiotics is recommended in VAP, as in any other type of severe infection, the prophylactic use of broad-spectrum &&

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antibiotics is more controversial in patients at risk of respiratory infection. In a recent study of patients on mechanical ventilation for at least 48 h after major cardiac surgery, pre-emptive treatment with broadspectrum antibiotics reduced the incidence of lower respiratory tract infection and delayed its onset [20 ]. However, its impact on the development of bacterial resistance requires careful further evaluation. &&

MANAGEMENT OF MECHANICAL VENTILATION The use of high tidal volume in patients with ARDS can produce ventilation-induced injury and has been associated with an increased risk of death [21]. This negative effect can be similar in patients without ARDS but with risk factors for its development [22,23 ]. Ventilation with a high tidal volume, in cardiac surgery patients, is associated with the release of inflammatory mediators that contribute to the ventilation-induced biotrauma [24]. A tidal volume above 10 ml/kg in the immediate postoperative period has been associated with prolonged mechanical ventilation, organ dysfunction, and a longer ICU stay [25 ], especially in women and obese patients. The use of low tidal volumes and adequate PEEP levels to avoid lung collapse has been recommended. This strategy avoids increasing the systemic immune response, which is already accentuated by the use of CPB and transfusions, and exacerbating ventilation-induced injury. In cardiac patients, the use of a tidal volume of around 6 ml/kg in the intraoperative and postoperative period has been found to reduce the duration of mechanical ventilation and the reintubation rate [26]. The application of tidal volumes between 6 and 8 ml/kg ‘ideal body weight (IBW)’ is considered suitable in cardiac surgery patients, both during and after the surgery. Recruitment maneuvers are designed to open the maximum possible number of alveoli by increasing the transpulmonary pressure. It is mainly indicated in cases of hypoxemia due to alveolar collapse, as observed in anesthetized patients. A randomized clinical trial [27] found no beneficial effects of these maneuvers during coronary artery bypass grafting (CABG), although other studies in the cardiac surgery setting reported that these maneuvers improved the respiratory function in the perioperative period, reducing atelectasis and improving the gas exchange [28–30]. &&

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EARLY EXTUBATION Early extubation should be the goal in adults after cardiac surgery. It is considered a well tolerated and Volume 27  Number 2  April 2014

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Respiratory complications after cardiac surgery Garcı´a-Delgado et al.

cost-effective intervention for the majority of these patients and is associated with a reduction in hospital stay [31]. In pediatric cardiac surgery, early extubation in the first 6 h is also a well tolerated procedure associated with a shorter stay, with no increase in adverse effects [32]. The definition of ‘early’ extubation varies in the literature, but is generally considered to be that which is performed during the first 6–8 h, once the preoperative homeostatic state has been re-established. The patient should be awake and alert, normothermic, hemodynamically stable, with no significant bleeding and with good oxygenation and ventilation. The preoperative identification of cardiac risk is of major assistance for the intraoperative and postoperative management of sedation and analgesia or the application of an early extubation protocol, especially in patients with a low surgical risk. Low-risk patients can be identified by using standardized risk scores, like Euroscore or Society of Thoracic Surgeons (STS) score, and can benefit from an individualized sedation and analgesia regimen (using propofol and boluses of opiods). This allows quick reversal of sedation and early extubation, thereby reducing the time on mechanical ventilation [33]. In contrast, the timing of extubation is independent of the sedation and analgesia regimen in moderate or high-risk patients [34]. Patients at greater risk require a diligent preoperative preparation, management of modifiable factors in the preoperative and operative periods, followed by a good postoperative fast-track protocol that facilitates early discharge from the hospital. Although the impact on stays and costs is not universally reported [35,36], all studies show that early extubation in the first postoperative hours is well tolerated and does not increase respiratory complications. A recent Cochrane review [37 ] evaluated the efficacy and safety of fast-track cardiac care in adults undergoing cardiac surgery, including early postsurgical extubation and the use of lowdose opiates in the general anesthesia. No differences in mortality were observed between the earlyextubation and conventional extubation groups or as a function of opiate administration. No increased risk of postoperative complications or reintubation was found with early extubation. It was concluded that early extubation and the use of low-dose opiates in patients with low and moderate risk is safe and produces a reduction in the intubation time and length of ICU stay. Less than 10% of cardiac surgery patients require prolonged mechanical ventilation, that is, for more than 12 h, which has been associated with longer &&

hospital stay and higher morbidity and mortality rates. Early extubation favors a complication-free postoperative period. The prognosis is worse when mechanical ventilation is continued for more than 16 h [38]. Prolonged mechanical ventilation is usually required in high-risk patients, who can be identified by their characteristics before surgery and on their ICU admission. Factors that predict prolonged mechanical ventilation include [35,39–41]: age above 65 years, female sex, renal or lung failure, history of stroke, emergency surgery, perioperative angina and infarction, NYHA greater than 3, leftventricular ejection fraction less than 30%, intraoperative transfusion of more than 4 units of red blood cells or fresh plasma, CPB for more than 77–91 min, clamping time more than 60 min, bleeding, and postoperative oxygenation. Very early (

Preventing and managing perioperative pulmonary complications following cardiac surgery.

To provide an update of research findings on the mechanisms underlying respiratory complications after cardiac surgery, especially acute respiratory d...
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