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Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Review Article

Pearls and Pitfalls in Short-Term Mechanical Circulatory Assist: How to Avoid and Manage Complications Prashant N. Mohite, Olaf Maunz, and Andre R. Simon Department of Cardiothoracic Transplantation and Mechanical Support, Royal Brompton & Harefield NHS Foundation Trust, London, UK

Abstract: In today’s era, given the worsening risk profiles of patients undergoing cardiac surgery, the increasing number of complex cardiac surgeries, and the increasing number of patients undergoing thoracic organ transplantation, short-term mechanical circulatory assist (MCA) devices are indispensable. MCA devices are capable of supporting heart and lung function and have emerged as potentially lifesaving instruments, but may prove to be as hazardous as helpful due to their inherent tendency toward hemolysis, thromboembolism, and hemorrhage. Although MCA devices are being used regularly at some specialized centers, surgeries involving MCA are not as common as other routine cardiac surgeries, and even though professionals implanting and maintaining short-term MCAs are well acquainted with operating such devices, it is not uncommon to come across complications as a result of

minor mistakes committed while dealing with them. Avoiding simple mistakes and taking proper precautions while implanting and maintaining these devices can prevent major catastrophes. We discuss commonly encountered problems and complications during the implantation and maintenance of short-term MCAs and offer reasonable and practical solutions. In addition, crucial issues such as anticoagulation, replacement of the device circuit, and management of the distal perfusion cannula are discussed. Continuous and efficient monitoring of the MCA device and the patient supported on MCA, together with anticipation and avoidance of complications, is key for successful short-term MCA support. Key Words: Ventricular assist device—Extracorporeal membrane oxygenation— End-stage heart failure—End-stage lung disease— Complications.

Short-term mechanical circulatory assist (MCA) devices are employed to stabilize patients hemodynamically and to mitigate or reverse any end-organ damage or failure by immediately improving cardiac output. The use of such devices gives clinical care teams time so that a definitive treatment strategy can be formulated according to the patient’s myocardial, pulmonary, neurological, and end-organ function. Short-term MCA is now used routinely in postcardiotomy cardiogenic shock and acute cardiogenic shock, as well as to support the right ventricle after long-term left ventricular assist device (VAD)

implantation (1–3). MCA devices are the backbone of any thoracic organ transplant program due to their vital roles as a bridge to heart and lung transplantation and as a circulatory and/or respiratory support in case of primary graft failure (4–6). Short-term MCA interventions can be categorized broadly into VAD and extracorporeal membrane oxygenation (ECMO) which could be central (sternotomy access) or peripheral (groin/neck access). Peripheral ECMO can be venovenous or venoarterial. The main components of short-term VADs are inflow and outflow cannulae, a pump, tubing connecting them, and a console controlling the pump and monitoring the system. In the case of ECMO, an oxygenator with an integrated heat exchanger is added to the circuit after the pump. A number of devices certified for short-term MCA are currently available on the market. Catheterbased devices such as the Impella Recover

doi:10.1111/aor.12267 Received September 2013; revised November 2013 Address correspondence and reprint requests to Dr. Prashant N. Mohite, Department of Cardiothoracic Transplantation and Mechanical Support, Harefield Hospital, Royal Brompton & Harefield NHS Foundation Trust, Middlesex, London, UB9 6JH, United Kingdom. E-mail: [email protected]

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Percutaneous approach Percutaneous approach Peripheral approach (groin) 7 to 14 14 5 Thoracotomy/percutaneous Thoracotomy/percutaneous Thoracotomy/percutaneous Impella Recover LD TandemHeart Medtronic Biopump

5 5 10

Thoracotomy Abiomed AB5000

6

30

Pulsatile flow

Sternotomy Requires anastomoses for aortic and pulmonary artery cannulation; requires weekly pump exchange Requires anastomoses for aortic and pulmonary artery cannulation; requires weekly pump exchange Partial support, short duration Partial support, limited mobility Stringent anticoagulation; requires continuous supervision; limited mobility Full and prolonged support Pulsatile flow 30 14 10 6 Thoracotomy Thoracotomy CentriMag Abiomed BVS5000

Advantage Access Device

Needless to say, patients on short-term circulatory support should be treated with continuous monitoring of hemodynamic parameters and regular checks of the circulatory support system. MCA devices are not routinely used in the intensive therapy unit; therefore, clinical staff should be well versed in monitoring the device and should be able to recognize any problem at an early stage. As a number of professionals are involved in the care of such patients, it is essential to document any change in pump speed and flow, oxygenator air flow, or fraction of inspired oxygen (FiO2); the reason behind the change; and its effect on hemodynamics and the system. Otherwise, it will be difficult to retrospectively detect why changes were made. This documentation is helpful during weaning trials as well. The most common problem faced in the use of a short-term MCA device is a low-flow alarm, frequently accompanied by chattering of the tubing. This is commonly due to hypovolemia, although it may have other causes. As most patients with circulatory shock present with generalized edema, the goal in such patients supported on MCA is generally to achieve a negative fluid balance, but unless done gradually, attempting this could potentially lead to hypovolemia and low flows due to suction events at the cannula inflow site. Low central venous pressure in combination with negative fluid balance confirms hypovolemia. The first response in such a case should be to rapidly administer fluids and to decrease the speed of the pump temporarily to reverse the suction

Maximum duration (days)

MAINTENANCE OF SUPPORT

Maximum flow (L/min)

(Abiomed, Danvers, MA, USA) and the TandemHeart (CardiacAssist, Pittsburgh, PA, USA) are easy to implant and remove; however, they have a relatively short lifetime and provide only partial circulatory support (up to 5 L/min) (7–10). Fairly durable (lasting more than 2 weeks) devices that provide full support (more than 5 L/min) include, among others, the AB5000 (Abiomed) and CentriMag (Thoratec, Pleasanton, CA, USA), but these require access to the heart through sternotomy, and complications such as bleeding are sometimes reported (2,6,11,12). Considerable experience with these devices has been reported in the literature. A brief comparison of currently available short-term MCA in terms of duration, maximum flow, advantages, and drawbacks is given in Table 1. The first reported experience of the CentriMag short-term MCA device as a bridge to decision, bridge to heart transplantation, and support in primary graft failure came from our institute (6,13,14).

Drawback

P.N. MOHITE ET AL.

TABLE 1. Comparison of short-term MCA devices

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SHORT-TERM MECHANICAL CIRCULATORY ASSIST events causing chattering of the tubing. Once 250– 500 mL fluid has been given, the speed can be increased gradually. In case of recurrent chattering, administering colloids or blood and decreasing the speed permanently to achieve an acceptable flow might help. A thrombus in the venous cannula may be suspected in case of persistent chattering and low flows despite adequate filling. A dislocated cannula, for example one touching the atrial roof and therefore occluded or one being pulled back into the inferior vena cava, can also cause such issues. In case of doubt, examination of the cannula position with transesophageal echocardiography is advisable. Desaturation of patient blood is not an uncommon problem with ECMO. A difference in color between inflow and outflow tubing is the first thing to check for in such a situation. If there is no significant color difference, it is certain that there is a problem with either gas flow or blood flow in the oxygenator. One should check the amount of oxygen left in the cylinder and the connection of the gas line to the oxygenator. Accumulation of condensation in the oxygenator may block passage of gas through the hollow fibers and lead to inadequate gas exchange. The gas sweep flow should be increased momentarily to at least 10 L/min to get rid of condensation. In any case, an arterial and venous blood gas should give further information about the status of the ECMO apparatus. An oxygenator change-out might be the last resort after all other possibilities have been ruled out. Any significant resistance to the flow of blood through the oxygenator would increase the transmembrane pressure gradient (pressure difference between preoxygenator and postoxygenator tubing). A gradient of >150 mm Hg suggests thrombosis in the oxygenator, and one should consider its replacement. On the other hand, if a significant color difference between the inflow and outflow tubing is observed with adequate blood flow, one should suspect either a problem in mechanical ventilation or deterioration of pulmonary function. In the case of venovenous ECMO, increased recirculation, malposition of cannula, or deterioration of heart function may cause desaturation. In such situations, repositioning of the neck cannula, insertion of an additional cannula in the femoral vein for improved drainage and oxygenation, and conversion to venoarterial ECMO as a last resort could be considered. Rolling, cleaning, and mobilizing sedated and unconscious patients supported with MCA is a regular event in the intensive care unit. It is a team task and should involve three staff nurses (two for support and one for cleaning), an intensivist (airway

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care), and a perfusionist (care of tubing, cannulae, and the system). The pump head should be brought as close to the bed as possible to ensure an adequate length of tubing during movement. In case of short tubing, the pump may be removed from the stand and held in the hand near the patient. Abrupt movements should be avoided, as these can cause a shower of microemboli. The cannula exit sites should be supported with a hand to avoid pulling or bending the cannulae. Special care is required in the case of distal perfusion cannula (DPC), as, being short and narrow, it is the most commonly dislodged cannula. In the unfortunate event of a cannula being dislodged, the tubing to the DPC should be clamped and pressure applied to the cannulation site to prevent bleeding. Immediate surgical help should be called (to explore the groin and relocate the DPC), and volume should be administered if necessary. Deposition of fibrin in the circuit is common, and it imparts a risk of embolization. A daily check by a perfusionist is mandatory. Once detected, fibrin deposition should be marked on the tubing and documented in the notes, and the development of the deposit should be followed daily. Fibrin is most commonly deposited in connectors, under flow probes, and in bends. Figure 1 shows the usual sites of fibrin clot formation in an oxygenator. Fibrin clots bigger

FIG. 1. Oxygenator, with arrowheads showing usual spots for thrombus development. Artif Organs, Vol. 38, No. 10, 2014

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than 5 mm mandate a change of tubing. Tubing can be replaced by (i) cutting the tubing, (ii) detaching the tubing from the connector, or (iii) cutting the cannulae. Cutting the tubing is the easiest and fastest way of changing the tubing but has the disadvantage of necessitating the addition of connectors to the circuit, creating the potential for further fibrin deposition. Detaching the tubing from the connector does not necessitate additional connectors but risks damaging the original connectors while cutting tubing over them. Cutting the cannulae allows old connectors to be replaced with new ones, but it can be done only once due to the shortness of the unwired portions of cannulae. The tubing should be pushed over the cannulae as far as possible to avoid accidental disconnection. The use of cable ties is advisable, especially if high line pressures are anticipated. A sufficient number of tubing clamps (at least 4) should be kept with each unit in an easily visible place in case of a system leakage, disconnection, or emergency oxygenator change-out. BLEEDING AND ANTICOAGULATION Appropriate anticoagulation management is essential for the smooth operation of the MCA device. Unmonitored anticoagulation can lead to severe events such as clotting in the oxygenator, thrombi in connectors and cannulae resulting in subsequent systemic embolism, or coagulopathy with unmanageable bleeding. In patients supported with MCA, thrombin is constantly generated, and the coagulation/anticoagulation processes are strongly activated—keeping them in a state of equilibrium is a challenge. Anticoagulation is achieved with continuous intravenous administration of unfractionated heparin and is regularly monitored by measuring activated clotting time (ACT, target range 160–180 s) and/or activated partial thromboplastin time (aPTT, target range 60–80 s). ACT, generally less sensitive than aPTT, is an acceptable but not accurate monitor of anticoagulation; however, it is still the best available bedside test. ACT is prolonged by hemodilution, thrombocytopenia, and thrombopathy; aPTT, in contrast, is not affected by platelet numbers. A relatively new approach is direct quantitative measurement of plasma heparin levels (Anti-Xa assay). The therapeutic range of Anti-Xa for MCA is 0.3–0.7 U/mL, which is equivalent to an aPTT of 63–101 s (15). Other important tests that should be carried out on a regular basis are fibrinogen, platelet count, antithrombin III, and thromboelastography. Particular emphasis should be given on maintaining Artif Organs, Vol. 38, No. 10, 2014

antithrombin III level above 50% to ensure sufficient heparin function. Plasma free hemoglobin should be measured daily, and if it falls below 0.1 g/L, the source of the hemolysis should be investigated. Often a partially clotted oxygenator or pump head causes hemolysis and therefore has to be changed out. Care must be taken during transport and sampling, as forceful aspiration can cause hemolysis. During the first 24 h of MCA, the heparin dose should be monitored every 2 h and later every 4 h with ACT measurements (target range 160–180 s). After the first day, only aPTT (target range 60–80 s), taken every 4–6 h, should be used to titrate the heparin dose. Anti-Xa is essential, together with aPTT, and should be done at least once a day to confirm the reliability of the aPTT value. To avoid a so-called yo-yo effect, one should try not to overreact to very high or very low aPTT/ACT when changing the heparin dose. In a situation of high aPTT/ACT one should not suspend the heparin infusion; rather, one should try to decrease the rate in small steps, trying to find a steady state between infusion and metabolism. The same applies for low anticoagulation. A slow incremental increase, maybe together with a small bolus to improve the anticoagulation and to help reach a steady state, will prevent big swings in coagulation levels. Bleeding in patients supported with MCA is not uncommon, despite stringent anticoagulation protocols. Bleeding can occur at the cannula exit site, operative site (e.g., in the case of a thoracotomy), nose, mouth, respiratory tract, or gastrointestinal (GI) tract. Bleeding remains underreported; a metaanalysis of 12 studies involving almost 1800 patients showed an incidence of 33% (16). Bleeding at the cannula exit site is quite common. The blood soaks the dressing over the site, and it is tempting to put a purse-string suture around the cannula in a bid to control the bleeding. However, this is futile. If there is very little bleeding, the bleeding is from the skin, and it is better to leave it alone as a needle puncture site over the skin because of a new purse-string will also cause bleeding. If the bleeding is severe it is from inside the pericardium in the case of central cannulation, and putting a purse-string over the skin will direct that blood into the chest drains or, worse, can cause a tamponade if the drains are blocked or removed. Bleeding from the nasal cavity and mouth may require temporary packing with gauze. Bleeding in the respiratory tract, which can be detected by bronchoscopy, usually occurs from the tracheobronchial mucosa and may be managed with flushes of saline mixed with 1% adrenaline. Although rare,

SHORT-TERM MECHANICAL CIRCULATORY ASSIST significant bleeding from a bronchus may flood itself as well as the contralateral bronchus and may require temporary seclusion of the bleeding bronchus with a double-lumen endotracheal tube and selective contralateral ventilation. Bleeding from the GI tract is located by upper and/or lower GI-scopy and managed with transcatheter arterial embolization or excision of the bleeding loop of intestine. One should keep in mind that all these measures are temporary, and it is essential to control anticoagulation and maintain an adequate level of clotting factors and platelets to control the bleeding. Apart from monitoring ACT/aPTT and titrating heparin dosage, it is essential to address other laboratory markers such as platelet count, prothrombin time, and fibrinogen level. According to our institutional protocol, platelets should be topped up when the count goes below 50 × 109/L, fresh frozen plasma should be given when prothrombin time is more than 17 s, and cryoprecipitate should be given when the fibrinogen level drops below 2 g/L. The earlier we supplement these factors, the lesser the chance of bleeding. At our institute, we use a tip-to-tip heparin-coated circuit. We believe that it improves the anticoagulation status of the patient and allows lower heparin levels at higher flows if necessary in case of bleeding. Nevertheless, during lower flows and during weaning of the patient, the heparin levels should be increased to prevent clot formation, especially at the tips of the cannulae. INFECTION The probability of infection increases with the duration of support and the severity of illness before initiation of ECMO. A meta-analysis of 12 studies involving almost 1800 patients showed a significantly high incidence of bacterial pneumonia (33%) and sepsis (26%) in patients supported on ECMO (16). In another study, bloodstream infection (16%), ventilator-associated pneumonia (16%), and catheter-associated urinary tract infection (3%) were the most common infections, while Enterobacteriaceae and Candida were the most common pathogens found in patients supported with ECMO (17). Traditionally, MCA patients are sedated and intubated to avoid cannula dislodgment and are placed on mechanical ventilation. Patients on MCA, especially those on ECMO, are susceptible to ventilator-associated pneumonia; this is because the gas exchange is dependent on ECMO, and therefore lung recruitment, pulmonary hygiene, and chest physiotherapy take a back seat. Awakening the

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MCA patients for nursing is feasible, and we suggest this should be considered in every patient. This strategy reduces complications related to mechanical ventilation, sedation, and immobilization. The patient can participate in active chest physiotherapy and pulmonary hygiene, improving the overall prognosis significantly. Usually, the patients supported with short-term MCA are critically ill; they remain bedridden and experience prolonged recovery, making them prone to infections. In addition, the venous perfusion catheters, chest drains, urinary tract catheters, and most importantly the MCA cannula sites are potential sources of infection. In MCA patients, inotropes should be reduced expeditiously so that the venous catheters can be removed quickly. Chest drains and urinary catheters should be removed as soon as possible. Patients should be actively mobilized, offered physiotherapy, and made ambulatory. DISTAL PERFUSION CANNULA IN PERIPHERAL ECMO Limb ischemia is a common complication in peripheral ECMO and can lead to amputation if not treated promptly. Limb ischemia remains underreported; a meta-analysis of 12 studies involving almost 1800 patients showed an incidence of 10% (16). It can be due to vessel obstruction by a large cannula, a nonpulsatile flow, low systolic blood pressure, injury to the vessels during cannula insertion, or coagulopathy. A distal perfusion cannula (DPC) can be used for continuous perfusion of the distal limb; however, it has its own shortcomings and requires frequent observation, care, and maintenance. The DPC, owing to its small caliber (usually 10–14Fr), has a high tendency to develop thrombi. It is very difficult to notice thrombosis in the DPC, and usually it is not detected until the flow stops completely and the separation of the clot and plasma is clearly visible. One good policy to avoid this is to use a separate flow meter for the DPC. Flow in the DPC depends on pump flow, resistance in the cannula, systemic vascular resistance, and mean arterial pressure. A gradual decrease in DPC flow is suggestive of the development of a thrombus in it; however, a rapid drop in flow could be because of bends or obstruction in the tubing or the DPC itself. Use of a cannula with a side port (see Fig. 2) is very useful in such a situation. The side port can be used to check patency, aspirate clots, and flush with heparinized saline. In case of recurrent DPC thrombosis, continuous infusion of heparinized saline through a side port is an option. If the DPC is without a sideport, one can Artif Organs, Vol. 38, No. 10, 2014

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P.N. MOHITE ET AL. ately and manual pressure should be applied over the groin. Emergency reexploration of the groin and reinstitution of the DPC is essential. Other options for perfusing the distal limb are the use of a smaller outflow cannula, vessel-sparing cannulation (fitting the outflow cannula onto a prosthetic graft stitched to the femoral artery), and retrograde perfusion of the limb through a small cannula into the posterior tibial artery. AIR IN THE CIRCUIT

FIG. 2. Side port in distal perfusion cannula.

put a connector with a side port in the DPC tubing. Caution must be taken not to flush the thrombus into the distal artery while working with it. A three-way tap should be left on the side port to avoid accidental disconnection, and the Luer connector should be tightly capped. Sometimes, an acceptable flow cannot be achieved through the DPC. Instead of utilizing the Luer port from the outflow cannula to feed the DPC, using a Y connector with 1⁄4-inch tubing for the DPC will allow higher flows and better flow dynamics in the DPC (see Fig. 3). It also helps prevent hemolysis by avoiding acute bends and Luer taps. Continuous intraarterial prostaglandin E1 can be administered through the DPC side port to dilate the distal artery and improve flow. Accidental bending or dislocating the DPC is not uncommon, especially when rolling a sedated patient or mobilizing an “awake” patient. It can be prevented by allowing adequate tubing length. In case of such an event, the DPC should be clamped immedi-

The MCA device is a closed-circuit unit, and accidental entry of air into the circuit may stop the pump or cause severe air embolism; both can be fatal for the patient. The recent Extracorporeal Life Support Organization registry reports the incidence of this complication as 3.9% in pediatric ECMO and 1.6% in adult ECMO (18). It may happen due to an accidental puncture of the inflow cannula, most commonly while it is being fixed to the skin or while a purse-string suture is being placed over the skin at the cannula exit site. The inflow cannula is constantly under high negative pressure, and any small puncture can cause air to be sucked into the circuit. One should be cautious not to prick the outflow cannula while fixing it and should avoid fixing the cannula close to the skin exit site (see Fig. 4). The trick is to make a small incision over the skin so that the cannula fits the exit site snugly. Air can be sucked into the circuit while a pursestring suture is being placed in the atrial chamber

Inflow

Main arm

Outflow

DPC arm

FIG. 3. Y connector for distal perfusion cannula. Artif Organs, Vol. 38, No. 10, 2014

FIG. 4. Safe site for fixing a cannula to the skin. (Avoid pursestring sutures as shown at left. The safe way of fixing the cannula is shown at right).

SHORT-TERM MECHANICAL CIRCULATORY ASSIST around the cannula to control bleeding. With the pump on high revolutions, the atrial chamber is under negative pressure, and needle punctures from the purse-string are enough to aspirate air. The trick is to decrease the pump speed temporarily when placing purse-strings. In addition, the purse-strings for controlling bleeding around the cannula should be finely stitched (6-0 polypropylene). Air can also be sucked through the central line if any three-way taps attached to it are not closed properly or are capped with a perforated stopper. One should always use three-way taps, make sure caps over the three-way taps are well tightened, never use caps with holes, and give clear instructions about it at handover. Caution should be taken against accidental air entry when introducing a new central line or during percutaneous intervention in patients with right ventricular assist devices (RVADs) or on venoarterial ECMO. In case of accidental air entry into the circuit, rapid action is essential. The first reaction should be to isolate the patient by clamping the arterial line to prevent air embolism. If the chest is still open, the pricked cannula should be replaced with a new one, and the circuit should be deaired by refilling the tubes and reconnecting them with the cannulae. Small air bubbles can get trapped in the oxygenator and can conveniently be sucked out with a syringe. If the chest is closed, a sticky polythene dressing can be wrapped around the cannula at the needle-prick site and the circuit deaired or changed.

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quantity of contact with relatives. The only drawback of this strategy is that the voluntary movements of the patient may bend or dislodge the cannulae. Physiotherapy is essential for awake patients to keep them fit, reduce muscle atrophy, and increase their morale. It should start with limb movements with the patient lying in the bed; later, sitting up by the side of the bed, standing, and finally cycling on an exercise bike may be possible, especially when the jugularis vessels are used for cannulation, as with the Avalon cannula. Care should be taken during active physiotherapy sessions not to bend or dislodge the cannulae. In addition, excess movement of the cannulae and tubing can dislodge the fibrin clots in them, which if big enough can be fatal. Another potentially lethal problem in awake and ambulant patients is slow migration of cannulae, especially in the cases of central ECMO and VADs, where the cannulae exiting the chest are pulled down by gravity, as the patient tends to be upright. As skin exit sites are well healed by the time the patient is ambulant, the dressings at these sites are changed less often. The skin fixation ties may get loosened with time, and constant pulling and movement aggravates this. All these things make ambulant patients prone to cannula dislodgment. Regular changes of dressing, checking of fixation ties, and checking the skin-level marks on cannulae should be included in the protocol of patient care. The fixation sutures, if loose, should be retightened, and the cannulae should be strapped to the skin using broad sticky dressings so that they will not hang by the fixation sutures.

AWAKE PATIENTS Patients on temporary circulatory support can be weaned from mechanical ventilation and allowed to wake up (5,19). It enables a continuous assessment of the central and peripheral neurological status, facilitates physiotherapy, and maintains patients in an awake, less artificial psychophysiological state. In addition, letting the patient wake may allow earlier detection of symptomatic complications such as bowel or leg ischemia, retroperitoneal hematoma, or neurological changes. It allows improved quality and

USEFUL MANAGEMENT STRATEGIES Bending of tubing over the pump is not unusual and not only decreases the flow but also imparts high resistance to flow, potentially harming blood cells. To avoid this, the pump should be kept at or below the level of the bed. A plastic coil can be wrapped around the tubing at the pump exit site, or a bandage sling tied to the tubing can be used to hold it up (see Fig. 5). While the outflow cannula or its tubing is being fixed, it may accidentally be punctured. The puncture

FIG. 5. Bending of tubing over the pump and ways to avoid it.

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does not suck in air, but it leaks blood. Replacing the damaged cannula or cutting out the damaged portion of the tubing and putting a connector in between may be required. Sometimes, when a new cannula is not available or the chest is closed, one can apply bone wax on the puncture site and cover it with polythene or cable tie; however, one must still be watchful for leaking of blood. Sometimes, an RVAD is required before longterm LVAD implantation. In such cases, the inflow cannula of the RVAD can be utilized as the venous cannula for cardiopulmonary bypass, which saves a hole and purse-string in the right atrium and a venous cannula. One can pass this cannula through the skin before putting it into the right atrium to avoid having to do this during emergency RVAD insertion. A hemofilter can be attached with its inflow and outflow connected to the Luer lock connectors inserted in the tube connecting the pump and oxygenator. It saves a vein in the patient, which could be useful during future manipulation of ECMO cannulae. However, utmost care should be taken while connecting and disconnecting the hemofilter, as these Luer locks are potential sources of bleeding. Sometimes it is essential to keep the ECMO circuit ready at the bedside of a patient who may need it urgently. Once primed, the circuit needs to be discarded after 24 h as a potential source of infection. However, the circuit can be connected and kept on standby for up to 5 days without priming; it takes 5–10 min to prime in an emergency. When inserting an ECMO apparatus percutaneously, it is advisable to hit the femoral vessels below the level of the inguinal ligament, as bleeding above that level is difficult to detect and repair and may cause hemorrhage in the retroperitoneal space, especially with anticoagulation. The tip of the femoral venous cannula should lie in the inferior vena cava at the level of the liver, as in that area the wall of the vena cava is well supported by liver parenchyma and unlikely to be sucked into the holes of the cannula. CONCLUSION Short-term mechanical circulatory assist devices offer versatile support, and the outcomes of the patients supported with them are improving continuously due to rapid development in the design of the devices and the increasing experience of the professionals involved in care. Although most patients supported with short-term MCA are bridged to recovery, transplantation, or a long-term support device, a significant proportion fall prey to complicaArtif Organs, Vol. 38, No. 10, 2014

tions related to MCA that can be avoided or managed easily. Continuous and vigilant monitoring, early detection and management of complications, protocol-based anticoagulation, and strategic and early weaning remain key for good results. While a patient is on mechanical circulatory support, the patient and the support device should be treated as a single unit, as each is dependent on the other for proper functioning and favorable outcome. Conflict of Interest: None of the authors have any conflicts of interest or disclosures. None of the authors received funding for this work. REFERENCES 1. Hernandez AF, Grab JD, Gammie JS, et al. A decade of shortterm outcomes in post cardiac surgery ventricular assist device implantation: data from the Society of Thoracic Surgeons’ National Cardiac Database. Circulation 2007;116:606–12. 2. John R, Liao K, Lietz K, et al. Experience with the Levitronix CentriMag circulatory support system as a bridge to decision in patients with refractory acute cardiogenic shock and multisystem organ failure. J Thorac Cardiovasc Surg 2007;134:351–8. 3. Aissaoui N, Morshuis M, Schoenbrodt M, et al. Temporary right ventricular mechanical circulatory support for the management of right ventricular failure in critically ill patients. J Thorac Cardiovasc Surg 2013;146:186–91. 4. Haj-Yahia S, Birks EJ, Amrani M, et al. Bridging patients after salvage from bridge to decision directly to transplant by means of prolonged support with the CentriMag short-term centrifugal pump. J Thorac Cardiovasc Surg 2009;138:227–30. 5. Fuehner T, Kuehn C, Hadem J, et al. Extracorporeal membrane oxygenation in awake patients as bridge to lung transplantation. Am J Respir Crit Care Med 2012;185:763–8. 6. Thomas HL, Dronavalli VB, Parameshwar J, Bonser RS, Banner NR; Steering Group of the UK Cardiothoracic Transplant Audit. Incidence and outcome of Levitronix CentriMag support as rescue therapy for early cardiac allograft failure: a United Kingdom national study. Eur J Cardiothorac Surg 2011;40:1348–54. 7. Griffith BP, Anderson MB, Samuels LE, Pae WE Jr, Naka Y, Frazier OH. The RECOVER I: a multicenter prospective study of Impella 5.0/LD for postcardiotomy circulatory support. J Thorac Cardiovasc Surg 2013;145:548–54. 8. Manzo-Silberman S, Fichet J, Mathonnet A, et al. Percutaneous left ventricular assistance in post cardiac arrest shock: comparison of intra-aortic blood pump and IMPELLA Recover LP2.5. Resuscitation 2013;84:609–15. 9. Kar B, Adkins LE, Civitello AB, et al. Clinical experience with the TandemHeart percutaneous ventricular assist device. Tex Heart Inst J 2006;33:111–5. 10. Gregoric ID, Jacob LP, La Francesca S, et al. The TandemHeart as a bridge to a long-term axial-flow left ventricular assist device (bridge to bridge). Tex Heart Inst J 2008;35:125–9. 11. Samuels LE, Holmes EC, Thomas MP, et al. Management of acute cardiac failure with mechanical assist: experience with the ABIOMED BVS 5000. Ann Thorac Surg 2001;71:S67–72, discussion S82-5. 12. Lad V, Elhenawy A, Harwood S, et al. Mechanical circulatory support with the ABIOMED BVS 5000: the Toronto General Hospital experience. Can J Cardiol 2010;26:467–70. 13. De Robertis F, Birks EJ, Rogers P, Dreyfus G, Pepper JR, Khaghani A. Clinical performance with the Levitronix Centrimag short-term ventricular assist device. J Heart Lung Transplant 2006;25:181–6.

SHORT-TERM MECHANICAL CIRCULATORY ASSIST 14. Santise G, Petrou M, Pepper JR, Dreyfus G, Khaghani A, Birks EJ. Levitronix as a short-term salvage treatment for primary graft failure after heart transplantation. J Heart Lung Transplant 2006;25:495–8. 15. Brill-Edwards P, Ginsberg JS, Johnston M, Hirsh J. Establishing a therapeutic range for heparin therapy. Ann Intern Med 1993;119:104–9. 16. Zangrillo A, Landoni G, Biondi-Zoccai G, et al. A metaanalysis of complications and mortality of extracorporeal membrane oxygenation. Crit Care Resusc 2013;15:172–8.

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17. Aubron C, Cheng AC, Pilcher D, et al. Infections acquired by adults who receive extracorporeal membrane oxygenation: risk factors and outcome. Infect Control Hosp Epidemiol 2013;34:24–30. 18. Paden ML, Conrad SA, Rycus PT, Thiagarajan RR; ELSO Registry. Extracorporeal Life Support Organization Registry Report 2012. ASAIO J 2013;59:202–10. 19. Olsson KM, Simon A, Strueber M, et al. Extracorporeal membrane oxygenation in nonintubated patients as bridge to lung transplantation. Am J Transplant 2010;10:2173–8.

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