**7. Results and discussion**

Extracorporeal membrane oxygenation is now considered a validate tool to support very ill patients affected by refractory cardiogenic shock to conventional therapy or cardiac arrest [4, 7, 37-39] and it is a well-established technology to provide a rapid and full circulatory support and to reverse the severe hypoperfusion organ injury. The ECMO system has several advan‐ tages: a) it can easily be implanted at patient's bedside, b) it can be initiated through a peripheral percutaneous cannulation, c) it is possible to stabilize the patient in the out-center hospital [6,22] d) it provides a full cardiopulmonary support, e) it allows to take time for diagnosis and further decision f) it is a relative *low-cost* support and g) it is a validate system for a "bridge strategy" [40]. However, the use of ECMO for cardiogenic shock has several limitations. All patients need to be anticoagulated during the ECMO support and complica‐ tions such as neurological damage [41], infections [42], limb ischemia [43], bleeding and transfusion requiring [44] are frequently reported. However, the use of ECMO in patients with acute coronary syndrome complicated by advanced cardiogenic shock or by cardiac arrest is becoming an increasingly accepted procedure [3, 38, 39, 45].

Although the results about the use of IABP before and during ECMO are not univocal, the use of IABP seems to affect positively the early outcome. Some Authors [23, 24, 34, 46] found that the nonuse of IABP was one of the significant predictors of in-hospital death. On the other side, other Authors [39, 40, 47] could not find significant difference about the use of IABP during ECMO support. According to these different results, we cannot confirm whether the use of IABP has a determinant role in the cardiac function improvement. It can be argued that the use of IABP during ECMO, through the increase of coronary blood flow as reported by Madershahian [35], could favorite the cardiac recovery in ischemic patients.

Higher lactate levels are an index of severe acidosis and tissue hypoxia. The trends of blood lactate levels during the first three days of ECMO are considered as independent predictors of early mortality. Hyperlactatemia (level of blood lactate above 3 mmol/l) during cardiopul‐ monary bypass is associated with an increased mortality and morbidity, and appears to be related primarily to a state of inadequate perfusion [48]. We have already observed [44] that, when blood lactate level is > 3 mmol/l at 48 hours after ECMO initiation, the predicted probability of mortality is 52%. The earlier ECMO initiation should improve the organ perfusion and reduce dramatically the incidence of multi-organ failure. The persistence of hyperlactacidemia during the first days of ECMO support in nonsurvivors patients, even though the flow of the pump during the same period is similar to that of surviving patients, is likely to be referred to the persistent systemic and splanchnic hypoperfusion due to the extent of atherosclerotic disease or other unknown causes.

Bleeding and transfusion requiring can negatively affect the ECMO course and the early outcome and they are considered important complications during ECMO [23, 24, 47]. It is worthy to point out that lower number of RBCs transfused the number of RBCs units trans‐ fused was an independent predictor of in-hospital and late mortality. The need for RBCs transfusion depends not only by the fact that some patients on ECMO have undergone surgery; other factors such as systemic heparinization during ECMO and the use of platelet inhibitors after PTCA can cause bleeding and need for transfusions with increased risk of early mortality. Alternative therapy to conventional heparin anticoagulation therapy, such as bivalirudin or fondaparinux, to reduce the risk of bleeding and for the treatment of heparine induced thrombocitopenya have been recently published [49, 50].

including lateral systolic velocity, strain, and strain rate, are now considered important data [36] to drive a safe weaning from ECMO and they should be frequently collected in each ECMO

Extracorporeal membrane oxygenation is now considered a validate tool to support very ill patients affected by refractory cardiogenic shock to conventional therapy or cardiac arrest [4, 7, 37-39] and it is a well-established technology to provide a rapid and full circulatory support and to reverse the severe hypoperfusion organ injury. The ECMO system has several advan‐ tages: a) it can easily be implanted at patient's bedside, b) it can be initiated through a peripheral percutaneous cannulation, c) it is possible to stabilize the patient in the out-center hospital [6,22] d) it provides a full cardiopulmonary support, e) it allows to take time for diagnosis and further decision f) it is a relative *low-cost* support and g) it is a validate system for a "bridge strategy" [40]. However, the use of ECMO for cardiogenic shock has several limitations. All patients need to be anticoagulated during the ECMO support and complica‐ tions such as neurological damage [41], infections [42], limb ischemia [43], bleeding and transfusion requiring [44] are frequently reported. However, the use of ECMO in patients with acute coronary syndrome complicated by advanced cardiogenic shock or by cardiac arrest is

Although the results about the use of IABP before and during ECMO are not univocal, the use of IABP seems to affect positively the early outcome. Some Authors [23, 24, 34, 46] found that the nonuse of IABP was one of the significant predictors of in-hospital death. On the other side, other Authors [39, 40, 47] could not find significant difference about the use of IABP during ECMO support. According to these different results, we cannot confirm whether the use of IABP has a determinant role in the cardiac function improvement. It can be argued that the use of IABP during ECMO, through the increase of coronary blood flow as reported by

Higher lactate levels are an index of severe acidosis and tissue hypoxia. The trends of blood lactate levels during the first three days of ECMO are considered as independent predictors of early mortality. Hyperlactatemia (level of blood lactate above 3 mmol/l) during cardiopul‐ monary bypass is associated with an increased mortality and morbidity, and appears to be related primarily to a state of inadequate perfusion [48]. We have already observed [44] that, when blood lactate level is > 3 mmol/l at 48 hours after ECMO initiation, the predicted probability of mortality is 52%. The earlier ECMO initiation should improve the organ perfusion and reduce dramatically the incidence of multi-organ failure. The persistence of hyperlactacidemia during the first days of ECMO support in nonsurvivors patients, even though the flow of the pump during the same period is similar to that of surviving patients, is likely to be referred to the persistent systemic and splanchnic hypoperfusion due to the

Madershahian [35], could favorite the cardiac recovery in ischemic patients.

patient.

**7. Results and discussion**

284 Principles and Practice of Cardiothoracic Surgery

becoming an increasingly accepted procedure [3, 38, 39, 45].

extent of atherosclerotic disease or other unknown causes.

High incidences of central nervous system (CNS) injury meeting the criteria of brain death are reported. These patients usually are withdrawn from ECMO sooner than the rest of the other patients. Brain death is frequent in patients who presented with cardiac arrest and received V-A ECMO implantation during cardiopulmonary resuscitation maneuvers. The incidence of brain death is ranging between 10% and 40% [6, 7, 39, 51]. Thiagarajan et al.[5] analyzing data of 297 patients supported by ECPR and extracted from the Extracorporeal Life Support Organization (ELSO) Registry reported an incidence of 33% of CNS damage and 21% had irreversible hypoxic encephalopathy. Other Authors [3, 4] described a very low survival when cardiopulmonary resuscitation (CPR) time is 60 minutes and a survival approaching to 0% when the CPR was more than 90 minutes.

Left ventricular decompression during ECMO support is an important priority in cases in which the contractile activity of the heart is inadequate to allow the opening of the aortic valve. In such scenario, the risk of clotting formation inside the left cavities is very high and the clots may embolize.

Several techniques to unload the left ventricle such as atrial septostomy [4, 33], direct LV apex cannulation [21], insertion of PulseCath iVAC [31], use of Impella [52, 53], percutaneous insertion of a pigtail [32] or percutaneous pulmonary truck drainage [30] have been described. One of the most followed strategies is to use as soon as the IABP associated with low dose of inotrope (dobutamine 5 mcg/min/Kg) with the aim to reduce the systemic resistance, improve the coronary and cerebral flow and increase the cardiac contractility. Whether the use of IABP is a useful tool to dramatically reduce the afterload mainly in such patients with a peripheral retrograde arterial return [21], and whether the IABP simply increases the coronary blood flow [35], is still debated.

Peripheral percutaneous cannulation represents a big challenging for all ECMO teams. Several peripheral complications such as retroperitoneal hemorrhage, cannula dislocation, cannula‐ tion failure, leg ischemia and leg amputation are described [43, 54]. According to early or late vascular complication following peripheral cannulation, Huang et al. [25] suggested measur‐ ing the mean pressure of the superficial femoral artery and they indicate to insert a catheter for a distal perfusion if the mean pressure is lower than 50 mmHg. It is extremely important to verify the pulsatility of the anterior and posterior tibial artery by an ultrasound vascular Doppler and to restore the limb perfusion signs of hypoperfusion are observed. In such case an 8-9 F catheter is placed distally to the arterial cannula by means of vascular ultrasound scan. In female patients or in patients with a BSA less than 1.7 m2 or in patients with a severe peripheral vascular disease, the distal catheter is inserted as soon as possible.

**9. Conclusion**

**Acknowledgements**

**Author details**

**References**

Francesco Formica and Giovanni Paolini

terdisciplinary Medicine, University on Milano-Bicocca, Italy

perspective. Circulation 2009;119:1211-9.

hospital discharge. Resuscitation 2011;82:845-52.

oxygenation. J Am Coll Cardiol 2003;41:197-203.

The use of V-A ECMO in patients with acute myocardial infarction complicated by refractory cardiogenic shock and or cardiac arrest is widely increasing due to the improving in the early e mid-term results. The relatively low early survival rate in these very illness patients sup‐ ported by ECMO should be considered an encouraging data, because in these patients the mortality without the ECMO support is dramatically higher. Bleeding, infections and CNS irreversible damage remain still serious complications and efforts to reduce or prevent them

Veno-Arterial Extracorporeal Membrane Oxygenation for Refractory Cardiogenic Shock and Cardiac Arrest

http://dx.doi.org/10.5772/54719

287

The Authors wish to thank Dr Giorgia Pavan for her editing and English language support, all the cardiac surgeons and the cardiologist team, the anesthesiologist medical staff, the perfusionist service an the nurse staff of the operating room and the intensive care unit.

Cardiac Surgery Unit, San Gerardo Hospital, Monza, Department of Surgical Science and In‐

[1] Goldberg RJ, Spencer FA, Gore JM, Lessard D, Yarzebski J. Thirty-year trends (1975 to 2005) in the magnitude of, management of, and hospital death rates associated with cardiogenic shock in patients with acute myocardial infarction: a population-based

[2] Brady WJ, Gurka KK, Mehring B, Peberdy MA, O'Connor RE, American Heart Association's Get with the Guidelines (formerly NRCPI. In-hospital cardiac arrest: impact of monitoring and witnessed event on patient survival and neurologic status at

[3] Chen YS, Chao A, Yu HY, Ko WJ, Wu IH, Chen RJ et al. Analysis and results of prolonged resuscitation in cardiac arrest patients rescued by extracorporeal membrane

are necessary and strongly recommended to improve the outcome.

Patients with acute coronary syndrome complicated by advanced cardiogenic shock had a higher survival than patients presented with cardiac arrest. Kim et al. [45] reported an early survival of 59.2% in a group of 27 patients and described a long-term survival of 42.9% at 3 years. Bermudez et al. [39] described an early survival of 64% in a group of 33 patients affected by AMI and advanced CS. The 2-year survival was 48%. Sakamoto et al. [38] reported a cumulative early survival of 32.7% in a group of 98 patients affected by refractory CS following AMI in which 36.7% had CA on arrival. Other early survival rate ranging between 33.3% and 56.8% have been reported [37, 55, 56].

#### **8. Future implications**

Recently, some Authors have reported early results about the use of IABP in the setting of cardiogenic shock following acute myocardial infarction and in these articles the IABP seems to have not robust data to be still considered as the tool of first choice in the treatment of cardiogenic shock. Seyfart et al [57], in a randomized study of 25 patients with CS, randomly assigned to IABP (n=13) and percutaneous Impella 2.5 (n=12), reported a superior hemodi‐ namic parameter and a significative increasing of cardiac index in patients treated with Impella; the 30 days mortality (46%) was not different in both groups. In a meta-analisys published by Sjauw et al. [58] about the use of IABP in the setting of ST-elevation myocardial infarction complicated by cardiogenic shock, the Authors could not find robust data in favours of the use of IABP. Different complications such as stroke and bleeding and increasing of 30 days mortality in patients managed with IABP were observed. A very recent article by Thiele and al [59], 600 patients affected by CS following acute myocardial infarction, were randomly assigned to IABP therapy (n = 300) or conventional therapy (n = 298). The Authors could not find significant differences in 30-days mortality and in secondary end points or in process-ofcare measures, including the time to hemodynamic stabilization, the length of stay in the intensive care unit. No other significant differences with respect to the rates of major bleeding, peripheral ischemic complications and stroke were reported between the two groups. Ho‐ wewer all these results have received different criticisms due to small number of patients [57] or a high number of patients with a relatively low mortality risk if treated with conventional therapy [59] and therefore these report could be influenced from some confounding factors.

According to these recent results, in the next close future, it can be argued that the use of ECMO could be more encouraged and anticipated in such patient who are in the setting of "pre-shock", in order to reduce the complications linked to the low cardiac output and to reduce the rate of very late application of ECMO. The current systems are safe and simple to apply, due to the advance in miniaturized centrifugal pumps and circuits, to the increased biocompatibility (heparin-coated system), but they are still associated with major complications in a relatively high percentage. Big efforts are still needed to im‐ prove the current techniques and devices.
