Venoarterial Extracorporeal Membrane Oxygenation in Cardiac Surgery

Abstract

Owing to the growing demands of extracorporeal membrane oxygenation (ECMO)-designated support required for severe cardiac or respiratory failure, which is both potentially reversible and unresponsive to conventional management, novel ECMO indications emerge day after day. ECMO offers unique advantageous characteristics, which are compact pump-oxygenator design, percutaneous approach, flexible cannulae, and less inflammation making the modern venoarterial ECMO an ideal miniaturized cardiopulmonary bypass. We hereby discuss the background of ECMO success to backup complex high-risk cardiac surgical procedures.

1. Introduction

Demands for venoarterial extracorporeal membrane oxygenation (VA-ECMO) are growing worldwide to support the circulation in response to cardiogenic shock (CS) [1, 2]. One of the temporary mechanical circulatory support (tMCS) devices that are employed when there is circulatory failure is VA-ECMO [3]. Since its debut in 1972, VA-ECMO has been widely used to support clinicians in a variety of complex cardiac procedures on an emergency or preventative basis, including transcutaneous aortic valve implantation (TAVI) [4], complex percutaneous coronary intervention (PCI) [5], and postcardiotomy when it is difficult to wean the cardiopulmonary bypass (CBP) machine [6]. Considering ECMO is a more compact circuit than CPB and does not require cardiotomy suction or air-blood contact, it requires less anticoagulation, which could reduce coagulopathy and minimize systemic inflammation inflammatory response [4]. Refractory CS attributable to myocarditis, acute MI, acute cor pulmonale from a major pulmonary embolism, primary transplant graft failure, postcardiotomy CS, acute exacerbation of chronic heart failure, toxic ingestions, and intractable arrhythmias are only a few examples of specific indications for VA-ECMO (Table 1) [5].

Common indications	Selected contraindications
Refractory cardiogenic shock secondary to:	Relative:
Acute myocardial infarction	Severe uncontrolled bleeding or when anticoagulation is contraindicated
Acute exacerbation of chronic heart failure	Severe peripheral arterial disease
Fulminant myocarditis	Aortic dissection
Massive pulmonary embolism	Prognostic score reveals poor survival benefits (modified SAVE or PREDICT VA-ECMO)
Intractable arrhythmias	Severe AI
Postcardiotomy syndrome	Absolute:
Primary transplant graft failure	Irrecoverable condition
Toxins	Unwitnessed asystole
Periprocedural Support	Goals of care not in keeping with temporary mechanical support
ECPR

Table 1.

Common indications and contraindications for using VA-ECMO.

ECMO: extracorporeal membrane oxygenation; ECPR: extracorporeal cardiopulmonary resuscitation; SAVE: surviving after venoarterial ECMO trial; and VA: venoarterial.

This chapter will focus on the indications related to the cardiac surgery, ECPR, periprocedural support, refractory CS secondary to AMI, postcardiotomy syndrome, and other high-risk procedures that require VA-ECMO.

2. ECMO for ischemic cardiogenic shock

Despite the decline in the incidence of MI-related cardiogenic shock; myocardial infarction (MI) remains the top common cause of cardiogenic shock in more than 80% of cases [6]. Studies have shown that in the era of revascularization MI related cardiogenic shock is about 4 to 10 % [7, 8]. The largest of these studies, the SHOCK trial (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock) recommended an early invasive approach to treat MI-related shock state to reduce mortality. However, mortality in such devastating complications remains high approaching 30% to 50% [7, 8, 9].

The challenge in CS and refractory cardiac arrest is always how to maintain systemic circulation, and ECMO could be appropriate in this situation. In the setting of persistently poor CS outcomes and technological advances in VA-ECMO, patients treated with cardiovascular MCS have exponentially increased over the last decade [10, 11].

3. Extracorporeal cardiopulmonary resuscitation

Extracorporeal cardiopulmonary resuscitation (ECPR) refers to institution of VA-ECMO in the setting of stubborn cardiac arrest. The 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care stated that ECPR may be considered when spontaneous circulation interrupting time is short, appropriate resuscitation efforts, and the cardiac arrest reason is possibly reversible or could be handled with revascularization or heart transplantation [12]. The guidelines emphasize that ECPR use should be limited to special centers that got the capabilities of running this complex intervention, in the view of managerial requirements of advanced equipment and highly trained personnel.

4. ECMO for high-risk procedures

The introduction of VA-ECMO as cardiopulmonary support has paved the way for new operative indications for those patients who were previously relegated to conservative medical management. Patients with poor left ventricular function, CS with complex multivessel disease, or multiple other comorbidities now could be undergone revascularization with circulatory support of ECMO. Recent applications have shown ECMO to be potentially effective as a temporizing measure or bridge to therapeutic intervention in the setting of myocardial dysfunction and CS. Extracorporeal life support is now used in many more difficult situations due to recent advances in knowledge and familiarity. These include a number of high-risk catheter-based procedures, such as transcatheter aortic valve implantation (TAVI) and percutaneous coronary interventions (PCI) [13, 14, 15], post-infarct ventricular septal defect (PI-VSD) repair as well as surgery on the thoracoabdominal aorta, international retrievals for cardiac and respiratory failure [16], and in case of massive pulmonary thromboembolism as a bridge for embolectomy (PTE) [17].

4.1 ECMO support in high-risk percutaneous coronary intervention (HR-PCI)

Early reports of total cardiopulmonary support or cardiopulmonary bypass (CPB) during high-risk PCI were aimed at understanding the best time to initiate support, either prophylactically or to be on “standby” during the procedure. Prophylactic vs standby percutaneous CPB in HR-PCI was compared in a retrospective data analysis of 23 national registries with 569 patients. 180 patients were in the standby group and 389 patients were in the prophylactic CPB group. The procedural success rate was almost the same in both groups (88.7 % compared to 84.4 %); however, the periprocedural mortality rate was greater in the standby group (18.8 % versus 4.8 %, p = 0.05) [18]. Subsequent studies showed more evidence for the benefit of ECMO use in a patient with ST-segment elevation myocardial infarction (STEMI) complicated by CS unresponsive to inotropes and intra-aortic balloon pump (IABP) [19, 20].

4.1.1 Emergent PCI post myocardial infarction and cardiogenic shock

Koutouzis et al. [20] showed how ECMO assistance was used successfully and with good results during PCI in a patient with CS. Subsequently, Sheu et al. [19] recommended that patients with STEMI complicated by CS, unresponsive to inotropes and IABP placement, had lower 30-day mortality after prompt-ECMO support in the cath lab in comparison to a non-supported cohort with a similar presentation.

4.1.2 Elective PCI in high-risk patients and left main procedures

Other studies described the use of ECMO in elective, high-risk, complex PCI. In their single-center prospective investigation on the use of ECMO in these patients, Tomasello et al. [21] published their findings. 12 consecutive patients with complicated coronary artery disease who were at high risk for surgical revascularization underwent initiation of femoro-femoral VA ECMO before the indexed PCI. All patients responded favorably to the procedure, and there was only one access site hematoma that did not need to be transfused. At the 6-month follow-up, no deaths or MI were reported. Authors proposed that ECMO might serve as a viable substitute to ensure PCI success in unsuitable surgical candidates.

4.1.3 Complicated PCI needs surgical intervention

Following percutaneous coronary intervention (PCI), complications are often successfully managed in the catheterization laboratory, but certain complications require emergent surgical intervention. One of the most dreadful, albeit rare, complications is coronary artery perforation, which occurs from 0.1% to 3.0% [22]. Patients who have developed mechanical complications produced iatrogenically during diagnostic coronary angiography (CA) and PCI are usually in critical clinical status and require immediate corrective therapy, including inotropic support and mechanical ventilation. In the worst-case scenario, mechanical assist systems such as IABP or ECMO are required in hemodynamically unstable patients [23].

4.2 High-risk TAVI and ECMO support

Although transcatheter aortic valve implantation (TAVI) is an excellent alternative procedure for high-risk patients with severe symptomatic aortic stenosis, it is often associated with life-threatening complications. TAVI can cause profound hemodynamic perturbation in the perioperative period. VA-ECMO can be used to provide cardiorespiratory support during this time, either prophylactically or emergently. Michael et al. [24] described the utilization of ECMO for patients who had significantly high mean EuroSCORE and had undergone TAVI procedures. Postoperative outcomes were broadly comparable between TAVI patients who did not require ECMO and ECMO patients who had significantly higher mean EuroSCORE. Elective use of ECMO is usually considered in patients with severe pulmonary hypertension (over 60 mmHg) and/or markedly decreased left ventricular ejection fraction (LVEF under 20%) [25]. In selected cases, it may be advocated to avoid consequences of intraoperative complications, emergency VA-ECMO associated with higher mortality [24, 26].

4.3 ECMO support for postinfarct VSD

F. Ramponi et al. reported two cases with successful use of VA-ECMO in two high-risk patients’ postinfarction ventricular septal defect (VSD) and CS, with 80 % calculated mortality risk by logistic EuroSCORE. Both cases were in detrimental biventricular failure that was treated successfully with VA ECM surviving to hospital discharge [27].

4.4 ECMO and acute pulmonary embolism

The prognosis is dismal for patients who present with a massive acute pulmonary embolism (PE) exacerbated by right ventricular (RV) failure and CS [28]. Thrombolysis or embolectomy must be performed immediately, but due to logistical or hemodynamic instability, these therapeutic procedures may be postponed. As a stabilizing measure or stepping stone to additional therapies, the use of MCS in these situations is crucial [29]. In cases of RV failure brought on by pressure overload related to pulmonary obstruction, VA-ECMO is the best course of action. Few reports showed successful use of percutaneous VA-ECMO as an adjunct to thrombolytic therapy for circulatory collapse secondary to massive PE [30]. Indeed, successful rescue therapy with ECMO has been described in several cases of life-threatening PE [31, 32], even in patients with acute cardiopulmonary collapse [33]. In some cases, complete lysis of pulmonary artery clots has been reported after a few days of ECMO and heparin treatment [31, 34, 35].

4.5 ECMO and heart transplantation

In such cases, ECMO could be used as a bridge to heart transplantation or ventricular assist device (VAD) insertion in INTERMACS class I patients or as a bridge to a decision when the prognosis is uncertain [36, 37, 38, 39, 40]. Patients receiving ECMO assistance must stay in the intensive care unit, and since the duration of ECMO support is shorter than that of VADs, making transplantation or switching to a VAD is more urgent [41]. The effectiveness of ECMO as a bridge therapy varies widely and is mostly influenced by the characteristics of the pre-ECMO patient and the availability of organs in situations where transplantation is the eventual goal. Additionally, primary graft failure (PGF) after heart transplantation is also treated with ECMO assistance [42, 43]. Patients with PGF who require ECMO have a poorer overall survival rate than patients without PGF. Patients with ECMO-supported PGF, however, have equivalent long-term survival to non-PGF transplant recipients who live past the immediate post-transplant period [43, 44].

5. Intraoperative VA-ECMO

Advances in ECMO technology have led to a broader application of this technique. One example is the intraoperative use of VA-ECMO instead of classical cardiopulmonary bypass (CBP).

We reported two cases where patients underwent coronary artery bypass grafting (CABG) under the support of VA-ECMO in the setting of CS complicating acute myocardial infarction [45]. One of these is a 57-year-old male with multiple comorbidities. Admitted as a case STEMI complicated by CS while undergoing primary PCI. Eventually, he needed a further support with peripheral VA-ECMO. Keeping target ACT over 180 seconds and the target a (aPTT) between 60 and 80 seconds. Coronary angiography showed left main and three-vessel CAD not amenable for PCI. The patient was kept on ECMO support and CABG was done 24hrs after. Surgery was done as beating heart while on ECMO without conversion to conventional CPB. ACT value was kept as routine above 300 seconds. Intraoperatively, VA-ECMO flow has been optimized by adjusting the inotropic support of dopamine and noradrenaline infusion to keep mean arterial pressure (MAP) above 65 mmHg. Hemostasis was achievable while keeping ACT of 180 seconds. After revascularization, intraoperative transesophageal echocardiography (TEE) showed distended left ventricle (LV) and low-velocity time integral 9 cm (VTI); therefore, we decided to keep the ECMO support after revascularization. Decannulation of VA-ECMO was done on the third postoperative day. IABP was removed on the fourth postoperative day. The patient survived to discharge.

In primary PCI, VA-ECMO is a rescue measure for CS. Cases that require emergency surgical revascularization can be carried out utilizing the ECMO circuit instead of instituting CPB circuit, and by this means, the procedure is carried out with less aortic manipulation, prompter revascularization, and less priming volumes; therefore, it needs less anticoagulation, potentially reducing coagulopathy and attenuating systemic inflammatory response [46].

6. ECMO support for postcardiotomy low cardiac output syndrome

Postcardiotomy (PC) low cardiac output syndrome is generally defined as a shock state refractory to inotropic support and\or IABP, and it can manifest as an inability to separate from CPB or persistent CS despite maximal use of pharmacological agents and\or IABP in the immediate postoperative period. It is a rare but a detrimental complication after cardiac surgery.

ECMO has been used as a salvage in such complications more than 50 years ago mainly for cardiac surgery in pediatrics but remained quiescent in adult population. However, during the last several years, ECMO is being used more and more in adult patients, particularly for postcardiotomy low cardiac output syndrome. Since its introduction to be used to support PC shock, ECMO has been a lifesaver and an important prognosis changer in such complications. It is reported that from 2007 to 2011, non-percutaneous ECMO cannulation increased 2-fold, while the use of percutaneous ECMO increased by more than 15-fold. In a study that looked at more than 9,000 ECMO patients from the Nationwide Inpatient Sample database in the US from 1998 to 2009, 4,493 cases (approximately 50%) were cannulated for cardiogenic shock in the postoperative period. In the same database, researchers observed that PC-ECMO was the most frequent ECMO indication between the years 2002 and 2011 [47]. The usage of PC-ECMO has increased over the previous ten years, according to data from the Extracorporeal Life Support Organization (ELSO) registry [48]. Despite the growing evidence and the widened use of such expensive, highly debatable yet important surgical armament. Unfortunately, data is unpowered, limited, conflicting, and highly variable.

6.1 Indications, contraindications, and cannulation of VA-ECMO

6.1.1 Indications

Currently, there is no consensus regarding when to initiate extracorporeal life support (ECLS) in the setting of postcardiotomy low cardiac output syndrome. A recent paper, the 2020 EACTS/ELSO/STS/AATS Expert Consensus on PostCardiotomy Extracorporeal Life Support in Adult Patients, represents to date the first comprehensive guideline to provide structured and clinical recommendations about the most relevant issues surrounding its application in this setting [49].

In this joint effort, the authors considered that class I indications of ECMO in the postcardiotomy setting can be summarized as follows:

• ECMO support to be initiated prior to end-organ injury or onset of anaerobic metabolism (lactate level <4mmol/l) in patients with likelihood of myocardial recovery and in the absence of uncontrollable bleeding not amenable to surgical repair [49].

• In case the likelihood of myocardial recovery is low, ECMO is recommended in patients who are eligible for long-term mechanical support or heart transplantation (LT-MCS or an HTx) [49].

In addition, timely implantation prior to severe end-organ hypoperfusion and ischemic injury represents one of the most powerful predictors of ECMO outcome, the early use of ECMO after cardiac surgery in a patient with an IABP and optimal medical therapy, with failure to wean from CPB or marginal hemodynamics also has been listed as class 1 recommendation [49]. Scoring systems were developed to prognosticate the outcomes following ECMO patients in general and mainly to help clinicians when best to avoid or consider it and it gives guidance while exploring it as an option for the families and its complications. Of these scoring tools, the survival after venoarterial-ECMO (SAVE) score has been considered one of the best predicting tools for ECMO patients in general due to its independent variable cohort; however, it was not developed to meet the special physiologic milieu of postcardiotomy patients [50].

Recently, a single-center, retrospective study that included 166 postcardiotomy CS patients supported with VA-ECMO after CABG over a 14-year period created a 6-items bedside scoring system; the REMEMBER score has been able to predict the mortality in that study cohort. It was found that older age, left main disease, inotropic score > 75, CK-MB > 130 IU/L, serum creatinine > 150 umol/L, and platelet count < 100 × 109/L were identified as pre-ECMO prognosis factors of in-hospital mortality in the REMEMBER score [51]. In this setting, again lack of evidence calls for more powerful multicenter scoring system to accurately predict the prognosis in postcardiac surgery patients requiring ECMO for PC shock.

6.1.2 Contraindications

In General, for patients in whom PC failure is felt to be reversible, all contraindications should be considered relative, except for uncontrollable bleeding not amenable for surgical correction, which is by far the only absolute contraindications for postcardiac surgery patients [49].

6.1.2.1 Relative contraindications

• Age\although patients in their 80s have been supported with success, advanced age has been linked to worse outcomes, as we mentioned earlier, careful thought of patients’ appropriateness to ECMO in case they are not candidates for long-term support or heart transplantation [49].

• Comorbidities e.g., chronic lung disease, renal insufficiency, and peripheral vascular disease were also associated with poor outcomes [49].

• All degrees of aortic insufficiency need to be addressed either surgically or via transcatheter as it also affects the performance of the ECMO support by aggravating the LV distention [49].

6.1.3 Cannulation

It was found that following PC low cardiac output, approximately 40% of ECMO cannulation occurs in the operating room and 60% in the ICU [52]. As these patients’ chests are already opened via sternotomy or thoracotomy; central access is an additional modality to cannulate PC patients with ECMO centrifugal pump. However, it was found that peripheral cannulation is more common than central cannulation despite its easiness in terms of the already utilized access via right atrium and aorta, the presumed as well as the gathered evidence showed higher complications in terms of mortality, bleeding, infection, and compression in case of central cannulation in comparison to the peripheral access via the femoral or the axillary sites. In a retrospective multicenter study, Mariscalco et al. compared peripheral and central VA-ECMO in 781 patients with PCS at 19 cardiac surgery centers. Concluded that central cannulation was associated with greater in-hospital mortality than peripheral cannulation, pooled unadjusted risk ratio analysis of these patients showed that patients undergoing peripheral VA-ECMO had a lower in-hospital/30-day mortality than patients undergoing central cannulation, authors stated that results did not alter after cofounders’ readjustment [53].

6.1.3.1 Basic principles

6.1.3.1.1 Peripheral cannulation

It is the most frequently used access due to less complication rate and it allows sternotomy closure. It is performed via the common femoral artery and vein just below the inguinal ligament and should be above the bifurcations [54]. Arterial cannula should be adequate to supply sufficient flow to meet the patient’s needs, sizes larger than 19F cannulas may be considered only when higher flow is needed and is usually rare; keeping in mind the increased vascular complications, including limb ischemia with larger cannula [55]. If feasible, some opinions prefer to place each cannula in different legs as it is thought to reduce the vascular complications associated if both cannulas are placed in the same limb. Also, some experts prefer to insert the venous cannula into the right femoral vein as it is a more direct path to the IVC and right atrium. Nowadays, the Image-guided cannulation, particularly vascular ultrasound is the standard in percutaneous approach. Fluoroscopy can be useful if available. Vascular ultrasound should be started in the short axis and longitudinal views [56].

6.1.3.1.2 Central cannulation

Although peripheral access is linked to better survival and less complication, in some instances, especially with patients with peripheral vascular disease, the adoption of central cannulation is inevitable. Utilizing the same CPB cannula in the ascending aorta and the right atrium is the most common approach. Other methods have also been described to allow sternotomy closure via tunneling the cannulas through the skin below the sternum to allow the closure, although cardiac compression and kinking of the cannula have been described as complications of this method. Cannulation configuration and strategy can be summarized as follows (Table 2) [49].

	Advantages	Disadvantages
Central (aortic\atrial)	More efficient drainage via antegrade flow Direct access via established surgical site with possibility of sternotomy closure. Avoids harlequin syndrome	Opened chest* More bleeding Re-sternotomy is mandatory to decannulate
Peripheral
Percutaneous femoral artery	Can be done Bedside Avoids surgical incisions so less bleeding Less sepsis Can be switched to VAD implant easily	High limb ischemia complications LV afterload due to retrograde flow LV venting cannot be easily achieved Not suitable for long-lasting support
Open femoral artery	Appropriate cannulation sites via Direct visualization of femoral vessels Less bleeding Avoids sternotomy	limb ischemia complications LV afterload due to retrograde flow LV venting cannot be easily achieved Not suitable for long-lasting support
Pseudo-central
Axillary\Subclavian	Long lasting support Easy patient mobilization Avoidance of Harlequin (North/South) Syndrome	Time-consuming Upper limb vascular complications Lower ECMO flow

Table 2.

Cannulation configuration and strategy summary.

*

Closed chest is accessible; however, cardiac compression is likely with central approach.

6.2 Management VA-ECMO

Management of patients with VA ECMO for postcardiotomy shock is more complicated than for other indications, as surgical patients are usually sicker with many other comorbidities and an already injured heart. Arterial blood gases, lactates, mixed venous oxygen saturation (SvO2), and urine output are all indicators to follow and manage the ECMO patients. Close clinical follow-up using echocardiogram is also crucial to determine the overall cardiac function, right ventricular (RV) function in case RV is not supported, velocity time interval (VTI) are important parameters as well [49].

6.2.1 Sternotomy wound management

Despite the cannulation site, sternotomy wounds should always be closed to minimize bleeding and also to reduce infections. In case of peripheral cannulation, this can be easily achieved as cannulae are already apart from the wound, but central cannulation might add complexity to the closure. Some have proposed tunneling techniques to divert the cannula away from the wound although it has been shown that it might cause cardiac compression by the cannula themselves in case of subxiphoid tunneling, other tunneling techniques with less compression included externalization through the intercostal spaces, tunneling into the neck to the jugular area, or the anastomosis to prosthetic grafts, which is usually utilized in aortic surgery [57, 58].

6.2.2 Leg perfusion

In case of femoral cannulation, many ways have been adopted to reduce ischemic and vascular complications such as adopting the open technique as possible, using a smaller cannula, and using vascular graft instead of direct femoral cannulation, but most importantly using distal perfusion cannula to perfuse the cannulated leg. This cannula is then connected with a side way to the arterial cannula and its flow can be monitored using a sensor to ensure optimal leg perfusion. Moreover, continuous daily pulse monitoring should be ensured [49].

6.2.3 Flow management

Determining how much flow is best to achieve optimal peripheral perfusion with some heart ejection remains unclear. Some have argued that allowing the supported heart to eject is better than full support in terms that it prevents the blood stasis as well as the dilatation [59, 60, 61]; however, as mentioned earlier, PC patients are different as the heart is already damaged so allowing the heart to eject might add extra workload [62].

6.2.4 Left ventricular distention

Although infrequent, LV distention is one of the major issues facing the supported heart while on ECMO regardless of the site of the cannulation as retrograde ECMO flow adds more on the afterload, which can be hazardous for an already dysfunctional ventricle, which is usually the case in PC patients. Another important mechanism, it has been postulated that while on ECMO the aortic valve might exhibit a protracted closure due to the impedance of the forward flow, which causes blood stasis, blood pooling, LV wall tension, and LV workload even in the absence of poor myocardium. For that, several clinical studies have shown that IABP might be beneficial in eliminating the LV distention by restoring AV opening and reducing forward flow impendence [63]. However, in extreme cases of LV dysfunction, IABP might not be enough to alleviate the distention, in such cases more invasive methods should intervene such as direct cannulation of the LV through the apex, surgical or percutaneous cannulation of the pulmonary artery may be considered for indirect LV unloading as well. Trans-aortic devices such as impella and impella RP have also shown great benefit in this setting. Another approach including trans-septal approach surgically or percutaneously has been also used [64]. The true prevalence of LV distention and its clinical impact remains unproven, also the need for LV venting and whether its prophylactic implementation is useful is unknown.

6.2.5 Anticoagulation

The most adopted practice for PC ECMO is to partially reverse with half dose protamine and then wait for 24-48hrs for full heparin administration after excluding major bleeding. As mediastinal collection can be one of the most associated complications after ECMO institution as ECMO itself can exacerbate coagulopathy, management should be directed toward a balance between bleeding management with product transfusion and medication in facing clot formation prevention in the circuit [65, 66, 67]. Unfractionated heparin remains an antithrombotic agent of choice for anticoagulation in case of PC ECMO as per the ELSO guidelines. Although monitoring has not been standardized yet, it is recommended that either ACT targeting a level of 180–200s or aPTT up to 50–80s is accepted [68, 69]. In any case of prolonged use of heparin, the possibility of HITT occurrence is likely, in such case direct thrombin inhibitors (DTI) can be used, such as bivalirudin should be used, as an alternative. However, extra caution should be kept given the very short half-life of bivalirudin so the likelihood of developing clots can be life-threatening [70].

6.2.6 Intensive care monitoring

Systematic clinical examination along with physiological and laboratory monitoring with close adjustment of ECMO setting should be implemented. Monitoring of all peripheral arterial saturation should be done for early detection of harlequin syndrome in case of uneven distribution of saturation. Recognizing early signs of infection and early start of empiric antibiotics is crucial to avoid the burden of septic shock occurrence [49].

Timely detection of brain injury is considered an important aspect to consider while in ICU monitoring, and it has been shown that EEG and near-infrared spectroscopy (NIRS) play an important diagnostic and prognostic role in the timely detection of acute brain injury [71, 72]. Confirming the diagnosis with CT is also encouraged despite the complexity of transportation while on ECMO. Nonetheless, transesophageal echocardiographic (TEE) is an important tool to assess the overall cardiac function, cannula positions, and right ventricular dynamics and to guide the suitability of weaning. In our institute, we do not use the swan-Ganz catheter, but it might be useful in few cases to guide management.

6.3 Weaning from VA-ECMO

The consideration for weaning EMCO exists when absence of specific decompensation factors like supraventricular arrhythmia or severe septic shock could be managed. Recovery of pulsatile arterial waveform for at least 24 h, the patient should be hemodynamically stable, with mean arterial pressure more than 60 mmHg in the absence or reducing doses of inotropes and/or vasopressors [73]. Finally, pulmonary function should be adequate with PaO2/FiO2 more than 200 mmHg [74]. It is unlikely to start weaning trial in the first 72 hours of initiation [75]. Weaning trial starts usually with reducing ECMO blood flow, which eventually causes right ventricular preload increase and LV afterload reduction, therefore myocardial function could be assessed [76]. Patients should have a pulsatile flow with a minimum ECMO flow of 1–1.5 L/min [77]. If mean blood pressure is reduced below 60 mmHg the trial should be abandoned. The echocardiographic criteria favoring successful weaning include LVEF of more than 20–25 %. Patients successfully weaned had aortic velocity time integral above 10 cm, and TDSa of at least 6 cm/s at minimal ECMO flow support [75].

6.4 Complications and early and long-term outcomes

Despite the exponential increase in ECMO use, PC ECMO is still in the beginning although enormous improvement in ECMO cannulation and management; successful weaning from PC ECMO varies greatly among the published series from 30% to 70%, and the survival to discharge is even much lower [78]. In the most recent ELSO registry, survival for discharge for overall ECMO cases for cardiogenic shock is 50 % [79]. So far, no RCTs have been deployed to illustrate the real survival benefit or even the quality of life in the long term. Based on the most recent report from the ELSO registry, there has been a gradual decline in the survival after PC-ECMO, as low as 15% survival in some analyses [80]. Overall, bleeding is the most frequent complication occurring in up to 90% of patients as described in some series. Other anticoagulation-related complications also can happen such as heparin-induced thrombocytopenia, intracranial bleeding, and hemolysis. Other complications include high inflammatory markers manifested as inflammatory response that is like that in systemic inflammatory response syndrome, causing an increased risk of thrombosis, infections, sepsis, and end-organ damage thus worsening patient outcomes, steroids have been used as a prophylactic agent and shown to reduce it; However, it did not affect the overall mortality [81, 82]. The prevalence of infection during ECMO is 10% to 12%, with Staphylococcus aureus, Candida, Enterobacteriaceae, and Pseudomonas aeruginosa being the most common bloodstream infective organisms. ECMO site infections are common as well, so special care for ECMO wounds and early recognition are needed. Regular cultures could be done if an infection is suspected, especially with prolonged ECMO use [83]. Limb ischemia is a major vascular complication associated with ECMO, especially the peripherally cannulated; limbs should be frequently monitored by duplex ultrasound also ECMO flow through the distal perfusion cannula should be maintained [84].

6.4.1 Predicting mortality and quality of life

Predictors for PC ECMO outcome have been studied in many papers, as mentioned earlier scoring systems were also deficient and limited not to authentically predicting outcomes after cardiac surgery. One of the pre-ECMO factors, ECPR was found to have a strong negative predictor of survival in several series [85, 86]. Others have demonstrated that blood lactate level prior to ECMO and up to 48 hours after ECMO initiation is strong predictor value for survival [87]. Early initiation of ECMO has been shown to result in higher survival rates and decrease the dosage of vasoactive drugs by increasing cardiac output and rapidly decreasing arterial lactate levels after cardiovascular surgery [88].

The CESAR trial showed a significant increase in survival without severe disability when ECMO was used instead of conventional ventilation [89].

It is been demonstrated in many series that renal and liver failure, respiratory failure, and the duration of ECMO support are also strong negative predictor factors to affect ECMO outcome [90, 91]. Despite the advances in its use, the ethical and economic implications of ECMO are enormous for both patients and the health system. Psychological distress and memory problems were described in some analyses for post-ECMO survivors. Unfortunately, the long outcome of VA-ECMO survivors remains under investigation. Most studies concentrate on treatment outcomes and survival-to-hospital discharge. The outcomes of 138 patients treated with ECMO for cardiogenic shock are related to acute myocardial infarction. Burrell et al. determined that good long-term survival could be achieved following ECMO, observing 79% survival at 12 months. Survival data are available for only 66% of patients at 24 months [92]. Ørbo et al. identified 30 (41%) of 74 ECMO survivors in Norway and surveyed 23 survivors, with 40% of respondents reporting some degree of restriction in everyday activities and depression in 35% of cases [93]. According to ELSO’s data registry, CS was the most common cardiac indication in adult patients with over 2000 runs and with successful ECMO explanations in 56% of cases and an overall 42% survival-to-discharge in 2016 in participating centers. Although not evidenced by powered data, overall long-term outcomes for survivors can be promising especially with improved indications and guidelines.

7. Conclusions

Complex cardiac surgical procedures in high-risk patients may require extending the medical support to a mechanical one. VA-ECMO could offer additional advantages over CBP to support the circulation during CABG surgery in patients with complex coronary anatomy and unstable hemodynamics, with added hemodynamic and economic value.

Conflict of interest

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this work.