Understanding the "extracorporeal membrane oxygenation gap" in veno-arterial configuration for adult patients: Timing and causes of death

Clinical decision making for VA ECMO weaning in patients with cardiogenic shock A formative qualitative study

Weaning and liberation from VA ECMO in cardiogenic shock patients comprises a complex process requiring a continuous trade off between multiple clinical parameters. In the absence of dedicated international guidelines, we hypothesized a great heterogeneity in weaning practices among ECMO centers due to a variety in local preferences, logistics, case load and individual professional experience. This qualitative study focused on the appraisal of clinicians' preferences in decision processes towards liberation from VA ECMO after cardiogenic shock while using focus group interviews in 4 large hospitals. The goal was to provide novel and unique insights in daily clinical weaning practices. As expected, we found we a great heterogeneity of weaning strategies among centers and professionals, although participants appeared to find common ground in a clinically straightforward approach to assess the feasibility of ECMO liberation at the bedside. This was shown in a preference for robust, easily accessible parameters such as arterial pulse pressure, stable cardiac index ≥2.1 L/min, VTI LVOT and 'eyeballing' LVEF.

On-Support and Postweaning Mortality in Postcardiotomy Extracorporeal Membrane Oxygenation

BACKGROUND

Postcardiotomy venoarterial extracorporeal membrane oxygenation (VA ECMO) is characterized by discrepancies between weaning and survival-to-discharge rates. This study analyzes the differences between postcardiotomy VA ECMO patients who survived, died on ECMO, or died after ECMO weaning. Causes of death and variables associated with mortality at different time points are investigated.

METHODS

The retrospective, multicenter, observational Postcardiotomy Extracorporeal Life Support Study (PELS) includes adults requiring postcardiotomy VA ECMO between 2000 and 2020. Variables associated with on-ECMO mortality and postweaning mortality were modeled using mixed Cox proportional hazards, including random effects for center and year.

RESULTS

In 2058 patients (men, 59%; median age, 65 years; interquartile range [IQR], 55-72 years), weaning rate was 62.7%, and survival to discharge was 39.6%. Patients who died (n = 1244) included 754 on-ECMO deaths (36.6%; median support time, 79 hours; IQR, 24-192 hours), and 476 postweaning deaths (23.1%; median support time, 146 hours; IQR, 96-235.5 hours). Multiorgan (n = 431 of 1158 [37.2%]) and persistent heart failure (n = 423 of 1158 [36.5%]) were the main causes of death, followed by bleeding (n = 56 of 754 [7.4%]) for on-ECMO mortality and sepsis (n = 61 of 401 [15.4%]) for postweaning mortality. On-ECMO death was associated with emergency surgery, preoperative cardiac arrest, cardiogenic shock, right ventricular failure, cardiopulmonary bypass time, and ECMO implantation timing. Diabetes, postoperative bleeding, cardiac arrest, bowel ischemia, acute kidney injury, and septic shock were associated with postweaning mortality.

CONCLUSIONS

A discrepancy exists between weaning and discharge rate in postcardiotomy ECMO. Deaths occurred during ECMO support in 36.6% of patients, mostly associated with unstable preoperative hemodynamics. Another 23.1% of patients died after weaning in association with severe complications. This underscores the importance of postweaning care for postcardiotomy VA ECMO patients.

Patient-centered weaning from venoarterial extracorporeal membrane oxygenation: "A practice-oriented narrative review of literature"

Venoarterial extracorporeal membrane oxygenation (V-A ECMO) is increasingly used in cardiogenic shock for rapid stabilization and bridging towards recovery, long-term mechanical circulatory support or transplant. Although technological advances have instigated its widespread use, the complex, long-lasting ECMO care creates a significant strain on hospital staff and resources. Therefore, optimal clinical management including timely decisions on ECMO removal and further therapy are pivotal, yet require a well-structured weaning approach. Although dedicated guidelines are lacking, a variety of weaning protocols have distillated echocardiographic and hemodynamic predictors for successful weaning. Nevertheless, a strikingly high mortality up to 70% after initial successful weaning raises concerns about the validity of current weaning strategies. Here, we plead for a patient-tailored approach including a bailout strategy when weaning fails. This should account not only for left- but also right ventricular function and interdependence, as well as the temporal course of cardiac recovery in function of extracorporeal support. Patients with a high risk of weaning failure should be identified early, enabling timely transportation to an advanced heart failure center. This review summarizes predictors of successful weaning and discusses all relevant elements for a structured weaning approach with a central role for patient-specific clinical considerations and echocardiography.

Modifiable Mechanical Ventilation Targets Are Associated With Improved Survival in Ventilated VA-ECLS Patients

BACKGROUND

In acute respiratory distress syndrome (ARDS), lung protective ventilation (LPV) improves patient outcomes by minimizing ventilator-induced lung injury. The value of LPV in ventilated patients with cardiogenic shock (CS) requiring venoarterial extracorporeal life support (VA-ECLS) is not known, but the extracorporeal circuit provides a unique opportunity to modify ventilatory parameters to improve outcomes.

OBJECTIVES

The authors hypothesized that CS patients on VA-ECLS who require mechanical ventilation (MV) may benefit from low intrapulmonary pressure ventilation (LPPV), which has the same end goals as LPV.

METHODS

The authors queried the ELSO (Extracorporeal Life Support Organization) registry for hospital admissions between 2009 and 2019 for CS patients on VA-ECLS and MV. They defined LPPV as peak inspiratory pressure at 24 hours on ECLS of <30 cm H2O. Positive end-expiration pressure and dynamic driving pressure (DDP) at 24 hours were also studied as continuous variables. Their primary outcome was survival to discharge. Multivariable analyses were performed that adjusted for baseline Survival After Venoarterial Extracorporeal Membrane Oxygenation score, chronic lung conditions, and center extracorporeal membrane oxygenation volume.

RESULTS

A total of 2,226 CS patients on VA-ECLS were included: 1,904 received LPPV. The primary outcome was higher in the LPPV group vs the no-LPPV group (47.4% vs 32.6%; P < 0.001). Median peak inspiratory pressure (22 vs 24 cm H2O; P < 0.001) as well as DDP (14.5 vs 16 cm H2O; P < 0.001) were also significantly lower in those surviving to discharge. The adjusted OR for the primary outcome with LPPV was 1.69 (95% CI: 1.21-2.37; P = 0.0021).

CONCLUSIONS

LPPV is associated with improved outcomes in CS patients on VA-ECLS requiring MV.

Variables associated with in-hospital and postdischarge outcomes after postcardiotomy extracorporeal membrane oxygenation: Netherlands Heart Registration Cohort

OBJECTIVES

Extracorporeal membrane oxygenation (ECMO) for postcardiotomy cardiogenic shock has been increasingly used without concomitant mortality reduction. This study aims to investigate determinants of in-hospital and postdischarge mortality in patients requiring postcardiotomy ECMO in the Netherlands.

METHODS

The Netherlands Heart Registration collects nationwide prospective data from cardiac surgery units. Adults receiving intraoperative or postoperative ECMO included in the register from January 2013 to December 2019 were studied. Survival status was established through the national Personal Records Database. Multivariable logistic regression analyses were used to investigate determinants of in-hospital (3 models) and 12-month postdischarge mortality (4 models). Each model was developed to target specific time points during a patient's clinical course.

RESULTS

Overall, 406 patients (67.2% men, median age, 66.0 years [interquartile range, 55.0-72.0 years]) were included. In-hospital mortality was 51.7%, with death occurring in a median of 5 days (interquartile range, 2-14 days) after surgery. Hospital survivors (n = 196) experienced considerable rates of pulmonary infections, respiratory failure, arrhythmias, and deep sternal wound infections during a hospitalization of median 29 days (interquartile range, 17-51 days). Older age (odds ratio [OR], 1.02; 95% CI, 1.0-1.04) and preoperative higher body mass index (OR, 1.08; 95% CI, 1.02-1.14) were associated with in-hospital death. Within 12 months after discharge, 35.1% of hospital survivors (n = 63) died. Postoperative renal failure (OR, 2.3; 95% CI, 1.6-4.9), respiratory failure (OR, 3.6; 95% CI, 1.3-9.9), and re-thoracotomy (OR, 2.9; 95% CI, 1.3-6.5) were associated with 12-month postdischarge mortality.

CONCLUSIONS

In-hospital and postdischarge mortality after postcardiotomy ECMO in adults remains high in the Netherlands. ECMO support in patients with higher age and body mass index, which drive associations with higher in-hospital mortality, should be carefully considered. Further observations suggest that prevention of re-thoracotomies, renal failure, and respiratory failure are targets that may improve postdischarge outcomes.

ECMO Retrieval Program: What Have We Learned So Far

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly used for patients with cardiogenic shock or cardiac arrest. However, survival rates remain low. It is unclear to what extent ECMO patients benefit from the ECMO team learning curve. Therefore, we aimed to analyze our mobile ECMO program patients from the past seven years to evaluate if a learning curve benefits patients’ outcomes. We analyzed 111 patients from our databank who were supported with a VA-ECMO and brought to our hospital from January 2015 to December 2021. Patients were divided into two groups: survival (n = 70) and non-survival (n = 41). As expected, complications after ECMO implantation were more severe in the non-survivor group. The incidence of thromboembolic events (p = 0.002), hepatic failure (p < 0.001), renal failure (p = 0.002), dialysis (p = 0.002) and systemic inflammatory response syndrome (SIRS, p = 0.044) occurred significantly more often compared with the survivor group. We were able to show that despite our extensive experience in terms of ECMO retrieval program the high mortality and morbidity rates stay fairly the same over the years. This displays that we have to focus even more on patient selection and ECMO indication.

The ABCDE approach to difficult weaning from venoarterial extracorporeal membrane oxygenation

Venoarterial extracorporeal membrane oxygenation (VA ECMO) has been increasingly applied in patients with cardiogenic shock in recent years. Nevertheless, many patients cannot be successfully weaned from VA ECMO support and 1-year mortality remains high. A systematic approach could help to optimize clinical management in favor of weaning by identifying important factors in individual patients. Here, we provide an overview of pivotal factors that potentially prevent successful weaning of VA ECMO. We present this through a rigorous approach following the relatable acronym ABCDE, in order to facilitate widespread use in daily practice.

A Murine Model of Veno-Arterial Extracorporeal Membrane Oxygenation

The mechanisms driving the pathologic state created by extracorporeal membrane oxygenation (ECMO) remain poorly defined. We developed the first complete blood-primed murine model of veno-arterial ECMO capable of maintaining oxygenation and perfusion, allowing molecular studies that are unavailable in larger animal models. Fifteen C57BL/6 mice underwent ECMO by cannulating the left common carotid artery and the right external jugular vein. The mean arterial pressure was measured through cannulation of the femoral artery. The blood-primed circuit functioned well. Hemodynamic parameters remained stable and blood gas analyses showed adequate oxygenation of the animals during ECMO over a 1-hour timeframe. A significant increase in plasma-free hemoglobin was observed following ECMO, likely secondary to hemolysis within the miniaturized circuit components. Paralleling clinical data, ECMO resulted in a significant increase in plasma levels of multiple proinflammatory cytokines as well as evidence of early signs of kidney and liver dysfunction. These results demonstrate that this novel, miniature blood-primed ECMO circuit represents a functional murine model of ECMO that will provide unique opportunities for further studies to expand our knowledge of ECMO-related pathologies using the wealth of available genetic, pharmacological, and biochemical murine reagents not available for other species.