The State of the Art in Extracorporeal Membrane Oxygenation

Predictive models in extracorporeal membrane oxygenation (ECMO): a systematic review

PURPOSE

Extracorporeal membrane oxygenation (ECMO) has been increasingly used in the last years to provide hemodynamic and respiratory support in critically ill patients. In this scenario, prognostic scores remain essential to choose which patients should initiate ECMO. This systematic review aims to assess the current landscape and inform subsequent efforts in the development of risk prediction tools for ECMO.

METHODS

PubMed, CINAHL, Embase, MEDLINE and Scopus were consulted. Articles between Jan 2011 and Feb 2022, including adults undergoing ECMO reporting a newly developed and validated predictive model for mortality, were included. Studies based on animal models, systematic reviews, case reports and conference abstracts were excluded. Data extraction aimed to capture study characteristics, risk model characteristics and model performance. The risk of bias was evaluated through the prediction model risk-of-bias assessment tool (PROBAST). The protocol has been registered in Open Science Framework ( https://osf.io/fevw5 ).

RESULTS

Twenty-six prognostic scores for in-hospital mortality were identified, with a study size ranging from 60 to 4557 patients. The most common candidate variables were age, lactate concentration, creatinine concentration, bilirubin concentration and days in mechanical ventilation prior to ECMO. Five out of 16 venous-arterial (VA)-ECMO scores and 3 out of 9 veno-venous (VV)-ECMO scores had been validated externally. Additionally, one score was developed for both VA and VV populations. No score was judged at low risk of bias.

CONCLUSION

Most models have not been validated externally and apply after ECMO initiation; thus, some uncertainty whether ECMO should be initiated still remains. It has yet to be determined whether and to what extent a new methodological perspective may enhance the performance of predictive models for ECMO, with the ultimate goal to implement a model that positively influences patient outcomes.

[Ethics of resuscitation and end of life decisions]

These European Resuscitation Council Ethics guidelines provide evidence-based recommendations for the ethical, routine practice of resuscitation and end-of-life care of adults and children. The guideline primarily focus on major ethical practice interventions (i.e. advance directives, advance care planning, and shared decision making), decision making regarding resuscitation, education, and research. These areas are tightly related to the application of the principles of bioethics in the practice of resuscitation and end-of-life care.

European Resuscitation Council Guidelines 2021: Ethics of resuscitation and end of life decisions

These European Resuscitation Council Ethics guidelines provide evidence-based recommendations for the ethical, routine practice of resuscitation and end-of-life care of adults and children. The guideline primarily focus on major ethical practice interventions (i.e. advance directives, advance care planning, and shared decision making), decision making regarding resuscitation, education, and research. These areas are tightly related to the application of the principles of bioethics in the practice of resuscitation and end-of-life care.

Impact of interhospital transfer on clinical outcomes and costs of extracorporeal life support

BACKGROUND

The impact of interhospital transfers for extracorporeal life support have not been studied in large datasets. The present study sought to determine the impact of such patient transfers on survival, complications, and hospitalization costs.

METHODS

The 2010 to 2016 database of the National Inpatient Sample was used to identify all adults who underwent extracorporeal life support. Patients were categorized based on whether or not they were transferred to another facility. Trend analysis and multivariable models were used to characterize the impact of inter hospital transfer on in-hospital mortality, complications, duration of stay, and costs.

RESULTS

Of an estimated 29,298 extracorporeal life support hospitalizations during the study period, 36.8% were transferred from an outside facility. Extracorporeal life support hospitalizations experienced a 7-fold increase with no difference in mortality between transferred and not transferred cohorts in 2016 (4.79% vs 4.79%, P = .97). Mortality rates were less for patients transferred to high volume centers compared to low volume hospitals (48.7% vs 51.6%, P < .001). Transfer to a low volume hospital for cardiogenic shock was associated with greater odds of mortality (adjusted odds Rratio: 2.25, confidence interval 1.01-5.03).

CONCLUSION

Utilization of extracorporeal life support in both transferred and not transferred patients has statistically significantly increased with a decrement in mortality for those transferred. Survival in the transferred cohort is strongly associated with extracorporeal life support procedure volume of the center and this must be taken into account when considering extracorporeal life support transfer.

Clinical implications of the initial SAPS II in veno-arterial extracorporeal oxygenation

Background

Prediction of survival and weaning probability in VA ECMO (veno-arterial extracorporeal membrane oxygenation) patients could be of great benefit for real-time decision making on VA ECMO initiation in critical ill patients. We investigated whether the SAPS II score would be a real-time determinant for VA ECMO initiation and could be a predictor of survival and weaning probability in patients on VA ECMO.

Methods

Between January 1, 2010 and December 31, 2014, VA ECMO was carried out on 135 adult patients suffering from primary cardiogenic shock. To avoid selection bias, we excluded respiratory failure patients treated with VV or other types of ECMO. Successful VA ECMO weaning was defined as weaning, followed by stable survival for more than 48 hours. Survival after VA ECMO was defined as successful weaning and treatment of the underlying medical condition, followed by discharge without any further events.

Results

A total of 135 patients consisted of 41 women and 94 men, with a mean age of 59.4±16.5 years. Fifty-three patients had successful weaning, and 35 survived and were discharged uneventfully. Compared to the non-survivors, the survivors showed a lower SAPS II (67.77±20.79 vs. 90.29±13.31, P<0.001), a lower SOFA score (12.63±3.49 vs. 15.33±2.28, P<0.001), a lower predicted death rate (71.12±30.51 vs. 94.00±9.36, P<0.001), a higher initial ipH (7.14±0.22 vs. 6.98±0.15, P<0.001), and a lower initial lactate level (7.09±4.93 vs. 12.11±4.84, P<0.001). The average duration of hospital stay in the successful vs. failed weaning groups was 33.43±27.41 vs. 6.35±8.71 days, and the average duration of ICU stay in the successful vs. failed weaning groups was 20.60±16.88 vs. 5.39±5.95 days. By multivariate logistic regression analysis of initial parameters for VA ECMO assistance, the simplified acute physiology score II (SAPS II) (OR =1.1019, P=0.0389), ipH (OR =0.0010, P=0.0452), and hospital stay (OR =0.8140, P=0.001) had an association with in-hospital mortality on VA ECMO. The initial SAPS II score [area under the curve (AUC) =0.821] demonstrated significantly superior prediction of VA ECMO mortality than age (AUC =0.697), SOFA score (AUC =0.701), ipH (AUC =0.551), and the other parameters. By multivariable CoX regression analysis of survival, only the SAPS II score proved to have statistical significance (hazard ratio, 1.0423; 95% CI, 1.0083-1.0775; P=0.01).

Conclusions

Although the precise predictive scoring systems for VA ECMO still remains one of the most difficult challenges to ECMO physicians, the SAPS II score could provide valuable information on prognosis to patient himself, family members and caretakers, and might help physicians increase the survival rate and might avoid a waste of healthcare resources.

Accidental hypothermia

Accidental hypothermia causes profound changes to the body's physiology. After an initial burst of agitation (e.g., 36-37°C), vital functions will slow down with further cooling, until they vanish (e.g. <20-25°C). Thus, a deeply hypothermic person may appear dead, but may still be able to be resuscitated if treated correctly. The hospital use of minimally invasive rewarming for nonarrested, otherwise healthy patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionized the management of hypothermic cardiac arrest, with survival rates approaching 100%. Hypothermic patients with risk factors for imminent cardiac arrest (i.e., temperature <28°C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS center. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanic CPR can be helpful. Intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern postresuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimize prehospital triage, transport, and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and postresuscitation care.

Advanced Age as a Predictor of Survival and Weaning in Venoarterial Extracorporeal Oxygenation: A Retrospective Observational Study

Background. In most reports on ECMO treatment, advanced age is classified as a contraindication to VA ECMO. We attempted to investigate whether advanced age would be a main risk factor deciding VA ECMO application and performing VA ECMO support. We determined whether advanced age should be regarded as an absolute or relative contraindication to VA ECMO and could affect weaning and survival rates of VA ECMO patients. Methods. VA ECMO was performed on 135 adult patients with primary cardiogenic shock between January 2010 and December 2014. Successful weaning was defined as weaning from ECMO followed by survival for more than 48 hours. Results. Among the 135 patients, 35 survived and were discharged uneventfully, and the remaining 100 did not survive. There were significant differences in survival between age groups, and older age showed a lower survival rate with statistical significance (P = .01). By multivariate logistic regression analysis, age was not significantly associated with in-hospital mortality (P = .83) and was not significantly associated with VA ECMO weaning (P = .11). Conclusions. Advanced age is an undeniable risk factor for VA ECMO; however, patients of advanced age should not be excluded from the chance of recovery after VA ECMO treatment.

Accidental hypothermia-an update : The content of this review is endorsed by the International Commission for Mountain Emergency Medicine (ICAR MEDCOM)

BACKGROUND

This paper provides an up-to-date review of the management and outcome of accidental hypothermia patients with and without cardiac arrest.

METHODS

The authors reviewed the relevant literature in their specialist field. Summaries were merged, discussed and approved to produce this narrative review.

RESULTS

The hospital use of minimally-invasive rewarming for non-arrested, otherwise healthy, patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionised the management of hypothermic cardiac arrest, with survival rates approaching 100 % in some cases. Hypothermic patients with risk factors for imminent cardiac arrest (temperature <28 °C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS-centre. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanical CPR can be helpful. Delayed or intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern post-resuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimise pre-hospital triage, transport and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and post-resuscitation care.

CONCLUSIONS

Based on new evidence, additional clinical experience and clearer management guidelines and documentation, the treatment of accidental hypothermia has been refined. ECLS has substantially improved survival and is the treatment of choice in the patient with unstable circulation or cardiac arrest.

Predictors of survival in adults undergoing extracorporeal membrane oxygenation with severe infections

BACKGROUND

To identify novel factors associated with the survival of septic adults receiving extracorporeal membrane oxygenation (ECMO) to improve patient selection and outcomes.

METHODS

Cases were identified from our ECMO registry from 2001 to 2011 if they were ≥16 years and received ECMO for life-threatening sepsis.

RESULTS

A total of 151 adults with a median (25th-75th percentile) age of 51 (37-63) years were analyzed. Pneumonia (50%), myocarditis (20%), and primary bloodstream infections (15%) were the main types of infection, caused by predominantly nonfermentative Gram-negative bacteria (NFGNB) (26%), Enterobacteriaceae (24%), and Gram-positive cocci (21%). The in-hospital mortality of patients with NFGNB, enteric, and Gram-positive bacterial pneumonias were 100%, 68%, and 14%, respectively. Using the Cox-proportional hazards model, we found that age >75 years (hazard ratio [HR], 1.98, 95% confidence interval [95% CI], 1.30-3.02), pre-ECMO dialysis (HR, 3.20, 95% CI, 1.34-7.63), longer door-to-ECMO intervals (HR, 1.01, 95% CI, 1.00-1.02), venoarterial mode (HR, 2.58, 95% CI, 1.55-4.21), and fungal (HR, 2.83, 95% CI, 1.36-5.88) and NFGNB sepsis (HR, 2.48, 95% CI, 1.44-4.27) were associated with mortality. Gram-positive sepsis (HR, 0.20, 95% CI, 0.08-0.57), myocarditis (HR, 0.12, 95% CI, 0.06-0.27), pneumonia (HR, 0.54, 95% CI, 0.30-0.90), and effective empirical antimicrobial therapy were predictive of survival (HR, 0.57, 95% CI, 0.37-0.89); all P < .05. Excluding the 67 heavily premorbid patients, we found that 54% survived ECMO and 42% survived to discharge, with significantly more survivors with door-to-ECMO times of ≤96 hours than >96 hours (59% vs 15%, P < .0001).

CONCLUSIONS

Better outcomes were associated with door-to ECMO times of 96 hours or less, for Gram-positive rather than Gram-negative sepsis, and for pneumonia rather than primary bloodstream infections.