Mild hypothermia and neurologic outcomes in patients undergoing venoarterial extracorporeal membrane oxygenation

Background: Patients with venoarterial extracorporeal membrane oxygenation (VA-ECMO) are at risk of cerebral reperfusion injury after prolonged hypoperfusion and immediate restoration of systemic blood flow. We aimed to examine the impact of mild hypothermia during the first 24 h post-ECMO on neurological outcomes in VA-ECMO patients. Methods: This was a retrospective study of adult VA-ECMO patients from a tertiary care center. Mild hypothermia was defined as 32–36°C during the first 24 h post-ECMO. The primary outcome was a good neurological function at discharge measured by a modified Rankin Scale ≤3. Multivariable logistic regression analysis was performed for primary outcome adjusting for pre-specified covariates. Results: Overall, 128 consecutive patients with VA-ECMO support (median age: 60 years and 63% males) were included. Within the first 24 h of VA-ECMO cannulation, we found a median of 71 readings per patient (interquartile range 45–88). Eighty-eight patients (68.8%) experienced mild hypothermia within the first 24 h while 18 of those 88 patients (14.2%) had a mean temperature <36°C. ECMO indications included post-cardiotomy shock (39.8%), cardiac arrest (29.7%), and cardiogenic shock (26.6%). Duration of mild hypothermia, but not mean temperature, was independently associated with increased odds of good neurological outcome at discharge (odds ratio [OR] = 1.16, 95% confidence interval [CI] = 1.04-1.31, p =.01) after adjusting for age, the severity of illness, post-ECMO systemic hemorrhage, post-cardiotomy shock, acute brain injury, and mean 24-h PaO₂. Neither duration of mild hypothermia (OR = 0.93, CI = 0.84–1.03, p =.17) nor mean temperature (OR = 0.78, CI = 0.29–2.08, p =.62) was significantly associated with mortality. Similarly, duration of mild hypothermia (p =.47) and mean 24-h temperature (p =.76) were not significantly associated with the frequency of systemic hemorrhages. Conclusions: In this single-center study, a longer duration of mild hypothermia during the first 24 h of ECMO support was significantly associated with improved neurological outcomes. Mild hypothermia was not associated with an increased risk of systemic hemorrhage or improved survival.