Initial Arterial pCO(2) and Its Course in the First Hours of Extracorporeal Cardiopulmonary Resuscitation Show No Association with Recovery of Consciousness in Humans: A Single-Centre Retrospective Study

Background: Cardiac arrest is a severe condition with high mortality rates, especially in the case of prolonged low-flow durations resulting in severe ischaemia and reperfusion injury. Changes in partial carbon dioxide concentration (pCO(2)) may aggravate this injury. Extracorporeal cardiopulmonary resuscitation (ECPR) shortens the low-flow duration and enables close regulation of pCO(2). We examined whether pCO(2) is associated with recovery of consciousness. Methods: We retrospectively analysed ECPR patients ≥ 16 years old treated between 2010 and 2019. We evaluated initial arterial pCO(2) and the course of pCO(2) ≤ 6 h after initiation of ECPR. The primary outcome was the rate of recovery of consciousness, defined as Glasgow coma scale motor score of six. Results: Out of 99 ECPR patients, 84 patients were eligible for this study. The mean age was 47 years, 63% were male, 93% had a witnessed arrest, 45% had an out-of-hospital cardiac arrest, and 38% had a recovery of consciousness. Neither initial pCO(2) (Odds Ratio (OR) 0.93, 95% confidence interval 95% (CI) 0.78–1.08) nor maximum decrease of pCO(2) (OR 1.03, 95% CI 0.95–1.13) was associated with the recovery of consciousness. Conclusion: Initial arterial pCO(2) and the course of pCO(2) in the first six hours after initiation of ECPR were not associated with the recovery of consciousness.