Association of Pre-Extracorporeal Membrane Oxygenation PaCO2 with Mortality and Neurological Complications in Adult Extracorporeal Membrane Oxygenation Patients: A Retrospective Cohort Study

Background: Carbon dioxide plays a critical role in regulating cerebral blood flow and autoregulation.Patients requiring extracorporeal membrane oxygenation (ECMO) frequently present with hypercapnia due to refractory gas exchange failure or ventilatory limitations.While post-cannulation changes in PaCO 2 have been associated with neurological injury, the independent impact of pre-ECMO PaCO 2 on outcomes remains unclear.Objectives: To determine whether pre-ECMO PaCO 2 levels are associated with in-hospital mortality and neurological complications in adult ECMO patients. Materials and methods:We retrospectively analyzed data from 291 adult patients (≥18 years) supported with ECMO by an outreach ECMO team between 2010 and 2025.The worst (highest) arterial PaCO 2 value within the 6 hours before ECMO initiation was categorized into three groups (<45, 45-60, and >60 mm Hg).Outcomes included survival to hospital discharge and neurological complications (brain death or intracranial bleeding).Statistical analyses used Chi-square and Fisher's exact tests, with significance defined as p < 0.05.Results: Overall mortality was 58.76% (171/291).Although mortality was highest among patients with PaCO 2 >60 mm Hg (63.51%),PaCO 2 category was not significantly associated with mortality (Chi-square test, p = 0.244).Neurological complications occurred in 9.96% (29/291) and were not significantly associated with PaCO 2 category (Fisher's exact test, p = 0.592).Pre-ECMO pH categories showed a trend toward association with mortality (Chi-square test, p = 0.082).Conclusion: In this cohort, pre-ECMO PaCO 2 categories were not significantly associated with mortality or neurological complications.A trend toward outcome discrimination by pre-ECMO pH suggests that broader acid-base profiling may be more informative than PaCO 2 alone and warrants prospective multicenter evaluation.