Background

Neurological complications significantly contributed to mortality in patients with acute respiratory distress syndrome (ARDS) supported by venovenous extracorporeal membrane oxygenation (VV ECMO). Early fluctuations in arterial partial pressure of carbon dioxide (PaCO₂) during ECMO initiation may have affected cerebral perfusion and increased the risk of brain injury. This study investigated the association between early changes in PaCO₂ and pH levels and subsequent neurological outcomes in patients with ARDS receiving VV ECMO.

Methods

We conducted a retrospective cohort study using data from adult ARDS patients who underwent VV ECMO between January 2018 and December 2022, sourced from the Chinese Society of Extracorporeal Life Support (CSECLS) Registry. Patients were stratified into clusters based on absolute changes in PaCO₂ and pH using K-means clustering. Logistic regression models and restricted cubic splines were used to evaluate the associations between these clusters and the occurrence of neurological complications, adjusting for potential confounders.

Results

Among 983 patients included, the incidence of neurological complications was 2.95%. Cluster 1, characterized by significant reductions in PaCO₂ (median: -50 mmHg, relative reduction: -58%), exhibited the highest rate of neurological complications (11.94%). Cluster 3, with substantial increases in pH and minimal reductions in PaCO₂, showed a relatively lower rate of neurological complications (3.96%), suggesting that PaCO₂ fluctuations, rather than pH changes, were primarily associated with neurological complications.

Conclusions

Excessive reductions in PaCO₂ during the early initiation of VV ECMO, rather than pH elevation, were associated with an increased risk of neurological complications in ARDS patients. Close monitoring and management of PaCO₂ during ECMO initiation may mitigate this risk.