Association between base excess level at hospital arrival and neurological outcomes in adult out-of-hospital cardiac arrest: A multicentre cohort study

Aim: We aimed to assess the association between base excess (BE) levels and neurological outcomes in patients with out-of-hospital cardiac arrest (OHCA), accounting for the time from cardiac arrest onset to blood sampling. Methods: This multicentre study was conducted in Osaka, Japan, and enrolled consecutive patients with OHCA who were transported to 16 medical centres between 2012 and 2021. Patients aged ≥ 18 years with witnessed OHCA and available BE measurements upon hospital arrival were examined. Patients were stratified into Q1 (BE ≤ -21.1 mmol/L), Q2 (-21.1 < BE ≤ -15.7 mmol/L), Q3 (-15.7 < BE ≤ -10.4 mmol/L) and Q4 (BE > -10.4 mmol/L) groups based on BE levels. The primary outcome was 1-month survival with a favourable neurological outcome (Cerebral Performance Category scale score: 1 or 2). Results: Among the 23,854 patients with OHCA, only 6066 were included in the final analysis. Approximately 3.2 %, 4.7 %, 9.9 % and 23.7 % of patients in the Q1, Q2, Q3 and Q4 groups, respectively, achieved favourable neurological outcomes at 1 month. Compared with Q4, the adjusted odds ratio for a favourable neurological outcome in Q1 was 0.13. Subgroup analysis revealed a significant interaction between prehospital return of spontaneous circulation (ROSC) and neurological outcomes; neurological outcomes worsened as BE decreased in patients with ROSC but not in those without ROSC. Conclusion: Lower BE levels upon hospital arrival are associated with poorer neurological outcomes and may serve as prognostic indicators in patients with OHCA who achieved prehospital ROSC.