Abstract Su904: The association between base excess on arrival at the hospital and neurological outcome of adult out-hospital cardiac arrest: observational study

Background: The relationship between base-excess (BE) values, which take into account the time interval from cardiac arrest to blood test, and neurological outcome after out-of-hospital cardiac arrest (OHCA) is not well understood. The purpose of this study was to evaluate the association between BE on arrival at the hospital and neurological outcomes in OHCA patients. Methods: The CRITICAL study, a prospective, multicenter observational study in Osaka, Japan, registered consecutive OHCA patients who were transported to 16 participating critical care centers from 2012 to 2021. We included adult patients aged 18 years with witnessed OHCA whose BE values on hospital arrival was available, and divided patients into quartiles based on BE values of initial blood test on arrival at the hospital: 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). The primary outcome was one-month survival with favorable neurological outcome, defined as cerebral performance category scale 1 or 2. Results: A total of 23,854 patients were registered, and 6,066 of them were eligible for analyses. Neurologically favorable outcome was the lowest in the Q1 group (3.2% [49/1,528]), followed by the Q2 (4.7% [70/1,493]), Q3 (9.8% [148/1,515]), and Q4 (23.5% [359/1,530]) group. In the multivariable logistic regression analysis, the adjusted odds ratio of Q1 compared with Q4 for one-month favorable neurological outcome was 0.13 (95% CI 0.090–0.18). The proportion of one-month favorable neurological outcome decreased progressively across decreasing quartiles (p for trend < 0.001). In subgroup analysis, there was an interaction between presence of return of spontaneous circulation (ROSC) before blood test and neurological outcome (p for interaction < 0.001). The neurological outcome worsened as the BE values decreased among those who achieved ROSC before the blood test (p for trend < 0.001), but not in those without ROSC (p for trend = 0.078). There was not a significant interaction between BE values without ROSC before blood test and time from witness to blood test (p for interaction = 0.501). Conclusions: We demonstrated that lower BE values at hospital arrival were associated with worse neurological outcome. The BE values may be one of the effective prognostic indications for neurological outcome, especially in OHCA patients with ROSC before hospital arrival.