Background: Early prediction of outcome after out of hospital cardiac arrest (OHCA) is difficult. Previous work indicated that the combination of lactate and the need for vasopressors may stratify patients and predict outcome. We hypothesized that lactate and need for vasopressor support in the immediate post-arrest period would predict outcome, and addition of a biomarker to reflect mitochondrial injury would enhance performance of the tool.
Methods: To validate previous retrospective findings, we conducted a prospective observational study of all OHCA (age >18, non-traumatic) patients presenting to the Emergency Department of an academic medical center June 2007 to December 2015 with return of spontaneous circulation (ROSC). We conducted univariate and multivariate logistic regression.
Results: Patients were divided into groups based on two variables: 1) vasopressor status (receipt of vasopressors vs. no); and 2) initial blood lactate (categories: lactate <5 mmol/L, 5 to 10, >10). 352 OHCA patients with ROSC were evaluated; 260 had a lactate measured within 3 hours of ROSC and were included in the analysis. Median age of the cohort was 65 (IQR: 53-78); 73% underwent targeted temperature management. The overall in-hospital mortality for the cohort was 60%. Patients on vasopressors had significantly higher mortality compared to patients who did not receive vasopressors (72% vs 40%; p<0.001). A stepwise increase in mortality is associated with increasing lactate (43% lactate <5, 65% 5 to 10, and 84% >10; p<0.001). Multivariable models with lactate group and vasopressor use as predictors demonstrated excellent discrimination (AUC 0.73 [95 CI: 0.67-0.79]; when adjusted for additional covariates: AUC 0.81 [95 CI: 0.75-0.86]. 37 patients had cytochrome c levels available for inclusion. In these 37 patients, comparing the models with and without cytochrome c, there was no significant difference (AUC 0.89 [95 CI: 0.77-1.00] vs AUC 0.86 [95 CI: 0.74-0.98], respectively; p=0.36).
Conclusion: In this validation of previous findings, the combination of lactate and vasopressors in the immediate post-arrest period is predictive of mortality. Cytochrome c offered minimal additional predictive power but may have been limited by the small number of subjects with measured cytochrome clevels relative to the entire cohort. Multicenter validation of this tool is warranted.