Background: Despite aggressive resuscitation, out-of-hospital cardiac arrest (OHCA) survival is approximately 10-20% with 90% of survivors suffering severe neurologic injury and possible brain death. Few early prognostic indicators are available to guide decision making. Consequently, care may be provided despite medical futility, or care may be inappropriately withdrawn. In the hours to days after ischemic injury of OHCA, brain-specific proteins are released into the bloodstream. We hypothesize that higher protein biomarker levels will predict reduced rate of survival to discharge and higher degree of neurologic injury in survivors.
Methods: This is a blinded, single center, prospective observational study of 13 patients ≥18 years old with return of spontaneous circulation (ROSC) after nontraumatic OHCA. Blood was collected within 59 minutes of ROSC, every 6 hours for 24 hours, and every 24 hours until day 6, hospital discharge, or death. Five neuroinjury biomarkers were analyzed: NFL, GFAP, UCHL1, Tau, and S100B. Good vs poor neurologic outcome was quantified as Cerebral Performance Category (CPC 1 or 2 vs CPC 3, 4, 5, or death, respectively) at time of discharge and at 6 months post-OHCA. Serum biomarker level was quantified by a researcher blinded to patient outcome using quantitative enzyme linked immunosorbent assay (ELISA) and digital immunoassay. Wilcoxon rank sum test was used to assess differences in biomarker level between good vs poor outcome groups.
Results: Subjects had average age of 61 years, 62% were male. Initial rhythm was 38% ventricular fibrillation or ventricular tachycardia, 31% asystole, and 31% pulseless electrical activity. Survival to discharge with good outcome at 6 months occurred in 39% of subjects. CPC category of good vs poor outcome was unchanged between discharge and 6 month follow up for all subjects. Subjects with poor outcomes had significantly (p < 0.05) higher levels of all biomarkers than did subjects with good outcomes at H18, H24, H48. Tau and S100B were also significantly (p < 0.05) higher in poor outcome than good outcome at H6.
Conclusion: Pilot results support our hypothesis that patients with higher bloodborne neural biomarker level following OHCA predicts poorer neurologic outcome. Future studies will optimize positive predictive value (PPV) and negative predictive value (NPV) for clinical decision-making.