Late awakening, prognostic factors and long-term outcome in out-of-hospital cardiac arrest – results of the prospective Norwegian Cardio-Respiratory Arrest Study (NORCAST)

Outcome prediction after out-of-hospital cardiac arrest (OHCA) may lead to withdrawal of life-sustaining therapy if the prognosis is perceived negative. Single use of uncertain prognostic tools may lead to self-fulfilling prophecies and death. We evaluated prognostic tests, blinded to clinicians and without calls for hasty outcome prediction, in a prospective study. Comatose, sedated TTM 33-treated OHCA patients of all causes were included. Clinical-neurological/-neurophysiological/-biochemical predictors were registered. Patients were dichotomized into good/poor outcome using cerebral performance category (CPC) six months and > four years post-arrest. Prognostic tools were evaluated using false positive rates (FPR). We included 259 patients; 49 % and 42 % had good outcome (CPC 1–2) after median six months and 5.1 years. Unwitnessed arrest, non-shockable rhythms, and no-bystander-CPR predicted poor outcome with FPR (CI) 0.05 (0.02–0.10), 0.13 (0.08–0.21), and 0.13 (0.07–0.20), respectively. Time to awakening was median 6 (0–25) days in good outcome patients. Among patients alive with sedation withdrawal >72 h, 49 % were unconscious, of whom 32 % still obtained good outcome. Only absence of pupillary light reflexes (PLR) -and N20-responses in somato-sensory evoked potentials (SSEP), as well as increased neuron-specific enolase (NSE) later than 24 h to >80 μg/L, had FPR 0. Malignant EEG (burst suppression/epileptic activity/flat) differentiated poor/good outcome with FPR 0.05 (0.01–0.15). Time to awakening was over six days in good outcome patients. Most clinical parameters had too high FPRs for prognostication, except for absent PLR and SSEP-responses >72 h after sedation withdrawal, and increased NSE later than 24 h to >80 μg/L.