Estimated cerebral oxyhemoglobin as a useful indicator of neuroprotection in patients with post-cardiac arrest syndrome: A prospective, multicenter observational study

Introduction: Little is known about oxyhemoglobin (oxy-Hb) levels in the cerebral tissue during the development of anoxic and ischemic brain injury. We hypothesized that the estimated cerebral oxy-Hb level, a product of Hb and regional cerebral oxygen saturation (rSO₂), determined at hospital arrival may reflect the level of neuroprotection in patients with post-cardiac arrest syndrome (PCAS). Methods: The Japan Prediction of neurological Outcomes in patients with Post cardiac arrest (J-POP) registry is a prospective, multicenter, cohort study to test whether rSO₂ predicts neurologic outcomes after out-of-hospital cardiac arrest (OHCA). This study assessed a subgroup of consecutive patients who fulfilled the J-POP registry criteria and successfully achieved return of spontaneous circulation (ROSC) from OHCA. The primary outcome measure was the neurologic status at 90 days. Results: We analyzed data from 495 consecutive comatose survivors who were successfully resuscitated from OHCA, including 119 comatose patients with prehospital return of spontaneous circulation (ROSC; 24.0%) and 376 cardiac arrests at hospital arrival. In total, 75 patients (15.1%) presented with good neurologic outcomes. Univariate analysis revealed that the cerebral oxy-Hb levels were significantly higher in patients with good outcomes. Multivariate logistic regression using the backward-elimination method confirmed that the oxy-Hb level was a significant predictor of good neurologic outcomes (adjusted odds ratio, 1.27; 95% confidence interval (CI), 1.11 to 1.46). Analysis of the area under the receiver operating characteristic curve (AUC) revealed that an oxy-Hb cut-off of 5.5 provided optimal sensitivity and specificity for predicting good neurologic outcomes (AUC, 0.87; 95% CI, 0.83 to 0.91; sensitivity, 77.3%; specificity, 85.6%). The oxy-Hb level appeared to be an excellent prognostic indicator with significant advantages over rSO₂ and base excess, according to AUC analysis. The significant trend for good neurologic outcomes was consistent, even in the subgroup of patients who achieved return of spontaneous circulation on hospital arrival (1^st quartile, 0; 2^nd quartile, 16.7%; 3^rd quartile, 29.4%; 4^th quartile, 53.3%; P < 0.05). Conclusions: The cerebral oxy-Hb level may predict neurologic outcomes and is a simple and excellent indicator of neuroprotection in patients with PCAS. Trial registration: UMIN Clinical Trials Registry UMIN000005065. Registered 1 April 2011.