Relationship Between Cerebral Oximetry and Outcomes in Post-Cardiac Arrest Patients: A Systematic Review and Meta-Analysis

OBJECTIVES: Poor neurologic outcomes are common in post-cardiac arrest patients. Reduced cerebral perfusion and inadequate oxygen delivery may persist even following return of spontaneous circulation (ROSC), which may exacerbate hypoxic-ischemic brain injury. Cerebral oximetry is a noninvasive method of assessing brain oxygenation. We performed a systematic review to assess whether post-arrest regional oxygen saturation (rSO 2 ) during the initial 48 hours post-ROSC is associated with death or severe disability. DATA SOURCES: MEDLINE, Embase, Cochrane Central Register of Controlled Trials, World Health Organization Global Health Library. STUDY SELECTION: We included studies reporting outcomes in adult post-arrest patients who underwent continuous cerebral oximetry immediately following ROSC for at least 6 hours. DATA EXTRACTION: rSO 2 over the 48 hours post-arrest was compared between patients with favorable vs. unfavorable outcomes, as dichotomized within individual studies. DATA SYNTHESIS: Random effects models were used to pool studies. 10,876 records were identified, of which 16, with a total of 864 patients, met inclusion criteria. Twelve studies provided neurologic outcomes, and four reported only survival. rSO 2 was similar at baseline, but higher at 24 hours (3.3%, 0.9–5.7%, p = 0.009) and 48 hours (2.1%, 0.3–3.9%, p = 0.02) post-arrest among patients with favorable outcomes. There was significant heterogeneity between studies. rSO 2 averaged over time was significantly higher between 24 and 48 hours in patients with favorable outcomes (5.2%, 1.6–8.8%; p = 0.005). rSO 2 was lower in studies where cardiac arrest duration was relatively longer (modeled difference –7.1%, –3.1% to –11.1%, p = 0.0005). Although very low rSO 2 had high specificity for unfavorable outcome in two studies, no consistent threshold could be identified for use in neuroprognostication. CONCLUSIONS: Current evidence suggests that rSO 2 during the initial 48 hours following ROSC is slightly lower in post-cardiac arrest patients with unfavorable neurologic outcomes (low certainty of evidence). Prospective research is needed to determine whether treatment of reduced rSO 2 can improve outcomes.