Loss of Consciousness at Onset of Subarachnoid Hemorrhage as an Important Marker of Early Brain Injury.

IMPORTANCE Loss of consciousness (LOC) is a common presenting symptom of subarachnoid hemorrhage (SAH) that is presumed to result from transient intracranial circulatory arrest. OBJECTIVE To clarify the association between LOC at onset of SAH, complications while in the hospital, and long-term outcome after SAH. DESIGN, SETTING, AND PARTICIPANTS A retrospective analysis was conducted of 1460 consecutively treated patients with spontaneous SAH who were part of a prospective observational cohort study at a large urban academic medical center (the Columbia University SAH Outcomes Project or SHOP). Patients were enrolled between August 6, 1996, and July 23, 2012. Analysis was conducted from December 1, 2013, to February 28, 2015. EXPOSURES Loss of consciousness at onset was identified by structured interview of the patient and first responders. Patients (80.5%) were observed for up to 1 year to assess functional recovery. MAIN OUTCOMES AND MEASURES Modified Rankin scale scores were assigned based on telephone or in-person interviews of the patient, family members, or caregivers. Complications while in the hospital were predefined and adjudicated by the study team. RESULTS Five hundred ninety patients (40.4%) reported LOC at onset of SAH. Loss of consciousness was associated with poor clinical grade, more subarachnoid and intraventricular blood seen on admission computed tomographic scan, and a higher frequency of global cerebral edema (P < .001). Loss of consciousness was also associated with more prehospital tonic-clonic activity (22.7% vs 4.2%; P < .001) and cardiopulmonary arrest (9.7% vs 0.5%, P < .001) vs patients who did not experience LOC. In multivariable analysis, death or severe disability at 12 months was independently associated with LOC after adjusting for established risk factors for poor outcome, including poor admission clinical grade (adjusted odds ratio, 1.94; 95% CI, 1.38-2.72; P < .001). There was no association between LOC at onset and delayed cerebral ischemia or aneurysm rebleeding. CONCLUSIONS AND RELEVANCE Loss of consciousness at symptom onset is an important manifestation of early brain injury after SAH and a predictor of death or poor functional outcome at 12 months.