Cerebral Perfusion Pressure Thresholds for Brain Tissue Hypoxia and Metabolic Crisis After Poor-Grade Subarachnoid Hemorrhage

Background and Purpose-To identify a minimally acceptable cerebral perfusion pressure threshold above which the risks of brain tissue hypoxia (BTH) and oxidative metabolic crisis are reduced for patients with subarachnoid hemorrhage (SAH). Methods-We studied 30 poor-grade SAH patients who underwent brain multimodality monitoring (3042 hours). Physiological measures were averaged over 60 minutes for each collected microdialysis sample. Metabolic crisis was defined as a lactate/pyruvate ratio >40 with a brain glucose concentration <= 0.7 mmol/L. BTH was defined as PbtO(2) <20 mm Hg. Outcome was assessed at 3 months with the Modified Rankin Scale. Results-Multivariable analyses adjusting for admission Hunt-Hess grade, intraventricular hemorrhage, systemic glucose, and end-tidal CO2 revealed that cerebral perfusion pressure <= 70 mm Hg was significantly associated with an increased risk of BTH (OR, 2.0; 95% CI, 1.2-3.3; P = 0.007) and metabolic crisis (OR, 2.1; 95% CI, 1.2-3.7; P = 0.007). Death or severe disability at 3 months was significantly associated with metabolic crisis (OR, 5.4; 95% CI, 1.8-16; P = 0.002) and BTH (OR, 5.1; 95% CI, 1.2-23; P = 0.03) after adjusting for admission Hunt-Hess grade. Conclusions-Metabolic crisis and BTH are associated with mortality and poor functional recovery after SAH. Cerebral perfusion pressure levels <70 mm Hg was associated with metabolic crisis and BTH, and may increase the risk of secondary brain injury in poor-grade SAH patients. (Stroke. 2011;42:1351-1356.)