Delayed cerebral ischemia after subarachnoid hemorrhage: a systematic review of clinical, laboratory, and radiological predictors.

BACKGROUND AND
PURPOSE: Established predictors of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage are large amounts of extravasated blood and poor clinical condition on admission. The predictive value of other factors is uncertain.
METHODS: We searched MEDLINE (1960-2012) for clinical, laboratory, and radiological predictors routinely available within 72 hours after subarachnoid hemorrhage. The studies were categorized according to methodological quality. Crude data and effect estimates (odds ratio [OR], hazard ratios, and risk ratio) with 95% CI were extracted, (re-)calculated and pooled if possible. For every potential predictor we assessed all effect estimates on consistency (point estimates in equal direction) and clinical relevance (size and 95% CI).
RESULTS: Fifty-two studies on 33 potential predictors were included. There was strong evidence (≥3 high-quality studies) for a higher risk of delayed cerebral ischemia in smokers (pooled OR, 1.2; 95% CI, 1.1-1.4), and moderate evidence (2 high-quality studies) for an increased risk in patients with hyperglycemia (OR, 3.2; 1.8-5.8 and hazard ratios, 1.7; 1.1-2.5), hydrocephalus (OR, 1.3; 1.1-1.5 and OR, 2.6; 1.2-5.5), history of diabetes mellitus (pooled OR, 6.7; 1.7-26), and early systemic inflammatory response syndrome (pooled OR, 2.1; 1.4-3.3). Evidence was limited for increased risk in women (pooled OR, 1.3; 1.1-1.6) and in patients with history of hypertension (pooled OR, 1.5; 1.3-1.7). The evidence on initial loss of consciousness, history of migraine, previous use of selective serotonin reuptake inhibitors, hypomagnesemia, low hemoglobin, or high blood flow on early transcranial Doppler was also limited.
CONCLUSIONS: There is strong evidence that smoking is a predictor of delayed cerebral ischemia. For several other potential predictions the evidence is moderate, limited, or inconsistent.