Diagnostic impact of the spectrum of ischemic cerebral blood flow thresholds in sedated subarachnoid hemorrhage patients

Abstract

Ischemia is the main cause of secondary damage in sub-arachnoid hemorrhage (SAH). Cerebral blood flow (CBF) measurement is useful to detect critical values. We analyzed the diagnostic impact of CBF ischemic thresholds to predict a new low attenuation area on computed tomography (CT) due to failure of large vessel perfusion. We analyzed 48 xenon CT (Xe-CT) studies from 10 patients with SAH. CBF measurements were obtained by means of Xe-CT and cortical regions of interest (ROIs). The ROIs which appeared in a hypoattenuation area were recorded. Cortical CBF was tested for specificity and sensitivity as a predictor of hypoattenuation by means of a receiver operating characteristic curve. Mean age was 58 (SD ± 12.4) years. The median Fisher score and Hunt & Hess scale were 2 and 3, respectively. The area under the receiver operating characteristic curve was 0.912 (CI 0.896 to 0.926). The cut-off value for best accuracy was 6 mL/100 g/min, with a likelihood ratio of 37. The present study suggests a threshold of 6 mL/100 g/min as a predictor of a new low attenuation area. However, each clinician should choose the most useful threshold according to pre-test probability and the cost/effectiveness ratio of the applied therapies. © 2006 Springer-Verlag.