Effects of Acute ICH on Hemispheric Blood Flow and Metabolism
Background: Increased oxygen extraction fraction (OEF) suggesting reduced cerebral perfusion pressure below the autoregulatory limit has been reported in subacute hypertensive (HTN) ICH. We sought to confirm this finding in acute ICH. Methods: Nineteen HTN patients aged 63±15 years with spontaneous supratentorial ICH (.3–99 cc; median 12) were studied with PET 5–22 hours after onset. Five patients were re-studied after BP was lowered 23±9 mm Hg. Subsets of patients were age-matched to normal and HTN controls. Cerebral blood flow (CBF), metabolic rate (CMRO2), and OEF for each hemisphere were derived from a 2-cm cortical rim. All measurements were corrected for partial volume effect. Results: Ipsilateral OEF was elevated and CBF and CMRO2 reduced compared to normal controls, but not to levels sufficient to produce infarction. (Table.) OEF was no different from HTN controls, however. There was no correlation between OEF and size of clot or ventricles, suggesting that elevated OEF was not due to increased ICP or mass effect. Lowering of BP did not change CBF (-1.7±2.2 ml/100g/min); thus, there was no evidence for autoregulatory failure. Conclusions: Elevated hemispheric OEF in acute ICH may reflect the effects of chronic hypertension rather than increased ICP or other effects of the hematoma.