Abnormal Responses of the Human Cerebral Microcirculation to Papaverin During Aneurysm Surgery

BACKGROUND AND PURPOSE: The role of the cerebral microcirculation in delayed ischemia after subarachnoid hemorrhage remains obscure. To test the hypothesis that cerebral arterioles have a reduced capacity to dilate after subarachnoid hemorrhage, we studied the microvascular responses to papaverine (PPV) in patients undergoing aneurysm surgery. Method-In 14 patients undergoing aneurysm surgery, the diameter changes of cortical microvessels after topical application of PPV were observed using orthogonal polarizing spectral imaging. RESULTS: In control subjects, neither arterioles nor venules showed diameter changes in response to topical PPV. In patients operated <48 hours after subarachnoid hemorrhage, PPV resulted in vasodilatation of arterioles with 45+/-41% increase in arteriolar diameter (P=0.012). In 2 of these patients, arteriolar diameter returned below baseline value. In patients undergoing late aneurysm clipping, the diameter increase of the arterioles after PPV was 25+/-24% (not significant). In 2 patients of this group, no vasodilatation but focal arteriolar narrowing occurred. CONCLUSIONS: In patients with subarachnoid hemorrhage, unpredictable response patterns to PPV were observed with "rebound" vasoconstriction suggesting increased contractility of the microcirculation. Yet, diminished vasodilatory capacity of the cerebral microcirculation after subarachnoid hemorrhage was not confirmed by this study