The relationship of early hypertension following carotid endarterectomy to intraoperative cerebral ischemia.

The relationship between early hypertension following carotid endarterectomy, and intraoperative cerebral ischemia was investigated. Two measures of the adequacy of collateral cerebral circulation during carotid clamping were used: collateral cerebral perfusion pressure (delta P), and the ratio of collateral to ipsilateral cerebral vascular resistance (R/R). Change in blood pressure was measured by the ratio of mean early post to preendarterectomy pressure (P/P). Nitroprusside or nitroglycerin (NN) was used after endarterectomy to maintain systolic blood pressure less than 160 mmHg. The mean values for NN (n = 26) and no NN (n = 81) groups were: delta P = 30.0 and 40.2 mmHg (p less than 0.001); R/R = 1.93 and 1.24 (p less than 0.005); and P/P = 1.03 and 0.857 (p less than 0.001 p by unpaired t test). Linear regression analysis of the two measures of cerebral perfusion with the ratio of post-to preoperative blood pressure gave correlation coefficients between 0.629 and 0.841 with a probability that the slope of the regression line greater than 0 of less than 0.01. Low delta P and high R/R correlate with early postcarotid endarterectomy hypertension. These results support the hypothesis that one determinant of early post endarterectomy hypertension is inadequate collateral cerebral circulation during carotid clamping.