Technique and clinical results of carotid stump back-pressure to determine selective shunting during carotid endarterectomy

A method of confirming carotid back pressure accuracy, variability during carotid clamping, and the clinical results with a modified back pressure shunt criterion were evaluated in 665 carotid endarterectomies. Mean arterial pressure, back pressure, and internal jugular vein pressure were measured. Cerebral perfusion pressure (back pressure-jugular vein pressure) and the collateral to hemisphere vascular resistance ratio, (ratio = [arterial pressure-back pressure]/[back pressure-jugular vein pressure]) were calculated. A shunt was used when cerebral perfusion pressure less than 18 mm Hg. Back pressure accuracy was confirmed by test occlusion of the internal carotid artery distal to the plaque. Initial back pressure values were falsely high in 83 (12.5%) carotid endarterectomies. The mean SD (n = 665, mm Hg) were arterial pressure = 84.0 +/- 9.06, back pressure = 41.0 +/- 15.9, jugular vein pressure = 6.2 +/- 3.9, cerebral perfusion pressure = 35.1 +/- 5.7, and resistance ratio = 1.85 +/- 1.44. Perfusion pressure was less than 18 mm Hg in 82 (12.3%), of which 74 (11.1%) were shunted, and 8 (1.2%) had perfusion pressure increased greater than or equal to 18 mm Hg during carotid endarterectomy with phenylephrine. Back pressure was less than 25 mm Hg in 107 (16.1%), less than or equal to 25 in 114 (17.1%), and less than 50 mm Hg in 481 (72.3%). Pressures were continuously monitored during 28 carotid endarterectomies, and all had a positive linear relationship between arterial pressure and back pressure, and minimal variability in the back pressure/arterial pressure and resistance ratios. Only two patients (0.3%) had a new neurologic deficit in the first 12 hours after carotid endarterectomy.(ABSTRACT TRUNCATED AT 250 WORDS)