Effect of lignocaine injection in carotid sinus on baroreceptor sensitivity during carotid endarterectomy

Objectives: This study was undertaken to test the hypothesis that there is a neural basis for baroreceptor deterioration during carotid endarterectomy (CEA), by investigating intraoperative hemodynamic changes induced by intraluminal carotid stretch stimulation, before and after application of local anesthetic to the adventitial layer of the carotid sinus region. Methods: This was a prospective study of 20 patients undergoing elective CEA. During CEA, before removal of the atheroma, intraluminal stretch simulation of the carotid baroreceptors; (rub test) was performed before and after injection of 1% lignocaine into adventitial tissue of the artery in the region of the carotid sinus. Continuous measurements of mean arterial blood pressure (MAP), electrocardiographic r-r intervals (R-R), heart rate, cardiac vagal tone, and carotid sinus baroreflex were recorded to determine alterations in baroreceptor function. Results: Rub test before injection of lignocaine was associated with a decrease in MAP and heart rate and an increase in R-R, cardiac vagal tone, and carotid baroreflex response, indicating a functioning baroreflex. After lignocaine injection and repetition of the rub test, no significant change was seen in MAP, heart rate, R-I, cardiac vagal tone, or carotid baroreflex response, indicating a nonfanctioning baroreflex. Comparing the peak responses to the rub test stimulus before and after lignocaine injection showed significant differences for all variables (P < .05), with carotid baroreflex response and heart rate being highly significant (P < .0005). Conclusions: The baroreflex response to intraluminal stretch stimulation of the carotid sinus area is operational in patients undergoing CEA, and this response is abolished by infiltration of local anesthetic into the periadventitial tissue around the carotid sinus.