Deterioration in carotid baroreflex during carotid endarterectomy.

OBJECTIVE

Blood pressure instability after carotid endarterectomy (CEA) has been associated with a disturbance of the baroreflex control mechanism caused by the surgery in the carotid sinus region. The purpose of this study was to determine if a deterioration in carotid baroreceptors occurs during the surgery.

METHOD

Heart rate (HR) and blood pressure (BP) were recorded continuously in 60 patients undergoing CEA as well as preoperatively and postoperatively at 2 days and 6 weeks. The baroreflex sensitivity was determined by cross-spectral analysis of HR and systolic blood pressure (SBP). During the surgery, three tests were used to assess the baroreflex response. The first test simulated a sudden fall in systemic blood pressure by clamping the common carotid artery. The second test simulated a rise in systemic blood pressure by applying pressure by using a rubbing action on the luminal surface of the carotid sinus region. The rub test was performed twice, once with the atheromatous plaque in situ and once when the plaque had been removed. The third test is clamp removal and restoration of blood flow through the carotid sinus.

RESULTS

Carotid cross-clamping increased mean +/- standard error of the mean SBP from 117 +/- 3 mm Hg before clamping to 125 +/- 3 mm Hg (P <.05) at 30 beats after clamping. The first rub test with the plaque in situ decreased SBP from 121 +/- 3 mm Hg to 117 +/- 3 mm Hg (P <.01) at 10 beats after the rub test, indicating a functioning baroreceptor reflex. The second rub test increased SBP from 126 +/- 3 mm Hg to 128 +/- 3 mm Hg (P <.05). SBP dropped (P <.01) when unclamping suggesting a selective alteration of the baroreflex sensitivity. The baroreflex sensitivity was significantly reduced 2 days postoperatively when compared to preoperative values (P <.05).

CONCLUSIONS

These findings suggest that the act of plaque removal could be associated with a partial disruption of baroreceptor mechanism in the carotid artery. This could affect type I baroreceptors.