The influence of contralateral carotid stenosis and occlusion on cerebral oxygen saturation during carotid artery surgery.

OBJECTIVES

To study the effect of contralateral carotid stenosis on oxygen saturation (CsO2) of both cerebral hemispheres monitored by reflective near-infrared spectroscopy (NIRS) during carotid surgery.

METHODS

NIRS was compared to ipsilateral transcranial Doppler ultrasonography (TCD) of the middle cerebral artery and jugular bulb venous oxygen saturation (JvSO2) in 54 patients undergoing carotid endarterectomy.

RESULTS

Median operated side and contralateral CsO2 were 68(54-88)% and 69(55-85)% before carotid clamping falling to 63(44-80)% and 69(55-84)% respectively on clamping the carotid (p < 0.0001 and p = NS). JvSO2 fell from 78(38-98)% to 72(30-97)% on carotid clamping with a percentage fall in peak TCD of -28(0 to -100)% (p < 0.0001). Patients with a contralateral carotid artery occlusion experienced falls in ipsi and contralateral CsO2 of -8(-4 to -10)% and -3(2 to -7)% compared to -4(0 to -14)% and 0(-5 to 4)% in those with a lesser stenosis (p < 0.05). On declamping, median ipsilateral and contralateral CsO2 rose from 65(46-82)% and 67(52-87)% to 68(53-84)% respectively (p < 0.0001 and p = NS). JvSO2 increased from 75(33-95)% to 79(42-95)% (p < 0.0001) with an increase in median peak TCD of 35(-34 to 506)%.

CONCLUSIONS

The greatest changes in CsO2 occurred in the operated side cerebral hemispheres in those with a contralateral carotid artery occlusion. However, a contralateral carotid artery occlusion does not reliably predict the need for a shunt and cerebral monitoring remains essential; although is only required on the operated side.