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 (CsO 2 ) 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 (JvSO 2 ) in 54 patients undergoing carotid endarterectomy. Results: Median operated side and contralateral CsO 2 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 p = ns ). JvSO 2 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 2 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 2 rose from 65(46–82)% and 67(52–87)% to 68(53–84)% respectively ( p p = ns ). JvSO 2 increased from 75(33–95)% to 79(42–95)% ( p Conclusions: The greatest changes in CsO 2 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.