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 o xygen saturation (CsO2) of both cerebral hemispheres monitored by refl ective near-infrared spectroscopy (NIPS) during carotid surgery. Metho ds: NIRS was compared to ipsilateral transcranial Doppler ultrasonogra phy (TCD) of the middle cerebral artery and jugular bulb venous oxygen saturation (J nu SO2) in 54 patients undergoing carotid endarterectom y. 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). J nu SO2 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 ip si and contralateral CsO2 of-8(-4 to -10)% and -3(2 to -7)% compared t o -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 fr om 65(46-82)% and 67(52-87)% to 68(53-84)% respectively (p < 0.0001 an d p = Ns). JvSO(2) 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 h emispheres in those with a contralateral carotid artery occlusion. How ever a contralateral carotid artery occlusion does not reliably predic t the need for a shunt and cerebral monitoring remains essential; alth ough is only required on the operated side.