Supraorbital cutaneous blood flow rate during carotid endarterectomy

Background: The supraorbital skin region is supplied by the supraorbital artery, which is a branch of the internal carotid artery. The supraorbital cutaneous blood flow rate may therefore be influenced by changes in the internal carotid artery flow during carotid endarterectomy. Methods: The supraorbital cutaneous blood flow rate was measured by the application of heat to the skin and following the subsequent dissipation of the heat in seven patients undergoing carotid endarterectomy. At the same time, the oxygenation in the right and left frontal region was monitored by near-infrared spectroscopy (NIRS). Results: During cross-clamping of the carotid artery, the ipsilateral NIRS-determined frontal oxygenation tended to decrease [67 ± 13% to 61 ± 11% (P = 0.06); contralateral 68 ± 11% to 66 ± 8%] as did the supraorbital cutaneous blood flow rate from 56 ± 23 to 44 ± 7 ml 100g^-1min^-1. With the opening of the external carotid artery, the NIRS-determined frontal oxygenation reversed to 66 ± 8% (P < 0.05) on the ipsilateral side, with no significant change on the contralateral side and the supraorbital cutaneous blood flow rate increased to 53 ± 11 (P < 0.05). Opening of the internal carotid artery did not significantly affect the NIRS (67 ± 8% and 69 ± 9% ipsilateral, contralateral), but the supraorbital cutaneous blood flow rate increased to 88 ± 10ml 100g^-1min^-1 (P < 0.001). Conclusions: Cross-clamping of the internal carotid artery affects the supraorbital cutaneous blood flow rate as well as the frontal lobe oxygenation.