Supraorbital photoplethysmographic monitoring during carotid endarterectomy with the use of an internal shunt: an added dimension of safety.

Photoplethysmograph (PPG) has added a new dimension of safety to carotid endarterectomy operations. Used to monitor adequate shunt blood flow during carotid endarterectomy, the PPG has proven to be a sensitive, reliable, and accurate device. Temporary intraoperative shunt occlusion is immediately indicated by marked amplitude reductions in the supraorbital artery pulse waveform. The cause of the occlusion is usually found to be impingment of the distal end of the shunt against the arterial wall, which is easily corrected by proximal positioning of the shunt. Also, occasionally occlusion will occur from kinking of the internal carotid artery distal to the shunt, which is corrected by slight proximal retraction on the artery. Repositioning retractors in the upper extent of the operative field will alleviate any occlusions from retractor pressure on the internal carotid artery. Without a method of sensing hemodynamically significant decreases in shunt flow during operation for carotid endarterectomy, there exists a risk of prolonged unrecognized intraoperative cerebral ischemia.