BLOOD-FLOW VELOCITY IN THE MIDDLE CEREBRAL-ARTERY AND CAROTID-ARTERY STUMP PRESSURE DURING CAROTID ENDARTERECTOMY

Twentyone patients undergoing carotid endarterectomy were investigated by simultaneous intra-operative measurements of carotid stump pressur e (CSP) and transcranial Doppler (TCD) flow velocity in the middle cer ebral artery. The relationship between the two methods was evaluated a s well as the potential benefits of the intra-operative transcranial D oppler monitoring technique. Clamping of the carotid artery resulted i n a significant decrease in TCD flow velocity in the ipsilateral middl e cerebral artery as well as in CSP. There was no correlation between relative change in CSP and the simultaneously obtained relative change in TCD flow velocity during carotid clamping (r = 0.31, p = 0.26). Th e insertion of an intra-operative shunt was followed by an increase in flow velocity compared to the clamping value. One patient with clear TCD signs of a re-occlusion (a sudden decrease in flow velocity) durin g closure of the wound, demonstrated a thrombosis at re-exploration. T CD gives information of the collateral cerebral circulation during car otid clamping and is an alternative monitoring technique during caroti d endarterectomy. The method is useful intraoperatively for detecting embolic events as well as thrombosis during wound closure. Further stu dies are necessary to clarify the critical change in flow velocity dur ing clamping when the use of a peroperative shunt is indicated.