Blood flow velocity in the middle cerebral artery and carotid artery stump pressure during carotid endarterectomy.

Twenty-one patients undergoing carotid endarterectomy were investigated by simultaneous intra-operative measurements of carotid stump pressure (CSP) and transcranial Doppler (TCD) flow velocity in the middle cerebral artery. The relationship between the two methods was evaluated as well as the potential benefits of the intraoperative transcranial Doppler monitoring technique. Clamping of the carotid artery resulted in a significant decrease in TCD flow velocity in the ipsilateral middle 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). The 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) during closure of the wound, demonstrated a thrombosis at re-exploration. TCD gives information of the collateral cerebral circulation during carotid clamping and is an alternative monitoring technique during carotid endarterectomy. The method is useful intraoperatively for detecting embolic events as well as thrombosis during wound closure. Further studies are necessary to clarify the critical change in flow velocity during clamping when the use of a peroperative shunt is indicated.