During endarterectomy of the internal carotid artery (ICA) blood flow velocity of the ipsilateral medial cerebral artery (MCA) was continuously monitored in twelve patients with the help of a new transcranial pulsed Doppler system. Additionally, the basal cerebral arteries where examined pre- und postoperatively in order to evaluate criteria for selective intraoperative shunting and to document flow improvement following ICA reconstruction. All patients had symptoms, either of TIA or of minor stroke. Five of them had in addition a contralateral ICA occlusion. During intraoperative carotid cross-clamping on the patients with unilateral ICA lesions, MCA blood flow dropped to zero in only one of them. In the other cases, a 20 to 60% flow reduction occurred indicating cross-filling or/and collateral blood supply via the posterior circulation. More severe MCA flow reductions were found in patients with contralateral ICA occlusion, with the occurrence of a no-flow state in two of them. All patients were operated on with an indwelling shunt. Its effect on MCA blood flow varied considerably. Apparently, the shunt was necessary in some patients but was superfluous in the majority of them. Transcranial Doppler meets the basic criteria of an examination technique to be recommended for monitoring. The method is noninvasive. The parameter, i.e. MCA flow velocity, can be evaluated on-line. It is representative and highly sensitive for cerebral circulatory disturbances and impending ischemia in the carotid territory. Transcranial MCA flow monitoring does not affect the course of the operation.(ABSTRACT TRUNCATED AT 250 WORDS)
