TEMPORARY OCCLUSION OF THE MIDDLE CEREBRAL-ARTERY IN INTRACRANIAL ANEURYSM SURGERY - TIME LIMITATION AND ADVANTAGE OF BRAIN PROTECTION

The risk of focal infarction secondary to the induced reversible arres t of local arterial flow during microsurgical dissection of middle cer ebral artery (MCA) aneurysms was evaluated further to define the optim al approach to temporary arterial occlusion. To compare the effectiven ess of potential brain-protection anesthetics, a group of patients tre ated with the intravenous agents propofol, etomidate, and pentobarbita l, administered individually or in combination, was compared to a grou p treated with the inhalational agent isoflurane. Forty-nine consecuti ve MCA aneurysm surgeries involving the temporary clipping of the pare nt vessel were retrospectively reviewed. Thirty-eight patients receive d intravenous brain-protection (IVBP) anesthesia. Groups of patients w ith and without infarctions, and receiving and not receiving IVBP anes thesia, were compared based on the duration and nature of temporary ar terial occlusion. Postoperative radiographic evidence of new infarctio n was used as the threshold for failure of occlusion tolerance. The ov erall infarction rate was 22.4% (11 of 49 patients), including 15.8% ( six of 38 patients) in the IVBP group versus 45.5% (five of 11 patient s) in the group that did not receive brain protection (NBP). In the NB P group, the mean duration of temporary occlusion was 3.9 +/- 2.2 minu tes for patients without infarction versus 12.2 +/- 4.3 minutes for pa tients with focal infarction (p < 0.01). In contrast, the mean duratio n was 13.6 +/- 10.6 minutes for patients without infarction and 18.5 /- 9.9 minutes for patients with infarction in the IVBP group. All pat ients (four of four) in the NBP group who underwent occlusion lasting 10 minutes or longer suffered an infarction versus five of 23 patients in the NBP group (p < 0.0001). Patients with multiple aneurysms were found to be at increased risk of developing focal infarction, whereas those treated with intermittent temporary clip application were at dec reased risk. It is concluded that patients in whom focal iatrogenic is chemia is induced during MCA aneurysm clip ligation have a significant advantage compared with those receiving isoflurane when they are give n pentobarbital as the primary neuroprotective agent or when they rece ive propofol or etomidate titrated to achieve electroencephalographic burst suppression, particularly if more than 10 minutes of occlusion t ime is required. It is also concluded that 10 minutes is a general gui deline for safe, temporary occlusion of the MCA. The use of intermitte nt temporary arterial occlusion and its use in patients with multiple aneurysms need further evaluation before specific recommendations can be made.