✓ The adverse effect of a minimal cerebral blood flow (CBF) in models of global ischemia has been noted by many investigators. One factor believed important in this situation is the level of blood glucose, since a continued supply of this metabolite results in increased tissue lactate, decreased brain pH, and increased cell damage. The authors have extended these observations to a model of focal incomplete ischemia. Brain pH was measured in fasted squirrel monkeys in regions of focal incomplete ischemia after transorbital occlusion of the middle cerebral artery (MCA). In both control and hyperglycemic animals, CBF was reduced to less than 30% of baseline. At 3 hours after MCA occlusion, brain pH in the control group was 6.66 ± 0.68 as compared to 6.27 ± 0.26 in the glucose-treated group. This difference was statistically significant by Student's unpaired t-test (p < 0.05). Thus, hyperglycemia results in decreased tissue pH in regions of focal incomplete cerebral ischemia in monkeys.
W. Richard Marsh, Robert E. Anderson and Thoralf M. Sundt Jr.
Thoralf M. Sundt Jr., David G. Piepgras and W. Richard Marsh
✓ The authors describe their experience using booster clips to secure the closure of primary clips in the repair of giant and other thick-walled aneurysms. These clips were used for 21 aneurysms in 20 patients, comprising 12% of all aneurysms operated on during the 15-month period of the report, but representing about 50% of all giant aneurysms operated on during the same time frame. These clips are designed to encircle the primary clip and have fixation “shoes” to close upon the jaws of the primary clip. All aneurysms were opened for decompression and thrombectomy when necessary following temporary major vessel occlusion before placement of the primary clip. Cerebral blood flow measurements and continuous electroencephalographic monitoring were utilized to predict the brain's tolerance to temporary ligation of the internal carotid artery (ICA) in those cases with a giant aneurysm arising from that vessel. There were no complications attributable to the periods of intracranial or cervical ICA occlusion; these periods varied but did not exceed 8 minutes for the former nor the tolerance period for the latter, which was calculated as from 5 to 30 minutes. It was necessary to reoperate on two patients and reposition clips because of stenoses or occlusions identified on immediate postoperative angiography. Fifteen patients had normal neurological function at the time of discharge. Three patients had minor deficits which did not prevent employment; two of these were related to a preoperative deficit and one was a complication of delayed ischemia. There were two deaths: one from bleeding complications and probable damage to perforating vessels in a patient operated on under profound hypothermia (the only case in the series so managed), and one from respiratory complications in a patient with severe pulmonary problems.
Thoralf M. Sundt Jr., David G. Piepgras, W. Richard Marsh and Nicolee C. Fode
✓ The authors report their experience with the use of saphenous vein bypass grafts for treating advanced occlusive disease in the posterior circulation (77 patients, all of whom had failed medical management and showed severe ischemic symptoms), deteriorating patients with giant aneurysms of the posterior circulation (nine patients), progressive ischemia in the anterior circulation (26 patients, none of whom had a normal examination), and giant aneurysms in the anterior circulation (20 patients, all of whom presented with mass effect or subarachnoid hemorrhage). Graft patency in the first 65 cases treated was 74%. However, after significant technical changes of vein-graft preparation and construction of the proximal anastomosis, patency in the following 67 cases was 94%. Excellent or good results (including relief of deficits existing prior to surgery) were achieved in 71% of patients with advanced occlusive disease in the posterior circulation, 44% of those with giant aneurysms of the posterior circulation, 58% of those with ischemia of the anterior circulation, and 80% of those with giant aneurysms of the anterior circulation. Mean graft blood flow at surgery in the series was 100 ml/min for posterior circulation grafts and 110 ml/min for anterior circulation grafts. Experience to date indicates that this is a useful operation, and is particularly applicable to patients who are neurologically unstable from advanced intracranial occlusive disease in the posterior circulation or with giant aneurysms in the anterior circulation. The risk of hyperperfusion breakthrough with intracerebral hematoma restricts the technique in patients with progressing ischemic symptoms in the anterior circulation, and the intolerance of patients with fusiform aneurysms in the posterior circulation to the iatrogenic vertebrobasilar occlusion limits the applicability of this approach to otherwise inoperable lesions in that system.