The controlled delivery of thiopental and delayed cerebral revascularization

Temporary clipping in aneurysm surgery: technique and results

The use of temporary clipping has become an established tool in the armamentarium of the aneurysm surgeon. Our experience with 62 consecutive patients is presented, detailing operative protocols and results. Twenty-two had unruptured aneurysms (35%), 15 were grade I (24%), 16 grade II (25%), five grade III (8%), and four grade IV (7%). The aneurysms were mainly located in the middle cerebral artery (29 patients) and the anterior communicating artery (13 patients). Eleven of our 62 patients (17%) developed a new, persistent postoperative deficit. However, in only one case (2%) was temporary clipping felt to be implicated in the development of the deficit. In three other patients (5%), the effect of temporary clipping, although unlikely, could not be excluded. Overall, 92% of our patients with temporary clipping had good to excellent outcome, with 3% mortality and 5% morbidity. We believe that temporary clipping is a safe procedure that contributes significantly to a better outcome.

Selective occlusion of blood supply to the anterior perforated substance of the dog: a highly reproducible stroke model

We created a highly reproducible stroke model in dogs by the selective occlusion of middle and anterior cerebral artery branches that penetrate the anterior perforated substance and supply much of the basal forebrain. We also analyzed the anatomic organization of the arterial supply to this region in this animal. Perforators came from anterior communicating artery branches similar to the recurrent artery of Heubner in humans and from the middle cerebral artery at several sites distal to the bifurcation of the internal carotid artery. Although some animals had a single source of the perforating arteries, most had two or more. In 50% of our specimens, the anterior communicating artery was the dominant source of arterial supply, in 21% the middle cerebral artery was dominant, and in 24% neither source dominated. Occlusion of all microscopically visible perforators to the anterior perforated substance reliably resulted in infarction of the internal capsule (100%), caudate nucleus (91%-100%), putamen or globus pallidus (82%-91%), and anterior commissure (73%). Structures involved less frequently in infarctions include the external capsule, claustrum, anterior commissure, and septal nuclei. We believe this anatomic information is useful for understanding why previous focal ischemia lesions in the distribution of the middle cerebral artery in the dog have been highly variable as well as for planning and interpreting future studies in this species. The proposed model of focal ischemia may be of use for the study of stroke.

Comparison of superoxide dismutase, thiopental, and nimodipine for maintenance of somatosensory evoked responses during aortic cross-clamping and declamping in dogs

Paraplegia is a potential complication of aortic cross-clamping. The occurrence of this devastating sequela has caused increased interest in the use of somatosensory evoked responses (SER) to monitor spinal cord ischemia during aortic cross-clamping. This study was designed to examine changes in SERs during clamping and declamping of the canine aorta after injection of superoxide dismutase (SOD), thiopental (T), and nimodipine (N). In the control group, cross-clamping the aorta produced an increase in latency and a decrease in amplitude of the SER starting at two minutes. Isoelectric SERs were obtained after 16 minutes of aortic cross-clamping, but recovered with cross-clamp removal. When the aorta was clamped for more than 16 minutes in the control group, the isoelectric SERs obtained were irreversible. After the injection of SOD and T, SER latencies and amplitudes changed to a smaller degree with aortic cross-clamping and did not become isoelectric even after 20 minutes of clamping. During aortic cross-clamp removal in the control group, SERs initially improved and then showed signs of reperfusion ischemia, which disappeared after eight minutes. There were no significant SER changes due to reperfusion when SOD or T or the combination was given prior to aortic cross-clamping. There was no difference in SER changes from the control group during aortic cross-clamping and after release of cross-clamping when N was given. Nimodipine did not alter SER changes from aortic cross-clamping alone. In summary, SOD and T, alone or in combination, protect the spinal cord against ischemia during aortic cross-clamping and declamping.

Cerebral resuscitation: pathophysiology and therapy

The interest in the possibility of cerebral resuscitation has been growing exponentially during the last decade. It became clear that pharmacotherapeutic interaction can possibly alter the outcome of cerebral hypoxia/ischemia. The present review is an attempt to provide an organizational framework for a systematic integration of studies specifically dealing with pharmacological treatment post-insult.

Thiopentone cerebral protection under EEG control during carotid endarterectomy

Seventy patients who underwent a total of 77 consecutive carotid endarterectomies were given thiopentone (mean dose 19 mg/kg) under EEG control for cerebral protection during the period of carotid clamping. This technique was used instead of elective insertion of a temporary bypass shunt in response to adverse EEG changes occurring after clamping. The EEG was monitored continuously throughout operation. The EEG burst-suppression pattern with electrically inactive periods of 30-60 seconds was taken as indicating a depth of barbiturate anaesthesia adequate to provide brain protection. Patients exhibited a drop in blood pressure during barbiturate administration: in most the pressure recovered spontaneously but in twenty operations metaraminol was needed to re-establish an adequate pressure before clamping. No adverse cardiological effects were associated with the administration of thiopentone or metaraminol. There was no mortality and no neurological morbidity in this series.

Barbiturates for cerebral aneurysm surgery. A review of preliminary results

Ninety-two cerebral aneurysm cases treated by clipping under moderate hypothermia are reviewed. Twenty-three of these cases received pentobarbitone during surgery in doses sufficient to render the EEG flat. The overall combined mortality and morbidity (complication rate) among 69 non-barbiturate cases was 21.7%. There were significant differences in results between aneurysms in different anatomical locations. The complication rate among eight middle cerebral artery aneurysm cases was 62.5% and among ten internal carotid artery bifurcation cases 40%, while that among nineteen internal carotid artery cases was 16% and among 27 anterior communicating complex cases 7.4%. The overall complication rate among 23 pentobarbitone cases was 17%. There were no complications among eight middle cerebral artery cases; one of two internal carotid bifurcation cases became hemiplegic following occlusion of the middle cerebral artery at is origin. The complication rate among nine internal carotid cases was 22%. No difficulties were experienced regarding haemodynamic stability or cardiac rhythm while using pentobarbitone at normothermia or at 28 degrees C. It is suggested that cerebral aneurysms involving the middle cerebral artery which appear to be most at risk may have the most to gain by the prophylactic use of pentobarbitone during surgery.

Acute cerebral revascularization

Fifteen patients evaluated for acute cerebral ischemia underwent acute cerebral revascularization between March, 1979, and May, 1983. Clinical presentation included crescendo transient ischemic attacks (TIA's) in eight cases, progressing neurological dysfunction in three cases, and completed nonfluctuating deficits in four cases. Nine patients received intravenous heparin but did not improve neurologically. The patients with crescendo TIA's were operated on within 4 hours of their last event; those with progressing deficits were operated on while the deficit was developing, and those with established deficits were operated on 4, 6, 9, and 12 hours, respectively, after the event began. The clinical picture for 10 patients had resolved within 10 hours after surgery. One patient with crescendo TIA's, two with progressing deficits, and two with established deficits had postoperative residual deficits, of which three were mild and two severe. One patient, who had a saphenous vein graft to the middle cerebral artery, developed an intracerebral hematoma. In this prospective noncontrolled nonrandomized study, acute cerebral revascularization was performed safely, had limited risks, and offered the potential to help some patients. Further controlled randomized studies are indicated.

Thiopental bolus during carotid endarterectomy-rational drug therapy?

Ten studies were performed to examine the time course of arterial and venous thiopental concentrations following the administration of thiopental (4 mg X kg-1 over 3 min) for cerebral protection during carotid occlusion in nine patients undergoing elective carotid endarterectomy; in five patients the time course of EEG change was also studied. The arterial and venous thiopental concentrations were similar with no evidence of a sustained arterial-venous gradient. The average arterial concentration was 20.1 microgram X ml-1 +/- 10 (SD) at 2 min after thiopental, and fell rapidly to 13.0 micrograms X ml-1 +/- 3.2 at 5 min, 10.7 micrograms X ml-1 +/- 4.4 at 10 min and 6.2 micrograms X ml-1 at 30 min. After thiopental the EEG record showed an increase in delta activity and in four patients a burst suppression pattern was seen. The duration of burst suppression activity was variable (130 to 367 seconds) but in all instances cortical activity had returned to the pre-thiopental level by five to ten minutes. Thus concentrations of thiopental of 10-30 micrograms X ml-1 were associated with EEG burst suppression and both were seen only within the first five minutes after drug administration. In contrast the carotid artery was occluded for considerably longer (26 +/- 4) minutes. We conclude that, since there was no sustained arterial-venous gradient, either arterial or venous concentrations are adequate for the study of thiopental pharmacokinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Barbiturate coma in focal cerebral ischemia. Relationship of protection to timing of therapy

The therapeutic application of barbiturate-induced coma was evaluated in a primate model of focal cerebral ischemia. A standardized regimen of pentobarbital was used, and the times of initiation of administration were varied following a 6-hour middle cerebral artery occlusion in baboons. Three groups of five animals were treated at 30, 120, and 240 minutes after occlusion, while one group of five animals received no barbiturate therapy. Complete protection from intracranial pressure (ICP) elevation and ischemic damage was seen only in the group treated at 30 minutes. Those treated at 120 minutes, while doing better than untreated animals, still had ICP elevation and a marked neuropathological deficit. Animals treated at 240 minutes suffered a detrimental effect, in that malignant ICP and marked ischemic damage occurred earlier than in the untreated animals. The safe "therapeutic window" for barbiturate-induced coma in this animal model does not extend beyond 2 hours. Delayed administration results in a deleterious response and not merely a lack of protection.

Barbiturate protection in acute experimental spinal cord ischemia

Ischemia is the pathophysiological mechanism in many types of spinal cord injury. In the present study, the infrarenal segment of the aorta was occluded for 25 minutes to produce spinal cord infarction in rabbits. Paraplegia occurred in 100% of control animals. Thiopental administered before aortic occlusion resulted in paraplegia in only 40% of animals so treated (p less than 0.01). Histological study of the spinal cord demonstrated infarction of the gray matter in all paraplegic animals, whereas the microscopic appearance was normal in animals without neurological deficit. The protective influence of thiopental therapy in spinal cord ischemia was demonstrated.

Effect of extracranial-intracranial bypass and pentobarbital on acute stroke in dogs

Ninety-three mongrel dogs underwent intracranial carotid and middle cerebral artery occlusions. They were then randomized into four groups: 1) the untreated control group (no surgical or medical therapy) showed significant neurological deficit, 16% mortality, and 17% mean hemisphere infarction; 2) in the bypass group (superficial temporal to middle cerebral artery (STA-MCA) anastomosis completed within 3 hours of occlusion), neurological deficit was diminished, mortality was 7%, and mean infarction 5.66%; 3) in the pentobarbital group (single dose of pentobarbital, 35 mg/kg administered intravenously 30 minutes after occlusion), neurological deficit was essentially the same as in the previous group, there was no mortality, and mean infarction was 5.52%; and 4) in the pentabarbital/bypass group (pentabarbital dose plus STA-MCA bypass), neurological deficit was slightly lower than in previous treatment groups, there was no mortality , and mean hemisphere infarction was 1.78%. Extracranial-intracranial bypass produced an immediate 31.6% increase in regional cortical blood flow. The combination of pentobarbital postocclusive therapy and early extracranial-intracranial bypass beneficial synergism.