Effects of Anaesthetic Agents on Cerebral Blood Flow and Brain Oedema from a Focal Lesion in Rabbit Brain
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Anaesthetic agents reduce cerebral metabolism and may impair coupling of cerebral blood flow and metabolism. We analyzed the effects of isoflurane (I) (1 MAC), fentanyl (F), thiopental (T) (32.5 mg/ kg × hr) and α-chloralose (C) on rCBF and brain oedema formation after a focal cerebral injury (cold lesion) in rabbits (n = 6 per group). In the isoflurane group, angiotensin II (0.15 µg/kg × min) was given to maintain blood pressure. rCBF of cerebral cortex was measured 3 times per hr by H2-clearance with needle electrodes placed at different distances to the lesion during 6 hrs after induction of trauma. Thereafter, samples of white matter were obtained near the focal lesions and from corresponding areas of the contralateral hemisphere for measurement of specific gravity (SG) by a linear density column (Percoll R). Blood pressure was 78, 86, 72, and 88 mmHg for groups I, F, T, and C, respectively. After induction of the lesion, hyperemia of approximately 1 hr was observed in all groups. This was most pronounced distant to the lesion. Close to the lesion rCBF remained unchanged in groups C and T, but fell significantly below control in I and F. The blood flow response distant to the trauma was characterized by a moderate increase (C), or no alteration (T), while isoflurane animals had a pronounced secondary hyperemia for about 3 hrs. With fentanyl, however, rCBF was markedly reduced in this area. SG of white matter close to the lesion decreased significantly to values of 1.032 g/cm3 (I, F, T), or 1.031 (C), indicative of oedema. Specific gravity was 1.034 in the contralateral hemisphere (control). The differences in SG adjacent to the lesion between groups I, F, and T were statistically not significant. Further, no significant differences were observed between the specific gravity of group C and the other groups. It is concluded, that with an open skull preparation formation of posttraumatic brain oedema from a focal cerebral lesion does not seem to be markedly affected by either hyperemia, or a blood flow reduction from various anaesthetic agents, at least during the first hours after trauma.
KeywordsCerebral Blood Flow Specific Gravity Anaesthetic Agent Brain Oedema Focal Lesion
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