Effects of Isoflurane, Fentanyl, or Thiopental Anesthesia on Regional Cerebral Blood Flow and Brain Surface Po2 in the Presence of a Focal Lesion in Rabbits

Abstract

These studies were conducted to determine the effect of anesthetic drugs on tissue perfusion and O2 supply in the brain with focal cerebral edema. Using an open cranium preparation, we studied the effects of isoflurane (I; 1 minimum alveolar anesthetic concentration), of fentanyl (F; 0.5-1 microgram.kg-1 x min-1), or of thiopental (T; 32.5 mg.kg-1 x h-1) on regional cerebral blood flow (rCBF) and regional brain tissue PO2 in albino rabbits (n = 6 per group) with a focal brain lesion (cold injury). The doses of anesthetics were sufficient to suppress nociception. rCBF (H2 clearance) and tissue PO2 (multiwire surface electrode) were studied adjacent to and distant from the lesion. Cerebral hyperemia developed immediately after trauma in all groups, although the flow increase did not attain statistical significance. rCBF was subsequently reduced by about 25% in the vicinity of the lesion. Distant from the trauma, a continuing hyperemia (+30%) was later observed in animals with isoflurane, whereas rCBF was decreased then by 10%-20% in animals with fentanyl, or was unchanged with thiopental. Brain tissue PO2 was increased with isoflurane in areas distant from the lesion, but decreased with fentanyl. However, with thiopental, the PO2 level had already been lowered before trauma with a subsequent tendency toward normalization. The heterogeneity of the tissue PO2 in fentanyl anesthesia, as well as the increased frequency of hypoxic PO2 values with thiopental, might have resulted from microcirculatory disturbances. Thus, although isoflurane seemed to facilitate hyperemia with an increased O2 supply to the brain, fentanyl tended to induce the opposite response. Although these properties suggest the potential to manipulate perfusion and O2 supply in cerebral ischemia or hyperemia after head injury, the effects of such measures on intracranial pressure, neurologic status, and outcome have yet to be proven.

Regional Cerebral Blood Flow After Cortical Impact Injury Complicated by a Secondary Insult in Rats

“…39,40 PbtO 2 increases with CBF during isoflurane anesthesia. 41 Therefore, it is unlikely that the reductions in CBF that occur with trauma or during carotid occlusion can be explained by anesthetic effects. Isoflurane may contribute to the relatively high CBF values measured in the noninjured areas of the brain in the TBI group, but the normal PbtO 2 values in this group suggest that the measured CBF values are probably appropriate for metabolic requirements.…”

Emergency Interventions After Severe Traumatic Brain Injury in Rats: Effect on Neuropathology and Functional Outcome

“…for purposeful movement and complete blockade of this response (Kissin et al, 1983) and is similar to standard doses used in rat and cat models of central nervous system injury (Bedell et al, 1998;Miura et al, 1998;Murr et al, 1993Murr et al, , 1995Soonthon-Brant et al, 1999). Additionally, fentanyl-treated rats did not exhibit signs of increased stress vs isoflurane-treated rats, such as higher blood glucose, suggesting that anesthesia was adequate.…”

“…Although mu receptor agonists, such as morphine and fentanyl, have been shown to have some beneficial effects after central nervous system injury (Lyeth et al, 1993(Lyeth et al, , 1995, recent studies in cerebral ischemia and focal cryogenic lesion suggest that isoflurane may be neuroprotective compared to fentanyl (Miura et al, 1998;Murr et al, 1993Murr et al, , 1995Soonthon-Brant et al, 1999). In rats subjected to global cerebral ischemia, isoflurane reduced neuronal damage and improved motor function compared to fentanyl (Miura et al, 1998).…”

“…Isoflurane has been reported to enhance post-insult cerebral blood flow (CBF), produce widespread increases in brain surface P0 2 and reduce edema in a rabbit model of focal cryogenic lesion. Conversely, both CBF and regional P0 2 were decreased, and edema was increased, in rabbits anesthetized with fentanyl (Murr et al, 1993(Murr et al, , 1995. Using a fluid-percussion model in cats, De Witt et al, addressed the question of whether fentanyl was detrimental in TBI and found that fentanyl produced no adverse effects compared to vehicle.…”

Effects of Anesthesia on Polyamine Metabolism and Water Content in the Rat Brain

“…943 used for minor surgical procedures. In brain tissue, distant from a focal brain lesion, isoflurane has been shown to increase p02 (Murr et al, 1993). Isoflurane has also been shown to increase intracranial pressure (ICP) and to decrease cerebral metabolic rate for oxygen (CMR02) and cerebral vascular resistance (CVR) (Todd and Drummond, 1984).…”