Comparison of Systemic and Cerebrovascular Effects of Isoflurane and Halothane

Abstract

This study was carried out to compare the cerebral and systemic circulatory effect of halothane and isoflurane. Six mongrel dogs were anesthetized with 1.3 minimal alveolar concentration (MAC) (1%) halothane and were compared with six mongrel dogs anesthetized with 1.3 MAC (1.5%) isoflurane. Likewise, 6 dogs anesthetized with 1.7 MAC (1.3%) halothane were compared with 6 dogs anesthetized with 1.7 MAC (2%) isoflurane. Blood flow (using the radioactive microsphere technique) and cardiovascular measurements were obtained 2 hours after the induction of anesthesia and were repeated 5 more times at hourly intervals. The heart rate was similar in all groups of dogs, except that it was significantly lower with 1.7 MAC halothane. The mean arterial pressure was statistically higher with isoflurane at both concentrations than with halothane. The cardiac index was similar in all groups, except with 1.7 MAC isoflurane, when it was higher. At the early measurements, total cerebral blood flow (CBF) was above "normal" levels in all groups. At 1.3 MAC, the total CBF tended to be lower with isoflurane, but did not reach statistically significant levels. Blood flow decreased over time in all groups. The cerebral vascular resistance (CVR) mirrored the changes in blood flow, showing no difference between agents at 1.7 MAC, but the CVR with isoflurane was significantly higher at 1.3 MAC than it was with halothane. Regional cerebral blood flow showed marked differences. Regional flow to the hemispheres and the cortical gray matter showed that isoflurane tended to produce lower blood flow, particularly at the 1.3 MAC concentration. The reverse was true in the posterior fossa structures, with the brain stem and cerebellum showing higher blood flows with isoflurane, particularly at 1.7 MAC. Isoflurane may have several advantages over halothane for neurosurgical procedures.

Effects of sevoflurane and isoflurane on the ratio of cerebral blood flow/metabolic rate for oxygen in neurosurgery

“…Although CMRo 2 was not measured, it is unlikely that global CMRo 2 consistently changed over time, because the EEG pattern was relatively stable except for the appearance of occasional burst suppression during operation. CMRo 2 has also been reported to be maintained during prolonged anesthesia if the anesthetic depth is maintained stable [9][10][11][12]. The relatively constant CBF equivalent observed in our study suggests that the direction and magnitude of the changes in global CBF relative to cerebral metabolism are well preserved during a prolonged period of volatile anesthesia during craniotomy in the type of patients examined.…”

“…Many animal studies have found that cerebral hyperemia induced by isoflurane and halothane spontaneously decreases over time [9][10][11][12][13][14], but others have not [15,16]. In humans [17,18], no time decay in CBF during anesthesia was reported.…”

A comparison of the effects of isoflurane and ketamine anesthesia on auditory brainstem response (ABR) thresholds in rats

“…In contrast to ketamine, isoflurane may increase blood flow to the brainstem (Boarini et al, 1984). If the inverse relationship between tissue perfusion and glutamate release holds, increased blood flow would decrease excitatory neurotransmitter release and potentially reduce stimulus-driven activity.…”

Prediction of Plasma Hemoglobin Concentration by Near-Infrared Spectroscopy

“…Most vapor anesthetics increase cerebral blood flow (CBF) initially but decrease CBF to a steady state near pre-exposure levels in animals (12). This finding was not evident in humans (13).…”