A neurochemical hypothesis for halothane anesthesia

Flumazenil improves cognitive and neuromotor emergence and attenuates shivering after halothane-, enflurane- and isoflurane-based anesthesia

PURPOSE

To conduct a randomized, placebo-controlled, double-blinded, clinical experiment testing the hypothesis that flumazenil, a benzodiazepine antagonist, may affect recovery from halothane-, enflurane- and isoflurane-based anesthesia.

METHOD

Patients who underwent surgery under N(2)O/O(2) plus halothane (n=100), enflurane (n=100) or isoflurane (n=70) anesthesia were administered flumazenil 1 mg or placebo upon emergence from anesthesia, and their postanesthesia vital signs, vigilance, neurological recovery, shivering, amnesia reversal, and general subjective feeling were assessed.

RESULTS

A ten-point vigilance score showed better recovery of flumazenil-treated patients compared to those who received placebo (60-min after halothane anesthesia: 9.9 +/- 0.1 vs 9.5 +/- 0.2, P <0.01; after enflurane: 10 +/- 0 vs 9.4 +/- 0.2, P <0.01; after isoflurane: 10.0 +/- 0 vs 9.3 +/- 0.1, P <0.01). Halothane- and enflurane-flumazenil-treated patients (but not isoflurane) reached a better neurological score (2.97 +/- 0.05 or 3 +/- 0) compared to placebo (2.8 +/- 0.4 or 2.6 +/- 0.4, P <0.01), respectively. Reversal of amnesia was superior in the flumazenil group at 60 min and at 24 hr postsurgery, and more flumazenil patients rated recovery as "pleasant". Flumazenil patients shivered less than placebo patients despite their lower core temperature (at 30 min: halothane: 11% vs 28%, P <0.05; enflurane: 11% vs 30%, P <0.05; isoflurane: 17% for both groups).

CONCLUSION

Flumazenil improves recovery of high cortical and neuromotor functions following halothane, enflurane and isoflurane anesthesia, reduces shivering and improves the overall quality of emergence, including patients' subjective feeling.

Effect of dopamine content in rat brain striatum on anesthetic requirement: an in vivo microdialysis study

This study investigated the changes in anesthetic requirement caused by administration of two different concentrations (0.1 microM and 1. 0 microM/h) of dopamine into the rat striatum. During the measurement of minimum alveolar concentration (MAC), each dopamine solution was continuously injected directly into rat striatum by microdialysis technique. During perfusion of the lower dose, MAC did not change. During the higher dose of dopamine, MAC decreased by approximately 30%.

A hypothetical model on the mechanism of anesthesia

An hypothesis on the mechanism of action of general anesthetic agents is proposed. It is based on a potentiation of chloride influx due to the action of anesthetic agents on the GABA-receptor complex at the lipid-protein interface. This hypothesis accommodates various observations such as lipid solubility of anesthetic molecules, their lack of stringent structural requirement, pressure reversal of anesthetic action, and other neurochemical and neuropharmacological data.

Reinterpretation of the literature indicates differential sensitivities of long-sleep and short-sleep mice are not specific to alcohol

This paper reviews the findings and conclusions of the literature pertinent to the Long-Sleep and Short-Sleep selectively-bred lines of mice and challenges the widely-held notion that the selective breeding program was successful in separating alleles for specific sensitivities to just alcohol. Rather, it is argued that these lines of mice were selected for differing activity of a more general process. Recent evidence, as well as reevaluated previous evidence, indicates that Long-Sleep mice are more sensitive to the soporific effects of three major classes of CNS depressants (alcohols, barbiturates, and benzodiazepines), as well as many other anesthesia-inducing compounds (adenosine, chloral hydrate, trichloroethanol, paraldehyde, nitrous oxide, enflurane, and isoflurane). Further, much evidence also supports the conclusion that most of these hypnotic-depressants and anesthetics could exert their soporific influence by a potentiation of GABA activity. The other characteristic of interest in this regard is susceptibility to convulsions. Short-Sleep mice have significantly lower thresholds to both flurothyl-induced and bicuculline-induced convulsions, as well as being more likely to suffer from paroxysms during ethanol withdrawal.