Wb. Gentry et al., INDUCTION AND MAINTENANCE OF ANESTHESIA IN DOGS BY INTRAVENOUS ADMINISTRATION OF METHOHEXITAL, American journal of veterinary research, 57(7), 1996, pp. 1044-1049
Objective - To devise and test an IV methohexital infusion regimen for
induction and maintenance of surgical anesthesia in dogs from which t
hey would rapidly recover. Design - Dose-response and plasma concentra
tion-effect study. Animals - 11 clinically normal dogs. Procedure - Bo
lus methohexital pharmacokinetic variables were determined in ketamine
- and pentobarbital-anesthetized dogs. Plasma methohexital concentrati
ons required to inhibit purposeful movement in response to painful sti
muli were determined during a stepped methohexital infusion in the sam
e dogs on a second occasion. These pharmacokinetic/pharmacodynamic dat
a were next used to design a bolus and two-stage infusion regimen that
would result in stable plasma methohexital concentrations with prolon
ged infusion. This regimen was tested in a second group of dogs. Resul
ts - Mean steady-state volume of distribution of methohexital in the a
nesthetized dogs was 1.50 L/kg of body weight and mean elimination cle
arance was 10.2 ml/kg/min. Mean plasma concentrations required to prev
ent movement response to a noxious stimulus and at which the dogs coul
d be extubated were 11.8 and 6.9 mu g/ml, respectively. After a 6-hour
infusion, recovery of airway reflexes sufficient to allow extubation
required 67 minutes. Conclusions - An easily implemented IV methohexit
al infusion regimen for induction and maintenance anesthesia in dogs w
as developed. During a 6-hour infusion, hemodynamic variables did not
change. Use of this regimen resulted in anesthesia of sufficient depth
to prevent withdrawal in response to noxious stimuli and in reliable
and acceptable emergence times for use in canine survival studies in a
cost-effective manner.