Effect of intravenous administration of ketamine on the minimum alveolar concentration of isoflurane in anesthetized dogs.
OBJECTIVE
To determine the effect of 6 plasma ketamine concentrations on the minimum alveolar concentration (MAC) of isoflurane in dogs.


METHODS
6 dogs.


METHODS
In experiment 1, the MAC of isoflurane was measured in each dog and the pharmacokinetics of ketamine were determined in isoflurane-anesthetized dogs after IV administration of a bolus (3 mg/kg) of ketamine. In experiment 2, the same dogs were anesthetized with isoflurane in oxygen. A target-controlled IV infusion device was used to administer ketamine and to achieve plasma ketamine concentrations of 0.5, 1, 2, 5, 8, and 11 microg/mL by use of parameters obtained from experiment 1. The MAC of isoflurane was determined at each plasma ketamine concentration, and blood samples were collected for ketamine and norketamine concentration determination.


RESULTS
Actual mean +/- SD plasma ketamine concentrations were 1.07 +/- 0.42 microg/mL, 1.62 +/- 0.98 microg/mL, 3.32 +/- 0.59 microg/mL, 4.92 +/- 2.64 microg/mL, 13.03 +/- 10.49 microg/mL, and 22.80 +/- 25.56 microg/mL for target plasma concentrations of 0.5, 1, 2, 5, 8, and 11 microg/mL, respectively. At these plasma concentrations, isoflurane MAC was reduced by 10.89% to 39.48%, 26.77% to 43.74%, 25.24% to 84.89%, 44.34% to 78.16%, 69.62% to 92.31%, and 71.97% to 95.42%, respectively. The reduction in isoflurane MAC was significant, and the response had a linear and quadratic component. Salivation, regurgitation, mydriasis, increased body temperature, and spontaneous movements were some of the adverse effects associated with the high plasma ketamine concentrations.


CONCLUSIONS
Ketamine appears to have a potential role for balanced anesthesia in dogs.
Solano
Adrian M
AM
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Pypendop
Bruno H
BH
Boscan
Pedro L
PL
Ilkiw
Jan E
JE
D000704:Analysis of Variance; D000778:Anesthetics, Dissociative / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D004285:Dogs / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007530:Isoflurane / Q000378:metabolism; D007649:Ketamine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000378:metabolism; D012044:Regression Analysis
D000778:Anesthetics, Dissociative; D018686:Anesthetics, Intravenous; D007649:Ketamine; D007530:Isoflurane