Morphine-isoflurane interaction in dogs, swine and rhesus monkeys.
In monkeys, dogs and swine (six each) we tested the reduction of the isoflurane MAC (minimal alveolar concentration) produced by 2 mg.kg-1 morphine intravenously (i.v.) and the concurrent effect on PCO2 with spontaneous ventilation. MAC fell to a minimum of 55% of control at 53 min in monkeys, 50% at 38 min in dogs and 13% at 33 min in swine. PaCO2 rose at constant MAC with morphine to 55-60 mmHg, but did not fall over the next several hours despite the decline of plasma morphine concentration, and the resulting needed rise in isoflurane concentration to keep the anaesthesia depth at 1 MAC. After isoflurane concentration had returned to pre-morphine control levels, naloxone immediately reduced PaCO2 to or below control level. Morphine pharmacokinetics in the three species studied conformed to a two-compartment model.
Steffey
E P
EP
Department of Surgery, School of Veterinary Medicine, University of California, Davis 95616.
Baggot
J D
JD
Eisele
J H
JH
Willits
N
N
Woliner
M J
MJ
Jarvis
K A
KA
Elliott
A R
AR
Tagawa
M
M
D000758:Anesthesia / Q000662:veterinary; D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D002245:Carbon Dioxide / Q000378:metabolism; D004285:Dogs; D004347:Drug Interactions; D006439:Hemodynamics; D007275:Injections, Intravenous / Q000662:veterinary; D007530:Isoflurane / Q000494:pharmacology*; D008253:Macaca mulatta; D009020:Morphine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D010313:Partial Pressure; D011650:Pulmonary Alveoli / Q000187:drug effects; D011863:Radioimmunoassay / Q000662:veterinary; D013045:Species Specificity; D013552:Swine; D013556:Swine, Miniature
D002245:Carbon Dioxide; D009020:Morphine; D007530:Isoflurane