Cardiorespiratory effects of a combination of medetomidine, midazolam, and butorphanol in dogs.
OBJECTIVE
To characterize cardiorespiratory effects for a combination of medetomidine, butorphanol, and midazolam and to compare magnitude of cardiorespiratory depression with that induced by a commonly used inhalation anesthetic regimen (acepromazine-butorphanol-thiopental-halothane).


METHODS
10 clinically normal dogs (2 groups of 5).


METHODS
In treated dogs, medetomidine was administered (time, 0 minutes); midazolam and butorphanol were administered when effects of medetomidine were maximal (time, 20), and atipamezole was administered subsequently (time 60). In control dogs, drugs were administered after allowing effects of each agent to be achieved: acepromazine was given at time 0, butorphanol and thiopental were administered at time 35, and halothane was administered from time 45 until 110. Various cardiorespiratory and hematologic variables were measured or calculated.


RESULTS
Respiratory rate, arterial and venous pH, venous oxygen content, oxygen consumption, and oxygen delivery decreased significantly below baseline values for treated dogs; end-tidal CO2, arterial and venous P(CO)2, and O2 extraction increased significantly above baseline values. Compared with data obtained after anesthesia, arterial HCO3- concentration, venous P(O2) and S(O2), cardiac output, oxygen extraction, and oxygen delivery appeared more modified in treated dogs. Oxygen consumption and physiologic shunt fraction were less modified in treated dogs than control dogs.


CONCLUSIONS
Medetomidine-butorphanol-midazolam combination induced respiratory depression, comparable in magnitude to that induced by a widely used inhalation anesthetic regimen. Respiratory variables remained within acceptable limits during anesthesia; however, those associated with cardiovascular function were more severely affected.
Pypendop
B
B
Department of Small Animal Reproduction, School of Veterinary Medicine, University of Liege, Belgium.
Verstegen
J
J
D000075:Acepromazine / Q000008:administration & dosage / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D019162:Anesthetics, Combined / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D014151:Anti-Anxiety Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D001784:Blood Gas Analysis / Q000662:veterinary; D002077:Butorphanol / Q000008:administration & dosage / Q000494:pharmacology; D002302:Cardiac Output / Q000187:drug effects; D004285:Dogs / Q000502:physiology*; D018492:Dopamine Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D020926:Medetomidine / Q000008:administration & dosage / Q000494:pharmacology; D008874:Midazolam / Q000008:administration & dosage / Q000494:pharmacology; D010100:Oxygen / Q000502:physiology; D011897:Random Allocation; D012129:Respiratory Function Tests / Q000662:veterinary
D000316:Adrenergic alpha-Agonists; D000701:Analgesics, Opioid; D019162:Anesthetics, Combined; D014151:Anti-Anxiety Agents; D018492:Dopamine Antagonists; D000075:Acepromazine; D020926:Medetomidine; D002077:Butorphanol; D008874:Midazolam; D010100:Oxygen