Effects of a peripheral alpha2 adrenergic-receptor antagonist on the hemodynamic changes induced by medetomidine administration in conscious dogs.
OBJECTIVE
To evaluate the effects of administration of a peripheral alpha(2)-adrenergic receptor antagonist (L-659,066), with and without concurrent administration of glycopyrrolate, on cardiopulmonary effects of medetomidine administration in dogs.


METHODS
6 healthy adult dogs.


METHODS
Dogs received saline (0.9% NaCl) solution (saline group), L-659,066 (group L), or L-659,066 with glycopyrrolate (group LG). These pretreatments were followed 10 minutes later by administration of medetomidine in a randomized crossover study. Hemodynamic measurements and arterial and mixed-venous blood samples for blood gas analysis were obtained prior to pretreatment, 5 minutes after pretreatment, and after medetomidine administration at intervals up to 60 minutes.


RESULTS
After pretreatment in the L and LG groups, heart rate, cardiac index, and partial pressure of oxygen in mixed-venous blood (PvO2) values were higher than those in the saline group. After medetomidine administration, heart rate, cardiac index, and PvO2 were higher and systemic vascular resistance, mean arterial blood pressure, and central venous pressure were lower in the L and LG groups than in the saline group. When the L and LG groups were compared, heart rate was greater at 5 minutes after medetomidine administration, mean arterial blood pressure was greater at 5 and 15 minutes after medetomidine administration, and central venous pressure was lower during the 60-minute period after medetomidine administration in the LG group.


CONCLUSIONS
Administration of L-659,066 prior to administration of medetomidine reduced medetomidine-induced cardiovascular changes in healthy dogs. No advantage was detected with concurrent administration of L-659,066 and glycopyrrolate.
Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1H 2W1, Canada.
Saad S
SS
Enouri
Carolyn L
CL
Kerr
Wayne N
WN
McDonell
M Lynne
ML
O'Sullivan
Francisco J Teixeira
FJ
Neto
D018674:Adrenergic Antagonists / Q000494:pharmacology*; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D018592:Cross-Over Studies; D004285:Dogs / Q000502:physiology*; D004347:Drug Interactions; D006024:Glycopyrrolate / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D020926:Medetomidine / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D011807:Quinolizines / Q000494:pharmacology*; D011897:Random Allocation; D012119:Respiration / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
D018674:Adrenergic Antagonists; D018712:Analgesics, Non-Narcotic; D018727:Muscarinic Antagonists; D011807:Quinolizines; C055732:vatinoxan; D020926:Medetomidine; D006024:Glycopyrrolate