Hemodynamic effects of medetomidine in the dog: a dose titration study.
OBJECTIVE
To characterize the hemodynamic effects of medetomidine administered intravenously at doses ranging from 1 to 20 microg/kg, and to determine whether these effects are dose dependent.


METHODS
Prospective randomized multidose trial.


METHODS
Twenty-five clinically normal male beagles (5 groups of 5), aged 1 to 4 years and weighing 13.5 +/- 1.7 kg.


METHODS
Medetomidine, at a dose of 1, 2, 5, 10, or 20 microg/kg, was administered intravenously at time 0. Heart rate, arterial pressure, central venous pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, body temperature, cardiac output, and packed cell volume were measured immediately before and at selected times after medetomidine administration (3, 7, 10, 20, 30, 40, 50, and 60 minutes in all groups, at 90 minutes for the 10 and 20 microg/kg groups, and at 120 minutes for the highest dose). Cardiac index, stroke index, rate-pressure product, systemic vascular resistance index, pulmonary vascular resistance index, and left and right ventricular stroke work indices were calculated. The degree of sedation was subjectively scored by an observer who was blinded to the treatment used.


RESULTS
Heart rate, rate-pressure product, cardiac index, and left and right ventricular stroke work indices decreased below baseline values. Central venous pressure and systemic vascular resistance index increased above baseline measurements. Except in the 2 microg/kg group, after an initial and short lasting increase, a prolonged decrease in arterial pressure was observed.


CONCLUSIONS
Hemodynamic changes were observed with the intravenous (IV) administration of medetomidine, at any dose. However, the two lowest doses (1 and 2 microg/kg) produced less cardiovascular depression.


CONCLUSIONS
Medetomidine is an alpha-2 adrenoceptor agonist widely used in dogs, producing sedation, analgesia and cardiovascular depression. When using IV medetomidine, a reduction of the recommended dosage (ie, +/-30 to 40 microg/kg) by up to 6 times did not significantly influence the cardiovascular effects.
Pypendop
B H
BH
Department of Small Animal Reproduction, School of Veterinary Medicine, University of Liege, Belgium.
Verstegen
J P
JP
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D004285:Dogs / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects; D006400:Hematocrit / Q000662:veterinary; D006439:Hemodynamics / Q000187:drug effects*; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology*; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D007262:Infusions, Intravenous / Q000662:veterinary; D008297:Male; D020926:Medetomidine; D011446:Prospective Studies; D016037:Single-Blind Method; D013318:Stroke Volume / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D006993:Hypnotics and Sedatives; D007093:Imidazoles; D020926:Medetomidine