Cardiopulmonary and behavioral responses to computer-driven infusion of detomidine in standing horses.

Abstract

Cardiopulmonary and behavioral responses to detomidine, a potent alpha 2-adrenergic agonist, were determined at 4 plasma concentrations in standing horses. After instrumentation and baseline measurements in 7 horses (mean +/- SD for age and body weight, 6 +/- 2 years, and 531 +/- 48.5 kg, respectively), detomidine was infused to maintain 4 plasma concentrations: 2.1 +/- 0.5 (infusion 1), 7.2 +/- 3.5 (infusion 2), 19.1 +/- 5.1. (infusion 3), and 42.9 +/- 10 (infusion 4) ng/ml, by use of a computer-controlled infusion system. Detomidine caused concentration-dependent sedation and somnolence. These effects were profound during infusions 3 and 4, in which marked head ptosis developed and all horses leaned heavily on the bars of the restraining stocks. Heart rate and cardiac index decreased from baseline measurements (42 +/- 7 beats/min, 65 +/- 11 ml.kg of body weight-1.min-1) in linear relationship with the logarithm of plasma detomidine concentration (ie, heart rate = -4.7 [loge detomidine concentration] + 44.3, P < 0.01; cardiac index = -10.5 [loge detomidine concentration] + 73.6, P < 0.01). Second-degree atrioventricular block developed in 5 of 7 horses during infusion 3, and in 6 of 7 horses during infusion 4. Mean arterial blood pressure increased significantly from 118 +/- 11 mm of Hg at baseline to 146 +/- 27 mm of Hg at infusion 4. Similar responses were observed for mean pulmonary artery and right atrial pressures. Systemic vascular resistance (baseline, 182 +/- 28 mm of Hg.ml-1.min-1.kg-1) increased significantly during infusions 3 and 4 (to 294 +/- 79 and 380 +/- 58, respectively). (ABSTRACT TRUNCATED AT 250 WORDS)

• Authors: D A Daunt, C I Dunlop, P L Chapman, S L Shafer, H Ruskoaho, O Vakkuri, D S Hodgson, L M Tyler, M Maze
• Journal: American journal of veterinary research (Am J Vet Res) Vol. 54 Issue 12 Pg. 2075-82 (Dec 1993) ISSN: 0002-9645 [Print] United States
• PMID: 8116941 (Publication Type: Journal Article)

Chemical References

• Analgesics
• Imidazoles
• Carbon Dioxide
• detomidine
• Oxygen

Topics

• Analgesics (pharmacology)
• Animals
• Blood Pressure (drug effects)
• Carbon Dioxide (blood)
• Cardiac Output (drug effects)
• Computers
• Female
• Heart Rate (drug effects)
• Hemodynamics (drug effects)
• Horses (physiology)
• Imidazoles (administration & dosage, blood, pharmacology)
• Infusions, Intra-Arterial (veterinary)
• Lung (drug effects, physiology)
• Male
• Orchiectomy
• Oxygen (blood)
• Oxygen Consumption (drug effects)
• Posture
• Pulmonary Artery (drug effects, physiology)
• Respiration (drug effects)
• Stroke Volume (drug effects)
• Vascular Resistance (drug effects)