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Cardiopulmonary effects of prolonged anesthesia via propofol-medetomidine infusion in ponies

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  • 1 Veterinary Surgery Clinic, University of Zürich, Zürich, Switzerland.
  • | 2 Department of Farm Animal and Equine Medical Surgery, The Royal Veterinary College, University of London, Hatfield, UK.
  • | 3 Department of Farm Animal and Equine Medical Surgery, The Royal Veterinary College, University of London, Hatfield, UK.
  • | 4 Falkenstrasse 2, Munchen, Germany.
  • | 5 Clinic Barmelweid, Barmelweid, Switzerland.
  • | 6 Department of Veterinary Clinical Studies, University of Glasgow Veterinary School, Glasgow, Scotland.
  • | 7 Department of Farm Animal and Equine Medical Surgery, The Royal Veterinary College, University of London, Hatfield, UK.

Abstract

Objective—To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery.

Animals—10 ponies.

Procedure—After sedation was induced by IV administration of medetomidine (7 μg/kg of body weight), anesthesia was induced by IV administration of propofol (2 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 μg/kg per hour) and propofol (0.07 to 0.11 mg/kg per minute). Spontaneous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during anesthesia. Five ponies received atipamezole (60 μg/kg) during recovery.

Results—During anesthesia, mean cardiac index and heart rate increased significantly until 150 minutes, then decreased until cessation of anesthesia. Mean arterial pressure and systemic vascular resistance index increased significantly between 150 minutes and 4 hours. In 4 ponies, PaO2 decreased to < 60 mm Hg. Mean blood propofol concentrations from 20 minutes after induction onwards ranged from 2.3 to 3.5 μg/ml. Recoveries were without complications and were complete within 28 minutes with atipamezole administration and 39 minutes without atipamezole administration.

Conclusions and Clinical Relevance—During total IV anesthesia of long duration with medetomidine-propofol, cardiovascular function is comparable to or better than under inhalation anesthesia. This technique may prove suitable in equids in which prompt recovery is essential; however, in some animals severe hypoxia may develop and oxygen supplementation may be necessary. (Am J Vet Res 2001;62:1428–1435)

Abstract

Objective—To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery.

Animals—10 ponies.

Procedure—After sedation was induced by IV administration of medetomidine (7 μg/kg of body weight), anesthesia was induced by IV administration of propofol (2 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 μg/kg per hour) and propofol (0.07 to 0.11 mg/kg per minute). Spontaneous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during anesthesia. Five ponies received atipamezole (60 μg/kg) during recovery.

Results—During anesthesia, mean cardiac index and heart rate increased significantly until 150 minutes, then decreased until cessation of anesthesia. Mean arterial pressure and systemic vascular resistance index increased significantly between 150 minutes and 4 hours. In 4 ponies, PaO2 decreased to < 60 mm Hg. Mean blood propofol concentrations from 20 minutes after induction onwards ranged from 2.3 to 3.5 μg/ml. Recoveries were without complications and were complete within 28 minutes with atipamezole administration and 39 minutes without atipamezole administration.

Conclusions and Clinical Relevance—During total IV anesthesia of long duration with medetomidine-propofol, cardiovascular function is comparable to or better than under inhalation anesthesia. This technique may prove suitable in equids in which prompt recovery is essential; however, in some animals severe hypoxia may develop and oxygen supplementation may be necessary. (Am J Vet Res 2001;62:1428–1435)