Cardiovascular effects of the α2-adrenergic receptor agonist medetomidine in clinically normal cats anesthetized with isoflurane

A. L. Golden From the Department of Biological Sciences, 1000 Chastain Rd, Kennesaw State University, Kennesaw, GA 30144-5591 (Golden), and the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37901 (Bright, Daniel, Fefee, Schmidt, Harvey).

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J. M. Bright From the Department of Biological Sciences, 1000 Chastain Rd, Kennesaw State University, Kennesaw, GA 30144-5591 (Golden), and the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37901 (Bright, Daniel, Fefee, Schmidt, Harvey).

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G. B. Daniel From the Department of Biological Sciences, 1000 Chastain Rd, Kennesaw State University, Kennesaw, GA 30144-5591 (Golden), and the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37901 (Bright, Daniel, Fefee, Schmidt, Harvey).

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D. Fefee From the Department of Biological Sciences, 1000 Chastain Rd, Kennesaw State University, Kennesaw, GA 30144-5591 (Golden), and the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37901 (Bright, Daniel, Fefee, Schmidt, Harvey).

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D. Schmidt From the Department of Biological Sciences, 1000 Chastain Rd, Kennesaw State University, Kennesaw, GA 30144-5591 (Golden), and the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37901 (Bright, Daniel, Fefee, Schmidt, Harvey).

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R. C. Harvey From the Department of Biological Sciences, 1000 Chastain Rd, Kennesaw State University, Kennesaw, GA 30144-5591 (Golden), and the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37901 (Bright, Daniel, Fefee, Schmidt, Harvey).

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Abstract

Objective

To assess the cardiovascular effects of the α2-adrenergic receptor agonist medetomidine in healthy cats anesthetized with 2% isoflurane.

Animals

11 clinically normal cats.

Procedure

Cats were anesthetized with isoflurane, and catheters were inserted for measurement of aortic, left ventricular, and right atrial pressures. For data collection, end-tidal isoflurane concentration was reduced to 2%, and end-tidal CO2 was maintained at 35 to 40 mm of Hg by use of positive-pressure ventilation. After measurement of baseline data, medetomidine (0.01 mg/kg of body weight, IM) was administered and data were collected continuously for 75 minutes. At the end of data collection, incisions were closed and cats were allowed to recover from anesthesia.

Results

Medetomidine significantly increased mean arterial pressure and systemic vascular resistance. The increase in mean arterial pressure was maximal at 17.8 ± 7 minutes after medetomidine administration. Medetomidine also increased left ventricular peak systolic pressure, left ventricular end diastolic pressure, and right atrial pressure. Medetomidine significantly decreased heart rate and mean aortic flow.

Conclusions

The low dosage of medetomidine (0.01 mg/kg, IM) promoted severe vasoconstriction in isoflurane-anesthetized cats, and resulted in sustained increases in left ventricular preload and afterload. (Am J Vet Res 1998;59:509–513)

Abstract

Objective

To assess the cardiovascular effects of the α2-adrenergic receptor agonist medetomidine in healthy cats anesthetized with 2% isoflurane.

Animals

11 clinically normal cats.

Procedure

Cats were anesthetized with isoflurane, and catheters were inserted for measurement of aortic, left ventricular, and right atrial pressures. For data collection, end-tidal isoflurane concentration was reduced to 2%, and end-tidal CO2 was maintained at 35 to 40 mm of Hg by use of positive-pressure ventilation. After measurement of baseline data, medetomidine (0.01 mg/kg of body weight, IM) was administered and data were collected continuously for 75 minutes. At the end of data collection, incisions were closed and cats were allowed to recover from anesthesia.

Results

Medetomidine significantly increased mean arterial pressure and systemic vascular resistance. The increase in mean arterial pressure was maximal at 17.8 ± 7 minutes after medetomidine administration. Medetomidine also increased left ventricular peak systolic pressure, left ventricular end diastolic pressure, and right atrial pressure. Medetomidine significantly decreased heart rate and mean aortic flow.

Conclusions

The low dosage of medetomidine (0.01 mg/kg, IM) promoted severe vasoconstriction in isoflurane-anesthetized cats, and resulted in sustained increases in left ventricular preload and afterload. (Am J Vet Res 1998;59:509–513)

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