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  • Author or Editor: Leigh A. Lamont x
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Abstract

Objective—To determine the relationship between bispectral index (BIS) and minimum alveolar concentration (MAC) multiples of sevoflurane in cats.

Animals—8 domestic cats.

Procedure—Each cat was anesthetized twice with sevoflurane. First, the MAC of sevoflurane for each cat was determined by use of the tail clamp method. Second, cats were anesthetized with sevoflurane at each of 5 MAC multiples administered in random order. Ventilation was controlled, and after a 15- minute equilibration period at each MAC multiple of sevoflurane, BIS data were collected for 5 minutes and the median value of BIS calculated.

Results—The mean (± SD) MAC of sevoflurane was 3.3 ± 0.2%. The BIS values at 0.5 MAC could not be recorded as a result of spontaneous movement in all 8 cats. The BIS values at 2.0 MAC were confounded by burst suppression in all 8 cats. Over the range of 0.8 to 1.5 MAC, BIS values decreased significantly with increasing end-tidal sevoflurane concentrations. Mean (± SD) BIS measurements were 30 ± 3, 21 ± 3, and 5 ± 2 at 0.8, 1.0, and 1.5 MAC, respectively.

Conclusions and Clinical Relevance—Values of BIS are inversely and linearly related to end-tidal sevoflurane concentrations in anesthetized cats, and BIS may be a useful predictor of CNS depression in this species. The consistently low BIS values recorded in this study suggest that clinical BIS end points used to titrate anesthetic agents in humans may not be applicable to cats. ( Am J Vet Res 2004;65:93–98)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the cardiovascular effects of the α2-adrenergic receptor agonist medetomidine hydrochloride in clinically normal cats.

Animals—7 clinically normal cats.

Procedure—Cats were anesthetized with isoflurane, and thermodilution catheters were placed for measurement of central venous, pulmonary, and pulmonary capillary wedge pressures and for determination of cardiac output. The dorsal pedal artery was catheterized for measurement of arterial blood pressures and blood gas tensions. Baseline variables were recorded, and medetomidine (20 µg/kg of body weight, IM) was administered. Hemodynamic measurements were repeated 15 and 30 minutes after medetomidine administration.

Results—Heart rate, cardiac index, stroke index, ratepressure product, and right and left ventricular stroke work index significantly decreased from baseline after medetomidine administration, whereas systemic vascular resistance and central venous pressure increased. However, systolic, mean, and diastolic arterial pressures as well as arterial pH, and oxygen and carbon dioxide tensions were not significantly different from baseline values.

Conclusions and Clinical Relevance—When administered alone to clinically normal cats, medetomidine (20 µg/kg, IM) induced a significant decrease in cardiac output, stroke volume, and heart rate. Arterial blood pressures did not increase, which may reflect a predominant central α2-adrenergic effect over peripheral vascular effects. (Am J Vet Res 2001;62:1745–1762)

Full access
in American Journal of Veterinary Research