Minimum alveolar concentration of sevoflurane in spontaneously breathing llamas and alpacas

Tamara L. Grubb Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.
Present address is 2002 Schultheis Rd, Uniontown, WA 99179.

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John W. Schlipf Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Thomas W. Riebold Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Christopher K. Cebra Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Lisa Poland Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Xenia Zawadzkas Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Nicole Mailhot Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331.

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Abstract

Objective—To determine the minimum alveolar concentration (MAC) of sevoflurane in spontaneously breathing llamas and alpacas.

Design—Prospective study.

Animals—6 healthy adult llamas and 6 healthy adult alpacas.

Procedure—Anesthesia was induced with sevoflurane delivered with oxygen through a mask. An endotracheal tube was inserted, and a port for continuous measurement of end-tidal and inspired sevoflurane concentrations was placed between the endotracheal tube and the breathing circuit. After equilibration at an end-tidal-to-inspired sevoflurane concentration ratio > 0.90 for 15 minutes, a 50-Hz, 80-mA electrical stimulus was applied to the antebrachium until a response was obtained (ie, gross purposeful movement) or for up to 1 minute. The vaporizer setting was increased or decreased to effect a 10 to 20% change in end-tidal sevoflurane concentration, and equilibration and stimulus were repeated. The MAC was defined as the mean of the lowest end-tidal sevoflurane concentration that prevented a positive response and the highest concentration that allowed a positive response.

Results—Mean ± SD MAC of sevoflurane was 2.29 ± 0.14% in llamas and 2.33 ± 0.09% in alpacas. Conclusions and Clinical Relevance—The MAC of sevoflurane in llamas and alpacas was similar to that reported for other species. (J Am Vet Med Assoc 2003;223:1167–1169)

Abstract

Objective—To determine the minimum alveolar concentration (MAC) of sevoflurane in spontaneously breathing llamas and alpacas.

Design—Prospective study.

Animals—6 healthy adult llamas and 6 healthy adult alpacas.

Procedure—Anesthesia was induced with sevoflurane delivered with oxygen through a mask. An endotracheal tube was inserted, and a port for continuous measurement of end-tidal and inspired sevoflurane concentrations was placed between the endotracheal tube and the breathing circuit. After equilibration at an end-tidal-to-inspired sevoflurane concentration ratio > 0.90 for 15 minutes, a 50-Hz, 80-mA electrical stimulus was applied to the antebrachium until a response was obtained (ie, gross purposeful movement) or for up to 1 minute. The vaporizer setting was increased or decreased to effect a 10 to 20% change in end-tidal sevoflurane concentration, and equilibration and stimulus were repeated. The MAC was defined as the mean of the lowest end-tidal sevoflurane concentration that prevented a positive response and the highest concentration that allowed a positive response.

Results—Mean ± SD MAC of sevoflurane was 2.29 ± 0.14% in llamas and 2.33 ± 0.09% in alpacas. Conclusions and Clinical Relevance—The MAC of sevoflurane in llamas and alpacas was similar to that reported for other species. (J Am Vet Med Assoc 2003;223:1167–1169)

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