Cardiorespiratory effects of four α2-adrenoceptor agonist-ketamine combinations in captive red wolves

Kurt K. Sladky Environmental Medicine Consortium, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
North Carolina Zoological Park, Hanes Veterinary Medical Center, 4401 Zoo Pky, Asheboro, NC 27203.

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Brian T. Kelly Environmental Medicine Consortium, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
United States Fish and Wildlife Service, Alligator River National Wildlife Refuge, PO Box 1969, Manteo, NC 27954.

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Michael R. Loomis Environmental Medicine Consortium, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
North Carolina Zoological Park, Hanes Veterinary Medical Center, 4401 Zoo Pky, Asheboro, NC 27203.

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Michael K. Stoskopf Environmental Medicine Consortium, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.

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William A. Horne Environmental Medicine Consortium, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.
Anatomy, Physiological Sciences, and Radiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606.

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Abstract

Objective—To evaluate the cardiopulmonary effects of immobilizing doses of xylazine-ketamine (XK), medetomidine-ketamine (MK), medetomidine-ketamine- acepromazine (MKA), and medetomidine-butorphanol- ketamine (MBK) in captive red wolves.

Design—Prospective study.

Animals—32 adult captive red wolves.

Procedure—Wolves were randomly assigned to 1 of 4 treatment groups: XK, MK, MKA, or MBK. Physiologic variables measured included heart rate, blood pressure, respiratory rate, tidal volume, oxygen-hemoglobin saturation (SpO2), end-tidal CO2, arterial blood gases, and rectal temperature. Induction time, muscle relaxation, and quality of recovery were assessed.

Results—Heart rates were lower in wolves in the MBK group than for the other groups. All 4 drug combinations induced considerable hypertension, with diastolic pressures exceeding 116 mm Hg. Blood pressure was lowest in wolves receiving the MBK combination. Respiratory rate was significantly higher in wolves receiving XK, MK, and MKA. Tidal volumes were similar for all groups. Wolves receiving XK, MK, and MKA were well-oxygenated throughout the procedure (SpO2 > 93%), whereas those receiving MBK were moderately hypoxemic (87% < SpO2 < 93%) during the first 20 minutes of the procedure. Hyperthermia was detected initially following induction in all groups.

Conclusions and Clinical Relevance—The α2- adrenoceptor agonist-ketamine combinations provide rapid reversible anesthesia for red wolves but cause severe sustained hypertension. Such an adverse effect puts animals at risk for development of cerebral encephalopathy, retinal hemorrhage, pulmonary edema, and myocardial failure. Although the MBK combination offers some advantages over the others, it is advised that further protocol refinements be made to minimize risks associated with acute hypertension. (J Am Vet Med Assoc 2000;217:1366–1371)

Abstract

Objective—To evaluate the cardiopulmonary effects of immobilizing doses of xylazine-ketamine (XK), medetomidine-ketamine (MK), medetomidine-ketamine- acepromazine (MKA), and medetomidine-butorphanol- ketamine (MBK) in captive red wolves.

Design—Prospective study.

Animals—32 adult captive red wolves.

Procedure—Wolves were randomly assigned to 1 of 4 treatment groups: XK, MK, MKA, or MBK. Physiologic variables measured included heart rate, blood pressure, respiratory rate, tidal volume, oxygen-hemoglobin saturation (SpO2), end-tidal CO2, arterial blood gases, and rectal temperature. Induction time, muscle relaxation, and quality of recovery were assessed.

Results—Heart rates were lower in wolves in the MBK group than for the other groups. All 4 drug combinations induced considerable hypertension, with diastolic pressures exceeding 116 mm Hg. Blood pressure was lowest in wolves receiving the MBK combination. Respiratory rate was significantly higher in wolves receiving XK, MK, and MKA. Tidal volumes were similar for all groups. Wolves receiving XK, MK, and MKA were well-oxygenated throughout the procedure (SpO2 > 93%), whereas those receiving MBK were moderately hypoxemic (87% < SpO2 < 93%) during the first 20 minutes of the procedure. Hyperthermia was detected initially following induction in all groups.

Conclusions and Clinical Relevance—The α2- adrenoceptor agonist-ketamine combinations provide rapid reversible anesthesia for red wolves but cause severe sustained hypertension. Such an adverse effect puts animals at risk for development of cerebral encephalopathy, retinal hemorrhage, pulmonary edema, and myocardial failure. Although the MBK combination offers some advantages over the others, it is advised that further protocol refinements be made to minimize risks associated with acute hypertension. (J Am Vet Med Assoc 2000;217:1366–1371)

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