Comparative Physiological Effects of Immobilizing Agents in North American Ursids

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Comparative Physiological Effects of Immobilizing
Agents in North American Ursids

• Nigel Caulkett, University of Saskatchewan
• Marc Cattet, Canadian Cooperative Wildlife Health
  Centre
• Gordon Stenhouse, Alberta Sustainable Resources
  Development

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Historical Perspective

• Succinylcholine
• Phencyclidine
• Xylazine-ketamine
• Zolazepam-tiletamine (Telazol?)

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The Challenge

• Develop immobilizing agents that have the
  efficacy, safety, and reliability of Telazol?
• Address some of the drawbacks of Telazol?, i.e.
  lack of a suitable antagonist, lack of analgesia,
  large volume

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Methods

• Begin with detailed physiological studies in a
  controlled environment
• Cardiopulmonary data to determine safety
• Crossover studies, compared new combinations to
  Telazol?

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Polar bears

• Telazol? 8.2 mg/kg (ZT)
• Medetomidine 159 µg/kg ketamine 4 mg/kg (MK)
• Medetomidine 75 µg/kg Telazol? 2.2 mg/kg
  (MZT)
• Xylazine 2 mg/kg Telazol? 3 mg/kg (XZT)

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Black bears Medetomidine 52 µg/kg Telazol?
1.7 mg/kg
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Free-ranging bears

• Field test the drug combinations to determine
  efficacy and safety in field situations
• Obtain less detailed physiological information
• Used combinations to facilitate capture for other
  studies

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ZT, MK, MZT, and XZT in polar bears
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ZT and XZT in grizzly bears
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Heart rate in polar bears
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Mean arterial pressure (mmHg) in polar bears
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PaO2 (mmHg) in polar bears
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Rectal temperature in polar bears
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Physiological data in black bears immobilized
with MZT
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Polar bears field studies
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Grizzly bears field studies
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Discussion Telazol?

• Excellent cardiopulmonary stability. High margin
  of safety
• Large volume results in increased tissue trauma
• Lacks analgesia for painful procedures
• Cannot antagonize immobilization

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Medetomidine-ketamine

• Bradycardia and hypertension may not be well
  tolerated by animals with anemia, renal, hepatic
  or cardiac disease
• Potential for sudden recoveries decreases safety
  for handlers and bears
• Readily reversible with atipamezole
• Volume requirements approach those of Telazol?
• Temperature should be closely monitored as there
  is potential for hyperthermia to develop

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Medetomidine-Telazol?

• Hypertension may not be well tolerated by animals
  with anemia, renal, hepatic or cardiac disease
• Oxygenation should be monitored and supplemental
  oxygen should be available to treat hypoxemia
• Ability to impair thermoregulation

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Medetomidine-Telazol?

• Analgesia
• Smallest volume requirements of any mixture
• Rapid induction
• Readily reversible with atipamezole

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Xylazine-Telazol?

• Hypertension may not be well tolerated by animals
  with anemia, renal, hepatic or cardiac disease
• Oxygenation should be monitored and supplemental
  oxygen should be available to treat hypoxemia
• Ability to impair thermoregulation. Reversal of
  xylazine should be considered in severe cases
• Use yohimbine or atipamezole for reversal.
  Recoveries are quicker than Telazol? alone, but
  longer than MZT

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Xylazine-Telazol?

• Volume required is approximately half that of
  Telazol?
• Provides analgesia
• Reliable immobilization

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