Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA
Hyperkalemia is an often noted, but poorly understood, anesthetic complication of exotic felids induced with alpha-2 adrenergic agonists and maintained on isoflurane.1 Hyperkalemia is thought to develop as alpha-2 agonists bind receptors on pancreatic beta cells, inhibiting insulin release and resulting in increased plasma potassium and glucose levels.2,3 Ten cases of hyperkalemia (K+>5.5 mEq/L) were identified in anesthetized tigers (Panthera tigris, n=7) and lions (Panthera leo, n=3). These cases were compared to 30 procedures (25 tigers and 5 lions) of similar anesthetic protocol and duration in an effort to identify potential risk factors for the development of hyperkalemia. Plasma levels of potassium, glucose, magnesium, phosphorus, and insulin obtained throughout the duration of anesthesia were compared between felids which developed hyperkalemia and those which did not. Dosages of medetomidine or dexmedetomidine were also compared. Lions had significantly higher levels of potassium and were more likely to develop hyperkalemia (p=0.003). There were no significant differences between the groups in initial potassium, glucose, magnesium, phosphorous, or insulin levels or in alpha-2 dosage or anesthetic quality. Potassium increased progressively in all animals but occurred at a greater rate in those that developed hyperkalemia. This rise in potassium was associated with changes in pH and phosphorus but not with insulin or glucose. Administration of atipamezole significantly slowed the rate of potassium increase (p=0.0195). Routine electrolyte monitoring beginning at induction with early administration of alpha-2 antagonists is recommended for the prevention of hyperkalemia in anesthetized exotic felids.
The authors wish to thank Tiger Haven Inc. for their care and management of the cats in this study.
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