Historical and physical parameters as predictors of severe hyperkalemia in male cats with urethral obstruction

Objective: To evaluate selected historical and physical parameters as predictors of hyperkalemia in male cats with urethral obstruction. Design: Retrospective study. Setting: Veterinary teaching hospital. Animals: Two hundred and twenty‐three male cats. Interventions: None. Measurements and main results: The metabolic derangements of 223 male cats that presented with urethral obstruction from 1997 through 1999 were reported in a companion article. Approximately 12% of the cats had multiple, life‐threatening metabolic derangements. In the present study, historical and physical parameters were evaluated as predictors of hyperkalemia (K⁺≥8.0 mmol/L) in cats with urethral obstruction. The 4 historical parameters significantly associated with hyperkalemia were: first time obstruction, outdoor status, anorexia, or vomiting. The 5 physical parameters significantly associated with hyperkalemia were: rectal temperature, heart rate, respiratory rate, pulse quality, and the presence of arrhythmia. Of the physical parameters, a rectal temperature below 95–96.6°F (35–35.9°C) or a heart rate below 120 b.p.m. were the most accurate predictors. When used in combination (i.e., evidence of bradycardia and hypothermia), the specificity for hyperkalemia was 98–100%. Conclusions: Rectal temperature and heart rate were the best parameters for predicting hyperkalemia in this population.