Concentration of ionized calcium in plasma from cats with urethral obstruction

To measure ionized calcium concentration in plasma from cats with urethral obstruction and to correlate these values with results of clinical biochemical analyses and physical examinations.

Prospective study.

24 male cats.

Blood samples were obtained from each cat on admission, and PCV, pH, and concentrations of ionized calcium, total calcium, glucose, total solids, sodium, potassium, BUN, creatinine, chloride, magnesium, albumin, and phosphorus were determined. Mentation, tissue perfusion, and ECG recordings were also assessed.

18 (75%) cats had low ionized calcium concentrations (reference range, 2.4 to 2.8 mEq/L). Hypocalcemia was considered mild (2.0 to 2.36 mEq/L) in 9 (37.5%) cats, moderate (1.6 to 1.98 mEq/L) in 6 (25%), and severe (< 1.6 mEq/L) in 3 (12.5%). Significant positive correlations were found between ionized calcium concentration and heart rate, pH, and concentrations of sodium, chloride, and total calcium. Significant negative correlations were found between ionized calcium concentration and concentrations of potassium, BUN, creatinine, and phosphorus.

Most cats with urethral obstruction had a low concentration of ionized calcium. This may contribute to cardiac electrical and mechanical dysfunction in some severely affected cats. Although effects of i.v. administration of calcium were not evaluated, results of this study strengthen the rationale for its use in cats with urethral obstruction.