Evaluation of preoperative serum concentrations of ionized calcium and parathyroid hormone as predictors of hypocalcemia following parathyroidectomy in dogs with primary hyperparathyroidism: 17 cases (2001-2009).

OBJECTIVE: To determine whether preoperative serum ionized calcium (iCa) or parathyroid hormone (PTH) concentrations help predict postoperative hypocalcemia following parathyroidectomy in dogs with primary hyperparathyroidism.

DESIGN: Retrospective case series.

ANIMALS: 17 dogs with primary hyperparathyroidism treated with parathyroidectomy.

PROCEDURES: Medical records were evaluated from years 2001 to 2009. Data evaluated included age, breed, sex, clinical signs, diagnostic tests performed, preoperative and postoperative iCa concentrations, preoperative PTH concentrations, and whether calcium supplementation was provided following surgery. Two groups were identified on the basis of whether dogs became hypocalcemic (iCa < 1.2 mmol/L) following parathyroidectomy.

RESULTS: 12 dogs developed hypocalcemia after surgery. Preoperative (within 24 hours before surgery) iCa concentrations for the hypocalcemic group (mean ± SD, 1.82 ± 0.22 mmol/L) and the nonhypocalcemic group (1.83 ± 0.29 mmol/L) were not significantly different. Calcium concentrations decreased in a linear fashion during the 24 hours following parathyroidectomy, and the slopes of the decrease over that time were not significantly different between the 2 groups. Preoperative PTH concentrations were not significantly different between the hypocalcemic and nonhypocalcemic groups.

CONCLUSIONS AND CLINICAL RELEVANCE: Preoperative iCa and PTH concentrations were not predictive of postoperative hypocalcemia in dogs undergoing parathyroidectomy for primary hyperparathyroidism. Future studies to evaluate whether calcium supplementation should be provided on an individual basis with perhaps more emphasis on clinical signs than iCa concentrations after surgery may be warranted.