Association of Hypercalcemia Before Treatment With Hypocalcemia After Treatment in Dogs With Primary Hyperparathyroidism

Abstract

BackgroundDevelopment of hypocalcemia after treatment of hyperparathyroidism results in increased costs and risk of poorer outcomes. Previous studies have shown conflicting data about predictors of hypocalcemia after these procedures.Hypothesis/ObjectivesThe objective of this study was to investigate whether ionized calcium (iCa) concentrations before treatment are predictive of hypocalcemia or its clinical signs after surgical removal or heat ablation in dogs with primary hyperparathyroidism.AnimalsFifty‐four dogs with primary hyperparathyroidism (29 female, 25 male; 49 retrospective, 5 prospective).MethodsDogs were enrolled if they met the inclusion criteria: persistent hypercalcemia (iCa >1.41 mmol/L) due to primary hyperparathyroidism and absence of preemptive calcitriol treatment. All dogs were treated with parathyroidectomy (n = 37) or percutaneous ultrasound‐guided heat ablation (n = 17). After treatment, iCa was monitored twice daily until plateau or intervention.ResultsThere was a moderate correlation between before‐treatment hypercalcemia and after‐treatment hypocalcemia. The prospective study was terminated due to ethical concerns given findings in the retrospective section. All dogs were placed into groups according to their pretreatment iCa: 1.46–1.61 mmol/L, 1.62–1.71 mmol/L, iCa 1.72–1.81 mmol/L, or >1.81 mmol/L. After treatment, the mean lowest iCa for each group, respectively, was 1.19, 1.18, 1.13, and 1.01 mmol/L. There was a significant association between higher group and proportion of dogs with iCa <1.00 mmol/L (P = .014).Conclusions and Clinical ImportanceThis study demonstrates a moderate correlation between iCa concentration before treatment and hypocalcemia after treatment. Dogs with higher initial iCa concentrations should be treated to prevent rapid decline and development of clinical hypocalcemia.

Effect of Prophylactic Calcitriol Administration on Serum Ionized Calcium Concentrations after Parathyroidectomy: 78 Cases (2005–2015)

“…Some authors have suggested that preoperative serum calcium concentrations are indicative of the potential risk for postoperative hypocalcemia . The current veterinary literature contains conflicting information about the value of preoperative serum iCa and tCa concentrations for predicting postoperative hypocalcemia . In our study, a higher preoperative serum iCa concentration was not associated with a more rapid decrease in serum iCa concentration or risk hypocalcemia postoperatively, but was in fact protective.…”

“…Some authors have suggested that preoperative serum calcium concentrations are indicative of the potential risk for postoperative hypocalcemia . The current veterinary literature contains conflicting information about the value of preoperative serum iCa and tCa concentrations for predicting postoperative hypocalcemia .…”

“…Surgical removal or ablation of the affected parathyroid glands is the recommended treatment for dogs with PHPTH because of concern for the adverse effects of long‐term hypercalcemia . Studies in both humans and dogs have identified postoperative hypocalcemia as a risk factor for morbidity and mortality after parathyroidectomy . Previous studies showed a steep and linear decrease in serum PTH and serum iCa concentrations within the first 24 hours after parathyroidectomy, followed subsequently by a plateau.…”

“…Previous studies showed a steep and linear decrease in serum PTH and serum iCa concentrations within the first 24 hours after parathyroidectomy, followed subsequently by a plateau. The largest decrease in serum iCa concentrations typically occurs in the first 24–48 hours after removal of the abnormal parathyroid gland, with most dogs becoming normocalcemic within 48 hours of surgery . This rapid decrease is a consequence of the short half‐life of PTH (3–5 minutes), and the plateau results from reestablishment of normal parathyroid axis and parathyroid gland function with respect to PTH production.…”

“…Despite the potential to mitigate the risk of hypocalcemia, the benefit of prophylactic administration of calcitriol has not been well documented, and, in fact, its administration may not impact the rate of decrease in serum iCa concentrations . Furthermore, adverse effects associated with calcitriol administration may include continued suppression of PTH production, hypercalcemia, hyperphosphatemia, mineralization of soft tissues, and acute kidney injury . There currently are no widely accepted guidelines for perioperative calcitriol administration in dogs with PHPTH.…”