(938) Hypercalcemia-Induced Nephrogenic Diabetes Insipidus due to a Calcium Channel Blocker Overdose

Introduction: Management of calcium channel blocker overdose includes the use of intravenous calcium supplementation, high dose insulin therapy, and vasopressors. As first line therapy, calcium supplementation is used to improve vascular smooth muscle tone and inotropy. However, there is no consensus on a target calcium goal, and evidence suggests significant variability in patient’s response to differing calcium concentrations. Consequently, targeting a higher calcium concentration may result in harm such as nephrogenic diabetes insipidus due to the degradation of aquaporin channels.

Description: A 60 year-old male presented with hypotension, nausea, and vomiting following an intentional overdose of ninety amlodipine 5 mg tablets. At the outside hospital, epinephrine and vasopressin were started for profound hypotension despite receiving norepinephrine at 2 mcg/kg/min. On arrival, the patient was initiated on a calcium gluconate infusion with a target ionized calcium (iCal) of 2 - 2.6 (our hospital assay has a maximum value of 2) per toxicology recommendations. The calcium infusion was titrated to the same iCal goal for ~24 hours despite decreasing vasopressor requirements. On hospital day 2, the iCal goal was reduced to 1.8 - 2, and both the calcium infusion and all vasopressors were eventually discontinued on hospital day 4. Immediately following the discontinuation of vasopressin, his hourly urine output significantly increased to ~300 mL/hr, and he developed severe hypernatremia with serum sodium reaching up to 171 mmol/L. Despite giving dextrose 5% infusion at 250 mL/hr, his sodium levels and urine output remained high. He was then started on desmopressin, which reduced his urine output and serum sodium to 141 mmol/L. Resolution of the hypernatremia also coincided with normalization of the ionized calcium. No new neurological symptoms were noted during his hospital stay.

Discussion: This case highlights a rare complication of aggressive calcium supplementation to target an ionized calcium level twice the physiological normal. Given the potential for iatrogenic harm, use of specified calcium goals may not be appropriate, and titration based on clinical response such as vasopressor requirements should be considered.