MON-334 Severe Hypercalcemia Following Hip Joint Implantation of Stimulan® Calcium Sulfate Antibiotic Beads

Introduction: The diagnosis and management of hypercalcemia in hospitalized patients can be challenging. Hypercalcemia is often associated with significant morbidity and end-organ damage which may delay a patient’s recovery. Case report: A 63-years-old female presented for evaluation of left hip pain and was found to have an infection of the prosthetic joint. Past medical history was significant for type 2 diabetes and atrial fibrillation. No known history of malignancy or excess calcium, vitamins A or D intake. Past surgical history was significant for multiple left hip fixation surgeries and a left hip arthroplasty 4 months prior. Patient’s serum calcium on admission was 8.4 mg/dL (corrected 9.5 mg/dL, range 9.5-10.5 mg/dL), serum creatinine 1.2 mg/dL (range, 0.5 - 1.2 mg/dL). Three days later, she underwent surgical irrigation and debridement of the left hip with placement of 30 cc STIMULAN® antibiotic beads with vancomycin. On postoperative day (POD) 5, patient was found to be confused. Laboratory workup revealed serum calcium 13 mg/dL, ionized calcium 1.91 mmol/L (range, 1.12-1.32 mmol/L), serum creatinine 1.6 mg/dL, intact PTH 10 (range, 15- 65 pg/mL), PTH-rp 15 pg/mL (range, 14-27 pg/mL), 25-OH-vitamin D 18 ng/mL (range, 30-60 ng/mL), 1,25-OH2-vitamin D <8 ng/mL (range, 18-72 ng/mL). Clinical challenge: The differential diagnosis of non-PTH mediated hypercalcemia includes malignancy, granulomatosis and/or excess calcium intake. The patient’s history and laboratory data were not consistent with these etiologies. The temporal nature of the hypercalcemia in relation to implantation of antibiotic beads suggest causality of exogenous calcium sulfate and development of the patient’s hypercalcemia. Mild renal insufficiency, as well as immobilization in the setting of surgery, were likely also contributory. Treatment and outcome: This patient was first treated with aggressive intravenous saline and calcitonin. Serum calcium rose to 13.7 mg/dL and pamidronate 30 mg was administered. Hypercalcemia resolved on POD 11 with improvement in patient functional status. Discussion: Hypercalcemia due to implanted calcium sulfate antibiotic beads is not well described outside of case reports. Kallala found hypercalcemia in less than 0.01% of patients who underwent bead implantation, with all the affected patients presenting with preoperative renal failure. Conclusion: Hypercalcemia in the setting of calcium sulfate antibiotic beads implantation may contribute to a patient’s confusion and increase length-of-stay. We recommend serum calcium and creatinine to be closely monitored during the perioperative period in patients who receive calcium sulfate antibiotic beads. Risk factors for the development of hypercalcemia require additional study, though patients with pre-existing renal insufficiency may not be good candidates for the mechanism of antibiotic administration.