MON-345 Hypercalcemia After Placement of Antibiotic-Loaded Calcium Sulfate Beads

Calcium sulfate beads are used to fill bone voids in bone loss and nonunion, as well as in the management of bone and joint infections.(1) Specifically, Stimulan® is an absorbed form of antibiotic-loaded calcium sulfate beads which delivers high local antibiotic concentrations for treatment of infection, but has also been associated with hypercalcemia in 5.4% of cases.(1) Despite the significant morbidity associated with hypercalcemia, there is little published literature describing this important complication. In our institution, five patients hospitalized between March 2019 and September 2019 with normal baseline calcium levels developed hypercalcemia as a complication of Stimulan® placement. Typically, 10 to 60 cc of Stimulan® were inserted in each surgery, with the exception of 120cc in one surgery. Three patients required a second surgery with antibiotic bead placement, and hypercalcemia occurred with both initial and subsequent surgeries. The onset of hypercalcemia varied from post-operative day one to four. The peak corrected calcium was 10.7-16.1 mg/dL which corresponded to ionized calcium of 1.57 to >2.20 mmol/L (normal 1.09-1.29 mmol/L). The patient with the highest bead volume had the highest calcium. Calcium peaked on post-operative days three to five. Patients were treated with intravenous fluids, furosemide, calcitonin and anti-resorptives including denosumab and zoledronic acid. Four patients required hemodialysis. Three patients required dialysis for symptomatic hypercalcemia and in one patient the indication was multifactorial. Calcium typically normalized by post-operative day 14 to 21, but hypercalcemia duration was unknown in two patients (one died; one had hypercalcemia on hospital discharge). As illustrated in our cases, patients who develop hypercalcemia after their initial antibiotic bead placement may be at risk for recurrent hypercalcemia if additional surgeries use antibiotic beads. Higher bead volume may be associated with more significant hypercalcemia.(1) Although previous cases have reported milder hypercalcemia, our cases demonstrate that hypercalcemia can be more severe and prolonged, necessitating dialysis in addition to traditional therapies. (1-3) References: 1.Kallala R, Harris WE, Ibrahim M, Dipane M, McPherson E. Use of Stimulan absorbable calcium sulphate beads in revision lower limb arthroplasty: Safety profile and complication rates. Bone Joint Res. 2018 Nov 3;7(10):570-579. 2.Kallala R, Haddad FS. Hypercalcaemia following the use of antibiotic-eluting absorbable calcium sulphate beads in revision arthroplasty for infection. Bone Joint J. 2015 Sep;97-B(9):1237-41. 3.Carlson Jr. CR, Markulis E, Thompson E, Havill J. A novel case of hypercalcemia following the use of calcium sulfate beads. Nephrol Open J. 2015; 1(1): 17-19.