THU433 Spontaneous Vertebral Fractures In The Setting Of Prolonged CRRT

Disclosure: F. Akanbi: None. M. Kutahyalioglu: None. P. Gogineni: None. S. Raja: None. Introduction: Bone resorption and hypercalcemia due to prolonged immobilization are known complications in critically ill patients. This is more pronounced in patients with high bone turnover rates such as in secondary hyperparathyroidism. In this case report, the chelation of calcium by citrate masked the immobilization hypercalcemia, resulting in marked bone loss and spontaneous vertebral fractures in the context of normal calcium levels. Case report: 23 year old man with no past medical history was seen on account of concerns for calcium loss from his bones as he was on CRRT, for 4 months and the amount of calcium in the extracorporeal circuit was more than expected. He had presented with new onset systolic heart failure (EF 10%) secondary to fulminant post-COVID-19 myocarditis, and renal failure due to acute tubular necrosis. CRRT with citrate dextrose anticoagulation was initiated at presentation. He had received pulse dose prednisone for presumed post-viral myocarditis. He was awaiting heart and kidney transplantation. Greater than average calcium clearance during CRRT prompted workup for hypercalcemia. He denied personal or family history of hypercalcemia, renal stones, fractures, dental issues or hyperparathyroidism. He reported eating adequate amounts of dairy products. Labs showed corrected calcium 9.3 (8.6-10.3 mg/dl), elevated PTH 189 (10-65 pg/ml), low serum protein and albumin, and low 25OHVD that was 14 (25-100 ng/mL) on presentation and actively being replaced with ergocalciferol. Phosphorus, magnesium, liver and thyroid function were normal. The patient had complained of back pain after being immobile for 3 months. MRI showed subacute vertebral fractures of T12 and L1. Thereafter, spine X-ray showed multiple vertebral fractures of L2-L5. Beta CTX was 4153 (120-946 pg/ml) and DXA scan revealed low bone density for age with Z score -3.7 in the femoral neck, invalid in the spine due to the fractures, felt to be the source of high extracorporeal calcium concentration. A dose of Denosumab was given for treatment with improvement of calcium clearance during CRRT. Discussion: Acute fractures and infrequently, prolonged immobilization cause hypercalcemia with suppression of PTH. In our patient who was critically ill and immobilized for 4 months, the use of CRRT maintained normocalcemic blood levels, and renal failure with vitamin D deficiency caused secondary hyperparathyroidism. Only the declining requirements for calcium replacement during CRRT prompted workup for hypercalcemia that lead to identification of significant vertebral fractures and treatment. Declining need for calcium replacement during CRRT should prompt investigation and treatment of disorders of hypercalcemia and metabolic bone disorders in this patient population. Presentation: Thursday, June 15, 2023