Precipitation of Acute Hypocalcemia By Blood Transfusion in a Patient with Bony Metastases on Denosumab Therapy

Presentation Number: SUN 329
Date of Presentation: April 2nd, 2017

Sarah Fishman*, Erica Weitzner, Shawanda Patterson and Edward Merker
Northwell Health, Lenox Hill Hospital, New York, NY

Abstract

Background: Hypocalcemia can lead to life threatening arrhythmias, seizures, and severe muscle spasm. Denosumab may contribute to the development of hypocalcemia in patients with metastatic bone disease, especially those with CKD. Rarely, large volume blood transfusions can precipitate hypocalcemia due to chelation of calcium by citrate.

Clinical Case: An 84 year old male with CKD stage 3 presented with generalized weakness and fatigue. Twelve days prior, he was treated with denosumab infusion and seven days later underwent kyphoplasty for vertebral collapse due to bone metastases from carcinoid tumor. On presentation, temperature, heart rate, respiratory rate and oxygen saturation were normal. His exam was notable for cachexia, dry mouth, normal deep tendon reflexes, and normal muscle strength. Notable bloodwork included Cr of 1.57 mg/dl (0.50-1.30) (estimated GFR 40ml/min [>60ml/min]), calcium 7.9 mg/dL, (8.5-10.5); Albumin 2.5g/ml (3.4-5.0) and Hgb 7.4 g/dL, (13-17). Stool guaiac was negative. EKG showed QTc of 475ms (350-440). He was admitted for symptomatic anemia and was transfused one unit packed red blood cells. Two hours post transfusion, he developed muscle spasms and cramping. Repeat blood work revealed serum calcium < 5.0 mg/dL, magnesium 1.2 mg/dL (1.6 - 2.4) and Cr 1.50 mg/dl (0.50-1.30). Repeat EKG showed QTc of 508ms. He was given 4g magnesium sulfate IV and 2g IV calcium gluconate. Following this, his calcium level remained <5.0 mg/dl. Further tests showed iPTH 340 pg/mL (15-65), 1,25 dihydroxy vitamin D 22.3 pg/mL (19.9-79.3) and 25 hydroxy vitamin D 4.0 ng/ml (30-100.) He was started on continuous calcium gluconate infusion at 0.5mg/hr, along with oral calcium carbonate 1250mg every 8 hours, ergocalciferol 50,000 units weekly and 2000 units daily, and calcitriol 0.5 mg four times daily. The patient's calcium level improved to 7.9 mg/dl after 72 hours of the infusion, at which time it was stopped. Eight hours later, the infusion was restarted as the patient's calcium had dropped to 6.7mg/dl. It was continued for an additional 24 hours at which time the calcium level was 8.8mg/dl. The patient continued oral calcium supplementation, and was discharged home 3 days later with calcium level 7.8mg/dl. At follow up two months later, serum calcium was 8.7mg/dl (8.5-10.5).

Conclusion: This case demonstrates the combined effects of denosumab, impaired renal function, low vitamin D levels, and blood transfusion on the development of acute hypocalcemia. Patients with impaired renal function and bone metastases frequently develop symptomatic anemia due to chronic illness and malnutrition. Patients with these conditions undergoing treatment with denosumab may warrant strict adherence to guidelines advising against blood transfusion when hemoglobin levels are above 7.0g/dl to prevent precipitation of acute hypocalcemia and increased vitamin D supplementation.

 

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