Vitamin B12 as an Obstacle to Hemodialysis in the Intensive Care Unit (ICU)

Introduction: Normally total body stores of vitamin B12 are between 1 and 5mg. Log scales higher 5-10g amounts of hydroxocobalamin are used as antidote for cyanide, forming cyanocobalamine in equimolar proportion. Because of a catecholamine independent hypertensive effect such high doses are also used in vasoplegic shock, similar to methylene blue. Dialysis clearance of vitamin B12 has been used to estimate middle molecule clearance. Here we present a case where a 5g dose of hydroxocobalamine impeded hemodialysis by triggering blood leak alarms. Case Description: A 91 year old woman with metastatic breast cancer underwent surgery for a pathologic facture of her left femor. Her postoperative course was complicated by vasoplegic shock with AKI which was treated with three vasopressors and hydroxocobalamine. A drop in Hb and red colored urine (picture) raised concern for hemolysis but haptoglobin was normal and the urine sediment showed only rare RBC and calcium oxalate crystals. The patient developed oligoanuria and a family decision was made for a trial of dialysis support. However, the patient could not be dialyzed because of intractable blood leak alarms, despite several dialyzer sets used and the dialysate consistently testing negative for heme. The patient then was started on CVVH which was well tolerated. Red effluent was noted. The patient did not recover and passed away. Discussion: Very high doses of hydroxocobalamine cause urine to be colored red for weeks. Hydroxocobalamine is cleared by dialysis but interferes with the blood leak alarm on hemodialysis machines, effectively rendering hemodialysis impossible. As in our patient, CVVH is not impeded but red effluent is usually noted. This side effect is important to consider if hemodialysis is needed for the treatment of toxic alcohol ingestion or drug toxicity. As there was no autopsy we do not know if the patient had oxalate nephropathy, a reported side effect of hydroxocobalamine with unclear pathophysiology.