All That Is Red Is Not Blood: Reddish Discoloration of Dialysis Ultrafiltrate in a Heart Transplant Recipient

Introduction: Refractory vasoplegic shock is an uncommon yet potentially life-threatening complication of major cardiac surgery and involves activation of nitric oxide (NO) pathways. High dose hydroxocobalamin, a potential inhibitor of NO synthase and a NO scavenger is an emerging targeted rescue therapy for refractory vasoplegic shock in patients who fail to respond to first line therapy with catecholamine vasopressors. Benign discoloration of body fluids is a side effect of hydroxocobalamin, but potential exists for erroneous co-oximetric blood gas results and false blood leak alarm during hemodialysis. Case Description: A 53-year-old male with hypertension, type 2 diabetes, chronic kidney disease (CKD) stage 4 and severe ischemic cardiomyopathy underwent orthotopic heart transplantation. Because of severe intraoperative vasoplegia despite using norepinephrine, epinephrine, vasopressin and dopamine, the patient received intravenous infusion of 5-gram hydroxocobalamin (Cyanokit). Patient was initiated on CVVHDF on the same day due to hemodynamic mediated acute kidney injury superimposed on the underlying CKD. The ultrafiltrate started turning red (figure). Hemolysis work-up was negative and the fluid tested negative for blood. CVVHDF was continued without difficulty. The ultrafiltrate discoloration gradually faded over the next several days. Discussion: Dialysis ultrafiltrate discoloration from hydroxocobalamin may be confused with blood leak from membrane damage. This could shut off certain dialysis machines due to erroneous activation of the blood detector but CVVHDF systems such as Prisma Flex machines that use single optical emitter are not impacted. With increasing use of hydroxocobalamin in vasoplegic states and as an antidot in cyanide poisoning, the treating clinicians should be aware of this phenomenon.Reddish discoloration of the ultrafiltrate