Seeing Red: A Case of Hydroxocobalamin-Induced Blood Leak Alarm in Hemodialysis

Introduction: Hydroxocobalamin, a vitamin B12 analog, is used as an antidote for cyanide poisoning and as rescue therapy for refractory vasoplegic shock. It imparts a deep red color to plasma and body fluids, which can permeate the dialysis membrane and discolor the dialysate. Hemodialysis machines utilize optical blood-leak detectors that alarm when blood is detected in the effluent. This intense red chromophore can falsely trigger such alarms despite no true membrane rupture. This phenomenon is rarely reported and not widely recognized, posing a unique machine-patient interface issue. Case Description: A 39-year-old man with decompensated alcohol-associated cirrhosis and acute kidney injury requiring intermittent hemodialysis (iHD) underwent orthotopic liver transplantation. Intraoperatively, he developed refractory vasoplegia treated with 5 g IV hydroxocobalamin. Postoperatively, attempts to resume iHD were repeatedly aborted due to immediate activation of the machine’s blood leak alarm. The dialysis circuit remained intact with no visible blood leak, but the effluent appeared markedly red. Suspecting hydroxocobalamin-induced sensor interference, continuous veno-venous hemofiltration (CVVH) was initiated as an alternative. iHD was safely resumed two days later without further alarms or complications. Discussion: This case illustrates an uncommon cause of dialysis machine shutdown resulting from a pharmacologic agent rather than a true circuit leak. Such diagnostic confusion can delay renal replacement in critical settings. Nephrologists should be aware that hydroxocobalamin can trigger false blood-leak alarms. Unlike intermittent hemodialysis machines, which use optical sensors to detect red discoloration in the dialysate as a proxy for blood leaks, CVVH platforms typically do not rely on visual cues. Instead, they monitor for membrane compromise using pressure-based alarms such as transmembrane pressure, return pressure, or effluent pressure trends. Because these systems do not interpret dialysate color, they remain unaffected by chromogenic substances like hydroxocobalamin, enabling uninterrupted renal replacement therapy despite the vivid discoloration. As the use of hydroxocobalamin expands, this case emphasizes the need for heightened awareness of machine–patient interactions to avoid unwarranted treatment interruptions.