Acquired methemoglobinemia after hydroxocobalamin administration in a patient with burns and inhalation injury

Abstract

Context: Hydroxocobalamin is an effective cyanide antidote. While erythema, hypertension, and chromaturia are recognized side effects, methemoglobinemia has not been reported. Methemoglobin levels are most accurately measured by co-oximetry. We describe an extensively burned patient who developed methemoglobinemia within an hour of hydroxocobalamin administration.

Case details: A 47-year old man without genetic deficiencies or abnormal hemoglobin variants presented with 61% body surface area thermal burns and grade 1 inhalation injury sustained during a tugboat engine explosion. On admission, lactate was 9.24 mmol/L, methemoglobin 1%, and carboxyhemoglobin 0.2% by blood gas analysis with co-oximetry. Despite large-volume resuscitation, lactate remained elevated (7–8 mmol/L). Intravenous hydroxocobalamin (5 g) was administered at postburn hour 19 for possible cyanide toxicity. Immediately thereafter, he became hypertensive with reflex bradycardia. Lactate decreased to 5.51 mmol/L, methemoglobin rose to 4.10%, and oxygen saturation by pulse oximetry decreased to 74–80% (despite arterial oxygen saturation of 95% by cooximetry). Methemoglobin concentration peaked at 13.40% at postburn hour 33. Methylene blue was not administered.

Conclusions: Methemoglobinemia in our patient was temporally associated with hydroxocobalamin administration.

Keywords:

• Hydroxocobalamin
• methemoglobinemia
• burns
• co-oximetry
• cyanide

Disclosure statement

The authors report no declarations of interest. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense

Additional information

Funding

This work is funded by the U.S. Army Burn Center (AZJ, LCC) and by the Multi-Organ Support Technology Task Area (LCC) of the U.S. Army Institute of Surgical Research.