sulfhemoglobinemia

Q: The antidote for Sulfhemoglobinemia is methylene blue?

A) True

B) False

Answer: B

Relatively less known than methemoglobinemia, sulfhemoglobinemia can also occur with oxidizing drugs such as dapsone, sulfonamides, metoclopramide, and nitrate. It shifts the hemoglobin-oxygen dissociation curve to the right, which means it deloads oxygen to the tissues easily and is not as harmful as methemoglobinemia. But, it falsely reduces the SpO2 alike methemoglobin, and can deceive clinicians. Also, to make diagnosis difficult, multi-wavelength co-oximetry can not distinguish it from methemoglobin well. It requires specialized biochemical testing. 

Diagnosis is via discontinuation of suspected offending drugs, and if there is no response to methylene blue.

#hematology

References:

1. Lu HC, Shih RD, Marcus S, et al. Pseudomethemoglobinemia: a case report and review of sulfhemoglobinemia. Arch Pediatr Adolesc Med 1998; 152:803.

2. Aravindhan N, Chisholm DG. Sulfhemoglobinemia presenting as pulse oximetry desaturation. Anesthesiology 2000; 93:883.