Q: Nurse call you to report that patient's blood on draw appears to be bluish. What would be your concern?

Answer: Methemoglobinemia

Drugs are the most common cause of Methemoglobinemia in ICU including dapsone, trimethoprim, sulfonamides, local anesthetics, metoclopramide and iNO (commonly used in cardio-vascular ICUs).

It gives the blood a bluish or chocolate-brown color.

Treatment is methylene blue 1% solution 1 to 2 mg/kg administered intravenously slowly over five minutes. Supplemental oxygen should be added.