Drug-induced methemoglobinemia in a healthy 20-year-old soldier undergoing shoulder surgery

A young adult male, ASA status I, presented for left shoulder arthroscopy. His medications included indocin for shoulder pain and chloroquine, an antimalarial. He was anesthetized using propofol, midazolam, fentanyl, and a relaxant. His initial oximetry reading of 94% saturation was erroneously attributed to shivering and to the fact that the oximeter clip was distal to the blood pressure cuff on the right upper extremity, necessitated by proximity of surgery. The initial saturation level of 94% was persistent throughout the case. The methemoglobin level drawn immediately postoperatively was 9%. The patient was treated with methylene blue which resulted in an improvement in oxygen saturation to 98%. His remaining postoperative course was uneventful, and he was released one day later.