Topical anesthesia-induced methemoglobinemia in bariatric surgery patients.

Methemoglobinemia leads to rapid oxygen desaturation, requiring prompt recognition and treatment. We present two severely obese patients who developed methemoglobinemia following the use of topical or local anesthetic. This complication was detected by analysis of arterial blood gases, and was successfully treated with methylene blue i.v. and 100% O2 supplementation.