Abstract
Methemoglobinemia is caused due to an increase in methemoglobin in the blood, impairing oxygen transfer to tissues. Acquired methemoglobinemia is caused by various drugs like local anesthetics, antibiotics, nitrates, nitrites, and food additives. We present a case of a 73-year-old male who presented with cyanosis, altered mental status, and hypoxia following transesophageal echocardiography. Arterial blood gas analysis revealed methemoglobinemia. He had been given topical lidocaine and benzocaine spray before the procedure. He improved after the administration of methylene blue. The case highlights the importance of considering methemoglobinemia in patients presenting with cyanosis, altered mental status, and hypoxia after endoscopic procedures.