A rare side effect of transesophageal echocardiography: methemoglobinemia from topical benzocaine anesthesia.
BACKGROUND
Benzocaine induced methemoglobinemia is an uncommon, potentially fatal condition.


METHODS
A 44-year-old woman with a history of hepatitis C and intravenous drug use was referred for transesophageal echocardiography for bacteremia evaluation. During induction of topical anesthesia with benzocaine spray she became cyanotic. Pulse oximetry revealed marked desaturation (75%) but was discordant from arterial blood O(2) saturation (99%). Due to clinical suspicion, methemoglobin level was measured and noted to be 69%. The patient was treated with 2 mg/kg of methylene blue intravenously with resolution of her symptoms.


CONCLUSIONS
Physicians using topical anesthesia in endoscopic suites should be aware of this rare, potentially life-threatening treatable condition. High clinical suspicion and availability of methylene blue in endoscopy suites will facilitate prompt diagnosis and treatment.
Jaffery
Zehra
Z
Department of Internal Medicine, Heart and Vascular Institute, Henry Ford Hospital, 2799 West Grand Boulevard, K-14, Detroit, MI 48202, USA.
Ananthasubramaniam
Karthik
K
D000328:Adult; D000779:Anesthetics, Local / Q000009:adverse effects*; D001566:Benzocaine / Q000009:adverse effects*; D017548:Echocardiography, Transesophageal; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D019115:Fasciitis, Necrotizing / Q000175:diagnosis / Q000382:microbiology; D005260:Female; D006801:Humans; D008708:Methemoglobinemia / Q000139:chemically induced* / Q000188:drug therapy; D008751:Methylene Blue / Q000627:therapeutic use; D010092:Oximetry; D013203:Staphylococcal Infections / Q000175:diagnosis
D000779:Anesthetics, Local; D004791:Enzyme Inhibitors; D008751:Methylene Blue; D001566:Benzocaine