Benzocaine‐Induced Methemoglobinemia During an Outpatient Procedure

Abstract

Outpatient transesophageal echocardiography was performed in a 69-year-old man with a history of aortic valve repair. During the procedure the patient became markedly cyanotic and hypotensive. Oxygen saturation measured by pulse oximetry decreased from 97% to the mid-80s. The man's condition continued to deteriorate. On transfer to a critical care unit, blood analysis by co-oximetry showed methemoglobin saturation of 67.8%. The patient's condition improved significantly after intravenous administration of methylene blue 1 mg/kg. With increasing numbers of outpatient procedures performed under topical anesthesia, measures should be in place to deal with a potential life-threatening adverse event such as methemoglobinemia.

Severe Methemoglobinemia From Topical Benzocaine 7.5% (Baby Orajel) Use for Teething Pain in a Toddler

“…Certain risk factors that were suggested include hereditary lack of MetHb reductase, extremes of age (because most cases occurred in infants or elderly people), 6 breaks in the mucosal barrier, concomitant use of other oxidative agents, and in particular, an excessive dose of benzocaine. 7 In addition, underlying cardiac or respiratory conditions may exacerbate the symptoms of MetHb. It remains unclear why our patient developed toxicity if the administered dose was within the recommended range of 4 applications in a 24-hour period.…”

The effect of clove and benzocaine versus placebo as topical anesthetics

“…Benzocaine has been reported to cause methemoglobinemia in some endoscopy cases when used in large amounts. [22][23][24][25] This brings us to the fact that a non-local anesthetic substitute for topical anesthetics would be very useful clinically.…”

Presentation of dapsone-induced methemoglobinemia in a patient status post small bowel transplant

“…The most common etiology of methemoglobinemia in the perioperative period is topical benzocaine used to facilitate upper gastrointestinal endoscopy, laryngoscopy, or bronchoscopy in the awake patient [4][5][6]. Congenital methemoglobinemia has been reported to manifest during [7].…”