Methemoglobinemia from topical benzocaine

Area of Science:

• Anesthesiology
• Toxicology
• Emergency Medicine

Background:

• Benzocaine is a common topical anesthetic used in procedures like esophagogastroduodenoscopy.
• Adverse reactions to local anesthetics, though rare, require prompt recognition and management.

Observation:

• A patient developed acute cyanosis and methemoglobinemia after topical benzocaine application and partial ingestion during an esophagogastroduodenoscopy.
• Symptoms included cyanosis and potential neurologic symptoms.

Findings:

• The case highlights acute toxic methemoglobinemia as a potential complication of benzocaine use.
• Diagnosis relies on clinical presentation (cyanosis without cardiopulmonary disease) and laboratory confirmation of elevated methemoglobin levels.
• Laboratory tests should include oxygen saturation and methemoglobin concentration.

Implications:

• Clinicians should consider methemoglobinemia in patients presenting with cyanosis post-local anesthetic use.
• Prompt management with supplemental oxygen and intravenous methylene blue is essential for reversing methemoglobinemia and improving outcomes.
• This case underscores the importance of awareness regarding benzocaine-induced methemoglobinemia in procedural sedation and local anesthesia.