Suspected methemoglobinemia following awake intubation: one possible effect of benzocaine topical anesthesia--a case report.

Methemoglobinemia is a potential negative side effect associated with the use of benzocaine for topical anesthesia. A healthy patient admitted for an outpatient orthopedic procedure developed the clinical symptomatology of methemoglobinemia after topicalization of the airway with benzocaine. The patient subsequently responded to appropriate treatment and was fit for discharge the same day. Methemoglobinemia should be suspected in cases where decreased pulse oximeter readings develop in patients who have received benzocaine preoperatively. Appropriate steps should be taken to support the airway and oxygenation and monitor the patient while medication is administered to reduce methemoglobin to hemoglobin.