Varying presentations of methemoglobinemia: two cases

The cases of two patients with methemoglobin levels approaching 30% are presented. No history of exposure to an oxidant was ever determined for the first case; the second patient had taken amyl nitrate orally along with alcohol as well as a self-injected narcotic and antihistamine. Due to their symptomatology, both patients were treated with methylene blue with good results; however, the patient described in case one had a brief episode of symptoms and pulse oximetry changes, not previously emphasized, consistent with the administration of methylene blue. The pathophysiology of methemoglobinemia, the utility of bedside diagnostic techniques, and the use of pulse oximetry are discussed.