A 12-Day-Old Boy with Methemoglobinemia After Circumcision with Local Anesthesia (Lidocaine/Prilocaine)

A 12-day-old boy presented with duskiness 4 h after circumcision with local anesthesia: infiltration with lidocaine (6 mL 1 %) and topical EMLA cream (2.5 % lidocaine/2.5 % prilocaine). He had no respiratory distress, but a strikingly dark skin. A blood sample showed dark, chocolate brown blood with a raised methemoglobin of 49.8 % (normal <1.5 %) and a lactate of 10 mmol/L. A diagnosis of methemoglobinemia was made. The patient was treated with oxygen administration, but methemoglobin concentration was still 45 % 1 h later. After administration of two doses of intravenous methylene blue (total 0.7 mg/kg), the methemoglobin concentration decreased to 3.3 %, and had normalized to 1.3 % 1 day later. This confirmed the diagnosis of an acquired methemoglobinemia after local use of lidocaine and topical lidocaine/prilocaine. Hemoglobin can be oxidized to methemoglobin, which is unable to transport oxygen. The most common cause of acquired methemoglobinemia is ingestion or skin exposure to an oxidizing agent, for example lidocaine and prilocaine. Neonates are more susceptible to developing acquired methemoglobinemia but, according to most guidelines, local anesthesia is considered to be safe in this patient group. This is the first case report of a term neonate with methemoglobinemia of almost 50 % occurring in a Western country and successfully treated with intravenous methylene blue. In conclusion, severe methemoglobinemia may be observed after the use of local lidocaine/prilocaine for a circumcision, especially in neonates. The safety of local anesthesia in this patient group needs to be reconsidered.