A Case of Methemoglobinemia Thought to Have Been Caused by the Combined Use of Propitocaine and Nitroglycerin during General Anesthesia

Abstract

  We report a case of methemoglobinemia that was thought to have been caused by the combined use of propitocaine and nitroglycerin during general anesthesia.

  A 39-year-old woman (163.7 cm, 51.3 kg) required bimaxillary surgery for a jaw deformity. She had been diagnosed as having schizophrenia and was under treatment with an antipsychotic medicine that has an α-blocking effect. Therefore, we avoided using lidocaine with adrenaline and instead selected propitocaine with felypressin for local anesthesia.

  Anesthesia was induced and maintained with fentanyl, remifentanil, propofol, and rocuronium. Her percutaneous arterial oxygen saturation (Spo₂) level was 100%. After the administration of 10 ml of 3% propitocaine for local anesthesia, a continuous infusion of nitroglycerin (0.5γ) was started for hypotensive anesthesia. Fifteen minutes later, her Spo₂ level decreased to 96%. We performed an arterial blood gas analysis to check her methemoglobin level and observed an increase to 3.5%. We diagnosed her as having methemoglobinemia and changed the drug for the hypotensive anesthesia from nitroglycerin to prostaglandin E1 ; we also administered 60 mg of methylene blue to treat the methemoglobinemia. Twenty minutes later, her Spo₂ level had recovered to 100% and her methemoglobin level had decreased to 1.0%.

  Methemoglobinemia has been previously reported to be caused by the administration of propitocaine at a dose of 8 mg/kg or more. Meanwhile, 3γ or more of nitroglycerin can also trigger methemoglobinemia. In the presently reported patient, methemoglobinemia occurred despite the fact that neither drug was administered at the above-mentioned doses. Even if individual doses of drugs that can cause methemoglobinemia are low, the risk of methemoglobinemia may increase with the combined use of predisposing drugs.