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The presence of cyanosis is disturbing even in cases when its cause is known. When a patient under general anesthesia suddenly develops cyanosis, it may be particularly alarming for the surgeon and anesthesiologist. The sudden onset of cyanosis in patients under general anesthesia is most often caused by airway obstruction, cardiovascular collapse, massive embolism, or pneumothorax. In these cases, the cyanosis is caused by hypoxia. In some rare instances, cyanosis is the result of methemoglobinemia, where the hemoglobin’s oxygen-carrying capacity is

INTRODUCTION Methemoglobin (MetHb) is an oxidized form of hemoglobin (Hb) in which heme iron configuration is in the ferric state (Fe 3+ ) instead of the ferrous state (Fe 2+ ). MetHb normally constitutes approximately 1% of all Hb. Several symptoms develop as the level of MetHb increases. Methemoglobinemia may be caused by a variety of substances that exert oxidative effects, such as nitrogen oxides, acetaminophen, and local anesthetics, most commonly prilocaine and benzocaine. 1 , 2 In Japan, there have been 3 case reports of

Acquired methemoglobinemia can occur following exposure to oxidizing agents including high doses of certain local anesthetics. 1 Many studies have investigated the dose at which each causative drug causes methemoglobinemia. However, few studies have reported methemoglobinemia being caused by the combined use of causative drugs or agents. 2 This is a report of a methemoglobinemia case presumably caused by the combined use of prilocaine (propitocaine in Japan) and nitroglycerin (NTG) during general anesthesia. CASE REPORT

Dapsone is a leprostatic agent commonly prescribed for the management of leprosy, malaria, and the immunosuppression-induced infections of Pneumocystis carinii and Toxoplasma gondii . In susceptible patients, methemoglobinemia, a potentially life-threatening event, can occur. We report a case of dapsone-induced methemoglobinemia which was observed during general anesthesia for the management of a fractured mandible. CASE REPORT A 56-year-old Asian woman presented for the treatment of a fracture of the body of

remifentanil would be appropriate for patients with G6PD deficiency. Hence, sevoflurane was used only for the brief induction of anesthesia, while propofol and remifentanil were used for its maintenance. Methemoglobinemia is also a concern in patients with G6PD deficiency. Methemoglobin is reduced by reduced glutathione in the presence of NADPH. Therefore, patients with G6PD deficiency, with resultant deficient NADPH supply, have a greater tendency to develop methemoglobinemia. 6 , 7 It is known that methylene blue, which is used for the treatment of

mechanisms. This results in higher than normal blood levels of methemoglobin, causing the condition known as acquired methemoglobinemia. 4 , 11 Examples of medications that may cause elevated methemoglobin levels include nitrates (nitroglycerin), nitrites (amyl nitrite), antiemetics (metoclopramide), antibiotics (trimethoprim, sulfonamides, and dapsone), and local anesthetics (prilocaine and benzocaine). 4 , 8 – 10 , 12 The liberal use of benzocaine in infant teething gels and topical anesthetic sprays is a concern. 4 , 5 , 8 – 10 , 12 Exposure to industrial agents can