Prevalence of Abnormal Methemoglobinemia and Its Determinants in Patients Receiving Nitroglycerin During Anesthesia

BACKGROUND: One of the complications of nitroglycerin infusion during surgery is methemoglobinemia. OBJECTIVES: The aim of this study was to investigate the prevalence of methemoglobinemia and its association with nitroglycerin infusion for the treatment of hypertension during general anesthesia. METHODS: Patients received nitroglycerin infusion at a dose of 2 μ/kg/min. The aim of controlling blood pressure was to set the blood pressure at 20% of the patient’s baseline. Then, the amount of methemoglobin was recorded at 15-minute intervals. Backward stepwise logistic regression test was used to determine the factors affecting methemoglobinemia. RESULTS: Based on the criterion of methemoglobin level above 2%, the prevalence of pathologic methemoglobinemia was 56.6%. After adjusting for confounding variables in the final model, the total prescribed dose was the only factor affecting pathologic methemoglobinemia. CONCLUSIONS: For the first time, we showed that more than half of the patients undergoing surgery suffered from methemoglobin level above 2% after prescribing nitroglycerin, and the only predictor of abnormal methemoglobin level was the rate of nitroglycerin prescription. Anesthesiologists are recommended to be more careful about the speed of nitroglycerin infusion, and if the patient needs higher doses, patient care for the early detection of methemoglobinemia should be the priority.