Nitrobenzene induced methemoglobinemia treated with manual exchange transfusion in a resource-limited setting: a case report.

Introduction and importance: Nitrobenzene poisoning can result in life-threatening methemoglobinemia. Therefore, immediate management is critical. Case presentation: We report the case of a 45-year-old female, who was brought to our emergency department three hours after ingesting approximately 50 mL of a 35% solution of nitrobenzene. She displayed decreased consciousness, cyanosis, low peripheral oxygen saturation (SpO2) and a saturation gap of 21.9%. Despite high-flow oxygen supplementation, cyanosis persisted, and SpO2 remained low. Nitrobenzene poisoning with methemoglobinemia was diagnosed on the basis of her clinical features. She was treated with manual therapeutic whole blood exchange (TWBE), intravenous vitamin C, and supportive care. The patient underwent manual exchange transfusion of 2365 mL of whole blood (60% of her estimated total blood volume) over 5 days. After treatment, the patient recovered and was discharged from the hospital. Clinical discussion: The patient was diagnosed on the basis of clinical features because tests to measure the level of methemoglobin were unavailable. Methylene blue, which is first-line treatment for methemoglobinemia, was not available. Therefore, the patient was treated with manual TWBE and intravenous vitamin C. Several published reports have illustrated the successful use of TWBE in the treatment of methemoglobinemia in settings where methylene blue was unavailable. Conclusion: A thorough clinical evaluation is key in diagnosing methemoglobinemia in circumstances where specific tests to detect methemoglobin are not available. Treatment with methylene blue can be ineffective, contraindicated or unavailable in some circumstances. In such situations, alternative therapies such as TWBE and intravenous vitamin C should be considered.