Successful use of methylene blue for catecholamine-refractory vasoplegic shock due to metformin intoxication: A case report and literature review.

Background: Severe metformin intoxication can lead to lactic acidosis and vasoplegic shock, for which the optimal management strategy remains uncertain, especially in cases of severe circulatory collapse. Case Presentation: A 45-year-old diabetic woman on metformin therapy presented with impaired consciousness and seizures. She had experienced a cardiac arrest and undergone extracorporeal cardiopulmonary resuscitation. Blood gas analysis showed severe lactic acidosis. A 71-g metformin packet was found at the patient's home, suggesting an overdose. Despite extracorporeal support and blood purification, severe lactic acidosis and hypotension persisted. Methylene blue was administered 32 h from the onset, which improved her metabolic and circulatory status. We examined her blood sample throughout the case to check the transition of metformin blood concentration. Conclusion: Methylene blue may be beneficial for severe metformin toxicity, regardless of the blood concentration of metformin and the time since intoxication. However, further research is needed to establish its optimal use and effectiveness.