Successful treatment of metformin and rodenticide intoxication with prolonged hemodialysis and methylene blue: A case report

Abstract

Metformin is a first-line treatment for diabetes mellitus. In cases of suicidal overdose or chronic accumulation, lactic acidosis may develop and, if untreated, can be fatal. Renal replacement therapy plays a key role in reversing the condition. Refractory hypotension may be encountered both in the presentation of intoxication cases and as a complication of renal replacement therapy. Methylene blue is recommended to improve blood pressure in such cases. A 25-year-old male presented to the emergency department after ingesting a high dose of metformin and around 20 g of rodenticide in a suicide attempt. On admission, his condition was poor, tachycardic, with a blood pressure of 98/42 mmHg. Blood gas analysis revealed a pH of 7.015, pCO2 22.6 mmHg, pO2 64.4 mmHg, base excess −23.4 mmol/L, HCO3 5.5 mmol/L, and lactate 23 mmol/L. Conventional treatments failed, so intermittent hemodialysis was performed. Methylene blue was given for persistent hypotension, stabilizing his hemodynamics. The rodenticide contained difenacoum, a superwarfarin, but laboratory results showed no need for intervention, and no bleeding signs were observed. Blood gas values normalized during his stay in the toxicology unit. After failing a weaning trial, he tested positive for COVID-19 and was transferred to the ICU. After 23 days of care in the emergency and ICU, he was discharged in good health. Lactic acidosis from metformin overdose is a serious condition, and renal replacement therapy can significantly improve survival. Methylene blue may be beneficial in refractory shock, but further randomized controlled trials are needed to clarify its role, especially in cases with combined toxic exposures like rodenticides.