Veno-Arterial Extracorporeal Membrane Oxygenation for Treating Refractory Shock in Severe Metformin-Associated Lactic Acidosis: A Case Report

Abstract

Metformin-associated lactic acidosis (MALA) is a rare but life-threatening complication with mortality rates exceeding 10-30%. While renal replacement therapy (RRT) remains the cornerstone of treatment, mechanical circulatory support may be necessary in cases complicated by severe cardiovascular dysfunction. We report a case of severe MALA with unprecedented metabolic derangement successfully treated with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) and continuous renal replacement therapy (CRRT). A 39-year-old male with type 2 diabetes mellitus presented with altered mental status following influenza A infection. Initial assessment revealed severe metabolic acidosis (pH 6.355) with markedly elevated lactate (52.7 mmol/L), acute kidney injury, and cardiovascular collapse. Echocardiography demonstrated severe left ventricular dysfunction with an ejection fraction below 20%. Despite initial resuscitation efforts, including high-dose vasopressors, the patient developed cardiac arrest with pulseless electrical activity, requiring cardiopulmonary resuscitation. After the return of spontaneous circulation, VA-ECMO was initiated for refractory shock unresponsive to high-dose vasopressors. MALA was diagnosed based on the clinical presentation and medication history, although metformin levels could not be measured due to assay unavailability. Under combined VA-ECMO and CRRT support, the patient's metabolic parameters improved steadily, with a gradual decrease in lactate levels and an improvement in pH. Left ventricular function recovered significantly, allowing VA-ECMO discontinuation after 26 hours. The patient was successfully weaned from mechanical ventilation with subsequent rehabilitation, achieving discharge with intact cognitive function and no neurological sequelae. By this time, both cardiac and renal functions had normalized. This case demonstrates the successful use of mechanical circulatory support in extreme metabolic derangement and illustrates how viral illnesses can precipitate severe MALA through acute kidney injury. The successful outcome suggests that early recognition and aggressive intervention with combined VA-ECMO and CRRT might be beneficial in selected patients with MALA-induced cardiovascular collapse. This case also highlights the importance of considering MALA in unexplained severe lactic acidosis, particularly in diabetic patients during acute illness.

Keywords: continuous renal replacement therapy (crrt); metformin-associated lactic acidosis; refractory shock; severe acidemia; veno-arterial extracorporeal membrane oxygenation (va ecmo).

Figure 1. Temporal variation in the lactate concentration and pH after admission