Metformin Mayhem: A Rare Case of Its Toxicity and Its Unlikely Survival

Introduction: Metformin associated lactic acidosis is a serious toxicity that can occur in patients either from an acute overdose of metformin or from underlying conditions that impair metformin elimination, such as kidney injury or tissue hypoxia. Risk factors include kidney dysfunction, liver disease, alcohol use, heart failure, and a history of lactic acidosis. Mortality rates can be as high as 36% underscoring the severity of this condition. Case Description: We present a 72-year-old female with a history of type 2 diabetes, dyslipidemia, hypothyroidism, psoriasis, and coronary artery disease, who presented to the ED with 2 days of epigastric pain, vomiting, diarrhea, and shortness of breath. She had recently used moderate amounts of NSAIDs for left leg pain. On exam, she was alert but appeared acutely ill, with dry mucous membranes, muscle weakness, and distress. Labs showed leukocytosis, high anion gap metabolic acidosis (pH 7.01), lactate 14.4, and acute renal failure, with creatinine rising from a baseline of 1.1 to 6.3 mg/dL. Urinalysis and culture confirmed a urinary tract infection. Given her metformin use and renal dysfunction, she was diagnosed with acute renal failure and high anion gap metabolic acidosis secondary to metformin associated lactic acidosis and urosepsis. Due to high risk of cardiac arrest, she underwent rapid sequence intubation, received IV fluids, sodium bicarbonate, and IV antibiotics. Nephrology and Surgery were consulted for urgent dialysis catheter placement, and emergent hemodialysis was initiated. Her hospital course was prolonged, complicated by upper GI bleeding and heparin-induced thrombocytopenia, both successfully managed. She was extubated, transferred to the general ward, and discharged home to continue outpatient hemodialysis. Discussion: This case illustrates the importance of a thorough medication history and the identification of metformin use when evaluating high anion gap metabolic acidosis. It also emphasizes how timely intervention, including hemodialysis and management of underlying conditions, can substantially improve survival outcomes.