Severe Multifactorial Lactic Acidosis With Pulmonary Edema and Myocardial Injury in an Elderly Patient on Metformin Managed Conservatively: A Case Report

Severe lactic acidosis is a life-threatening condition in elderly patients with multiple comorbidities. We report a 90-year-old man with type 2 diabetes mellitus (HbA1c 7.1%), hypertension, and chronic kidney disease (CKD) stage 3a (baseline estimated glomerular filtration rate (eGFR) of 56 mL/min/1.73 m²) who presented with acute dyspnea, orthopnea, and oliguria. Laboratory evaluation revealed metabolic acidaemia (pH 7.22), marked hyperlactatemia (8 mmol/L), and acute-on-chronic kidney injury. Clinical findings were consistent with acute pulmonary edema and myocardial injury, with elevated cardiac biomarkers but no ischemic electrocardiographic changes. Lactic acidosis was multifactorial, driven by sepsis from a diabetic foot infection, renal dysfunction, and metformin as a potential contributor. Initial management included intravenous sodium bicarbonate, loop diuretics, ventilatory support, and antimicrobial therapy. Renal replacement therapy was declined by the patient, and intensive conservative management with close biochemical and clinical monitoring was pursued. The patient gradually improved, with normalization of acid-base status, renal function, lactate, and cardiac biomarkers, allowing successful extubation and transition to oral therapy. This case highlights the diagnostic and therapeutic challenges of severe lactic acidosis in elderly patients with multiple comorbidities and demonstrates that individualized supportive care can lead to favorable outcomes even when standard interventions such as dialysis are not feasible.