Acute renal failure and severe lactic acidosis due to metformin

Abstract

Introduction

Metformin may rarely cause lactic acidosis in patients with predisposing factors of acidosis or tissue hypoxia, like acute renal or heart failure, liver failure, dehydration, alcohol consumption or serious infection. Mortality may approach 50% in these cases.

Case description

A 70-year-old lady came to the emergency unit because of vomits and diffuse abdominal pain. Five days ago, she had visited our hospital for the same reason, with normal findings on physical and laboratory examination. Her medical history included diabetes mellitus under metformin/vildagliptin and dementia. The patient was confused and disoriented, afebrile, oliguric, with tachypnea and diffuse abdominal tenderness. Pressure was 130/70mmHg. Blood gases revealed severe lactic acidosis (lactate>15mmol/L), pH=6.84, PCO₂=7mmHg, pO2=133mmHg, glucose=57mg/dL, HCO3<3mmol/L. Abnormal laboratory tests included creatinine=5.3mg/dL, urea=152mg/dL, WBC=17000/µL, hemoglobin=12.3gr/dL, sodium=133mmol/L, potassium=4.4mmol/L, ESR=43mm/h. Chest x-ray, abdominal ultrasound (to exclude obstructive nephropathy) and echocardiography were normal.

Results and conclusions

The patient received 400mL bicarbonate 4.8%, aggressive hydration, dopamine (diuretic dose) and 160mg furosemide. Because of clinical deterioration she underwent hemodialysis. She was treated, according to guidelines, as for severe sepsis with meropenem. Blood and urine cultures were negative. On 1^st day, ECG showed ischemic lesions, which resolved with nitrates. Abdominal CT was normal. She remained afebrile after the 1^st day (low grade fever). Overall, the patient underwent three hemodialysis sessions (resistant severe lactic acidosis, low bicarbonates). On 2^nd day, she was well oriented. She was discharged 8 days later with urea=59mg/dL and creatinine=1.6mg/dL. After 20 days, creatinine was 1mg/dL.

Take-home message

Metformin may be a cause of severe lactic acidosis, disproportionate to the degree of renal failure, in patients with previous normal renal function and acute dysregulation. Hemodialysis is a lifesaving therapeutic intervention in these patients.