Metformin-induced lactic acidosis with acute renal failure in type 2 diabetes mellitus

Case Report: An 83-year-old patient was admitted to our hospital because of gastrointestinal symptoms, mental confusion and dysarthria. The patient suffered from type 2 diabetes mellitus and was taking metformin. A mild renal insufficiency was known. Oil admission, we found impaired consciousness, Kussmaul breathing, a body temperature of 32.1 degreesC, and hemodynamic instability. Laboratory testing revealed lactic acidosis (pH 6.71, base excess -30, standard bicarbonate 4.0 mmol/l, lactate 24.4 mmol/l) and acute renal failure with creatinine of 10.6 mg/dl and blood urea nitrogen of 134 mg/dl. Electrolytes were not altered; the blood glucose was elevated (147 mg/dl). According to history, physical examination, and laboratory testing the diagnosis metformin-induced lactic acidosis with acute renal failure was made. This diagnosis was confirmed by an elevated level of metformin. As soon as possible a bicarbonate hemodialysis was initiated. After 8 hours of hemodialysis the acid-base metabolism was almost balanced and the vigilance of the patient normalized. No further sessions of hemodialysis were needed and insulin therapy was started. Conclusions: Metformin-induced lactic acidosis is a common side effect in patients with renal insufficiency. For all early diagnosis, clinical symptoms of intoxication should be well known by physicians and patients. First-line therapy for correction of lactic acidosis and effective elimination of metformin is bicarbonate hemodialysis. Sodium bicarbonate infusions are not able to correct the acid-base metabolism sufficiently. For prevention the renal function should be monitored closely and metformin therapy should be stopped, if a deterioration of renal function is observed.