(287) A Case of Critical Metformin-Associated Lactic Acidosis

Introduction: Metformin-associated lactic acidosis (MALA) is a rare but severe complication of metformin. The cornerstone of management for critical severity MALA is prompt initiation of hemodialysis and supportive management of complications including shock and hypoglycemia. Despite this established management, mortality of MALA remains high at an estimated 25-50% in current literature and few cases of survival with pH < 6.9.

Description: A 65 year-old female with past medical history of type 2 diabetes on metformin, nephrolithiasis and stroke presented to the hospital with several days of worsening vomiting and encephalopathy. In the emergency room, laboratory work revealed: lactic acid 20.3 mmol/L, creatinine 7.68 mg/dL, bicarbonate < 5 mmol/L; arterial blood gas pH 6.78, pCO2 10 mmHg, pO2 169 mmHg. She was hypotensive requiring push doses of phenylephrine and a norepinephrine infusion. Bicarbonate injections and infusion were also given while hemodialysis catheter was placed. Urgent high flow hemodialysis was initiated upon patient’s arrival to the ICU. She was placed on high flow nasal cannula for adjunctive ventilatory effect. Broad spectrum antibiotics were started.

With the above interventions, patient improved clinically with resolution of acidosis. She was transitioned to continuous renal replacement therapy on hospital day two and to intermittent hemodialysis on day three. Infectious workup remained negative. The remainder of hospital course was largely uncomplicated, but patient remained anuric and underwent tunneled line placement. She discharged home on hospital day eight. A metformin level obtained on admission resulted at 26 mcg/mL (therapeutic range 1-2 mcg/mL).

Discussion: Metformin-associated lactic acidosis can precipitate life-threatening acidosis and shock as seen in this patient. This case demonstrates timely implementation of established treatment of MALA with additional adjunctive HFNC oxygen therapy. Conventional hemodialysis was used instead of CRRT despite severe shock to aggressively correct acidosis. Despite multiple risk factors for poor outcome, this patient’s survival with non-severe morbidity reiterates improved outcomes with shorter duration to dialysis. Further investigation may be considered on whether adjunctive oxygen therapy benefits this patient population.