Metformin-associated lactic acidosis following acute kidney injury. Efficacious treatment with continuous renal replacement therapy

Introduction Metformin is a biguanide anti-hyperglycaemic drug. Metformin-associated lactic acidosis may sometimes be life-threatening. Continuous renal replacement therapy has been suggested as a method for resolving this extremely dangerous metabolic state. We describe the history of six patients admitted to the intensive care unit over a 28-month period in pre-shock conditions because of severe lactic acidosis, attributed to metformin-associated lactic acidosis, and successfully treated. Methods We reviewed the charts of six patients admitted to our intensive care unit between January 2008 and May 2010. After initial assessment, all patients were treated with continuous renal replacement therapy. Admission serum lactate and creatinine levels, pH, need for ventilatory and cardiovascular support, as well as continuous renal replacement therapy details and length of stay were reviewed. Results Admission pH levels of the six patients ranged between pH6.63 and 7.0 and their serum lactate levels ranged between 12 and 27mmol/l; the estimated creatinine clearance ranged between 6 and 24ml min ^-11.73m ^-2. All patients required vasoactive support and five required ventilatory support. Lactate levels decreased to near zero with continuous renal replacement therapy within 7-19h in five of the patients whose intensive care unit length of stay ranged between 1 and 5days. One patient's length of stay reached 11days because of pneumonia, one died from multi-organ failure and another suffered permanent neurological damage following prolonged cardiopulmonary resuscitation before continuous renal replacement therapy was administered. All other patients recovered without sequellae. Conclusions Accurate recognition of metformin-associated lactic acidosis and prompt initiation of haemodialysis are paramount steps towards rapid recovery. Large series reports and controlled studies may better determine the optimal duration and best dialysis technique in these patients.