Metformin-Associated Lactic Acidosis Following Contrast-Induced Nephropathy

Abstract

Metformin has been recommended as the first-line therapeutic option for diabetes mellitus. Lactic acidosis is a rare but life-threatening side effect of metformin. In previously reported cases, the occurrence of metformin -associated lactic acidosis (MALA) was usually accompanied by acute kidney injury (AKI). Among these risk factors for AKI, concurrent use of nephrotoxic agent, such as contrast medium, is common but often ignored in clinical practice. We present an elderly diabetic patient who was initially hospitalized due to complete AV block associated with AKI. After supportive therapy and temporary pacemaker implantation, the renal function recovered 5 days later. Metformin was prescribed again for better glucose control; CT angiography of bilateral lower limbs was then performed to prepare for revascularization. Four days later, acute renal failure with high anion gap metabolic acidosis manifesting as bradycardia with conscious change was noted. After exclusion of other etiologies, the diagnosis of MALA following contrast medium-induced nephropathy (CIN) was made. In view of hypotension and increased respiratory distress, vasopressors and ventilator support were instituted immediately. To correct acidosis and remove lactate as well as metformin, emergent hemodialysis was also initiated within 2 hours. However, despite intensive support of cardiovascular, respiratory and renal system, the patient died of sepsis with multiple organ failure 6 days later. We present this case to remind clinicians that metformin should be discontinued in diabetic patients receiving intravascular contrast study. For hospitalized patients, metformin should only be reused if reassessed renal function 48 hours after contrast medium administration has not deteriorated.