We report a case of accidental metformin overdose with severe lactic acidosis and AKI treated effectively with sustained low-efficiency dialysis (SLED).
A 76-year-old man, discharged 3 days earlier after uncomplicated surgery for inguinal hernia, presented with vomiting, diarrhea, abdominal pain, hypotension and oliguria.
History: type 2 diabetes, hypertension, severe dilated cardiomyopathy (EF 20-25%), and CKD (usual sCr 1.8 mg/dL, eGFR 36 mL/min/1.73m2). Current drugs: metformin 1000 mg tid, aspirin 100 mg qd, ramipril 7.5 mg qd, atorvastatin 80 mg qd, bisoprolol 2.5 mg qd, furosemide 25 mg bid, glimepiride 1 mg qd, and febuxostat 80 mg qd. Physical examination: BP 90/50 mmHg (dopamine 8 μg/Kg/min), HR 56 bpm, respiratory rate 32/min, temperature 35.5° C, oliguria. Initial laboratory data: sGluc 221 mg/dL, sCr 8.1 mg/dL, BUN 96 mg/dL, sNa 136 mmol/L, sK 6.1, sCl 106, pH 6.91, PaO2 100 mmHg (PaO2/FiO2 200), PaCO2 20.8 mmHg, HCO3- 5.9 mmol/L, AG 26.7 mmol/L, lactate 17 mmol/L.
A 16-h SLED with an AK 200 ultra machine (Gambro/Baxter Italy) was started: Qb 200 mL/min, Qd 300 mL/min (32 mmol/L bicarbonate), citrate anticoagulation, 1.8 m2 polysulfone filter (F8 HPS, Fresenius Italy), +2.5 Kg BW change.
Plasma metformin levels measured by HPLC decreased rapidly within 8 hours, with a pronounced rebound after the end of SLED (Figure). BP gradually increased, and noradrenaline could be withdrawn. Acid-base parameters at the end of SLED were normal. Urinary output increased in the following 48 hours, hence no further dialysis was required.
SLED should be considered as an early treatment option in metformin intoxication. However, the peculiar pharmacokinetic issues of the drug are to be taken into account.
Metformim pharmacokinectic during SLED.
