Metformin Effect on Chest Tube Drainage After Coronary Artery Bypass Graft Surgery

Abstract

Increasing numbers of patients with diabetes mellitus are referred to cardiac surgery. Biguanides are still first-line treatment for type 2 diabetes in all over the world. According preoperative guidelines, oral diabetes medications should be held on the day of surgery because of increased risk of lactic acidosis, induced by Metformin in patients after heart surgery. However, not well described in medical literature mechanism of biguanides is its influence to coagulation. We observed patients, who were scheduled for an elective coronary artery bypass graft surgery (CABG). Eighteen were diabetics, fourteen were Metformin users, where medication was stopped 72 to 24 hours before surgery. Prothrombin time, activated partial thromboplastin time, platelet count, fibrinogen measurement were performed at the baseline, 2 hours and 6 hours after weaning from CPB. Chest tube drainage was checked at 2, 6 and 24 hours after weaning from CPB at the ICU. Presence of fibrinolysis was checked with rotational thromboelastometry testing (Rotem, Tem Innovation, Germany). Statistical analysis showed weak negative correlation between chest tube output in 24 hours and Metformin use (r=-0.255, p=0.03). Patients with Metformin preoperatively had less chest tube drainage (457.1 ± 143.9ml) compared to patients without Metformin (622.2 ± 269.9ml). Here was no significant fibrinolysis in ROTEM tests registered (ML 3.5 ± 2.5%) and apTEM didn`t show improved maximal cloth firmness (MCF) nor shor- ter clothing time (CF).