title: Recent metformin ingestion does not increase in-hospital morbidity or mortality after cardiac surgery.
abstract: BACKGROUND
  Perioperative treatment of type 2 diabetes with metformin, an oral hypoglycemic drug, is thought to increase the risk of life-threatening postoperative lactic acidosis. In contrast, metformin improves serum glucose control and has beneficial cardiovascular effects, which may decrease the risk of adverse outcomes. In this investigation we sought to determine the influence of metformin treatment on mortality and morbidity compared with treatment with other oral hypoglycemic drugs in diabetic patients undergoing cardiac surgery.
  
  
  METHODS
  In this retrospective investigation, 1284 diabetic patients, with recent oral hypoglycemic ingestion (presumed to be 8-24 h preoperatively), underwent cardiac surgery from 1994-2004. Propensity scores were calculated from a logistic model which included baseline characteristics and perioperative variables. Four-hundred-forty-three (85%) of the metformin-treated patients were matched on nearest propensity score using greedy matching techniques with 443 nonmetformin-treated patients. Postoperative outcomes were compared between matched metformin- and nonmetformin-treated patients.
  
  
  RESULTS
  In-hospital mortality, cardiac, renal, and neurologic morbidities were similar between groups. Metformin-treated patients had less postoperative prolonged tracheal intubation [OR (95% CI), 0.3 (0.1, 0.7), P = 0.003], infection [0.2 (0.1, 0.7), P = 0.007] and overall morbidities [0.4 (0.2, 0.8), P = 0.005].
  
  
  CONCLUSIONS
  These data suggest that recent metformin ingestion is not associated with increased risk of adverse outcome in cardiac surgical patients. Alternatively, metformin treatment may have beneficial effects.
authors.affiliation: Department of Cardiothoracic Anesthesia, Cleveland Clinic Foundation, Cleveland, OH 44195, USA. duncana@ccf.org
authors.forename: Andra I
authors.initials: AI
authors.lastname: Duncan
authors.forename: Colleen G
authors.initials: CG
authors.lastname: Koch
authors.forename: Meng
authors.initials: M
authors.lastname: Xu
authors.forename: Mariel
authors.initials: M
authors.lastname: Manlapaz
authors.forename: Brian
authors.initials: B
authors.lastname: Batdorf
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Pitas
authors.forename: Norman
authors.initials: N
authors.lastname: Starr
mesh_terms: D000284:Administration, Oral; D006348:Cardiac Surgical Procedures / Q000401:mortality* / Q000706:statistics & numerical data; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D008687:Metformin / Q000008:administration & dosage / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin