title: Systematic review of the impact of HbA1c on outcomes following surgery in patients with diabetes mellitus.
abstract: OBJECTIVE
  Diabetes is a significant risk factor for surgical complications and also increases the prevalence of comorbidities, thereby increasing surgical risk. The aim of this systematic review was to establish the relationship between long-term preoperative glycemic control as measured by HbA1c and postoperative complications.
  
  
  METHODS
  A systematic search was conducted to source articles published between 1980 and 2014 pertinent to the review. Full-text articles were included if they met the pre-determined criteria as determined by two reviewers. Studies reporting the impact of preoperative HbA1c levels on postoperative outcomes in all disciplines of surgery were included.
  
  
  RESULTS
  Twenty studies, including a total of 19,514 patients with diabetes mellitus from a range of surgical specialties, were suitable for inclusion. Preoperative glycemic control did not have a bearing on 30-day mortality. There were no significant differences in the incidence of stroke, venous thromboembolic disease, hospital readmission and ITU length of stay based on glycemic control. The majority of studies suggested no link between preoperative HbA1c levels and acute kidney injury or need for postoperative dialysis, dysrhythmia, infection not related to the surgical site and total hospital length of stay. The literature was highly variable with regards to myocardial events, surgical site infection and reoperation rates.
  
  
  CONCLUSIONS
  Elevated preoperative HbA1c was not definitively associated with increased postoperative morbidity or mortality in patients with diabetes mellitus. The studies included in this review were relatively heterogeneous, predominantly retrospective, and often contained small patient numbers, suggesting that good quality evidence is necessary.
authors.affiliation: Division of Gastrointestinal Surgery, Nottingham Digestive Diseases Centre National Institute for Health Research Biomedical Research Unit, Nottingham University Hospitals, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: Katie E
authors.initials: KE
authors.lastname: Rollins
authors.affiliation: Division of Gastrointestinal Surgery, Nottingham Digestive Diseases Centre National Institute for Health Research Biomedical Research Unit, Nottingham University Hospitals, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Varadhan
authors.affiliation: Elsie Bertram Diabetes Centre, Norfolk and Norwich University Hospitals NHS Foundation Trust, Colney Lane, Norwich NR4 7UY, UK.
authors.forename: Ketan
authors.initials: K
authors.lastname: Dhatariya
authors.affiliation: Division of Gastrointestinal Surgery, Nottingham Digestive Diseases Centre National Institute for Health Research Biomedical Research Unit, Nottingham University Hospitals, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK. Electronic address: dileep.lobo@nottingham.ac.uk.
authors.forename: Dileep N
authors.initials: DN
authors.lastname: Lobo
mesh_terms: D054058:Acute Coronary Syndrome / Q000097:blood / Q000453:epidemiology; D058186:Acute Kidney Injury / Q000097:blood / Q000453:epidemiology; D001145:Arrhythmias, Cardiac / Q000097:blood / Q000453:epidemiology; D001786:Blood Glucose / Q000378:metabolism; D003920:Diabetes Mellitus / Q000097:blood / Q000601:surgery*; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D015994:Incidence; D007902:Length of Stay; D009017:Morbidity; D064887:Observational Studies as Topic; D010359:Patient Readmission; D011183:Postoperative Complications / Q000097:blood / Q000453:epidemiology*; D018570:Risk Assessment; D012307:Risk Factors; D020521:Stroke / Q000097:blood / Q000453:epidemiology; D013530:Surgical Wound Infection / Q000097:blood / Q000453:epidemiology; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000097:blood / Q000453:epidemiology
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin
keywords: Complications; Diabetes mellitus; HbA1c; Outcome; Surgery