title: Raised haematocrit concentration and the risk of death and vascular complications after major surgery.
abstract: BACKGROUND
  Preoperative anaemia is associated with adverse postoperative outcomes. Data on raised preoperative haematocrit concentration are limited. This study aimed to evaluate the effect of raised haematocrit on 30-day postoperative mortality and vascular events in patients undergoing major surgery.
  
  
  METHODS
  This was a cohort study using the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database. Thirty-day mortality and vascular events, demographics and perioperative risk factors were obtained for adults undergoing major surgery. The adjusted effect of raised (over 0·50) compared with normal (0·41-0·50, American Medical Association reference range) preoperative haematocrit concentration on postoperative outcomes was assessed. Separate sex-specific analyses were also conducted, using haematocrit concentration thresholds commonly used in the diagnosis and management of apparent or absolute erythrocytosis.
  
  
  RESULTS
  Some 3961 (2·0 per cent) of 197 469 patients had a raised haematocrit concentration before surgery. After adjustment, the 30-day postoperative mortality rate was higher in patients with raised haematocrit than in those without (odds ratio (OR) 2·23, 95 per cent confidence interval 1·77 to 2·80). Thirty-day rates of deep vein thrombosis (OR 1·95, 1·44 to 2·64) and pulmonary embolism (OR 1·79, 1·17 to 2·73), but not myocardial infarction or stroke, were also higher in patients with a raised haematocrit concentration. The effect on mortality was noted beyond the haematocrit thresholds of 0·48 in women and 0·52 in men; the effect estimates were considerably higher for values exceeding 0·54. Values between 0·41 and 0·45 were not associated with increased mortality risk. Similar observations were noted for venous thrombosis, although with apparent sex differences.
  
  
  CONCLUSIONS
  A raised haematocrit concentration was associated with an increased risk of 30-day mortality and venous thrombosis following major surgery.
authors.affiliation: Department of Internal Medicine, American University of Beirut Medical Centre, Beirut, Lebanon.
authors.forename: K M
authors.initials: KM
authors.lastname: Musallam
authors.forename: J B
authors.initials: JB
authors.lastname: Porter
authors.forename: P M
authors.initials: PM
authors.lastname: Sfeir
authors.forename: H M
authors.initials: HM
authors.lastname: Tamim
authors.forename: T
authors.initials: T
authors.lastname: Richards
authors.forename: L A
authors.initials: LA
authors.lastname: Lotta
authors.forename: F
authors.initials: F
authors.lastname: Peyvandi
authors.forename: F R
authors.initials: FR
authors.lastname: Jamali
mesh_terms: D015331:Cohort Studies; D005260:Female; D006400:Hematocrit / Q000401:mortality; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000209:etiology / Q000401:mortality; D011086:Polycythemia / Q000401:mortality; D011183:Postoperative Complications / Q000209:etiology / Q000401:mortality*; D011300:Preoperative Care / Q000401:mortality; D011655:Pulmonary Embolism / Q000209:etiology / Q000401:mortality; D012307:Risk Factors; D020521:Stroke / Q000209:etiology / Q000401:mortality; D014652:Vascular Diseases / Q000209:etiology / Q000401:mortality*; D020246:Venous Thrombosis / Q000209:etiology / Q000401:mortality