title: The effects of mild perioperative hypothermia on blood loss and transfusion requirement.
abstract: BACKGROUND
  Anesthetic-induced hypothermia is known to reduce platelet function and impair enzymes of the coagulation cascade. The objective of this meta-analysis and systematic review was to evaluate the hypothesis that mild perioperative hypothermia increases surgical blood loss and transfusion requirement.
  
  
  METHODS
  The authors conducted a systematic search of published randomized trials that compared blood loss and/or transfusion requirements in normothermic and mildly hypothermic (34-36 degrees C) surgical patients. Results are expressed as a ratio of the means or relative risks and 95% confidence intervals (CI); P < 0.05 was considered statistically significant.
  
  
  RESULTS
  Fourteen studies were included in analysis of blood loss, and 10 in the transfusion analysis. The median (quartiles) temperature difference between the normothermic and hypothermic patients among studies was 0.85 degrees C (0.60 degrees C versus 1.1 degrees C). The ratio of geometric means of total blood loss in the normothermic and hypothermic patients was 0.84 (0.74 versus 0.96), P = 0.009. Normothermia also reduced transfusion requirement, with an overall estimated relative risk of 0.78 (95% CI 0.63, 0.97), P = 0.027.
  
  
  CONCLUSIONS
  Even mild hypothermia (<1 degree C) significantly increases blood loss by approximately 16% (4-26%) and increases the relative risk for transfusion by approximately 22% (3-37%). Maintaining perioperative normothermia reduces blood loss and transfusion requirement by clinically important amounts.
authors.affiliation: Division of Anesthesia, Critical Care, and Comprehensive Pain Management, Cleveland Clinic, Cleveland, Ohio 44195, USA.
authors.forename: Suman
authors.initials: S
authors.lastname: Rajagopalan
authors.forename: Edward
authors.initials: E
authors.lastname: Mascha
authors.forename: Jie
authors.initials: J
authors.lastname: Na
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
mesh_terms: D016063:Blood Loss, Surgical / Q000517:prevention & control; D001803:Blood Transfusion / Q000592:standards; D006801:Humans; D007036:Hypothermia, Induced / Q000009:adverse effects*; D007431:Intraoperative Complications / Q000453:epidemiology* / Q000209:etiology; D019990:Perioperative Care / Q000009:adverse effects* / Q000379:methods / Q000592:standards; D016032:Randomized Controlled Trials as Topic / Q000379:methods