title: A systematic evaluation of the effect of temperature on coagulation enzyme activity and platelet function.
abstract: BACKGROUND
  Hypothermia is associated with an increased risk of bleeding and is a significant contributing factor to the morbidity and mortality of trauma and complicated surgical procedures. A core temperature of 33 degrees C is associated with a significantly increased risk of death after trauma compared with 37 degrees C. Hypothermia-associated bleeding has been hypothesized to result from dysregulation of enzymatic function, reduced platelet activity, and/or altered fibrinolysis.
  
  
  METHODS
  We systematically evaluated the effects of temperature on isolated pro- and anticoagulant enzyme processes and platelet activation and adhesion. We also evaluated the effects of temperature on complete coagulation systems (activated partial thromboplastin time and an in vitro, cell-based model of coagulation).
  
  
  RESULTS
  Enzyme activities were only slightly reduced at 33 degrees C versus 37 degrees C, and this reduction was not statistically significant (p > 0.05). Platelet activation was also not significantly reduced at 33 degrees C versus 37 degrees C. Conversely, platelet aggregation and adhesion were significantly reduced at 33 degrees C compared with 37 degrees C (p < 0.05). Below 33 degrees C, however, both enzyme activity and platelet function were significantly reduced.
  
  
  CONCLUSIONS
  Our results suggest that bleeding observed at mildly reduced temperatures (33 degrees - 37 degrees C) results primarily from a platelet adhesion defect, and not reduced enzyme activity or platelet activation. However, at temperatures below 33 degrees C, both reduced platelet function and enzyme activity likely contribute to the coagulopathy.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, North Carolina, USA.
authors.forename: Alisa S
authors.initials: AS
authors.lastname: Wolberg
authors.forename: Zhi Hong
authors.initials: ZH
authors.lastname: Meng
authors.forename: Dougald M
authors.initials: DM
authors.lastname: Monroe
authors.forename: Maureane
authors.initials: M
authors.lastname: Hoffman
mesh_terms: D000328:Adult; D001777:Blood Coagulation / Q000502:physiology*; D015951:Factor Xa / Q000502:physiology; D006801:Humans; D007035:Hypothermia / Q000503:physiopathology; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D010973:Platelet Adhesiveness / Q000502:physiology*; D010974:Platelet Aggregation / Q000502:physiology*; D013696:Temperature; D013917:Thrombin / Q000096:biosynthesis
chemical_list: D013917:Thrombin; D015951:Factor Xa