title: Hemostatic effects of fresh frozen plasma may be maximal at red cell ratios of 1:2.
abstract: BACKGROUND
  Damage control resuscitation targets acute traumatic coagulopathy with the early administration of high-dose fresh frozen plasma (FFP). FFP is administered empirically and as a ratio with the number of packed red blood cells (PRBC). There is controversy over the optimal FFP:PRBC ratio with respect to outcomes, and their hemostatic effects have not been studied. We report preliminary findings on the effects of different FFP:PRBC ratios on coagulation.
  
  
  METHODS
  This is a prospective observational cohort study of trauma patients requiring >4 U of PRBCs. Blood was drawn before and after each 4-U PRBC interval for prothrombin time and analysis by rotational thromboelastometry. Interval change in coagulation parameters were compared with the FFP:PRBC ratio received during each interval.
  
  
  RESULTS
  Sixty 4-U PRBC intervals from 50 patients were available for analysis. All measures of coagulation deteriorated with low FFP:PRBC ratios (<1:2). Maximal hemostatic effect was observed in the 1:2 to 3:4 group: 12% decrease in prothrombin time (p=0.006), 56% decrease in clotting time (p=0.047), and 38% increase in maximum clot firmness (p=0.024). Transfusion with ≥1:1 ratio did not confer any additional improvement. There was a marked variability in response to FFP, and hemostatic function deteriorated in some patients exposed to 1:1 ratios. The beneficial effects of plasma were confined to patients with coagulopathy.
  
  
  CONCLUSIONS
  Interim results from this prospective study suggest that FFP:PRBC ratios of ≥1:1 do not confer any additional advantage over ratios of 1:2 to 3:4. Hemostatic benefits of plasma therapy are limited to patients with coagulopathy.
authors.affiliation: Trauma Clinical Academic Unit, Blizard Institute of Cell and Molecular Science, the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom.
authors.forename: Ross
authors.initials: R
authors.lastname: Davenport
authors.forename: Nicola
authors.initials: N
authors.lastname: Curry
authors.forename: Joanna
authors.initials: J
authors.lastname: Manson
authors.forename: Henry
authors.initials: H
authors.lastname: De'Ath
authors.forename: Amy
authors.initials: A
authors.lastname: Coates
authors.forename: Claire
authors.initials: C
authors.lastname: Rourke
authors.forename: Rupert
authors.initials: R
authors.lastname: Pearse
authors.forename: Simon
authors.initials: S
authors.lastname: Stanworth
authors.forename: Karim
authors.initials: K
authors.lastname: Brohi
mesh_terms: D000328:Adult; D001777:Blood Coagulation / Q000502:physiology; D001803:Blood Transfusion / Q000379:methods / Q000592:standards; D004906:Erythrocyte Count; D005260:Female; D006470:Hemorrhage / Q000628:therapy; D006487:Hemostasis / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010949:Plasma / Q000502:physiology*; D011517:Prothrombin Time; D013916:Thrombelastography; D016896:Treatment Outcome; D014947:Wounds and Injuries / Q000628:therapy*