title: Increased blood product use among coronary artery bypass patients prescribed preoperative aspirin and clopidogrel.
abstract: BACKGROUND
  The administration of antiplatelet drugs before coronary artery bypass graft surgery (CABG) is associated with an increased risk of major hemorrhage and related surgical reexploration. Little is known about the relative effect of combined clopidogrel and aspirin on blood product use around the time of CABG. We evaluated the associated risk between the combined use of aspirin and clopidogrel and the transfusion of blood products perioperatively.
  
  
  METHODS
  We retrospectively studied a cohort of 659 individuals who underwent a first CABG, without concomitant valvular or aortic surgery, at a single large Canadian cardiac surgical centre between January 2000 and April 2002. The four study exposure groups were those prescribed aspirin (n = 105), clopidogrel (n = 11), the combination of both (n = 46), or neither drug (n = 497), within 7 days prior to CABG. The primary study outcome was the excessive transfusion of blood products during CABG and up to the second post-operative day, defined as > or = 2 units of packed red blood cells (PRBC), > or = 2 units of fresh frozen plasma, > or = 5 units of cryoprecipitate or > or = 5 units of platelets. Secondary outcomes included the mean number of transfused units of each type of blood product.
  
  
  RESULTS
  A greater mean number of units of PRBC were transfused among those who received clopidogrel alone (2.9) or in combination with aspirin (2.4), compared to those on aspirin alone (1.9) or neither antiplatelet drug (1.4) (P = 0.001). A similar trend was seen for the respective mean number of transfused units of platelets (3.6, 3.7, 1.3 and 1.0; P < 0.001) and fresh frozen plasma (2.5, 3.1, 2.3, 1.6; P = 0.01). Compared to non-users, the associated risk of excessive blood product transfusion was highest among recipients of aspirin and clopidogrel together (adjusted OR 2.2, 95% CI 1.1-4.3). No significant association was seen among lone users of aspirin (adjusted OR 1.0, 95% CI 0.6-1.6) or clopidogrel (adjusted OR 0.7, 95% CI 0.2-2.5), compared to non-users.
  
  
  CONCLUSIONS
  While combined use of aspirin and clopidogrel shortly before CABG surgery may increase the associated risk of excess transfusion of blood products perioperatively, several study limitations prevent any confident conclusions from being drawn. Beyond challenging these findings, future research might focus on the value of both intraoperative monitoring of platelet function, and the effectiveness of antifibrinolytic agents, at reducing the risk of postoperative bleeding.
authors.affiliation: Division of Critical Care, Department of Medicine, McMaster University, Hamilton, Canada. rayjg@mcmaster.ca
authors.forename: Joel G
authors.initials: JG
authors.lastname: Ray
authors.forename: Stacy
authors.initials: S
authors.lastname: Deniz
authors.forename: Anthony
authors.initials: A
authors.lastname: Olivieri
authors.forename: Erika
authors.initials: E
authors.lastname: Pollex
authors.forename: Marian J
authors.initials: MJ
authors.lastname: Vermeulen
authors.forename: Kurian S
authors.initials: KS
authors.lastname: Alexander
authors.forename: David J
authors.initials: DJ
authors.lastname: Cain
authors.forename: Irene
authors.initials: I
authors.lastname: Cybulsky
authors.forename: Cindy M
authors.initials: CM
authors.lastname: Hamielec
mesh_terms: D000368:Aged; D001241:Aspirin / Q000008:administration & dosage*; D000077144:Clopidogrel; D015331:Cohort Studies; D001026:Coronary Artery Bypass; D004359:Drug Therapy, Combination; D017707:Erythrocyte Transfusion / Q000706:statistics & numerical data*; D005260:Female; D006400:Hematocrit; D006801:Humans; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D017713:Platelet Transfusion / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D013223:Statistics as Topic; D013988:Ticlopidine / Q000008:administration & dosage* / Q000031:analogs & derivatives*
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin