title: Aspirin response variability after major orthopedic surgery.
abstract: BACKGROUND
  Variability in platelet response to aspirin has been reported in patients undergoing cardiac surgery but has rarely been described in other operative settings and its mechanism remains uncertain. We performed a prospective cohort study to investigate the variability in platelet response to aspirin and to explore its mechanism in patients undergoing major orthopedic surgery.
  
  
  METHODS
  Twelve aspirin-treated patients undergoing elective hip or knee replacement were recruited. Once-daily aspirin was continued throughout the perioperative period. We measured platelet function using light transmission aggregation (LTA) in response to arachidonic acid (PL(AA)) and serum thromboxane B(2) (TXB(2)) at baseline (before surgery) as well as on days 1, 2, 3, 4, 5, 6, and 8 after surgery. We defined aspirin low response as a PL(AA)>20%.
  
  
  RESULTS
  Six patients exhibited aspirin low response, which typically started on post-operative days 3 or 4; the remaining 6 patients had normal response to aspirin. Compared to aspirin responders, patients with aspirin low response showed significantly higher serum TXB(2) levels, a more pronounced early decrease in platelet count, and a significantly more rapid recovery of the platelet count after surgery.
  
  
  CONCLUSIONS
  Aspirin response variability occurred in patients after major orthopedic surgery, with one-half of the patients in our study exhibiting post-operative aspirin low response. Increased platelet turnover might be a contributor to aspirin response variability after orthopedic surgery.
authors.affiliation: Department of Cardiology, First Affiliated Hospital of Nanjing Medical University, Nanjing, China. lijay@njmu.edu.cn
authors.forename: Chunjian
authors.initials: C
authors.lastname: Li
authors.forename: Jack
authors.initials: J
authors.lastname: Hirsh
authors.forename: Debi
authors.initials: D
authors.lastname: Sloane
authors.forename: Yan
authors.initials: Y
authors.lastname: Liang
authors.forename: Jianling
authors.initials: J
authors.lastname: Bai
authors.forename: Jeremy
authors.initials: J
authors.lastname: Paikin
authors.forename: Marilyn A
authors.initials: MA
authors.lastname: Johnston
authors.forename: Justin
authors.initials: J
authors.lastname: DeBeer
authors.forename: John W
authors.initials: JW
authors.lastname: Eikelboom
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016718:Arachidonic Acid / Q000378:metabolism; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects; D001241:Aspirin / Q000494:pharmacology / Q000627:therapeutic use*; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D010976:Platelet Count; D011446:Prospective Studies; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D010975:Platelet Aggregation Inhibitors; D016718:Arachidonic Acid; D013929:Thromboxane B2; D001241:Aspirin