title: In vitro and in vivo assessment of platelet function in healthy dogs during administration of a low-dose aspirin regimen.
abstract: OBJECTIVE
  To assess the in vitro and in vivo platelet function of healthy dogs during administration of a low-dose aspirin regimen.
  
  
  METHODS
  16 dogs.
  
  
  METHODS
  Dogs received aspirin (1 mg/kg, PO, q 24 h) for 7 days. Blood and urine samples were collected before (day 1; baseline) and on days 3 and 7 of the low-dose aspirin regimen. Platelet function was evaluated by use of turbidimetric and conventional impedance aggregometry, multiple-electrode impedance aggregometry, a platelet function analyzer (PFA), and determination of urine 11-dehydro-thromboxane B2 concentration. Turbidimetric aggregometry results were compared with the results obtained by the other 4 methods. Fourteen days after cessation of aspirin, platelet-rich plasma was incubated with acetylsalicylic acid and platelet function was assessed by turbidimetric aggregometry to determine whether this technique could accurately identify dogs that responded to the low-dose aspirin regimen.
  
  
  RESULTS
  Of the 16 dogs, 13 had turbidimetric and conventional impedance aggregometry results that were decreased by > 25% from baseline on days 3 and 7, and 4 and 7 dogs had PFA closure times > 300 seconds on days 3 and 7, respectively. The median urine 11-dehydro-thromboxane B2 concentration-to-creatinine concentration ratio decreased by 49% between days 1 and 7. Turbidimetric aggregometry results were correlated with conventional impedance aggregometry results. There was poor agreement between the turbidimetric aggregometry and PFA results. The multiple-electrode impedance aggregometry protocol failed to reliably detect aspirin-induced platelet dysfunction. In vitro incubation of platelet-rich plasma with acetylsalicylic acid followed by turbidimetric aggregometry did not predict whether dogs responded to the low-dose aspirin regimen.
  
  
  CONCLUSIONS
  Results indicated that the response to a low-dose aspirin regimen varied among healthy dogs.
authors.forename: Jillian M
authors.initials: JM
authors.lastname: Haines
authors.forename: John M
authors.initials: JM
authors.lastname: Thomason
authors.forename: Eileen C
authors.initials: EC
authors.lastname: Seage
authors.forename: Robert W
authors.initials: RW
authors.lastname: Wills
authors.forename: Camilo
authors.initials: C
authors.lastname: Bulla
authors.forename: Kari V
authors.initials: KV
authors.lastname: Lunsford
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Mackin
mesh_terms: D000818:Animals; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects*; D004285:Dogs / Q000097:blood*; D004305:Dose-Response Relationship, Drug; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D010975:Platelet Aggregation Inhibitors; D001241:Aspirin