title: Platelet function one and three months after coronary bypass surgery in relation to once or twice daily dosing of acetylsalicylic acid.
abstract: BACKGROUND
  Current guidelines recommend acetylsalicylic acid (ASA) treatment after coronary artery bypass grafting (CABG) to reduce thrombotic vein graft occlusion. The optimal dosage of ASA is not known.
  
  
  METHODS
  Forty-two patients undergoing elective CABG were randomized to receive either ASA 75mg or 160mg once daily (OD) or 75mg twice daily (BID) after the operation. Platelet function testing was performed before, and one and three months after the operation.
  
  
  RESULTS
  White blood cell counts increased during the initial postoperative days whereas platelet counts were initially slightly reduced after the operation but increased after one month without any major changes of mean platelet volumes. Serum thromboxane B2was more effectively suppressed at one and three months after the operation with ASA 75mg BID or 160mg OD than with 75mg OD (p<0.001). ASA 75mg BID and 160mg OD were equally effective. Adenosine diphosphate stimulated platelet aggregation in whole blood (Multiplate®) was increased one and three months after the operation, and this was counteracted by ASA 75mg BID but not by 75 or 160mg OD. Arachidonic acid-induced aggregation was more effectively inhibited by 75mg BID or 160mg OD compared to 75mg OD at three months.
  
  
  CONCLUSIONS
  Less effective inhibition of platelet activation was obtained with ASA 75mg OD than with ASA 160mg OD or 75mg BID up to three months after CABG. Especially the latter dose is of interest for further studies of efficacy and clinical outcomes after CABG.
authors.affiliation: Department of Cardiothoracic Surgery and Anesthesiology, Karolinska University Hospital and Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden. Electronic address: torbjorn.ivert@ki.se.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Ivert
authors.affiliation: Department of Cardiothoracic Surgery and Anesthesiology, Karolinska University Hospital and Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Dalén
authors.affiliation: Department of Clinical Pharmacology, Karolinska University Hospital and Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Ander
authors.affiliation: Department of Clinical Pharmacology, Karolinska University Hospital and Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ragnhild
authors.initials: R
authors.lastname: Stålesen
authors.affiliation: Center for Safety Research, KTH Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Näsman
authors.affiliation: Faculté de pharmacie, Université de Montréal and Research Center, Montreal Heart Institute, Montréal, Québec, Canada.
authors.forename: Marie
authors.initials: M
authors.lastname: Lordkipanidzé
authors.affiliation: Department of Clinical Pharmacology, Karolinska University Hospital and Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Paul
authors.initials: P
authors.lastname: Hjemdahl
mesh_terms: D000368:Aged; D001241:Aspirin / Q000008:administration & dosage / Q000627:therapeutic use*; D001792:Blood Platelets / Q000187:drug effects*; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000627:therapeutic use*; D010979:Platelet Function Tests; D011446:Prospective Studies; D013927:Thrombosis / Q000097:blood / Q000209:etiology* / Q000517:prevention & control*; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D010975:Platelet Aggregation Inhibitors; D013929:Thromboxane B2; D001241:Aspirin
keywords: Aspirin; Coronary artery bypass grafting; Individualized therapy; Platelet function; Thromboxane