title: An observational study investigating the effect of platelet function on outcome after colorectal surgery.
abstract: BACKGROUND
  Previous studies have assumed patients have uniform responses to aspirin, yet significant numbers are occult hypo- or hyper-responders. A new validated test of platelet function measures platelet P-selectin expression, which rises with increased platelet activity. This study investigated the measured perioperative changes in platelet function in response to aspirin, and subsequently whether quantitative variations in platelet activity affected perioperative complication severity and frequency.
  
  
  METHODS
  107 patients undergoing major colorectal surgery were recruited and assigned to either control (no antiplatelet therapy) or aspirin groups. P-selectin was measured following platelet stimulation at recruitment prior to cessation of medication, and at surgery before intervention. Perioperative complications, hemoglobin changes and blood transfusions were also recorded.
  
  
  RESULTS
  Platelet function was higher in control (n = 87) than aspirin group (n = 20) at recruitment (median 1303u [IQR 1102-1499] vs 77u [IQR 63.5-113.5],P < 0.01) and surgery (median 1224u [IQR 944-1496] vs 281.5u [IQR 106.8-943], P < 0.01). There was a positive correlation between length of aspirin cessation and platelet function at surgery (R(S) = 0.66, P < 0.01). Complication rates and hemorrhagic complication rates (P < 0.05) were higher with aspirin than control, although complication severity was not increased. Platelet function of the entire cohort at surgery was not associated with complication rate, severity or transfusion use.
  
  
  CONCLUSIONS
  Although complication rates were higher in aspirin group, impaired platelet function within ranges seen with aspirin continuation did not affect complication severity or rate or blood transfusion use. Consequently, aspirin continuation may not affect clinical outcome in patients undergoing major colorectal surgery and requires further investigation with a large randomized trial.
authors.affiliation: Division of Gastrointestinal Surgery, University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK; Department of Gastrointestinal Surgery, Nottingham University Hospitals NHS Trust, Queen's Medical Centre, Nottingham NG7 2UH, UK. Electronic address: barriekeeler@doctors.org.uk.
authors.forename: Barrie D
authors.initials: BD
authors.lastname: Keeler
authors.affiliation: Division of Gastrointestinal Surgery, University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK; Department of Gastrointestinal Surgery, Nottingham University Hospitals NHS Trust, Queen's Medical Centre, Nottingham NG7 2UH, UK.
authors.forename: J Alastair
authors.initials: JA
authors.lastname: Simpson
authors.affiliation: Division of Cardiovascular Medicine University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: Susan C
authors.initials: SC
authors.lastname: Fox
authors.affiliation: Division of Gastrointestinal Surgery, University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK; Division of Cardiovascular Medicine University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: Christiana L
authors.initials: CL
authors.lastname: Stavrou
authors.affiliation: Division of Gastrointestinal Surgery, University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK; Division of Cardiovascular Medicine University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Briggs
authors.affiliation: Division of Gastrointestinal Surgery, University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK; Division of Cardiovascular Medicine University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: Priya
authors.initials: P
authors.lastname: Patel
authors.affiliation: Division of Cardiovascular Medicine University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK.
authors.forename: Stanley
authors.initials: S
authors.lastname: Heptinstall
authors.affiliation: Division of Gastrointestinal Surgery, University of Nottingham, Queen's Medical Centre, Derby Road, Nottingham NG7 2UH, UK; Department of Gastrointestinal Surgery, Nottingham University Hospitals NHS Trust, Queen's Medical Centre, Nottingham NG7 2UH, UK.
authors.forename: Austin G
authors.initials: AG
authors.lastname: Acheson
mesh_terms: D000368:Aged; D001241:Aspirin / Q000627:therapeutic use*; D001780:Blood Coagulation Tests; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D003107:Colorectal Surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use; D013927:Thrombosis / Q000097:blood / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D010975:Platelet Aggregation Inhibitors; D001241:Aspirin
keywords: Bleeding; Blood transfusion; Colorectal surgery; Perioperative care; Platelet activation; Postoperative complications