Platelet function assessed by whole-blood aggregometry in patients undergoing non-cardiac surgery.

Background: The risk/benefit of continuing low-dose acetylsalicylic acid (aspirin) for secondary prevention in the perioperative period is still debated. The primary aim of this study was to determine the effect of acetylsalicylic acid compared with placebo on platelet function in the perioperative period.

Methods: This is a subgroup analysis of a randomised, double-blind, placebo-controlled multicentre study. High-risk patients undergoing major non-cardiac surgery were randomised to 75 mg acetylsalicylic acid or placebo 7 days preoperatively, until the third postoperative day. In 36 patients, platelet function in response to arachidonic acid was assessed by whole-blood impedance aggregometry using a multiplate analyser 1 h before surgery, directly after surgery and 48 h postoperatively.

Results: The platelet function was significantly reduced in patients treated with acetylsalicylic acid compared with placebo in the preoperative period [200 aggregation units (AU) min (interquartile range [IQR] 133-261 AU min⁻¹) vs. 860 AU min (IQR 800-1010 AU min), P < 0.001] as well as postoperatively [198 AU min (IQR 138-270 AU min) vs. 605 AU min (IQR 434-836 AU min), P < 0.001]. The platelet response was significantly reduced postoperatively compared with preoperatively in patients receiving placebo [860 AU min (IQR 800-1010 AU min) vs. 605 AU min (IQR 434-861 AU min), P = 0.0009]. No significant differences were found between pre- and postoperative platelet function in patients on acetylsalicylic acid [200 AU min (IQR 133-261 AU min) vs. 198 AU min (133-270 AU min), P = 0.21].

Conclusion: Multiplate whole-blood impedance aggregometry demonstrates acetylsalicylic affect in preoperative as well as postoperative samples derived from patients undergoing non-cardiac surgery.