Aspirin is insufficient in inhibition of platelet aggregation and thromboxane formation early after coronary artery bypass surgery.
BACKGROUND
Aspirin administered early after coronary artery bypass grafting surgery (CABG) improves graft patency and patients survival. However, the antiplatelet effect of aspirin seems to be variable and aspirin resistance is currently still being discussed. The aim of the study was to assess aspirin efficacy in the early postoperative period.


METHODS
Forty patients undergoing elective CABG surgery (20 in on-pump and 20 in off-pump) were enrolled in the study. Functional and biochemical responses to aspirin were evaluated by arachidonic acid (ARA)-induced platelet aggregation and urine 11-dehydro Thromboxane B2 metabolite excretion. Samples were collected before surgery (baseline; > or =7 days after aspirin withdrawal) and on days 1, 2 and 5 after surgery.


RESULTS
Median baseline ARA aggregability was 55%. On day 1, platelet aggregability decreased (12%, P < 0.001). On day 2, despite the aspirin administration, platelet aggregability exceeded the values from day 1 (38%, P < 0.001). Only on day 5, sufficient inhibition of platelet aggregation was achieved (8%, P < 0.001). Median preoperative urine concentration of 11-dehydroTxB2 was 106 ng/mmol of creatinine. On day 1, the concentration decreased only slightly and insignificantly (97 ng/ml, P = NS), similarly as on day 2 (86 ng/ml, P = NS). Only on day 5, significant decrease in concentration of thromboxane metabolite was achieved compared to preoperative values (46 ng/ml, P = 0.001).


CONCLUSIONS
Aspirin did not sufficiently inhibit platelet aggregation and thromboxane formation in the early postoperative period. Thus, antiplatelet treatment strategy should be intensified or modified in patients early after bypass surgery.
Bednar
Frantisek
F
Cardiocenter, Department of Cardiac Surgery, 3rd Medical School, Charles University and University Hospital Kralovske Vinohrady, Srobarova 50, 100 34 Prague, Czech Republic. fandabednar@email.cz
Osmancik
Pavel
P
Hlavicka
Jan
J
Jedlickova
Vera
V
Paluch
Zoltan
Z
Vanek
Tomas
T
D000368:Aged; D001241:Aspirin / Q000494:pharmacology* / Q000627:therapeutic use*; D002318:Cardiovascular Diseases / Q000097:blood / Q000188:drug therapy / Q000601:surgery; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects* / Q000502:physiology; D011446:Prospective Studies; D013931:Thromboxanes / Q000097:blood*
D013931:Thromboxanes; D001241:Aspirin