SAN FRANCISCO – Preoperative light transmission aggregometry assessments of platelet aggregation may help identify which patients on dual antiplatelet therapy are at greater risk of sustained bleeding from noncardiac surgery, a prospective study of 147 consecutive patients suggests.
The light transmission aggregometry (LTA) assessments of blood drawn immediately before noncardiac surgery were significantly lower in the 32% of patients with sustained bleeding than in the other patients.
All patients were on dual antiplatelet therapy, 95% of them on maintenance therapy with aspirin plus clopidogrel. The timing of the surgery was at the discretion of the surgeons. Treating physicians were blinded to LTA results. The average preoperative washout period for dual antiplatelet therapy was 1.5 days (range, 0-6 days).
The findings of the ongoing study might help define a "bleeding cutoff" measure by LTA to better individualize the timing of surgery, Dr. Wolfgang Toller and his associates suggested in a poster presentation at the annual meeting of the American Society of Anesthesiologists.
In general, approximately 5% of patients in their first year of dual antiplatelet therapy undergo noncardiac surgery, which creates a conundrum for management. Discontinuing dual antiplatelet therapy before noncardiac surgery has been associated with a 20% risk of major adverse cardiac events, but there’s a 20%-40% risk of moderate to severe bleeding if dual antiplatelet therapy is continued during noncardiac surgery, said Dr. Toller of the Medical University of Graz, Austria.
The 147 patients in the study underwent vascular surgery (76%), orthopedic surgery (10%), abdominal surgery (7%), or other surgical procedures (7%). All had been on P2Y12 receptor inhibitors within 7 days before surgery.
Investigators used the Chronolog 700 Lumi-Aggregometer to assess platelet aggregation in preoperative blood, using 5 mcm of adenosine diphosphate as the specific inductor for platelet aggregation.
Overall, they found an average 40% maximum change in light transmission from baseline after adding the adenosine diphosphate to blood samples. In patients with increased bleeding, however, the mean maximum change in light transmission was approximately 30% (suggesting less platelet aggregation), compared with a more than 40% change in patients who bled less from the surgery.
The study used a composite definition of increased bleeding that included TIMI (Thrombolysis in Myocardial Infarction) criteria for major or minor bleeding, any postoperative bleeding requiring reoperation, any platelet transfusion, or at least two packed red blood cells more than the average surgery-specific transfusion requirements at the surgical site.
Dr. Toller reported having no financial disclosures.
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