More and more of our patients are being placed on drugs that interfere with clotting in one way or another. I’ve written a number of articles on the trauma implications of warfarin and some of the newer anticoagulants, and provided some sample algorithms for reversal.
But what about antiplatelet agents? These are commonly used in patients with vascular disease, but can create problems when injury causes bleeding in dangerous areas like the inside of the skull. Can’t you just give a few bags of platelets and stop worrying?
A French group performed a prospective, observational study that monitored the response to platelet infusion in patients taking aspirin or clopidogrel. Patients requiring emergency surgery who were taking one or both of these agents and who were also confirmed as responding to therapy by the Verify Now device (Accumetrics, San Diego, CA) were enrolled.
Here are the factoids:
- 25 patients were enrolled during the 3 year study period
- 13 were taking aspirin, 8 clopidogrel, and 4 were taking both
- Patients received an average platelet infusion of 0.1U/kg
- Platelet function normalized in all but one of the aspirin patients
- Platelet function improved but did not normalize in any of the clopidogrel patients
Bottom line: Surprised? The existing literature supports platelet infusion for aspirin, and suggests that it can correct platelet dysfunction after a loading dose of clopidogrel. But what about established therapy? This study shows that it improves function, but not necessarily enough to be safe.
Why? Most likely, the long-acting active metabolites of this drug are still circulating in the plasma and poison the new platelets as soon as they are given. Additional strategies (and more platelets?) will be needed to reverse the effect of clopidogrel in injured patients who are on established therapy.
Reference: Is platelet infusion sufficient to establish platelet reactivity in patients who are responders to aspirin and/or clopidogrel before emergency surgery? J Trauma 74(5):1367-1369, 2013.