Platelet dysfunction and platelet transfusion in traumatic brain injury.

BACKGROUND: Both aspirin therapy and trauma impair platelet function. Platelet dysfunction is associated with worse outcomes in patients with traumatic intracranial hemorrhage (ICH). Platelet transfusion is often used to limit progression of ICH in patients on aspirin, but has not been shown to improve platelet function or outcomes. We hypothesized that platelet transfusion would improve aspirin-induced, but not trauma-induced, platelet dysfunction.
MATERIALS AND METHODS: In this prospective trial, blood samples were collected from patients evaluated in our level 1 trauma center with traumatic ICH, at the time of arrival and at the next clinical laboratory draw after admission. Patients on aspirin therapy were transfused one apheresis unit of platelets. Platelet function was assessed using a Multiplate multiple electrode aggregometer. Platelet activation was induced by collagen (COL) and arachidonic acid (AA). Agonist responses are reported as area under the aggregation curve in units (U). Reference ranges for agonist response were provided by the manufacturer, based on studies of healthy controls.
RESULTS: Seventeen patients with isolated ICH were enrolled, twelve taking aspirin and five not taking aspirin. All patients on aspirin received platelet transfusion. Median admission platelet function in patients taking aspirin was abnormal in response to both agonists. After transfusion, median platelet function in response to AA improved from 19.0 U to 26.0 U (P = 0.012), whereas there was no improvement in the COL response. In patients not on aspirin, platelet response to COL was abnormal at both time points.
CONCLUSIONS: Patients with isolated ICH have trauma-induced platelet dysfunction. In addition, patients on aspirin have drug-induced abnormalities in platelet response to AA. Platelet transfusion improves aspirin-induced, but not trauma-induced, platelet dysfunction.