Platelet dysfunction in patients with severe traumatic brain injury.

Coagulopathy is a common phenomenon in traumatic brain injury (TBI) and a major contributor to a poor outcome. Thrombocytopenia is a strong negative prognostic factor in TBI, but bleeding tendency can be present even with a normal platelet count. We investigated platelet function in patients with TBI by means of modified thromboelastography (i.e., platelet mapping [TEG-PM]). Four groups were studied: (1) patients with severe isolated TBI (n = 20), (2) patients with general trauma without TBI (the ICU group, n = 10), (3) patients with chronic alcohol abuse (n = 7; as alcohol abuse is common in patients with TBI), and (4) healthy volunteers (n = 10). We measured platelet counts in venous blood (Plt), Ivy bleeding time, standard TEG parameters, and platelet responses to arachidonic acid (AA) and adenosindiphosphate (ADP), using TEG-PM. TBI patients had a lower Plt (180 +/- 68 x 10(9) ; mean +/- SD) and a longer bleeding time (674 +/- 230 sec) than healthy controls, (256 +/- 43 x 10(9), p < 0.01) and (320 +/- 95 sec, p < 0.005), respectively. TBI patients had dramatically lower platelet responses to AA (0-86%, mean 22%) compared to healthy controls (57-89%, mean 73%), the ICU group (4-75%, mean 49%), and the alcohol abusers (17-88%, mean 64%; p < 0.001). Responses to ADP did not differ significantly between the groups. Patients with low responsiveness to AA at admittance to the hospital were likely to develop bleeding complications later. Patients with TBI develop platelet dysfunction, which most likely contributes to bleeding complications. The observed platelet dysfunction appears to involve the cyclooxygenase pathway. TEG-PM analysis can be used to identify patients with a high risk of bleeding complications.