Thrombocytosis after trauma: incidence, aetiology, and clinical significance.

BACKGROUND Our aim was to assess the occurrence, aetiology, and clinical significance of a platelet count greater than 600 x 10(3)/mm(3) in trauma patients. METHODS All trauma patients admitted to the intensive care unit (ICU) during a 13-month period were prospectively studied. Platelet counts were performed daily. We recorded the patient's age, sex, nature of trauma, severity of illness scores, episodes of infections in the ICU, acute lung injury, bleeding, and thromboembolic events. Patients with thrombocytosis were also followed during their hospital stay and 1 month after hospital discharge. RESULTS A total of 176 patients were included. Thrombocytosis developed in 36 patients (20.4%) at a mean (sd) time of 14.0 (4.0) days and the platelet count normalized 35.0 (13.0) days after admission to the ICU. All patients with thrombocytosis had one or more possible predisposing conditions before the occurrence of thrombocytosis: nosocomial infection occurred in 30 patients (83%), acute lung injury in 17 (47%), bleeding in 27 (75%), and administration of cathecholamines in 24 (67%). Three venous thromboembolic complications occurred in the ICU (1.7%) and one during follow-up. Only one patient presented thrombocytosis at the time of diagnosis. Despite the fact that patients with thrombocytosis had a greater severity of illness, the ICU mortality was comparable among patients with and without thrombocytosis (8 vs 14%, P=0.34). CONCLUSIONS Reactive thrombocytosis is a common finding after severe trauma and was found to be associated with a better survival than predicted by severity of illness score. Unless additional risk factors are present, reactive thrombocytosis is not associated with an increased risk of thromboembolic events.