The clinical significance of platelet counts in the first 24 hours after severe injury

BACKGROUND: Admission platelet (PLT) counts are known to be associated with all-cause mortality for seriously injured patients admitted to a trauma center. The course of subsequent PLT counts, their implications, and the effects of PLT therapy are less well known. STUDY DESIGN AND METHODS: Trauma center patients who were directly admitted from the scene of injury, received 1 or more units of uncrossmatched red blood cells in the first hour of care, survived for at least 15 minutes, and had a PLT count measured in the first hour were analyzed for the association of their admission and subsequent PLT counts in the first 24 hours with injury severity and hemorrhagic and central nervous system (CNS) causes of in-hospital mortality. RESULTS: Over an 8.25-year period, 1292 of 45,849 direct trauma admissions met entry criteria. Admission PLT counts averaged 228x109 +/- 90x109/L and decreased by 104x109/L by the second hour and 1x109/L each hour thereafter. The admission count was not related to time to admission. Each 1-point increase in the injury severity score was associated with a 1x109/L decrease in the PLT count at all times in the first 24 hours of care. Admission PLT counts were strongly associated with hemorrhagic and CNS injury mortality and subsequent PLT counts. Effects of PLT therapy could not be ascertained. DISCUSSION: Admission PLT counts in critically injured trauma patients are usually normal, decreasing after admission. Low PLT counts at admission and during the course of trauma care are strongly associated with mortality.