Change in hematocrit during trauma assessment predicts bleeding even with ongoing fluid resuscitation.

This study tests the hypothesis that a change in hematocrit (ΔHct) during initial trauma work-up is as reliable as conventional vital signs for detecting bleeding, even with ongoing fluid resuscitation. Consecutive trauma patients admitted to a Level I trauma center receiving two Hct measurements during initial resuscitation between January 2010 and January 2011 were stratified based on estimated blood loss greater than 250 mL (bleeding) or nonbleeding. Sensitivity, specificity, and receiver operating characteristic curves were calculated for systolic blood pressure (SBP), heart rate, base deficit, and ΔHct. In 168 (72%) nonbleeding versus 64 (28%) bleeding patients, age and gender were similar. Arrival SBP was highly specific (90 to 99%) but poorly sensitive (13 to 31%) for detecting bleeding. Combinations of vital signs increased specificity, albeit at the expense of sensitivity. For bleeding versus nonbleeding patients (all receiving resuscitation fluid), ΔHct was 9.0 versus 1.8, ΔHct/liter was 4.8 versus 1.5, and ΔHct/liter/hour was 2.8 vs 0.6 (all P < 0.001). Only SBP (area under the curve [AUC] 0.608 to 0.695) and ΔHct (AUC 0.731 to 0.921) were significant for identifying bleeding with ΔHct 6 or greater being the best predictor (sensitivity 89%, specificity 95%, AUC 0.921). During ongoing fluid resuscitation of a trauma victim, ΔHct is the single most reliable indicator of continuing blood loss. A ΔHct 6 or greater during initial resuscitation is highly suspicious for ongoing blood loss, but even lesser changes have predictive value. Altogether, these results support the idea that fluid shifts are rapid after hemorrhage and Hct can be valuable during initial trauma assessment.

Admission hematocrit and transfusion requirements after trauma.

BACKGROUND: The decision to transfuse packed RBCs (PRBC) during initial resuscitation of trauma patients is based on physiologic state, evidence for blood loss, and potential for ongoing hemorrhage. Initial hematocrit (Hct) is not considered an accurate marker of blood loss. This study tests the hypothesis that admission Hct is associated with transfusion requirements after trauma. METHODS: From June to December 2008, data from 1,492 consecutive admissions at a Level I trauma center were retrospectively reviewed to determine whether initial Hct was associated with PRBC transfusions. From October 2009 through October 2011, data from 463 consecutive transfused patients were retrospectively reviewed to determine whether Hct correlated with number of PRBC units received. RESULTS: Packed RBC transfusion was not correlated with heart rate and was more highly correlated with Hct (r = -0.45) than with systolic blood pressure or base deficit (r = -0.32 or r = -0.26). Hematocrit was a better overall predictor than systolic blood pressure (sensitivity 45% vs 29%, specificity 94% vs 98%, area under receiver operator characteristic curve 0.71 vs 0.64). Lower Hct was associated with hypotension, more advanced shock, higher blood loss, and increased transfusion of PRBC, plasma, platelets, or cryoprecipitate (all, p < 0.01). CONCLUSION: Admission Hct is more strongly associated with the PRBC transfusion than either tachycardia, hypotension, or acidosis. Admission Hct is also correlated with 24-hour blood product requirements in those receiving early transfusions. These findings challenge current thinking and suggest that fluid shifts are rapid after trauma and that Hct can be important in initial trauma assessment.