Abstract 284: Real Time Blood Pressure Dynamics During Fluid Resuscitation Predict 6-Hour Survival in a Swine Model of Polytrauma with Uncontrolled Hemorrhage
Objective: Blood pressure responses to fluid resuscitation during trauma can reflect blood loss and shock severity. We examine early blood pressure responses to fluid resuscitation to test the hypothesis that rapid blood pressure dynamics during trauma resuscitation may also predict longer-term survival.
Methods: Mean arterial pressure (MAP) during the initial fluid resuscitation was abstracted from a study using an anesthetized swine model of traumatic brain injury and catheter/free hemorrhage by aortic tear. Animals were hemorrhaged to MAP=30mmHg for 15 minutes prior to resuscitation. Lactated Ringers (LR, 20ml/kg) or a Hemoglobin-based Oxygen Carrier (HBOC, 10ml/kg) was then given over 10 minutes and repeated every 15 minutes thereafter for MAP < 60mmHg for up to 105 minutes. The aortic tear was then repaired and the animal further resuscitated using Normal Saline and shed blood to predefined criteria for up to 6 hours. Serial invasive MAP measurements recorded in 5 minute intervals over the first 15 minutes of fluid infusion were correlated with blood loss and survival time. MAP dynamics as predictors of 6 hour survivorship were examined by nominal logistic regression.
Results: 50% of animals (7/14) survived to 6 hours. There were no differences in initial MAP responses between LR and HBOC groups (p=0.85). Survivors demonstrated a more rapid and prolonged positive blood pressure response to the initial fluid bolus by a higher MAP at 5 minutes of fluid infusion (43.1 mmHg vs. 34.7 mmHg in nonsurvivors, T-test, p value=0.04) and a faster rate of increase (survivors = 3.0 mmHg/min vs. nonsurvivors= 1.4mmHg/min, Wilcoxon p value= 0.0008). MAP was sustained in survivors after the initial fluid infusion ended, but immediately declined in nonsurvivors. MAP increase was associated with total survival time (R=0.77, p=0.0012). A MAP rate of increase of at least 2.2mmHg/min over the first 5 minutes of fluid resuscitation predicted survival to 6 hours with 100% sensitivity and 75% specificity (AUC= 0.93, p< 0.0001). There was no association between blood pressure response and intraperitoneal hemorrhage volume.
Conclusion: In this swine model, very early resuscitation MAP dynamics predicted longer-term survival and may reflect retained physiological reserve.
- © 2011 by American Heart Association, Inc.