Abstract 494: Platelet Aggregation in a Model of Simulated Arterial Flow: Red Blood Cells Are Integral Players in Hemostatic Control Resuscitation
Background: Approximately one in four trauma patients exhibits an early bleeding diathesis, termed the acute coagulopathy of trauma and defined by an initial INR >1.2, which is associated with a 3-fold increase in mortality. In recent years, the concept of damage control resuscitation has been developed to address this problem. This approach emphasizes hemorrhage control and early resuscitation with blood products in a 1:1:1 ratio of plasma:platelets:RBCs in an attempt to replace whole blood lost in hemorrhage. The optimal ratio of blood components has not been established and few pre-clinical studies have explored this problem under arterial shear conditions.
Objective: Our objective is to establish stepped ranges of hematocrit values and platelet counts to identify the component and concentration of that component most responsible for the largest loss of platelet-collagen interaction.
Methods: Donor citrated whole blood containing calcein tagged platelets was flowed at an arterial shear rate of 1000/second through a 70μm x 350μm x 5mm collagen-coated chamber at 37°C for 10 min, n=6. Images were captured every 15 seconds and analyzed for fluorescence intensity.
Results: Linear regression analysis generated slopes (fluorescent intensity units/second) that were most different as hematocrit dropped below physiologic levels (HCT40control=100%, HCT25=39.5%, HCT20=21.4%, HCT18=17.4%, HCT16=11.6%). Non-linear fitting of slopes vs. HCT yielded the equation y=1.27e4 x2 -3.51e4 x +4.43e5 describing an exponential decrease in platelet-collagen interaction with linear decreases in HCT.
Conclusions: The largest drop in platelet adherence to collagen in a physiological model of arterial flow occurs as hematocrit falls from 40%. The commonly suggested 30HCT target for minimal RBC transfusion during resuscitation may not adequately support hemostasis and should be reconsidered.
- © 2012 by American Heart Association, Inc.