United States Army Institute of Surgical Research San Antonio, Texas, United States
Background/Case Studies: Chemical formulation of anticoagulants used in blood samples contribute to laboratory aberrancies. For example, sodium citrate is used for coagulation assays, but its calcium-chelating effects necessitate heparin anticoagulation for measuring ionized calcium. In austere environments, having a diverse set of reagents provides a logistical challenge and may not be feasible. Values such as creatinine may also be masked by chelating reagents such as citrate. Conversion factors have been established using human samples based on specific reagents, but similar evaluation has not been completed in animal models which remain the standard for trauma studies.
Study
Design/Methods: Isoflurane anesthetized Sprague-Dawley adult male rats were subjected to blunt polytrauma (crush injury to the ileum, liver, and skeletal muscle, and femur fracture) followed by 40% hemorrhage. Whole blood samples using heparinized or citrated syringes were taken at cannulation as a baseline (BL) (n=11) and 4 hours (n=23) post trauma before euthanasia. Values for electrolytes, creatinine, anion gap, and glucose were measured by iSTAT CHEM-8 cartridge and compared between heparin and citrated samples at each time point. An index ratio of heparin to citrate was used to evaluate changes secondary to trauma. Data are presented as means ± standard deviation (SD) with significance at p< 0.05.
Results/Findings: There were significant differences between samples at all time points. The largest significant differences were noted at 4 hr post-trauma. Mean values of heparinized and citrate samples are shown in table one, and all values demonstrated a significant difference between the two samples at 4 hr post-trauma. Using the index ratio, the only significant changes between BL and 4 h were found in creatinine, anion gap, TCO2, and HCT.
Conclusions: Significant differences arose with electrolyte and chemistry lab values, likely associated with the chelating properties of citrate. Blood samples in sodium citrate syringes varied in electrolyte readings, masked renal changes, and provided a greater anion gap estimate compared to the blood in heparin, which may lead to an implicit bias in evaluating organ function in response to trauma while sampling with inconsistent anticoagulants in an animal model. The development of a universal anticoagulant for laboratory tests is warranted, especially at the point of injury and in emergency settings.
