Accession Number:

ADA616560

Title:

Platelet Activation after Presyncope by Lower Body Negative Pressure in Humans

Descriptive Note:

Journal article

Corporate Author:

ARMY INST OF SURGICAL RESEARCH FORT SAM HOUSTON TX

Report Date:

2014-12-29

Pagination or Media Count:

13.0

Abstract:

Central hypovolemia elevates hemostatic activity which is essential for preventing exsanguination after trauma, but platelet activation to central hypovolemia has not been described. We hypothesized that central hypovolemia induced by lower body negative pressure LBNP activates platelets. Eight healthy subjects were exposed to progressive central hypovolemia by LBNP until presyncope. At baseline and 5 min after presyncope, hemostatic activity of venous blood was evaluated by flow cytometry, thrombelastography, and plasma markers of coagulation and fibrinolysis. Cell counts were also determined. Flow cytometry revealed that LBNP increased mean fluorescence intensity of PAC-1 by 1959 - 455 units P0.001 and percent of fluorescence-positive platelets by 27 - 18-points P0.013. Thrombelastography demonstrated that coagulation was accelerated R-time decreased by 0.8 - 0.4 min P0.001 and that clot lysis increased LY60 by 6.0 - 5.8-points P0.034. Plasma coagulation factor VIII and von Willebrand factor ristocetin cofactor activity increased P0.011 and P0.024, respectively, demonstrating increased coagulation activity, while von Willebrand factor antigen was unchanged. Plasma protein C activity and tissue-type plasminogen activator increased P0.007 and P0.017, respectively, and D-dimer increased by 0.03 - 0.02 mg l21 P0.031, demonstrating increased fibrinolytic activity. Plasma prothrombin time and activated partial thromboplastin time were unchanged. Platelet count increased by 15 - 13 P0.014 and red blood cells by 9 - 4 P0.002. In humans, LBNP-induced presyncope activates platelets, as evidenced by increased exposure of active glycoprotein IIbIIIa, accelerates coagulation. LBNP activates fibrinolysis, similar to hemorrhage, but does not alter coagulation screening tests, such as prothrombin time and activated partial thromboplastin time. LBNP results in increased platelet counts, but also in hemoconcentration.

Subject Categories:

  • Anatomy and Physiology
  • Medicine and Medical Research

Distribution Statement:

APPROVED FOR PUBLIC RELEASE