Endogenous heparin decreases the thrombotic response to hemorrhagic shock in rabbits.
OBJECTIVE
The purpose of this study was to determine if endogenous heparin release would modulate the hemostatic response to hemorrhagic shock in rabbits.


METHODS
Anesthetized rabbits (n = 13) underwent hemorrhagic shock (MAP 30-40 mm Hg) for 60 minutes. Blood samples obtained before and 60 minutes after hemorrhagic shock had thrombelasto-graphic variables (R, reaction time [min]; angle, alpha [ degrees ]; and G [dynes/cm(2)]) determined. Hemostatic function was assessed by modified thrombelastography under four conditions: (1) unmodified sample; (2) platelet inhibition with cytochalasin D; (3) heparinase I exposure; and (4) platelet inhibition and heparinase I exposure.


RESULTS
Thrombelastographic variable values in samples without platelet inhibition or heparinase exposure did not significantly change after hemorrhage (before hemorrhage: R = 22.01 +/- 0.7 min, alpha 43.6 +/- 1.3 degrees, G 7,089 +/- 379 dyne/cm(2); after hemorrhage: R 22.1 +/- 2.4, alpha 41.6 +/- 3.9, G = 5,662 +/- 564; mean +/- SEM). However, blood samples exposed to heparinase after hemorrhage demonstrated enhanced hemostatic function with thrombelastographic values (R = 13.4 +/- 1.5, alpha 56.0 +/- 3.4, G = 7012 +/- 565) significantly different (P <.05) from samples not exposed to heparinase. Samples with platelet inhibition demonstrated a similar pattern.


CONCLUSIONS
Hemorrhagic shock significantly increased circulating endogenous heparin activity, attenuating the thrombotic response to hemorrhage in rabbits. Heparin-mediated regulation of hemostasis may serve as a protective mechanism in shock states.
Nielsen
V G
VG
Department of Anesthesiology, Division of Cardiothoracic Anesthesia, The University of Alabama at Birmingham, 35249, USA.
D000704:Analysis of Variance; D000818:Animals; D006487:Hemostasis / Q000502:physiology*; D006493:Heparin / Q000502:physiology*; D008297:Male; D011817:Rabbits; D012771:Shock, Hemorrhagic / Q000097:blood*; D013916:Thrombelastography
D006493:Heparin