Hemodilution as a result of aggressive fluid resuscitation aggravates coagulopathy in a rat model of uncontrolled hemorrhagic shock

BACKGROUND: The relationship between dilution caused by fluid resuscitation and blood coagulability during ongoing, uncontrolled hemorrhagic shock (UHS) remains unclear. We hypothesized that dilution caused by fluid resuscitation may impair blood coagulability in UHS. METHODS: Eighteen rats underwent under halothane anesthesia. The UHS model consisted of the following phases: (1) an initial blood withdrawal of 2.5 mL per 100 g during 15 minutes, followed by UHS via tail amputation and fluid resuscitation with lactated Ringer's (LR) solution (0-60 minutes); (2) hemostasis and reinfusion of withdrawn blood and additional LR solution (60-100 minutes); and (3) observation of awake rats for 72 hours. Rats were randomized into three resuscitation regimens (n = 6 per group) during Phase I. LR solution was infused at a rate of 0.1 mL/min in Group 1, 0.25 mL/min in Group 2, and 0.75 mL/min in Group 3. Blood coagulability was assessed with a Sonoclot analysis, and survival to 72 hours were compared between groups. RESULTS: Both resuscitation regimens of Groups 2 and 3 increased the blood pressure and bleeding volume from the tail stump compared with Group 1 (p < 0.05). At the end of Phase I, the hematocrit decreased to 29% (3%) in Group 1, 23% (3%) in Group 2, and 12% (3%) in Group 3 (p < 0.05). Sonoclot analysis revealed a decreased clot rate of 16 (9) clot signal per minute in Group 2 and 14 (10) clot signal per minute in Group 3 compared with Group 1 (40 [10] clot signal per minute; p < 0.01). There was a significant correlation between clot rate and hematocrit values (r = +0.67, p < 0.01). Compared with Group 1, survival improved in Groups 2 and 3 (p < 0.05). CONCLUSION: In a rat model of UHS, aggressive fluid resuscitation aggravated hemodilution and blood coagulability as well as and bleeding but improved the hemodynamics and survival. There was a positive correlation between hemodilution and coagulation indexes. Hemodilution, as part of fluid therapy, may affect coagulopathy in UHS. (J Trauma Acute Care Surg. 2013;74: 808-812. Copyright (c) 2013 by Lippincott Williams & Wilkins)