A Pilot Study on Early Versus Delayed Hypertonic Saline Dextran Resuscitation in a Porcine Model of Near-Lethal Liver Injury: Early Hemodynamic Response and Short-Term Survival

Fluid therapy in uncontrolled hemorrhage--what experimental models have taught us

Intravenous fluid is life-saving in hypovolemic shock, but fluid sometimes aggravates the bleeding. During the past 25 years, animal models have helped our understanding of the mechanisms involved in this unexpected effect. A key issue is that vasoconstriction is insufficient to arrest the bleeding when damage is made to a major blood vessel. 'Uncontrolled hemorrhage' is rather stopped by a blood clot formed at the outside surface of the vessel, and the immature clot is sensitive to mechanical and chemical interactions. The mortality increases if rebleeding occurs. In the aortic tear model in swine, hemorrhage volume and the mortality increase from effective restoration of the arterial pressure. The mortality vs. amount of fluid curve is U-shaped with higher mortality at either end. Without any fluid at all, irreversible shock causes death provided the hemorrhage is sufficiently large. Crystalloid fluid administered in a 3 : 1 proportion to the amount of lost blood initiates serious rebleeding. Hypertonic saline 7.5% in 6% dextran 70 (HSD) also provokes rebleeding resulting in higher mortality in the recommended dosage of 4 ml/kg. Uncontrolled hemorrhage models in rats, except for the 'cut-tail' model, confirm the results from swine. To avoid rebleeding, fluid programs should not aim to fully restore the arterial pressure, blood flow rates, or blood volume. For a hemorrhage of 1000 ml, computer simulations show that deliberate hypovolemia (-300 ml) would be achieved by infusing 600-750 ml crystalloid fluid over 20-30 min or 100 ml of HSD over 10-20 min in an adult male.

Resuscitation after hemorrhagic shock: the effect on the liver--a review of experimental data

The liver is currently considered to be one of the first organs to be subjected to the hypoxic insult inflicted by hemorrhagic shock. The oxidative injury caused by resuscitation also targets the liver and can lead to malfunction and the eventual failure of this organ. Each of the various fluids, vasoactive drugs, and pharmacologic substances used for resuscitation has its own distinct effect(s) on the liver, and the anesthetic agents used during surgical resuscitation also have an impact on hepatocytes. The aim of our study was to identify the specific effect of these substances on the liver. To this end, we conducted a literature search of MEDLINE for all types of articles published in English, with a focus on articles published in the last 12 years. Our search terms were "hemorrhagic shock," "liver," "resuscitation," "vasopressors," and "anesthesia." Experimental studies form the majority of articles found in bibliographic databases. The effect of a specific resuscitation agent on the liver is assessed mainly by measuring apoptotic pathway regulators and inflammation-induced indicators. Apart from a wide range of pharmacological substances, modifications of Ringer's Lactate, colloids, and pyruvate provide protection to the liver after hemorrhage and resuscitation. In this setting, it is of paramount importance that the treating physician recognize those agents that may attenuate liver injury and avoid using those which inflict additional damage.

Development of a lethal, closed-abdomen grade V hepato-portal injury model in non-coagulopathic swine

BACKGROUND

Hemorrhage within an intact abdominal cavity remains a leading cause of preventable death on the battlefield. Despite this need, there is no existing closed-cavity animal model to assess new hemostatic agents for the preoperative control of intra-abdominal hemorrhage.

METHODS

We developed a novel, lethal liver injury model in non-coagulopathic swine by strategic placement of two wire loops in the medial liver lobes including the hepatic and portal veins. Distraction resulted in grade V liver laceration with hepato-portal injury, massive bleeding, and severe hypotension. Crystalloid resuscitation was started once mean arterial pressure (MAP) fell below 65 mm Hg. Monitoring continued for up to 180 min.

RESULTS

We demonstrated 90% lethality (9/10) in swine receiving injury and fluid resuscitation, with a mean survival time of 43 min. Previous efforts in our laboratory to develop a consistently lethal swine model of abdominal solid organs, including preemptive anticoagulation, a two-hit injury with controlled hemorrhage prior to liver trauma, and the injury described above without resuscitation, consistently failed to result in lethal injury.

CONCLUSION

This model can be used to screen other interventions for pre hospital control of noncompressible.

A new survivable damage control model including hypothermia, hemodilution, and liver injury

BACKGROUND

The purpose of this article is to describe a new model of traumatic intra-cavitary hemorrhage in a hypothermic, hemodiluted liver injury model that incorporates damage control principles and allows for survival.

MATERIALS AND METHODS

Twenty swine underwent a standardized 35% blood volume hemorrhage followed by resuscitation. Ten animals sustained nonsurgical and 10 a surgical high-grade liver injury. In the surgical liver injury, damage control gauze packing was performed. No operative treatment was provided for the nonsurgical liver injury, which was designed to test the efficacy of systemic hemostatic agents. After a 15 min treatment phase, the abdominal cavity was closed, with the packing in place for the surgical injury, and all animals were resuscitated. Necropsy was performed at 48 h post-injury.

RESULTS

At the time of liver injury, the animals were hemodiluted and hypothermic. Both injuries caused a 20% drop in the mean arterial pressure from baseline (P<0.001). Comparing baseline thromboelastography results with the results after hemodilution, hypothermia, and liver injury, a hypercoagulopathic state was observed. Mortality was 30% for both types of liver injury. The mean volume of intra-abdominal blood present at autopsy was similar for both types of liver injuries (202 ± 161 mL and 214 ± 203 mL, respectively).

CONCLUSION

A new model of traumatic intra-cavitary hemorrhage in a hypothermic, hemodiluted liver injury model with damage control that allows for survival has been described. The mortality rate of 30% allows for the comparison of therapeutic interventions that may lead to improved survival.