Blood pressure at which rehleeding occurs after resuscitation in swine with aortic injury

Background: The appropriateness of vigorous fluid resuscitation to normal blood pressure following hemorrhage in uncontrolled bleeding has recently been questioned due to the possibility of dislodging clots and exacerbating hemorrhage. To develop a rational blood pressure target that maximizes the metabolic benefits of resuscitation without causing increased blood loss, it was first necessary to determine whether there is a reproducible mean arterial pressure (MAP) at which rebleeding occurs. The purpose of this study was to explore the relationship between the rate and time of resuscitation after injury and the rebleeding MAP in an uncontrolled hemorrhage model. Methods: Sixty-two anesthetized pigs were instrumented with catheters and splenectomized, and suction tubes were placed in the lateral peritoneal recesses to continuously capture shed blood. With the abdomen open, an aortotomy was made in the infrarenal aorta. At either 5, 15, or 30 minutes after the end of the initial hemorrhage, resuscitation with warmed lactated Ringer's solution was begun at either 100 or 300 mL/min. The rebleeding MAP was determined at the moment blood appeared in the suction tubes. Results: The average pressure at the rebleeding point for all animals was MAP = 64 +/- 2, Systolic = 94 +/- 3, and Diastolic = 45 +/- 2 mm Hg. The pressure at which rebleeding occurred in this aortotomy model was not affected by either time of resuscitation (5-30 min), nor was the rebleeding pressure affected by the rate (100 vs. 300 mL/min) of resuscitation. Conclusions: There was a reproducible pressure at which rebleeding occurred in this model of uncontrolled hemorrhage. The optimal endpoint of resuscitation in patients without definitive hemorrhage control would then be below this rebleeding pressure.