Eight Hours of Hypotensive versus Normotensive Resuscitation in a Porcine Model of Controlled Hemorrhagic Shock

Abstract

The aim of this study was to compare hypotensive and normotensive resuscitation in a porcine model of hemorrhagic shock. This was a prospective, comparative, randomized survival study of controlled hemorrhagic shock using 28 male Yorkshire-Landrace pigs (15 to 25 kg). In 24 splenectomized pigs, the authors induced hemorrhagic shock to a systolic blood pressure (sBP) of 48 to 58 mm Hg (approximately 35% bleed). Pigs were randomized to undergo normotensive resuscitation (sBP of 90 mm Hg, n = 7), mild hypotensive resuscitation (sBP of 80 mm Hg, n = 7), severe hypotensive resuscitation (sBP of 65 mm Hg, n = 6), or no resuscitation (n = 4). The authors also included a sham group of animals that were instrumented and splenectomized, but that did not undergo hemorrhagic shock (n = 4). After the initial 8 hours of randomized pressure-targeted resuscitation, all animals were resuscitated to a sBP of 90 mm Hg for 16 hours. Animals that underwent severe hypotensive resuscitation were less likely to survive, compared with animals that underwent normotensive resuscitation. Mean arterial pressure (MAP) decreased with hemorrhage and increased appropriately with pressure-targeted resuscitation. Base excess (BE) and tissue oxygen saturation (StO2) decreased in all animals that underwent hemorrhagic shock. This decrease persisted only in animals that were pressure target resuscitated to a sBP of 65 mm Hg. In this model of controlled hemorrhagic shock, initial severe hypotensive pressure-targeted resuscitation for 8 hours was associated with an increased mortality rate and led to a persistent base deficit (BD) and to decreased StO2, suggesting persistent metabolic stress and tissue hypoxia. However, mild hypotensive resuscitation did not lead to a persistent BD or to decreased StO2, suggesting less metabolic stress and less tissue hypoxia.