Sprague Dawley Severe Hemorrhagic Shock Model Assessed by Systemic and Microcirculatory Parameters

Abstract

Traumatic injury with hemorrhage is a primary cause of death in young, healthy adults with a significant portion of mortality occurring post‐resuscitation. Three factors contribute to outcomes: severity of hemorrhage, duration of hemorrhagic shock (HS), and resuscitation. To evaluate the efficacy of resuscitative intervention, we have developed a severe HS model sensitive to various techniques and solutions of resuscitation. Male Sprague Dawley rats were cannulated with arterial and venous lines to facilitate blood withdrawal, reperfusate infusion, continuous infusion of anesthesia, and monitoring of systemic variables (heart rate, mean arterial pressure [MAP]) with a pressure transducer (MP‐150; BIOPAC Systems Inc., Goleta, CA). The thin spinotrapezius muscle was exteriorized and secured in situ to a thermoregulated platform, which fit onto the stage of an upright microscope (Axio Imager.A2m, Carl Zeiss, Germany) for intravital microscopy of the microcirculation. Phosphorescence quenching microscopy assessed tissue oxygenation (ISF PO2). A 45% estimated blood volume withdrawal rate of 3.5 ml × kg−1 × min−1 produced a rapidly lethal (~1 h) model in sham (no treatment) animals with a good extension of survival times in animals resuscitated with either a non‐oxygen carrying colloid (Hextend™; Hospira, Inc, Lake Forest, IL) or whole blood. Hemorrhage produced a MAP of 20–25 mmHg and a non‐detectable ISF PO2. Following the 30 min HS phase, reperfusion of 20% estimated blood volume with Hextend™ elevated MAP to near baseline and increased survival times to 3 hours. However, Hextend™ did not change ISF PO2, which remained non‐detectable until the animals expired. Reperfusion of 20% estimated blood volume with whole blood elevated MAP back to baseline and elevated tissue ISF PO2 to normoxic levels. Additionally, whole blood extended survival times to 8 hours – the time of experiment termination. In summary, we have developed an in vivo model of severe hemorrhagic shock that allows for simultaneous characterization of systemic and microcirculatory metrics. The model is sufficiently severe to ensure consistency in post‐hemorrhage ischemia and mortality, while providing outcome sensitivity to reperfusion solutions and techniques.Support or Funding InformationSong Biotechnologies