Effects of Sanguinate™ on Systemic and Microcirculatory Variables in a Model of Prolonged Ischemic Shock

Abstract

Hemorrhage after trauma is the leading cause of preventable death in young adults. In cases of severe blood loss, outcomes are dependent on prompt hemorrhage control and restoration of volume and oxygen carrying capacity. There is a dire need for oxygen carrying resuscitants that overcome the perishability, compatibility, and bioreactivity issues of blood.To study the effects of prolonged hypoxia and the effects of resuscitative fluids, a new model of prolonged ischemic shock (PIS) was developed by subjecting 17 male Sprague Dawley rats to a controlled, stepwise blood withdrawal (45% by volume), which mimicked conditions of post‐injury progressive hemorrhage control. Animals were then maintained in a state of untreated ischemic shock for at least 60 minutes and then received a 20% hypovolemic resuscitation with one of three test solutions: a crystalloid (Lactated Ringer's Solution; LRS), a colloid (Hextend™), or a novel PEGylated carboxyhemoglobin‐based oxygen carrier (Sanguinate™). Measurements of post‐resuscitative survival, spinotrapezius muscle interstitial oxygenation (PISFO2), arteriolar diameters, and systemic cardiovascular parameters were obtained throughout the experimental time course.The PIS hemorrhage protocol produced peripheral tissue hypoxia as measured by phosphorescence quenching microscopy and was lethal in sham (untreated) animals after 90 min. Survival was significantly different among treatment groups (p < 0.01), where LRS, Hextend™ and Sanguinate™‐treated animals survived 16 ± 3.4, 76 ± 11.1 and 193 ± 33.4 mins, respectively. Only Sanguinate™ produced a significant rise in tissue PISFO2 by two hours post‐resuscitation (p < 0.01). Mean arterial pressure (MAP) was significantly increased in Sanguinate™ versus LRS (p < 0.05) post‐resuscitation, and higher than Hextend™ by 60 min post‐resuscitation (p < 0.0001). Post‐resuscitative increases in MAP and PISFO2 correlated with increased survival times.We present a new model of evaluating prolonged tissue ischemia in the setting of hemorrhagic shock. Using this PIS model, we have shown that resuscitation with a carboxyhemoglobin‐based oxygen carrier (Sanguinate™) results in improved survival compared to standard resuscitation fluids. The PIS model provides a platform to investigate outcomes due to prolonged ischemia as opposed to acute hemorrhagic shock, and may therefore be more clinically applicable to current resuscitation protocols. Additionally, the PIS model may be useful in studies of reperfusion injury.Support or Funding InformationSupport: Song Biotechnologies, LLC & Prolong Pharmaceuticals, LLC