resuscitation from hemorrhagic shock with high molecular weight polymerized hemoglobin
Name: Alexander Thomas Williams
Grad Year: 2019
Background Hemoglobin (Hb) based oxygen carriers (HBOCs) have been proposed as an alternative to red blood cells (RBCs) for transfusion medicine. Lack of mechanistic analysis lead to clinical evaluation of low molecular weight (MW) HBOCs, which failed in phase III clinical trials due to a myriad of side effects not seen in pre-clinical trials. Increasing the MW of HBOCs can decrease these side effects by confining HBOCs to the vascular space and increasing nitric oxide generation. HBOCs are advantageous to blood due to their non-immunogenic properties and potential to use non-human hb sources, among others. In this study we compare the efficacy of fresh blood, freshly synthesized polymerized bovine hb (PolybHb), and PolybHb stored for 2 years in restoring cardiac function after hemorrhagic shock. Methods PolybHb was synthesized in the low oxygen affinity (T) state with a 35:1 ratio of glutaraldehyde to bovine Hb, and then subjected to 8-9 cycles of diafiltration. This resulted in a PolybHb solution containing only polymerized Hb molecules < 0.2 uM and >500kDa. PolybHb was then frozen at -80°C and stored until used. Fresh red blood cells were prepared from the blood removed during hemorrhage by centrifugation at 1000g for 7 minutes, removal of the buffy coat, and removal of plasma until a hematocrit of 50%. Rats (200-250g) were hemorrhaged for 50% of their blood volume, held in hypovolemia for 30 minutes, and resuscitated to recover blood pressure to 90% pre-hemorrhage with fresh autologous blood (fresh blood), PolybHb generated within 3 months of the study (PolybHb 2017), or PolybHb generated two years prior to the study (PolybHb 2015). Results Shock resulted in impaired oxygen delivery and cardiac function. Resuscitation with fresh blood, PolybHb 2017, and PolybHb 2015 restored cardiac function and systemic vascular resistance. Slightly more PolybHb was infused before restoration of 90% pre-hemorrhage MAP was achieved, but the volume was not statistically significant. Likely as a result of the higher resuscitation volume, stroke volume and stroke work increased more in animals resuscitated with PolybHb than fresh autologous blood. PolybHb did not impair cardiac contractility nor cause excessive vasoconstriction. Conclusions Studies indicate that PolybHb is as efficacious as fresh autologous blood in restoring cardiac function in rats after hemorrhagic shock. Additionally, PolybHb can be safely stored at -80°C for two years and retain efficacy, unlike red blood cells.
Industry Application Area(s)
Life Sciences/Medical Devices & Instruments