The development of an alternative to blood transfusion to treat severe hemorrhage remains a challenge, especially in far forward scenarios when blood is not available. Hemoglobin (Hb) based oxygen (O2) carriers (HBOCs) were developed to address this need. Hemopure® (HBOC-201, bovine Hb glutamer-250, OPK Biotech, Cambridge, MA, USA), one such HBOC, has been approved for clinical use in South Africa and Russia. At the time of its approval, however, few studies aimed to understand Hemopure’s function, administration, and adverse effects compared to blood. We used intravital microscopy to study the microcirculation hemodynamics (arteriolar and venular diameters and blood flow and functional capillary density (FCD)) and oxygenation implications of Hemopure® administration at different Hb concentrations —4, 8, and 12 gHb/dL— compared to fresh blood transfusion during resuscitation from hemorrhagic shock. Experiments were performed in unanesthetized hamsters instrumented with a skinfold window chamber, subjected to hemorrhage (50% of the blood volume, BV), followed by 1 hour hypovolemic shock and fluid resuscitation (50% of the shed volume). Our results show that fluid resuscitation with Hemopure® or blood restored systemic and microvascular parameters. Microcirculation O2 delivery was directly correlated with Hemopure® concentration, though increased vasoconstriction was as well. FCD reflected the balance between enhanced O2 transport and reduced blood flow: 12 gHb/dL of Hemopure® and blood decreased FCD compared to the lower concentrations of Hemopure® (p<0.05). The balance between O2 transport and tissue perfusion can provide superior resuscitation from hemorrhagic shock compared to blood transfusion by using a low Hb concentration of HBOCs relative to blood.

Nitric oxide (NO) is an important factor during an ischemia/reperfusion (I/R) injury. Protective actions of NO during I/R are attributed to antioxidant and anti-inflammatory effects, as well as cell-signaling-based inhibition of nuclear proteins. The therapeutic potential of supplemented NO during I/R is nonetheless uncertain, since peroxynitrite formed from NO near superoxide can be potentially harmful due to NF-κB up-regulation and direct cytotoxicity. This study investigates new technology to provide the magnet-assisted delivery of therapeutic levels of localized NO to targeted I/R tissues using biocompatible gadolinium-oxide-based paramagnetic nanoparticles coated with S-nitrosothiols (SNO-PMNPs). Hamsters fitted with a window chamber were subjected to ischemia by application of a tourniquet at the periphery of the window chamber for 1 h. The SNO-PMNPs were intravenously infused (10 mg/kg) during the reperfusion phase, during which time a localized external magnetic field was either applied or not applied to the I/R area. The microvascular hemodynamics, functional capillary density (FCD), rolling and adherent leukocytes, reactive oxygen and nitrogen species, and tissue viability were assessed using intravital microscopy. Control animals did not receive SNO-PMNPs. Treatment with SNO-PMNPs plus a magnet but not without a magnet increased reflow, decreased leukocytes rolling and sticking in postcapillary venules, limited cell death, and restored the FCD. The absence of the magnet resulted in systemic changes in heart rate and mean arterial blood pressure, consistent with the systemic delivery of NO by the SNO-PMNP. These results indicate that the localized delivery of NO during reperfusion counters the deleterious consequences of peroxynitrite and other reactive species generated upon reperfusion as reflected in localized increases in blood flow and tissue viability, all with minimal systemic effects. This technology can provide the basis for a timely treatment of a localized ischemia-associated disease to prevent injury in different tissues and organs.