Blood soluble polymers for enhancing near-vessel-wall RBC traffic in presence of hemoglobin based oxygen carrier

The development and clinical applications of hemoglobin based oxygen carriers (HBOC) have been limited by vasoactivity, putatively related to the HBOC ability to scavenge nitric oxide (NO) in the circulatory compartment. NO scavenging by HBOCs may be especially important in microvessels where flowing red blood cells (RBCs) have a tendency to travel in the vessel center, creating a cell-free layer near the vessel wall that is fully occupied by HBOC molecules. Our previous studies demonstrated that minute concentrations of soluble polymeric molecules, “drag reducing polymers” (DRPs), added to blood, selectively attenuated the near-wall plasma layer and significantly increased the near-wall concentration of RBCs in microchannels. The same polymers were previously shown to significantly improve impaired blood circulation in various animal models. The current study was performed to investigate whether DRPs produce the same microrheological effects in the microflow of RBCs suspended in HBOC solutions and whether concentrated HBOC solutions affect polymer ability to reduce resistance to turbulent flow in a pipe. If proven to be still effective, DRPs may be used to reduce vasoconstrictive effects of HBOC in microvessels without affecting its gas transport function in capillaries. Two polymers (one synthetic, polyethylene oxide, and one natural, hyaluronic acid) were tested in this study, confirming that DRPs maintain their micro and macro rheological activity in HBOC solutions. Some potential clinical applications of DRPs combined with HBOC solutions are discussed.