Hemoglobin binders reduce inflammation and tissue injury from hemolysis in venovenous extracorporeal circulation

This study investigated the pathophysiological effects of cell-free hemoglobin (Hb) generated by mechanical hemolysis during venovenous extracorporeal circulation (VVECC). We hypothesized that Hb scavenger protein constructs that bind Hb, heme, and iron could attenuate end-organ injury caused by intravascular hemolysis during VVECC. Scavenger constructs consisted of an apohemoglobin-haptoglobin (apoHb-Hp) complex designed to bind Hb and heme, as well as a separate preparation of haptoglobin, albumin, hemopexin, and transferrin, termed the protein cocktail. To test the hypothesis, Golden Syrian hamsters were instrumented with dorsal window chambers and catheters, and VVECC was maintained for a total of 2 hours, with a maximum flow rate equivalent to 50% of the animal's cardiac output. VVECC circuits were primed with either 2 binding materials, apoHb-Hp and the protein cocktail, or a control solution of 5% human serum albumin (HSA). Microvascular Hb oxygen saturation in arterioles (saO2) and venules (svO2) were studied. All groups displayed a significant decrease in saO2 and svO2 at maximum VVECC when compared with baseline, whereas statistically significant changes between treatment groups showed no consistent trend. The protein cocktail bound 24% of cell-free Hb, whereas the apoHb-Hp bound 66% of cell-free Hb. In addition, markers of renal damage and inflammation, such as plasma creatinine, urinary NGAL (neutrophil gelatinase-associated lipocalin), 4-HNE (4-hydroxynonenal), and KIM-1 (kidney injury molecule 1), were significantly reduced in both Hb scavenger groups compared with those in the HSA control group. Results from this study suggest that Hb, heme, and iron scavenging solutions used to prime VVECC circuits support organ function.