Recombinant human hemoglobin with reduced nitric oxide-scavenging capacity restores effectively pancreatic microcirculatory disorders in hemorrhagic shock

Abstract

Background: Scavenging of nitric oxide by hemoglobin-based oxygen carriers could aggravate microcirculatory failure in splanchnic organs after hemorrhagic shock as a consequence of vasoconstrictive side effects. The aim of this study was to compare the effects of two recombinant human hemoglobin solutions, a second-generation product bearing reduced nitric oxide-scavenging properties (rHb2.0) due to site directed mutagenesis of the heme pocket and a first-generation recombinant hemoglobin (rHb1.1) with scavenging capacity similar to native hemoglobin, on the pancreatic microcirculation after hemorrhagic shock. Methods: Twenty-eight pentobarbital-anesthetized rats were bled to a mean arterial pressure of 40 mmHg and maintained at this level for 1 h. Using an intravital microscope, the length of erythrocyte-perfused pancreatic capillaries per observation area (functional capillary density) were measured in animals resuscitated by volumes of hydroxyethyl starch, rHb1.1, or rHb2.0 equivalent to the shed blood volume. Animals without shock induction served as control. Results: As compared with control (438 ± 10 cm -1). animals treated with hydgoxyethyl starch (315 ± 44 cm-1) and rHb1.1 (288 ± 67 cm-1) showed a significant reduction of functional capillary density after 2 h of resuscitation. rHb2.0 was able to restore functional capillary density (410 ± 42 cm-1) and mean arterial pressure to baseline values. Conclusion: rHb2.0 was effectively able to restore pancreatic microcirculation after hemorrhagic shock. This may be related to the compound's effective lack of nitric oxide-scavenging properties. This hemoglobin solution or ones similar to it might be uniquely valuable for resuscitation from hemorrhagic shock.