Acute effects of normal saline and lactated Ringer’s with erythropoietin on microcirculatory perfusion, tissue bioenergetics, and gut permeability of the small intestine in a hemorrhagic shock and resuscitation rat model

Abstract

Introduction: Erythropoietin (EPO) has acute hemodynamic and anti-inflammatory effects in addition to its erythropoietic action. We tested the hypothesis that recombinant human EPO (rHuEPO) given at the time of resuscitation with normal saline (NS) or lactated Ringer’s (LR) will improve capillary perfusion and tissue bioenergetics in a hemorrhagic shock and resuscitation (HS/R) rat model. Methods: Anesthetized rats’ ileal muscular layer was prepared for intra-vital microscopy. The rats were hemorrhaged 30 millitres per kilogram over 10 minutes with uncontrolled mean arterial pressure for 50 minutes. They were then randomized to one of four groups (NS, NS + rHuEPO, LR, and LR + rHuEPO; n = 6/group) and underwent a 60-minute resuscitation period. Intravenous rHuEPO (1,000 U/kg) was given at the start of fluid resuscitation. Gut microcirculation and nicotinamide adenine dinucleotide dehydrogenase (NADH) fluorescence were recorded for off-line analysis at baseline, 50 minutes of shock, and 60 minutes of resuscitation. In a separate HS/R experiment ( n = 10/group), gut permeability to fluorescein isothiocyanate dextran and endotoxin levels, tissue damage, and portal vein blood levels of interleukin (IL)-6 and tumour necrosis factor (TNF) were examined. Results: LR alone demonstrated better gut microcirculation and decreased gut injury than NS alone. NS + rHuEPO, compared with NS alone, improved functional capillary density (22.9 ± 0.6 Cap/mm and 20.2 ± 1.0 Cap/mm, respectively; p < 0.01), red blood cell flow scores (2.1 ± 0.2 and 1.3 ± 0.2, respectively; p < 0.01), and tissue NADH fluorescence (54.5 ± 0.3% and 59.7 ± 0.8%, respectively; p < 0.01). Compared with LR, LR + rHuEPO did not result in significant improvement in microcirculation. Adding rHuEPO to NS improved gut permeability, inflammatory mediators (IL-6, TNF), and tissue injury, but adding it to LR did not. Discussion: LR improved tissue microcirculation, decreased permeability to macromolecules, and reduced mucosal injury in the ileum compared with NS alone. The beneficial effects of rHuEPO administration were mostly observed in the NS resuscitation group.