Abstract
IntroductionThe relationship between oxygen delivery and consumption in sepsis is impaired, suggesting a microcirculatory perfusion defect. Recombinant human erythropoietin (rHuEPO) regulates erythropoiesis and also exerts complex actions promoting the maintenance of homeostasis of the organism under stress. The objective of this study was to test the hypothesis that rHuEPO could improve skeletal muscle capillary perfusion and tissue oxygenation in sepsis.MethodsSeptic mice in three experiments received rHu-EPO 400 U/kg subcutaneously 18 hours after cecal ligation and perforation (CLP). The first experiment measured the acute effects of rHuEPO on hemodynamics, blood counts, and arterial lactate level. The next two sets of experiments used intravital microscopy to observe capillary perfusion and nicotinamide adenine dinucleotide (NADH) fluorescence post-CLP after treatment with rHuEPO every 10 minutes for 40 minutes and at 6 hours. Perfused capillary density during a three-minute observation period and NADH fluorescence were measured.ResultsrHuEPO did not have any effects on blood pressure, lactate level, or blood cell numbers. CLP mice demonstrated a 22% decrease in perfused capillary density compared to the sham group (28.5 versus 36.6 capillaries per millimeter; p < 0.001). Treatment of CLP mice with rHuEPO resulted in an immediate and significant increase in perfused capillaries in the CLP group at all time points compared to baseline from 28.5 to 33.6 capillaries per millimeter at 40 minutes; p < 0.001. A significant increase in baseline NADH, suggesting tissue hypoxia, was noted in the CLP mice compared to the sham group (48.3 versus 43.9 fluorescence units [FU]; p = 0.03) and improved with rHuEPO from 48.3 to 44.4 FU at 40 minutes (p = 0.02). Six hours after treatment with rHuEPO, CLP mice demonstrated a higher mean perfused capillary density (39.4 versus 31.7 capillaries per millimeter; p < 0.001) and a lower mean NADH fluorescence as compared to CLP+normal saline mice (49.4 versus 52.7 FU; p = 0.03).ConclusionrHuEPO produced an immediate increase in capillary perfusion and decrease in NADH fluorescence in skeletal muscle. Thus, it appears that rHuEPO improves tissue bioenergetics, which is sustained for at least six hours in this murine sepsis model.
Highlights
The relationship between oxygen delivery and consumption in sepsis is impaired, suggesting a microcirculatory perfusion defect
cecal ligation and perforation (CLP) mice demonstrated a 22% decrease in perfused capillary density compared to the sham group (28.5 versus 36.6 capillaries per millimeter; p < 0.001)
Conclusion Recombinant human erythropoietin (rHuEPO) produced an immediate increase in capillary perfusion and decrease in NADH fluorescence in skeletal muscle
Summary
The relationship between oxygen delivery and consumption in sepsis is impaired, suggesting a microcirculatory perfusion defect. Whether the tissue distress seen in sepsis is caused by microcirculatory hypoxia or disturbances in cellular metabolic pathways is a source of much debate. Persistent regional tissue dysoxia has been demonstrated in sepsis despite adequate resuscitation procedures that correct global variables of DO2 [4]. These observations can be explained, in part, by a pathological redistribution of blood flow giving rise to hypoxic microcirculatory units next to well-perfused or even overperfused normoxic units [6,7,8]. Even in the absence of systemic hypotension, blood flow and capillary perfusion distribution in both endotoxin and focal models of sepsis can be highly heterogeneous between and within organ systems such as skeletal muscle and the small bowel mucosa [7,9,10,11,12,13,14]
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