Study On Alterations Of Tissue Oxygen Extraction Ratio In Rabbits With Septic Shock

Background Septic shock is the main cause of death which may induce multiple organ dysfunction syndrome(MODS).Because intestine is so-called the "primus motor" of MODS, it has special meanings to investigate its oxygen transport and pathological changes during septic shock, however, we have rarely seen such reports in chinese journals.Objective The purpose of present study was to observe alterations of systemic and jejunum oxygen extraction in rabbits with septic shock and whether focal cells apoptosis of intestine occurred . Methods Anesthetized New Zealand white rabbits [(2.20±0.15)kg] were randomly divided into septic shock group (SS group n=10, receiving a continously intravenous pumping of E.ColiO111B5) and control group (C group n=5 receiving normal saline ). The right jugular vein (right atrium),left femoral artery,the approximal branch of superior mesenteric vein were cannulated ,.mean arterial pressure(MAP) and heart rate were monitored. .At 6 time points with half hour interval from 0 to 2.5 hours after pumping of E.ColiO111B5 and NS ,arterial and venous blood samples were simultaneously collected and blood gas analysis were done, then systemic O2 extraction ratio (SO2ER) and intestine O2ER(IO2ER) were calculated according to formula.In the present study, immunohistochemical staining(TUNEL) was used to detect apoptosis. Results In the SS group, SO2ER slightly increased which did not show significant difference compared to the C group(P>0.05). However, the PH values and base excess of the blood samples from right jugular vein decreased remarkablly with good correlation after 1.5 hours which showed significant difference compared to the control group (P<0.05). Whereas the IO2ER increased from 0.24 to 0.44 , it gradually increased at 0.5 hour time point then showed significant difference at 1 hour time point (P<0.05) and very significant difference at 1.5,2.0 and 2.5 time points(P<0.01)compared to control group. Meanwhile , the PH and base excess of the blood samples from superior mesenteric vein decreased in the same situation.Conventional light microscopy of hematoxylin and eosin(H&E) and immunohistochemical staining showed no apoptosis occurred in intestine. Conclusion During septic shock, the hemodynamics showed abnormal blood distribution while the cardiac output could be normal even higher which is different from other kinds of shock with lower cardiac output, therefore, the oxygen delivery and O2ER could keep normal even higher in septic shock while the tissues are poorly perfused. Although IO2ER -remains high in order to meet its high metabolic needs during septic shock which may be different from other abdominal organs, the higher O2ER may not be able to improve the local oxygenation which may be caused by mitochondrion dysfunction in cells.Focal apoptosis of intestine does not occur within 2.5 hours after septic shock.