The Clinical And Experimental Study Of Acute Kidney Injury Induced By Septic Shock

ObjectiveSeptic acute kidney injury(AKI) that induced by severe sepsis and septic shock usually has a high incidence and poor prognosis.The pathogenesis of septic AKI involves multiple factors,among which hemodynamics is a key one.In our clinical,animal and fundamental study,by analyzing the characteristic and the effects on septic AKI of systemic and renal hemodynamics and oxygen metabolism in septic shock,we discussed the role of hemodynamics in the pathogenesis of septic AKI and the methods to improve septic AKI by optimization of hemodynamics.We also studied the impacts of poly(ADP-ribose) polymerizer(PARP) inhibitor on renal hemodynamics and renal function in endotoxic shock, in order to find a new path to treat septic AKI.MethodsThree parts were included in our study.In the first part,we retrospectively investigated the patients of septic shock who had been placed pulmonary artery catheter(PAC) continuously admitted in Beijing Union Hospital from January of 2002 to July of 2008. Mortality and incidence of AKI were compared among groups of different AKI stages, survival analysis and prognosis evaluation was performed.And the impacts of hemodynamics on the incidence of AKI were studied.In the second part,the hemodynamics of endotoxic dogs were monitored by PAC and pulse indicator continous cardiac output(PiCCO) monitor, and the renal blood flow were measured by ultrasonic blood flowmeter.Then the kidney sample were examined for morphologic changes by hematoxylin-eosin(HE) stain,for apoptosis by TUNEL(terminal deoxynucleotidyl transferase mediated dUTP-nick-end labeling) and for energy substances such as adenosine triphosphate(ATP),adenosine diphosphate(ADP),nicotinamide adenine dinucleotide(NAD) and phosphocreatine(PCr) by high performance liquid chromatography.In the third part,changes of hemodynamics and renal function were observed after 3-aminobenzamide(3-AB,15mg/kg),one kind of PARP inhibitors,being given to endotoxic dogs,and then the expression of poly(ADP-ribose)(PAR) in renal tissue were examined by immunohistobiology and western blot.ResultsClinical study:Altogether 158 cases of septic shock were enrolled in this retrospective study.Of all the patients,the incidence of all AKI and stage 1-3 was 79.7%(126/158),16.5% (26/158),16.5%(26/158) and 46.8%(74/158) respectively;45.6%(72/158) of all the patients needs renal replacement therapy.The mortality of all the patients on the 28^th day was 59.5%(94/158),while the mortality of those without AKI and those at stagel-3 of AKI was 12.5%,38.5%,69.5%and 83.8%respectively(p＜0.05).The mortality of all patients with AKI was 71.4%with the OR value at 17.50.The main parameters of hemodynamics such as MAP and CI had impacts on the incidence of AKI.Animal and fundamental study:1. Changes of hemodynamics and oxygen metabolism:After the injection of LPS,the mean arterial pressure(MAP),systemic vascular resistance(SVR),renal vascular resistance(RVR), urinary output at the second hour,renal oxygen consumption and extraction rate all decreased (p＜0.05);RBF didn't increase or decrease compaed with control(p＞0.05).PARP inhibitor could improve them.RBF correlated negatively with RVR(R²=0.381,p=0.025) and SVR (R²=0.336,p=0.038 ),and positively with CO(R²=0.630,p=0.001);however,RBF didn't correlate with MAP(R²=0.009,p=0.758).2.Changes of renal function and metabolic parameters:After the injection of LPS,the PH value,base excess(BE),creatinine clearance rate(CCr),urine osmotic pressure,urinary sodium and fractional excretion of sodium (FENa) all decreased(p＜0.05);while blood lactate concentration,serum creatinine(SCr) and urinary N-acetyl-β-D-glucosaminidase(NAG) all increased(p＜0.05).PARP inhibitor could inmprove them.CCr correlated positively with MAP(R²=0.415,p=0.003 ),however,it didn't correlate with RBF and CO(p＞0.05).CCr correlated with CO at low CO level(R²=0.437, p=0.019),while not at high CO level.The autoregulation curve of GFR had a shift to the right.Renal oxygen consumption correlated positively with CCr(R²=0.390,p=0.003).3. Changes of energy substances:NAD,ADP,ATP and PCr all decreased after the injection of LPS in renal cortex(p＜0.05);while only ADP decreased in the renal medulla.PARP could improve the levels of NAD,ADP and ATP without affecting the level PCr.4.Morphologic changes:Edema and vacuolar degeneration could be seen in tubular cells of renal cortex and corticomedullary junction after the injection of endotoxin,and they became obvious as time went on;while no obvious changes could be found in renal medulla and glomeruli.PARP inhibiting could partly prevent the morphologic changes.5.Apoptosis:TUNEL positive cells could be seen in tubules of renal cortex and corticomedullary junction after the injection of endotoxin,and they became obvious as time went by(p＜0.01);while no obvious TUNEL positive cells could be found in renal medulla and glomeruli.PARP inhibiting could reduce the number of TUNEL positive cells(p＜0.01).6.PAR expression in renal tissue: Immunohistobiology showed that positive expression of PAR appeared in tubular nuclei of renal cortex and corticomedullary junction after the injection of LPS,and they increased with the time course(p＜0.05).Western Blot revealed that the expression of PAR with molecular weight at above 100kD increased more(p＜0.01).There were no obvious PAR expression in glomerluli and renal medulla.PAR expression were less in the PARP inhibited group (p＜0.05).Conclusion1.Septic AKI is associated with a high incidence and the risk of death increases with the AKI stages.2.Renal pressure perfusion may decrease obviously without renal flow perfusion decreasing.3.The shift of renal autoregulation which mainly caused by pressure perfusion occurs at the early stage of septic shock.4.PARP over-activity ocurrs in the tubular cells of renal cortex at the early stage of endotoxic shock.Inhibiting PARP over-activity can improve metabolic acidosis and hemodynmics by reducing the consumption of energy substance and protecting tubular cells from injury and apoptosis.Inhibiting PARP over-activity can reduce the occurrence of AKI.