Hemofiltration With High-volume Attenuates Myocardial Mitochondrial Respiratory Chain Complex Activities In Pocrine Septic Shock

BackgroundSepsis is the leading cause of mortality in the critically ill.Its incidence is increasing;over 750,000 episodes are reported annually in the United States, carrying an estimated annual healthcare cost in excess of $17 billion.Mechanisims by which sepsis leads to organ dysfunction remain to be established and the treatment needs further study.Despite new insights,the cornerstone of therapy continues to be early recognition,prompt initiation of effective antibiotic therapy,and eliminating the source of infection.To date,the adjuvant treatment of sepsis remains a major therapeutic challenge.Hemofiltration,based on the humoral theory of sepsis,is a safe and well-established treatment in critically patients with renal failure,and has also been used in the treatment of severe sepsis.The mechanisms of hemofiltration in sepsis remain obscure.There is substantial disagressment whether the beneficial clinical effects observed during treatment with hemofiltration can be attributed to removal of specific inflammatory mediators.To date,no specific inflammatory mediators solely responsible for sepsis-induced organ injury have been identified.Moreover,as hemofiltration is a nonspecific blood purification technique,anti-inflammatory and beneficial mediators may be removed as well.Therefore,the mechanism of hemofiltration in sepsis needs further study.Recently,increasing evidence indicates that mitochondrial dysfunction play an important role in modulating the development of manifestations of septic shock in patients with bacterial infection.First,increasing oxygen delivery in patients with septic shock does not consistently increase oxygen consumption and decrease the level of anaerobic metabolism as measured by arterial lactate concentration.Second, normal levels of tissue oxygen tension and elevated arterial lactate concentrations have been reported in patients with septic shock.Third,a number of the mediators implicated in septic shock have been demonstrated to directly impair mitochondrial function.Finally,measures intended to protect myocardial mitochondria have been confirmed effective.However,it remains unknown whether treatment with hemofiltration exerts a specific effect on the mitochondrial dysfunction.If the hypothesis was confirmed,we could find the valuable theory evidence of hemofiltration in preventing and treating septic shock. PartⅠSet up of septic shock in porcineObjectiveIn the study,we set up peritonitis and septic shock model by infusion of autologous feces and observed the hemodynamics parameters and the severity of organ dysfunction.MethodsSeven pigs were randomly divided into two groups which were subjected to normal group(Normal,n=6)and model group(Peritonitis,n=4).About 0.5g·kg^-1 weight autologous feces was collected by operation and was infused into abdominal cavity 1 hour later.In normal group,the cecum was also disassociated,however feces was not collected.Their tracheas were intubated,and respiration was supported by breathing machine.All animals received 2L lactated Ringer's solution during the surgical procedure and 10-15 ml·kg^-1·h^-1during the rest of the experiment,with a rate adjusted to keep pulmonary artery occlusion pressure(PAOP)8-12mmHg.Blood pressure,breath,heart rate and temperature were monitored continuously.Mean arterial pressure(MAP),central venous pressure(CVP),mean pulmonary artery pressure(MPAP)and PAOP were recorded with quartz pressure transducers.Arterial blood samples were collected at every time points for blood gas and serum was collected for ALT,AST,Cr,BUN.Alive animals were sacrified in 24 hours and tissue of vital organ was collected for lighr microscope.Results1.There is significant difference of live time between the two groups.The mortality of model group is 100%in 24 hours.However,there is no death in normal group.2.Hemodynamics parameters showed that cardic output of peritonitis animal increased in the early phase,and followed by decrease.MAP was normal in early phase,and decreased in the following time.There was no significant change in the normal group.3.Arterial Ph decreased progressively in peritonitis animals,and was significantly lower than that in normal animals.At the same time,the level of lactate was increased.ConclusionsThe septic shock model could be successfully reproduced by infusion of autologous feces.The model reproduces characteristic features of sepsis,such as causative factors of injury,progression of illness and clinical presentation. Furthermore,the model is stable and reproduced better. PartⅡHemofiltration with high-volume attenuates myocardial mitochondrial dysfunction in porcine septic shockObjectiveIn the study,we observed the impact of high-volume hemofiltration(HVHF)on myocardial mitochondrial respiratory chain complex activities in peritonitis-induced septic shock and further investigated the possible mechanism.MethodsSixteen pigs were randomly divided into three groups which were subjected to normal group(Normal,n=4),model group(Peritonitis,n=6)and HVHF group (HVHF,n=6).As the partⅠ,septic shock model was reproduced by infusion of autologous feces.HVHF was applied 1 hour after induction of peritonitis and the support therapy was employed as the partⅠ.Blood pressure,breath,heart rate and temperature were monitored continuously.Mean arterial pressure(MAP),central venous pressure(CVP),mean pulmonary artery pressure(MPAP)and PAOP were recorded with quartz pressure transducers.Arterial blood samples were collected at every time points for blood gas and plasm was collected for NO,IL-6,IL-10,TNF-α. Alive animals were sacrified at 13 hours after induction of peritonitis and cardiac tissue was collected for further investigation,such as ATP,ADP,AMP and NO.Results1.In both peritonitis groups,fluid resuscitation provoked a typical hyperdynamic septic shock followed by hypodynamic shock.During the first 6h,hemodynamic parameters were similar in two peritonitis groups.With the progression of septic shock,cardiac output declined.Compared with animals without CVVH,cardiac output and stroke volume were substantially better maintained in the CVVH-treatment animals throughout the entire experiment period.This improvement of cardiac output was not associated with differences in ventricular filling pressures,as reflected by comparable PAOP in both groups.With the improved cardiac contractility,systolic MAP was significantly higher in animals with CVVH versus without CVVH.The divergence of this physiologic parameter was apparent only after 6h of the experimental protocol.2.3-7 hours after induction of peritonitis,DO2 and VO2 slightly increased and then declined.However,there is no significant difference between normal group and peritonitis group.Compared with peritonitis group,DO2 in HVHF group was better kept.There was no difference among the three groups.3.Compared with normal animals,arterial lactate was progressively increased and Ph was dcreased in peritonitis animals.HVHF could prevent the decline of Ph and decreased the level of lactate.4.Compared with normal control,the activity of respiratory-chain complexⅠin myocardium was 37%lower for peritonitis animals.However,the activity of complexⅠwas better maintained in animals with CVVH(P＜0.05).No significant differences were found for complexⅡ,ⅢandⅣ.5.Compared with normal group,the level of cardiac ATP and ATP/ADP in peritonitis animals was significantly decreased and AMP increased(P＜0.05).However, HVHF could prevent the decline of ATP and keep the ATP/ADP better(P＜0.05).6.At the start of hemofiltration,1h after peritonitis challenge,plasma nitrite-nitrite concentrations did not differ between groups.However,plasma nitrate-nitrite increased in peritonitis-challenge animals,but was about normal in animals receiving CVVH at 13h after peritonitis induction.As for concentration of nitrate-nitrite in myocardial homogenate,there was no difference between groups.7.Low-level expression of TNF-α,IL-6 and IL-10 was found in normal pigs.After induction of peritonitis,TNF-αwas increased sharply and then decreased to normal when the animals were killed.IL-6 was also increased and kept at high level during the procedure.There was no significant change of IL-10 during the disease.HVHF could decrease the expression of IL-6,but not influence the level of TNF-α.Conclusions1.HVHF improves cardiac dysfunction and hemodynamics in peritonitis-induced septic shock.2.HVHF could ameliorate myocardial mitochondrial respiratory chain complex activities and improve the bioenergetics metabolism,which may be attributed to the decrease of plasma NO.3.HVHF could decrease the level of IL-6 in peritonitis animals.4.The improvement of cardiac dysfunction by HVHF in septic shock may be attributed to the amelioration of myocardial mitochondrial respiratory chain complex activities.