Application Of Plasmadiafiltration In Sepsis

Part I Application of plasmadiafiltration in an in vitro sepsis modelBackgroundRemoval of pro- and anti-inflammatory cytokines may play an important role in the treatment of sepsis. Membranes with a higher molecular weight cut-off can reduce cytokines plasma levels more effectively since molecule weight of most cytokines are large. Plasma diafiltration (PDF) with a selective plasma separator was performed to investigate the cytokine and plasma protein permeability profiles of the membrane in an in vitro sepsis model.MethodsIn vitro sepsis model was constructed by exposure of human whole blood to bacterial lipopolysaccharide. Evacure 2 A, a selective plasma separator made of EVAL membrane with an industrial albumin sieving coefficient of 0.2-0.3, was placed in the blood circuit of PDF. Sieving coefficient of cytokines and plasma protein were tested in post-dilution PDF mode at the following operating parameters which were combined in turn:fixed blood flow rate 150 ml/min;dialysate flow rate 2000,4000 ml/h; replacing fluid flow rate 400,800 ml/h; net ultra filtration rate 0,300,600 ml/h. An enzyme linked immunoadsorbent assay was used to measure the concentrations of tumor necrosis factor-α(TNF-α), high-mobility group box 1 protein (HMGB1), interleukin-1β(IL-1β), interleukin-1 receptor antagonist (IL-1ra), interleukin-2 (IL-2), interleukin-2 receptor (IL-2r), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10(IL-10) in plasma and ultrafiltrate.ResultsSieving coefficients of different solutes ranged from 0.1-1.0 at first, decreased 10%-60% after 1 hour's PDF, and then kept stable. Most sieving coefficients did not change with the flow rate of replacing fluid and dialysate. Total clearance rates of cytokines ranged from 15-80 ml/min. The concentrations of cytokines decreased 20-80% after 1 hour's PDF. Sieving coefficient of albumin was 0.105±0.007 at first and then decreased to 0.061±0.012 after 1 hour's therapy. The clearance rate of albumin was 2.02±1.39,0.28±0.15 ml/min at 0, 120 min respectively. The rate of albumin loss averaged 0.54±0.07g an hour.ConclusionPDF with Evacure 2A plasma separator can remove almost all of the inflammatory mediators commonly seen in sepsis. It can provide an acceptable balance between high cytokine and low albumin clearances. BackgroundAlthough it is widely accepted that cytokines play pivotal roles in the pathophysiology of sepsis, few of cytokine-targeting regiments tested clinically in the past 20 years has exhibited satisfied effects. Blood purification, which can unselectively remove excess proinflammatory and anti-ininflammatory mediators by sieving and or by adsorption, has not yet been proven survival benefit. One of the explanation would be that the pore size of the membrane with a cut-off point of 30kD applied in blood purification these years was not large enough to meet the needs of sieving cytokines with molecular weights higher than 30kD, such as TNF-a trimer, HMGB1, IL-10, and so on. The present study examines whether a newly-designed filter with a cut-off point of 60-70kD can facilitate the filtration of inflammatory mediators with large molecular weight and lower the levels of these mediators in the circulation of pigs underwent cecal ligation and puncture. Furthermore, whether the decreased concentrations of cytokines in the circulation can lead to the improvement of organ function and mortality.Methods12 male domestic pigs that underwent cecal ligation and rupture (CLP) were randomized 24 hours later to receive plasmadiafiltration (PDF) or no PDF for 8 hours, and then 6 hours later, all the living animals were sacrificed. PDF was performed with a newly developed high permeability Poly(ethylene/vinyl alcohol) membrane (EVAL) with a nominal cut-off point of 60-70 kD. Blood concentrations, sieving coefficients and clearance rates of cytokines including TNF-a trimer, HMGB1, IL-6, IL-8 and IL-10 were evaluated at 0,4,8 hours of the procedure, as well as the accessments of hemodynamic status, pulmonary function and renal function. Endpoints of decreased systolic blood pressure (SBP), decreased pulmonary arterial wedged pressure (PAWP) averaged cardiac output (CO), decreased partial pressure of oxygen in arterial blood (PaO2) and urine output (UO) were priorly set to facilitate the accessment of outcomes of different organs. Survival time after CLP was collected for survival analysis. The primary outcome measure was death within 38 hours after CLP.ResultsAll animal developed sepsis in various degrees 24 hours after CLP. At the beginning of PDF, the sieving coefficient of TNF-a trimer, HMGB1, IL-6, IL-8, IL-10 and albumin was 0.063±0.012,0.052±0.022,0.364±0.021,0.155±0.039,0.149±0.007,0.013±0.003, respectively. Most sieving coefficients did not decrease with time except IL-6 and IL-10. The clearance rate of TNF-a trimer, HMGB1, IL-6, IL-8, IL-10 and albumin was 16.20±10.60,7.77±5.22,25.48±1.55,28.57±3.79,17.67±1.94,2.15±1.72 ml/min, respectively. The concentrations of these cytokines in the circulation of the control group increased with time, while in PDF treatment group, decreased. The odds ratio of PDF vs control for lowering the blood level of TNF-a trimer, HMGB1, IL-6, IL-8 and IL-10 was 1.97 (95% confidence interval [CI],1.64-2.51, P=0.012),1.97 (95% CI,1.67-2.46, P=0.007),1.70 (95% CI,1.33-2.70, P=0.047),1.56 (95% CI,1.20-3.02, P=0.081),1.40 (95% CI,1.07-5.36, P=0.183), respectively. The serum concentration of albumin decreased with time in both group, and no difference was found between the groups. During the course of sepsis, the declining tendency of blood pressure (BP), PAWP averaged CO, PaO2 and UO could be commonly seen in control, whereas in PDF group, it was reversed. The odds ratio of PDF vs control for improving the SBP, PAWP averaged CO, PaO2 and UO was 1.07(95% CI,1.00-2.59, P=0.001),6.34(95% CI,2.89-25.3, P=0.032),4.33(95% CI, 2.33-23.1, P=0.042),4.18(95% CI,2.75-7.54, P=0.042), respectively. It took more hours in PDF group than in control to reach the endpoints of SBP (PDF 30.7 hours, control 26.8 hours, hazard ratio 0.112 for PDF, P=0.045), PAWP averaged CO (PDF 31.8 hours, control 27.0 hours, hazard ratio 0.064 for PDF, P=0.013), PaO2 (PDF 31.3 hours, control 26.7 hours, hazard ratio 0.085 for PDF, P=0.025), and UO (PDF 31.4 hours, control 25.7 hours, hazard ratio 0.197 for PDF, P=0.029). The averaged survival time was 36.3 hours for PDF group, 31.5 hours for control. The hazard ratio of death was 0.11 for PDF treatment (P=0.046).ConclusionPDF with a high permeability filter can remove cytokines with large molecular weight effectively. PDF can attenuate the upregulation of cytokines in the circulation during the ongoing of sepsis, accompanied by improving the function of different organs. PDF may represent a new blood purification able to improve survival in sepsis. BackgroundAlthough the pathological sequelae of sepsis are characterized by the inflammatory cascade mediated by cytokines and toxic molecules, experimental therapeutics that target specific inflammatory mediators such as tumor necrosis factor a (TNF-a) and interleukin-1βhave not yet been proven efficacious in human clinical trials. Since blocking a specific inflammatory mediator can cause a new imbalance of pro- and anti-inflammatory mediators, non-specific removal of soluble mediators in the blood, whether pro- or anti-inflammatory, without completely eliminating their effect may be the most logical and adequate approach to the complex status of sepsis.Extra-corporeal blood purification can efficiently eliminate septic mediators of which elevated levels in the blood have been shown to correlate with increased mortality. Many studies show promise of blood purification with improvements in hemodynamics and mortality.Conventional hemofiltration (HF) performed with a filter which has a cutoff point of approximately 20-30 kilodalton (kD) failed to demonstrate either the alteration of plasma levels of inflammatory mediators or an improvement in organ dysfunction and survival when a "renal dose" hemofiltration rate of 2000 ml/h is applied at the same time. A few studies show some improvements in mortality as the rate increases to a "septic dose", but they are limited by number and or design. This reflects the fact that the ability of conventional hemofliter to remove large molecules such as TNF-a trimer (54kD), high-mobility group box 1 protein (30kD) is limited. This problem may be resolved by the introduction of a high permeability hemofilter with a nominal cutoff point of 60-70 kD which is characterized by an increased pore size designed to facilitate the elimination of large inflammatory mediators in sepsis. Supplement of plasma is needed to compensate the loss of plasma protein during the procees of hemofiltration with high cutoff hemofilters. Plasmadiafiltration (PDF) is one of high cutoff renal replacement therapy in which convention modality is combined with a diffusion one.The aim of this study is to evaluate the effect of hemofilter pore size on the efficacy of blood purification in improving morbidity and mortality in patients with septic acute kidney injury by way of comparing the efficacy of PDF with that of HF.Methods12 patients with septic acute kidney injury were randomized to receive one session of PDF or HF for 8 hours. At the same time and thereafter, all of the patients received subsequent blood purification which was not specified and the standard sepsis therapy according to the Surviving Sepsis Campaign guidelines for management of severe sepsis and septic shock. PDF was performed with a newly developed high permeability Poly(ethylene/vinyl alcohol) membrane (EVAL) with a nominal cut-off point of 60-70 kD while HF was performed with a polysulfen membrane with a cut-off point of 20-30 kD. The major operating parameters of PDF were set as following:replacing fluid which was consisted of isotonic saline solution and plasma in a 2:1 ratio was infused in a post-dilution mode at the rate of 8ml/kg/h, dialysate rate was 40 ml/kg/h and net ultra filtration rate was 0-900ml/h according to the clinical need. As to HF, the replacement fluid rate was above 40 ml/kg/h and net ultra filtration rate was the same as PDF. At 0,4,8 and 24 hours of this session of blood purification (name as time0,4,8,24), organ functions including function of circulation, lung and kidney, accompanied with the score of the acute physiology, age, chronic health evaluationⅡ(APACHEⅡ) and the prediction of death risk were evaluated. Survival time of every patient was collected for survival analysis.ResultsIn both group, increased volume-expanding reaction incluing elevated blood pressure and urine output can be observed with time during the course of blood purification. Mean arterial pressure increased much higher in PDF group with reaction to volume-expanding at time4 and time8. The odds ratio of PDF vs HF for improving the volume-expanding reaction of mean arterial pressure was 2.94 (95% confidence interval [CI],2.83-3.03, P=0.000).And PDF group had a higher reaction of urine output at time4 and time8, and the odds ratio was 4.30 (95%CI,2.91-7.29,P=0.017). Both group demonstrated increased pressor effects with reaction to doubling the dose of pressor agent as the procedure was going on. The odds ratio of PDF vs HF for improving the pressor effects was 2.91 (95%CI, 2.81-3.00, P=0.000). Compared with HF, PDF group had a less reaction of decreased oxygen saturation to withdrawing the suppply of oxygen and the odds ratios was 2.78 (95%CI,2.72-2.81, P=0.027). Both group had improved APACHEⅡscore at time8 and time24, but PDF was superior to HF in decreasing APACHEⅡscore with odds ratio of 1.01(95%CI,1.00-1.99, P=0.013). Both group have been shown a reduced death risk with time. The odds ratio of PDF vs HF for down-regulating the death risk was 2.34 (95%CI, 2.11-2.64, P=0.015). The averaged survival time was 75.2±69.9 days for PDF group, 63.0±57.2 days for HF group (P=0.941). The hazard ratio of death was 0.94 for PDF treatment (P=0.944). There was no difference between the two group as to the serum level of albumin (adjusted value-expressed as propotion of basline-PDF 1.261±0.406, HF1.064±0.225, P=0.289), volume balance (positive balance means input water is more than output water, PDF1234±882ml, HF563±1144ml, P=0.282), time-averaged blood urea nitrogen (PDF15.22±7.07mmol/L, HF21.2±8.31, P=0.209).ConclusionCompared with HF, PDF with a higher permeability filter has been shown to exert a better effect on improving the circulating function, pulmonary function, renal function and APACHEⅡscore in septic patients with acute kidney injury. The superior performance of PDF vs HF indicates that the key to improve the efficacy of blood purification is to enlarge the pore size of hemofilter applied in sepsis.