Presentation on theme: "Hemodiafiltration and Hemofiltration By Dr Tamaddondar Hormozgan university of medical science."— Presentation transcript:
Hemodiafiltration and Hemofiltration By Dr Tamaddondar Hormozgan university of medical science
Diffusion V of solution used is 5fold higher than replacement in hemofiltration Convection +/-Diffusion HDF 8 – 15 L HF 20-40L replacement solution
A. Review of diffusion versus convection- based clearances B. Hemodiafiltration versus hemofiltration C. Clearance due to diffusion (dialysis) versus filtration in HDF D. Predilution versus postdilution mode E. Technical issues F.Risk and benefits
Hemodiafiltration permits β2-microglobulin removal and high Kt/V, and is probably the best way to treat chronic renal failure (CRF).
Clearance due to diffusion (dialysis) versus filtration in HDF K total = K Diffusive + F/2 (if UF<100ml/min)
Predilution versus postdilution mode The administration may take place either before (predilution) or after (postdilution) the hemofilter. Infusing replacement solution in predilution mode in HDF reduces significantly the effect on clearance due to a dilution of the blood entering the dialyzer.
Technical issues Water Fluid paths(HF/HDF) Online preparation of replacement solution and dialysis solution Vascular access Membrane
Water ultrapure water (virtually sterile and nonpyrogenic water) Current AAMI recommendations <200(CFU)/mL of bacteria <2.0 endotoxin units (EU)/mL of endotoxin ultrapure dialysis solution<0.1 CFU/mL and <0.03 EU/mL endotoxin The ultrafilters are replaced periodically to prevent supersaturation and release of endotoxins.
Online preparation of replacement solution and dialysis solution Bicarbonate-based dialysate solution is universally used as the starting point. The production of sterile and nonpyrogenic dialysis fluid (ultrapure dialysate) is achieved by cold sterilization of the freshly prepared dialysate using an ultrafilter.
balancing chamber flow-metric equalizer 0- 250 mL/min Infusion module Gambro 3-filter hemodialysis system U8000S polyamide S
FME 2-filter hemodialysis system Diasafe® plus, Polysulfone®
Vascular access Patients treated with HF/HDF require an access capable of delivering an extracorporeal blood flow of at least 350 mL per minute, and preferably higher.
Membrane Flux Measure of ultrafiltration capacity Low and high flux are based on the ultrafiltration coefficient (Kuf) Low flux: Kuf <10 mL/h/mm Hg High flux: Kuf >20 mL/h/mm Hg Permeability Measure of the clearance of the middle molecular weight molecule (eg, β 2-microglobulin) General correlation between flux and permeability Low permeability: β 2-microglobulin clearance <10 mL/min High permeability: β 2-microglobulin clearance >20 mL/min Efficiency Measure of urea clearance Low and high efficiency are based on the urea KoA value Low efficiency: KoA <500 mL/min High efficiency: KoA >600 mL/min
Membrane The membrane should have a high hydraulic permeability (K UF 50 mL / hour / mm Hg), high solute permeability (K 0 A urea >600) and beta 2 -microglobulin clearance >60 mL/ min), and large surface of exchange (1.50-2.10 m 2 ).
Typical prescriptions and substitution fluid infusion rates The conventional HDF/HF treatment schedule is based on three dialysis sessions per week of 4 hours (12 hours per week).
the substitution volume HF postdilution= Kt/v *55% body weight predilution= 2*Kt/v *55% body weight Kt/v=1 BW=60KG Pre=60cc/min Post=30cc/min
the substitution volume HDF QB=500ml/min QD=500-1000ml/min Typical replacement fluid infusion flow rates= 100 mL/min (24 L for a 4-hour session) in postdilution HDF and 200 mL/min(48 L for a 40-hour session) in predilution HDF mode simple rule of thumb Pre=1/3*QB Post=1/2*QB
Anticoagulation 1-increased sheer forces( activate blood platelets) 2-significant loss or clearance of heparin The large loss of the initial bolus (>50% for unfractionated heparin (12,000-15,000 daltons) and >80% for low molecular weight heparin (3,000-6,000 daltons
Sample protocol using LMWH Lovenox 0.5 mg/kg body weight or 50 IU/kg body weight,Allow to systemically circulate 3- 4 minutes before starting treatment No additional LMWH required unless treatment exceeds 4 hours If >4 hours inject 400 IU at mid point of treatment via venous injection port
unfractionated heparin Initial bolus 80-100 IU/kg body weight Inject bolus systemically via venous needle allowing 3-5 minutes for circulation of heparin systemically Continuous infusion of heparin via pump at 25-35 IU/kg per hr
Potential risks and hazards 1-Related to dialysate/water contaminants Acute reactions- fever, hypotension, tachycardia, breathlessness, cyanosis, and general malaise Leukopenia Chronic reactions- asymptomatic,chronic microinflammation 2- Protein loss(albumin, β 2-microglobulin) 3- Deficiency syndromes/Soluble vitamins, trace elements, small peptides, and proteins (vit c 500mg/weekly)
Overall survival/hospitalization benefit Canaud B, et al. Mortality risk for patients receiving hemodiafiltration versus hemodialysis: European results from the DOPPS. Kidney Int 2006a;69:2087- 2093. ( 35% lower mortality than those treated with low- flux hemodialysis) Locatelli F, et al. Comparison of mortality in ESRD patients on convective and diffusive extracorporeal treatments. The Registro Lombardo Dialisi E Trapianto. Kidney Int 1999;55(1):286-293 (10% reductions in mortality compared to low-flux dialysis)
Potential clinical benefits Intradialytic symptoms. Residual renal function. Lower levels of serum inflammatory markers. Anemia correction? Malnutrition? Dyslipidemia and oxidative stress β 2 microglobulin amyloidosis small protein-bound compounds
Diffusion(dialysis) depends on solute size (limited capacity to clear middle- and large-size uremic toxins) random molecular motion the volume of solution used is fivefold higher than the amount of replacement solution used with hemofiltration convection (hemofiltration) all solutes below the membrane pore size are removed at approximately the same rate(increased capacity to clear middle- and large-size uremic toxins) Water driven (solvent drag) low volume of replacement solution
Convective Clearances as a Function of Ultrafiltration in L/Week,as a Function of Sieving Coefficient
HDF HF Hemodiafiltration combines the characteristics of conventional HD with hemofiltration, which permits increased clearance for middle and small molecules. only 8 – 15 L of replacement solution is used, which is infused into the venous return of the extracorporeal circuit. the ultrafiltrate flow through highly permeable membranes is augmented by increasingTMP and hydraulic permeability with absence of dialysate flow The total volume of exchange for classic hemofiltration ranges from 20 – 40 L per treatment
Intermittent HDF versus slow continuous HDF (C-HDF) Those who have read through Chapter 13 will notice that this Gupta-Jaffrin clearance equation is different from what was described for C-HDF (continuous hemodiafiltration), where the additive effect of replacement solution to clearance is almost 1:1 in postdilution mode. The difference is this: In C-HDF, unless quite high dialysate flow rates are used, the solute concentration of blood in the dialyzer is reduced only slightly (since the ratio of Q B :Q D is quite high). Because of this, increasing ultrafiltration across the membrane markedly increases solute removal. In intermittent HDF, the relatively high-efficiency dialysis taking place (with a much higher ratio of dialysate to blood flow) lowers the solute concentration of the blood in the dialyzer substantially. Adding a filtration component is less efficient because the ultrafiltrate now contains a lower concentration of solute