1 / 15

Solute Mass Transfer in CRRT Garred et al., AJKD 1997

Post-Dilution CVVH. CVVHD. Q r. Q b. Q b. Q eff. Q eff. Q d. Q r. Q r. Q b. Q b. Q eff. Q eff. Q d. Pre-Dilution CVVH. CVVHDF. Solute Mass Transfer in CRRT Garred et al., AJKD 1997. Mechanisms of Solute Removal: IHD vs CRRT Clark and Ronco, Kidney Int 1998. IHD CRRT

Download Presentation

Solute Mass Transfer in CRRT Garred et al., AJKD 1997

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Post-Dilution CVVH CVVHD Qr Qb Qb Qeff Qeff Qd Qr Qr Qb Qb Qeff Qeff Qd Pre-Dilution CVVH CVVHDF Solute Mass Transfer in CRRTGarred et al., AJKD 1997

  2. Mechanisms of Solute Removal: IHD vs CRRTClark and Ronco, Kidney Int 1998 IHD CRRT Small Solutes Diffusion* Diffusion** (CVVHD)(mw < 300) Convection (CVVH) Middle Molecules Diffusion Convection(mw 500-5,000) Convection Diffusion LMW Proteins Convection Convection(mw 5,000-50,000) Diffusion Adsorption Adsorption Large Proteins Convection Convection(mw > 50,000) * Determinants: flow rates, membrane thickness** Determinants: effluent dialysate flow rate

  3. QP ( ) QP +QR Solute Clearance in CRRT Concentration in effluent dialysate ( ) E = • CVVHD K = E . QD • Post-Dilution CVVH K = S . QUF • Pre-Dilution CVVH K = S . QUF . Concentration in blood Concentration in filtrate ( ) S = Concentration in blood

  4. Dialytic Solute Removal Mechanisms • Diffusion • transmembrane solute movement in response to a concentration gradient • importance inversely proportional to solute size • Convection • transmembrane solute movement in association with ultrafiltered plasma water (“solvent drag”) • mass transfer rate determined by ultrafiltration rate (pressure gradient) and membrane sieving properties • importance directly proportional to solute size

  5. 33.9 28.7  = -15% QUF (mL/h) Urea Clearance in Pre-Dilution CVVHBrunet et al., AJKD 1999 Clearance (mL/min)

  6. Effect of Dialysate Flow Rate onSmall Solute Clearances in CVVHDBonnardeaux et al., AJKD 1992 Dialysate Out Urea Clearance or Flow Rate (mL/min) Creatinine Ultrafiltration Inlet QD (mL/min)

  7. D/P Ratio Urea Creatinine Inlet QD (mL/min) Effect of Dialysate Flow Rate onSolute Equilibration in CVVHDBonnardeaux et al., AJKD 1992

  8. Solute Equilibration in CVVHDBrunet et al., AJKD 1999 Clearance (mL/min) QE (mL/h)

  9. Components of Small Solute Clearance in CRRTSigler et al., AJKD 1987 Urea clearance, cc/min Ultrafiltration, (QF)cc/min

  10. Urea and Creatinine Kinetic Parameters in ARF PatientsLeblanc et al., AJKD 1998 nPCR (gm/kg/d) 1.75 ± 0.82 Creatinine Index (mg/kg/d) 13.7 ± 4.7 LBM (kg) 38.3 ± 11.9 LBM/BW (%) 49.5 ± 14.0

  11. Effect of Solute Molecular Weight on EquilibrationJeffrey et al., Artif Organs 1994 Solute (MW) Sieving Coefficient (HF) Diffusion Coefficient (HD) Urea (60) 1.01 ± 0.05 1.01 ± 0.07 Creatinine (113) 1.00 ± 0.09 1.01 ± 0.06 Uric Acid (168) 1.01 ± 0.04 0.97 ± 0.04* Vancomycin (1448) 0.84 ± 0.10 0.74 ± 0.04** *P<0.05 vs sieving coefficient**P<0.01 vs sieving coefficient

  12. Factor CRRT vs IHD K . t Favors CRRT (due to “t”) Anticoagulation Favors IHD Hypotension Favors CRRT Compartment Effects Favors CRRT Access Recirculation Favors CRRT “Down-Time” Favors IHD Defined Target Favors Neither Factors Influencing RRT Dose in ARF

  13. Prescribed vs Delivered RRT in ARF • CRRT • “Down-time”: procedures, filter changes • Decline in filter performance:  SC or CDo/CBi, UFR • Access recirculation • IHD • Failure to achieve prescription (QB, time) • Compartment effects (rebound) • Access recirculation

  14. Effect of CVVH on Hemodynamic Parametersin Septic PatientsDe Vriese et al., JASN 1999 Cardiac output (l/min)and PAOP (mm Hg) Systemic Vascular Resistance(dyne.s/cm5) Time (hours)

  15. 8 7 6 5 4 Number of Animals Alive 3 2 1 0 0 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 Survival Time (hr) Effect of Filter Pore Size on Survivalin Experimental SepsisLee et al., Crit Care Med 1998

More Related