Pediatric CRRT Terms and Nomenclature Timothy E. Bunchman

How does dialysis work? Solute clearance is related to Sieving coefficient Molecular weight of the solute Charge of the solute Gradient across the membrane This can be convective or diffusive

Solute Molecular Weight and clearance Solute (MW)Convective Coefficient Diffusion Coefficient Urea (60)1.01 ± ± 0.07 Creatinine (113)1.00 ± ± 0.06 Uric Acid (168)1.01 ± ± 0.04* Vancomycin (1448)0.84 ± ± 0.04** Cytokines (large)adsorbedminimal clearance *P<0.05 **P<0.01

Definitions and Terms CVVH/CAVH Convective clearance Replacement Solutions Physiologic sterile solution that is either infused pre filter (NA) or post filter (outside of NA) that infused at a set rate (Qr)

CAVH/CVVH: Convective Clearance

Blood Flow (Qb) BUN 70 mg/dl, K 7 meq/dl, Na 140 meq/d (ultrafiltrate space) Convective (CAVH/CVVH) Semi-permeable membrane Sterile Replacement fluid infused into blood (Qr) Ultrafiltrate (Qef) contains BUN and K of ~ 90% of what was in blood and Na of 140)

Definitions and Terms CVVHD/CAVHD Diffusive clearance Dialysate Physiologic sterile solution that is infused countercurrent to the blood flow rate (Qd)

CAVHD/CVVHD Diffusive Clearance

Blood Flow (Qb) BUN 70 mg/dl, K 7 meq/dl, Na 140 meq/d Bun 0 mg/dl, K 0 meq/dl, Na 140 meq/dl Dialysis Flow (Qd) Diffusive (CAVHD/CVVHD) Semi-permeable membrane Ultrafiltrate (Qef) contains BUN and K of ~ 90% of what was in blood and Na of 140)

Definitions and Terms CVVHDF/CAVHDF Convective clearance Replacement Solutions Diffusive clearance Dialysis solution

CAVHDF/CVVHDF Convective and Diffusive Clearance

Blood Flow (Qb) BUN 70 mg/dl, K 7 meq/dl, Na 140 meq/d Bun 0 mg/dl, K 0 meq/dl, Na 140 meq/dl Dialysis Flow (Qd) Convective & Diffusive (CAVHDF/CVVHDF) Semi-permeable membrane Ultrafiltrate (Qef) contains BUN and K of ~ 90% of what was in blood and Na of 140) Sterile Replacement fluid infused into blood (Qr)

Definitions and Terms SCUF (surgeons cant understand fluid) Slow continuous ultrafiltration (UF) ultrafiltrate (water and solute) come across the membrane at a rate based upon TMP Transmembrane pressure (TMP) The pressure difference between the blood side and the ultrafiltrate side of the membrane Greater the TMP the greater the UF rate

Blood Flow (Qb) BUN 70 mg/dl, K 7 meq/dl, Na 140 meq/d SCUF Semi-permeable membrane Ultrafiltrate (Qef) contains solute based upon sieving coefficient

Blood TMP = O O Uf TMP = Net TMP TMP Semi-permeable membrane

Adsorption Concept when solute (e.g. plasma proteins) adhere or get adsorbed to a membrane Commonly discussed with column plasma-adsorption or the clearance of cytokines during SIRS

Blood Flow (Qb) Cytokines seen in SIRS Adsorption Semi-permeable membrane with cytokines adherent

Terms and Nomenclature Conclusion Terminology is confusing and often redundant paper on Definitions by Gibney, Kimmel and Lazarus