Pediatric CRRT Terms and Nomenclature Timothy E Bunchman

Pediatric CRRT Terms and Nomenclature Timothy E. Bunchman

How does dialysis work? n Solute clearance is related to n Sieving coefficient n n 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. 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** Cytokines (large) *P<0. 05 **P<0. 01 adsorbed minimal clearance

Definitions and Terms n n n CVVH/CAVH Convective clearance Replacement Solutions n 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

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

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

CAVHD/CVVHD Diffusive Clearance

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

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

CAVHDF/CVVHDF Convective and Diffusive Clearance

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

Definitions and Terms n SCUF (surgeons can’t understand fluid) n n Slow continuous ultrafiltration (UF) ultrafiltrate (water and solute) come across the membrane at a rate based upon TMP Transmembrane pressure (TMP) n n The pressure difference between the blood side and the ultrafiltrate side of the membrane Greater the TMP the greater the UF rate

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

TMP Blood TMP = 0 100 100 ----------O----↓--------O------↑ Semi-permeable membrane Uf TMP Net TMP =0 0 0 100 0 200 - 100

Adsorption n n 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

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

Terms and Nomenclature Conclusion n n Terminology is confusing and often redundant www. adqi. net paper on Definitions by n Gibney, Kimmel and Lazarus