Pediatric CRRT Terms and Nomenclature

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Pediatric CRRTTerms and Nomenclature

• Timothy E. Bunchman

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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

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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) adsorbed minimal
clearance Plt0.05 Plt0.01
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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)

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CAVH/CVVH Convective Clearance
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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
• ----?------------------?----------------------?---
  ----
• (ultrafiltrate space)

Semi-permeable membrane
Ultrafiltrate (Qef) contains BUN and K of 90
of what was in blood and Na of 140)
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Definitions and Terms

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

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CAVHD/CVVHDDiffusive Clearance
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Diffusive (CAVHD/CVVHD)

• 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)

Semi-permeable membrane
Ultrafiltrate (Qef) contains BUN and K of 90
of what was in blood and Na of 140)
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Definitions and Terms

• CVVHDF/CAVHDF
• Convective clearance
• Replacement Solutions
• Diffusive clearance
• Dialysis solution

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CAVHDF/CVVHDFConvective and Diffusive Clearance

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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
• ----?------------------?--------------------------
  ?---
• Bun 0 mg/dl, K 0 meq/dl, Na 140 meq/dl
• ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
• Dialysis Flow (Qd)

Semi-permeable membrane
Ultrafiltrate (Qef) contains BUN and K of 90
of what was in blood and Na of 140)
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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

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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
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TMP

• Blood TMP 0 100 100 100
• -------------------O--------?----------------O----
  -------?-
• Uf TMP 0 0 100 200
• Net TMP 0 100 0 - 100

Semi-permeable membrane
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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

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Adsorption

• Blood Flow (Qb)
• ? ? ? ? ? ? ? ? ? ? ? ? ?
• Cytokines seen in SIRS
• ? ? ?
• --------------------------------------------------
  -----

Semi-permeable membrane with cytokines adherent
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Terms and NomenclatureConclusion

• Terminology is confusing and often redundant
• www.adqi.net paper on Definitions by
• Gibney, Kimmel and Lazarus