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Basics of CRRT: Terminology
Theresa Mottes, MSN, RN, CPNP-AC Cincinnati Children’s Hospital Center for Acute Care Nephrology
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Standardization of Terminology
Patient safety Comparing modalities Common language I want to thank the planning committee for the opportunity to present at this conference. I’m honored to be following in Jordan Symons foot steps in presenting on this topic. Also for sharing his slides as well. The importance of understanding the current terminology, both within your institutions as well as in the literature.
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Diffusion or Convection
Continuous Renal Replacement Therapy Extracorporeal circuit Continuous in nature Particle removal Diffusion or Convection Fluid removal via ultrafiltration
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Nomenclature for CRRT Modalities
SCUF Slow Continuous Ultrafiltration CVVH Continuous Veno-Venous Hemofiltration CVVHD Continuous Veno-Venous Hemodialysis CVVHDF Continuous Veno-Venous Hemodiafiltration
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Basis for Nomenclature
V H Interval Therapy Blood Access Method of Solute Removal
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CRRT Schematic SCUF CVVH CVVHD CVVHDF
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Convection Small/large molecules move equally
Limit is cut-off size of membrane Higher UF rate yields higher convection but risk of hypotension May need to Replace excess UF volume Net Pressure H2O H2O H2O H2O
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Diffusion Dialysate required Small molecules diffuse easily
Concentration gradient Faster dialysate flow increases mass transfer Small molecules diffuse easily Larger molecules diffuse slowly
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CRRT Dose = Effluent Flow Rate
QR 600ml/hr QB 150ml/min QD 600ml/hr Effluent 1200ml/hr +
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Effluent Flow Rate is Limiting Factor in CRRT
QR 1000ml/hr QB 150ml/min QD 1000ml/hr Effluent 2000ml/hr +
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Fluid Removal via CRRT Ultrafiltration Rate = Patient Fluid Removal Rate Movement of fluid (plasma water) by a pressure gradient Net Fluid Balance Even Positive Negative
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Rate Limitations of Volume Removal
BP Extra-Vascular Compartment Vascular Compartment
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Improved Volume Removal with Slower Ultrafiltration Rates
Vascular Compartment Extra-Vascular Compartment BP Stable
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CRRT Pressure Related Terms
Arterial/Access/Pull/Inlet Blood moving from patient to extracorporeal circuit Venous/Return/Push/Outlet Blood moving from the extracorporeal circuit to the patient
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CRRT Pressure Related Terms
Transmembrane Pressure Reflects the efficiency of the filter fibers Pressure Drop Reflect the ability of the blood to pass through the membrane fibers
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Summary CRRT modalities differ based on solute transport:
SCUF, CVVH, CVVHD, CVVHDF Solution rates drive clearance rates Standardize your institutional language Align your language with your machinery
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Thank You Questions?
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