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PrismaFlexSTEPP
Basic CRRT Principles
Course ObjectivesBy the end of the Gambro CRRT training course the participant will be able to:
Define CRRT and the associated therapies Discuss the basic CRRT principles Discuss the basic principles of the solute transport mechanisms Identify the clinical indications for administering CRRT, including an overview of patient selection and therapy application Have a working knowledge of basic CRRT machine set up, run, end treatment and troubleshooting skills. Describe the CRRT machines safety management features, pressure monitoring and fluid balance principles.
Continuous Renal Replacement Therapy (CRRT)
Any extracorporeal blood purification therapyintended to substitute for impaired renal function over an extended period of time and applied for or aimed at being applied for 24 hours/day.
Bellomo R., Ronco C., Mehta R, Nomenclature for Continuous Renal Replacement Therapies, AJKD, Vol 28, No. 5, Suppl 3, Nov 1996
Why CRRT?CRRT closely mimics the native kidney in treating ARF and fluid overload
Removes large amounts of fluid and waste products over time Tolerated well by hemodynamically unstable patients
CRRT Treatment Goals Maintain fluid, electrolyte, acid/base balance Prevent further damage to kidney tissue Promote healing and total renal recovery Allow other supportive measures; nutritional support
Determinants of OutcomeInitiation of Therapy Ronco Study Gettings Study ADQI Consensus Initiative - Rifle Criteria
Dose Ronco Study Kellum Meta-Analysis Saudan Study
GFR Criteria Risk Injury Failure LossIncreased creatinine x 1.5 or GFR decrease >25%
Urine Output CriteriaUO 50%
UO 75% or Serum Creatinine > 4mg/dl
UO 4 weeks
ESRD
End-stage renal disease (>3 months)
Effects of different doses in CVVH on outcome of ARF - Ronco & Bellomo study. Lancet . july 00
Cumulative Survival (%) vs Treatment Dose
100 90 80
p < 0.001
Survival (%)
70 60 50 40 30 20 10 0
p < 0.001
p n..s.
41 %
57 %
58 %
Group 1(n=146) ( Uf = 20 ml/h/Kg)
Group 2 (n=139) (Uf = 35 ml/h/Kg)
Group 3 (n=140) (Uf = 45 ml/h/Kg)
SummaryEvidenced Based Research reports that patient survival is improved by: Early initiation: Utilization of RIFLE Criteria Minimum dose delivery of 35 ml/kg/hr eg. 70 kg patient = 2450 ml/hEffects of different doses in CVVH on outcomes of ARF C. Ronco M.D., R. Bellomo M.D. Lancet 2000; 356:26-30.
Anatomy of a Hemofilter 4 External ports blood and dialysis fluid
Potting material support structure
Hollow fibers Semi-permeable membrane
Outer casing
CRRT Transport Mechanisms
Molecular Transport MechanismsUltrafiltration Diffusion Convection Adsorption Fluid Transport
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Solute Transport
Ultrafiltration Movement of fluid through a semipermeable membrane caused by a pressure gradient Positive, negative and osmotic pressure from non-permeable solutes
UltrafiltrationBlood Out(to patient)
Fluid Volume Reduction to waste Blood In(From patient)
LOW PRESS
HIGH PRESS
Molecular WeightsDaltons
Inflammatory Mediators (1,200-40,000)
large
middle
small
Diffusion Movement of solutes from an area of higher concentration to an area of lower concentration. Dialysate is used to create a concentration gradient across a semipermeable membrane.
Hemodialysis: Diffusion
Dialysate In
Blood Out(to patient)
Dialysate Out(to waste) LOW CONC HIGH CONC
Blood In(from patient)
Convection Movement of solutes with water flow, solvent drag. The more fluid moved through a semipermeable membrane, the more solutes that are removed. Replacement Fluid is used to create convection
Hemofiltration: ConvectionBlood Out(to patient)
Repl. Solution
to waste
Blood In(from patient) LOW PRESS HIGH PRESS
Electrolytes & pH BalanceAnother primary goal for CRRT, specifically: Sodium Potassium Calcium Glucose Phosphate Bicarbonate or lactate buffer
Dialysate and replacement solutions are used in CRRT to attain this goal.
Adsorption
Molecular adherence to the surface or interior of the membrane.
Small vs. Large Molecules Clearance100
Kidney Convection
80
Clearance in %
60
40
20
Diffusion0 Urea (60) 2.500 Creatinine (113) 5.000 20.000 Myoglobin (17.000) 35.000 55.000 65.000 Albumin (66.000)
What is the transport mechanism associated with dialysate and replacement solutions?
Flow Control Unit Pumps
Effluent Pre Blood Pump
Dialysate: Diffusion Replacement: Convection Blood
Effluent Flow RateEffluent = Total Fluid Volume: Patient Fluid Removal Dialysate Flow Replacement Flow Pre-Blood Pump Flow
CRRT Modes of TherapySCUF - Slow Continuous Ultrafiltration CVVH - Continuous Veno-Venous Hemofiltration CVVHD - Continuous Veno-Venous HemoDialysis CVVHDF - Continuous Veno-Venous HemoDiaFiltration
SCUF Slow Continuous UltraFiltration Primary therapeutic goal: Safe and effective management of fluid removal from the patient
SCUF Slow Continuous UltraFiltrationReturn Acces s
Blood Pump
Effluent Pump
PBP Pump
Effluent
Infusion or Anticoagul ant
CVVHD Continuous VV HemoDialysisPrimary therapeutic goal: Small solute removal by diffusion Safe fluid volume management
Dialysate volume automatically removed through the Effluent pump
Solute removal determined by Dialysate Flow Rate.
CVVHD Continuous VV HemoDialysisReturnHemofilter
Blood Pump
Acces s
Dialysat e Pump
Efflue nt Pump
PBP Pum p
Dialysat e Fluid
Efflue nt
Infusion or Anticoagul ant
Dialysate Solutions Flows counter-current to blood flow Remains separated by a semi-permeable membrane Drives diffusive transport dependent on concentration gradient and flow rate
Facilitates removal of small solutes Physician prescribed Contains physiologic electrolyte levels Components adjusted to meet patient needs
CVVH: Continuous VV HemofiltrationPrimary Therapeutic Goal: Removal of small, middle and large sized solutes Safe fluid volume management
Replacement solution is infused into blood compartment pre or post filter Drives convective transport Replacement fluid volume automatically removed by effluent pump
Solute removal determined by Replacement Flow Rate.
CVVH Continuous VV HemofiltrationReturn
Blood Pump
Acces s
Replacemen t Pump 2
Efflue nt Pump
Replacemen t Pump 1
PBP Pum p
Replacemen t2
Efflue nt
Replacemen t1
Infusion or Anticoagul ant
Pre-Dilution Replacement SolutionReturn Acces s
Hemofilter
Blood Pump
Decreases risk of clotting Higher UF capabilities Decreases Hct. In filter
Efflue nt Pump
Replacemen t Pump
PBP Pum p
Efflue nt
Replacemen t Fluid
Infusion or Anticoagul ant
Post-Dilution Replacement SolutionConsider lowering replacement rates (filtration %) Higher BFR (filtration %) Higher anticoagulation More efficient clearance (>15%)Hemofilter
Return
Blood Pump
Acces s
Replacemen Efflue t nt Pump Pump
Replacemen t Pump
PBP Pum p
Replacemen t Fluid
Efflue nt
Replacemen t Fluid
Infusion or Anticoagul ant
Replacement Solutions Infused directly into the blood at points along the blood pathway Drives convective transport Facilitates the removal of small middle and large solutes Physician Prescribed Contains electrolytes at physiological levels Components adjusted to meet patient needs
CVVHDFPrimary therapeutic goal: Solute removal by diffusion and convection Safe fluid volume management Efficient removal of small, middle and large molecules Replacement and dialysate fluid volume automatically removed by effluent pump
Solute removal determined by Replacement + Dialysate Flow Rates.
CVVHDF Continuous VV HemoDiaFiltrationReturn
Blood Pump
Acces s
Dialysat e Pump
Efflue nt Pump
Replacemen t Pump
PBP Pum p
Dialysat e Fluid
Efflue nt
Replacemen t Fluid
Infusion or Anticoagul ant