Renal Replacement Therapy

Renal Replacement Therapy

* What is it?
* How does it work?
Where did it come from?
History of Pediatric Hemofiltration
Mechanisms of Action: Convection
* Hydrostatic pressure pushes solvent across a semi-permeable membrane
* Solute is carried along with solvent by a process known as “solvent drag”
* Membrane pore size limits molecular transfer
* Efficient at removal of larger molecules compared with diffusion
* Solvent moves up a concentration gradient
* Solute diffuses down an concentration gradient

Mechanisms of Action: Diffusion
Semi-permeable Membranes
o Urea
o Creatinine
o Uric acid
o Sodium
o Potassium
o Ionized calcium
o Phosphate
o Almost all drugs not bound to plasma proteins
* Allow easy transfer of solutes less than 100 Daltons
o Bicarbonate
o Interleukin-1
o Interleukin-6
o Endotoxin
o Vancomycin
o Heparin
o Pesticides
o Ammonia
* Sieving Coefficient
* Sieving Coefficient is “1” for molecules that easily pass through the membrane and “0” for those that do not
* Continuous hemofiltration membranes consist of relatively straight channels of ever-increasing diameter that offer little resistance to fluid flow
* Intermittent hemodialysis membranes contain long, tortuous inter-connecting channels that result in high resistance to fluid flow

How is it done?
* Peritoneal Dialysis
* Hemodialysis
* Hemofiltration
* The choice of which modality to use depends on
o Patient’s clinical status
o Resources available

Peritoneal Dialysis
* Fluid placed into peritoneal cavity by catheter
* Glucose provides solvent gradient for fluid removal from body
* Can vary concentration of electrolytes to control hyperkalemia
* Can remove urea and metabolic products
* Can be intermittent or continuously cycled
* Simple to set up & perform
* Easy to use in infants
* Hemodynamic stability
* No anti-coagulation
* Bedside peritoneal access
* Treat severe hypothermia or hyperthermia
* Unreliable ultrafiltration
* Slow fluid & solute removal
* Drainage failure & leakage
* Catheter obstruction
* Respiratory compromise
* Hyperglycemia
* Peritonitis
* Not good for hyperammonemia or intoxication with dialyzable poisons

Intermittent Hemodialysis
* Maximum solute clearance of 3 modalities
* Best therapy for severe hyperkalemia
* Limited anti-coagulation time
* Bedside vascular access can be used
* Hemodynamic instability
* Hypoxemia
* Rapid fluid and electrolyte shifts
* Complex equipment
* Specialized personnel
* Difficult in small infants

Continuous Hemofiltration
* Easy to use in PICU
* Rapid electrolyte correction
* Excellent solute clearances
* Rapid acid/base correction
* Controllable fluid balance
* Tolerated by unstable patients
* Early use of TPN
* Bedside vascular access routine
* Systemic anticoagulation (except citrate)
* Frequent filter clotting
* Vascular access in infants

SCUF:Slow Continuous Ultrafiltration
* Pros
* Cons
Continuous Venovenous Hemofiltration
Dialysis Fluid
Continuous Venovenous Hemodialysis
Continuous Venovenous Hemodialysis with Ultrafiltration
Is there a “Best” Method?
Indications for Renal Replacement Therapy
Indicators of Circuit Function
Filtration Fraction
QP: the filter plasma flow rate in ml/min
Blood Flow Rate & Clearance
Pediatric CRRT Vascular Access: Performance = Blood Flow!!!
Urea Clearance
Solute Molecular Weight and Clearance
Cytokines (large) adsorbed minimal clearance
Replacement Fluids
Physiologic Replacement Fluid
Anticoagulation
Mechanisms of Filter Thrombosis
Heparin - Problems
Sites of Action of Citrate
Anticoagulation: Citrate
What are the targets?
Unknowns of Hemofiltration for Sepsis
Pediatric CRRT in the PICU
Renal Replacement Therapy in the PICU Pediatric Literature

Renal Replacement Therapy.ppt