pediatric renal replacement therapy in the icu

Pediatric Renal Replacement Therapy In The ICU

Introduction

• Pediatric RRT – growing role in PICU

• Volume overload and metabolic imbalance complicate course of critically ill patients

• Improving techniques coupled with the realization that early supportive therapy may improve outcomes have combined use of RRT for critically ill patients

Indications For Renal Support

• Acute renal failure

• Acute intoxication and metabolic disorders

• Renal Support - MODS

Conservative Management

• Optimization of clinical status• Maintenance of fluid balance , renal

perfusion, cardiac output , adequate blood pressure

• Judicious use of diuretics• Fluid restriction• Careful dietary management• However early initiation of RRT improves

mortality and morbidity

Basic Physiology of Dialysis And Ultrafiltration

• Molecular movement across semipermeable membrane

• Basic mechanisms of water and particle removal include

• Diffusion

• Convection

• Ultrafiltration

• Diffusion

• Movement of dissolved particles across semi- permeable membrane from area of high concentration to area of low concentration

• Favors movement of smaller particles

• Stops when concentration gradient achieves equilibrium

• Convection

• Dissolved particles pass across semi permeable membrane due to effects of pressure gradient

• Ultrafiltration

• Describes movement of water across semipermeable due to pressure

3 modalities

• Peritoneal dialysis

• Intermittent Hemodialysis

• Continuous Renal Replacement Therapy

PERITONEAL DIALYSIS• Physiology • Peritoneum can be used as a dialysing

membrane• Instillation of a dialysate into the peritoneal

space permits diffusion of particles out of the blood across the peritoneum

• Through the use of a hypertonic solution , water also passes across the membrane generating an ultrafiltrate

• Water movement tends to drag particles across the peritoneum by convection

• After the dwell is complete , the spent dialysate is drained from the abdomen and fresh dialysate may be introduced

Indications

• Remove excess fluid and provide volume control in the patient with oligoanuria

• Much slower than intermittent hemodialysis

• Preferable in the critically ill patient

• Provides metabolic control

Technique

• Instill sterile dialysate into peritoneal cavity• Allow it to dwell • End of dwell time the dialysate is removed• Dialysate contains base in the form of lactate• Ultrafiltration accomplished by osmotic

pressure thro dextrose• Should be warmed to body temp • Start with 10 – 20 ml/kg ( 500 ml/m2)• Can increase upto 1100ml/m2• Dwell period of 30 - 60 min

Disadv

• Placement of an intra-abd catheter • Patients who undergone intra – abd

surgery are poor candidates for PD• Peritonitis• Perforation of abdomen or pelvic

structures• Kinking , fibrin plugs , omental obstruction• Hemodialysis prefered where rapid

removal of toxins are reqd

Issues

• Loss of protein – supplement it

• Hyperglycemia

• GER – stomach comp

• Critically ill – inc intra abd pressure leading to dec Venous return and dec diaphragm excursion

Intermittent Hemodialysis

• Rapid metabolic correction and fluid removal

• Technically difficult in small children and infant

• Therapy of choice for some critically ill pediatric patients

• Requires expereinced personnel

PHYSIOLOGY

• Dialyser – semi permeable memb• Hollow fiber dialyser with microscopic fenestration• Vary in surface area , permeability , priming volume and

memb composition• Requires high blood flow , hence a high quality vascular

access• Ultrafilt occurs because of hydrostatic pressure across

memb• Increasing blood flow , dialysate flow or dialyser size will

inc rate of diffusion• Ultrafilt occurs because of hydrostatic pressure across

the membrane• Removes only the intravascular volume

Indications

• Best method for removal of toxic ingestion , drug overdoses , metabolic derangements

• Hyperkalemia

• Tumor lysis syndrome

Technique

• Vascular access – 1st step• Most patients require heparin for anticoagulation• Some patients require little or no heparin• Monitor clotting time to determine the need for

heparin ( ACT -120 – 180 )• Blood pump rate chosen based on quality of

vascular access and clinical status of the patient• Chosen dialyser should permit sufficient

clearance to achieve the goals of dialysis AN69

Disavantages and complic

• Vascular access – infection , bleeding , thrombosis

• Critically ill patients donot tolerate rapid clearing

• Unstable patients require priming of extra corporeal volume

• Complications of heparin

ISSUES

• Special attention to fluid and electrolyte balance

• One should limit potassium and phosphorus delivery

• Medication doses and schedule may require adjustment

Continuous Renal Replacement Therapy

• Broad name applied to several techniques of extracorporeal support

• More popular in pediatric patients

Physiology

• Membranes made from polysulfone or polyacrylonitrile

• More porous to permit greater removal of water

• Both convection and diffusion can be used to remove particles during CRRT

• Clearance is slower than IHD

Types of CRRT

• Continuous veno – venous hemofiltration – high convective clearance

• Continuous veno – venous hemodialysis

Uses dialysate

• Continuous veno – venous hemodiafiltration

Indications

• Slow , continuous removal of fluid

• Maintains cardiovascular stability

• Useful in critically ill patients

• Maintains metabolic balance

Technique

• Large vascular access

• Anticoagulation

• Dialysate

• Clearance

Disavantages

• Vascular access

• Heparin

• Citrate

Issues

• Can cause profound electrolyte dist

• Increased nitrogen losses

• Increased nutritional support

• Medication adjustment

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