liverpool sdl crrt

8/11/2019 Liverpool SDL CRRT

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Liverpool Health Service

Intensive Care Unit

Self Directed Learning Package:

Continuous Renal Replacement Therapy

Written by: Nicholas Mifflin & Sharon-Ann Shunker


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How to use this package

This package is designed to be used in the clinical area as a self directedlearning tool.

The package is divided into sections. At the end of each section is a self testto determine how well you have understood the information contained inthat section. You will need to complete the self tests at the end of eachsection and ensure that you have mastered the content before moving on tothe next section.

If you have any trouble with the self test, go back over the section and revisethe content. If you are still unsure then you will need to speak with one ofthe educators in your area.

The answers to each of the self test questions are contained at the end of the

package. To gain the most benefit from this package attempt the questionsfirst before seeking this reference.

GOOD LUCK!!!


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Learning package objectives

By the completion of this package, the registered nurse will be able to:

1.

Define and classify acute renal failure according to its aetiology

2. Identify the signs and symptoms of acute renal failure

3. Discuss the various modalities of renal replacement therapy including

advantages and disadvantages

4.

Identify the indications for continuous renal replacement therapy

5. Describe the basic principles of fluid and waste removal involved in

CRRT

6. Describe the various modes of CRRT

7. Recognise the importance of access in CRRT

8.

Explain the process for troubleshooting a vascath

9. Differentiate solutions used for CRRT

10.

Discuss the safety precautions required for commencing CRRT

11.

Differentiate pre dilution from post dilution

12.State the complications of CRRT

13.Describe methods that optimise clearance of fluid and waste

14.

Describe methods of prolonging filter life

15.Discuss the indications for ceasing therapy

16.Recognise common reasons for CRRT machine alarms

17.

Discuss the nursing management of the patient on CRRT


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A Brief Look at Renal Anatomy & Physiology

Structures of the Renal System: The renal system is comprised of theKidneys and those structures includingthe ureters, bladder and urethra thatform the urinary system.

The primary role of the kidneys is toremove metabolic wastes and maintainfluid and electrolyte balance. Thekidneys also have a role in:

Blood Pressure Control

Red Blood Cell Synthesis

Bone Metabolism Acid- Base Balance

Renal dysfunction can negatively impacton all of these roles. 11

Adrenal Gland

Ureter

Kidney

BladderUrethra

The kidneys are situated in theretroperitoneum located between T12and L3 on each side of the vertebralcolumn. 12

Two layers form them internally. Theouter layer is the Cortexthat contains:

Glomeruli

Proximal Tubules

Cortical Portions of Loops ofHenle

Distal Tubules

Cortical Collecting Ducts 11,12

The inner layer or Medullais comprisedof Renal Pyramids. The pyramidscontain:

Medullary portions of Loops ofHenle

Medullary Portions of CollectingDucts 12

Multiple pyramids taper and joinforming a minor calyx. Several

combined make a major calyx. Themajor calyces join and enter a funnelshaped renal pelvisthat directs urineinto the ureter. 11

Cross Section of the Kidney:


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Components of the Nephron:

Approximately one million nephrons

comprise each kidney. The nephronconsists of:

Glomerulus

Bowman Capsule

Proximal Convoluted Tubule

Loop of Henle

Distal Convoluted Tubule

Collecting Duct 11,12

There are two types of nephron:

Cortical Nephrons

Juxtamedullary Nephrons 11

Cortical Nephrons:

Approximately 85 % Perform excretory and regulatory

functions 11

Juxtamedullary Nephrons:

Approximately 15 %

Responsible for concentration anddilution of urine 11

Urine Formation:

Three processes required for urine formation include: Glomerular Filtration

Tubular Reabsorption

Tubular Secretion 11,12

Glomerulus

Filters fluid and solutes from bloodProximal Convoluted Tubule

Reabsorbs Na+, K+, Cl-, HCO3-, urea, glucose & aminoacids

Filtrate Continues

Loop of Henle Reabsorbs Na+, K+& Cl-

Blocks reabsorption of H2O

Dilutes/Concentrates Urine

Filtrate ContinuesDistal Tubule

Na+, K+, Ca++, PO4 selectively reabsorbed

H2O reabsorbed in presence of Antidiuretic Hormone(ADH)

Filtrate Continues

Collecting Duct

Reabsorption similar to distal tubule HCO3-& H-reabsorbed/secreted to acidify urine

Filtrate leaves hyperosmotic/hypoosmotic depending on 11,12


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Composition of Urine:H2OElectrolytes- Na+, K+, Cl-, HCO3-

End products of protein metabolism- urea, creatinine, PO4, SO4

End products of nucleic acid metabolism- uric acidBreakdown products of phosphoric and sulphuric acidH+ions excreted bound to buffers such as PO4and NH3 11

Renal Anatomy & Physiology in Summary:

Kidneys filter blood of waste products

Functional units of the kidneys are called nephrons

Nephrons consist of a glomerulus, tubule and collecting duct

Urine is formed through glomerular filtration, tubular reabsorption

and tubular secretion

Urine moves from the collecting duct via the renal pelvis and uretersinto the bladder, where it is excreted from the body through theurethra

Some substances are reabsorbed into the blood and others excretedinto the filtrate


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Self Test 1

Q1.State the primary and secondary functions of the kidneys.

Q2.Name the functional units of the Kidneys and list their components.

Q3.Discuss the processes involved in urine formation


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Summary of Acute Renal Failure

Definition:

Acute renal failure (ARF) is a clinical syndrome, characterised by anabrupt decline in glomerular filtration rate (GFR). There is a subsequentretention of metabolic waste products and an inability to maintainelectrolyte and acid-base homeostasis. Regulation of fluid volume isalso affected. 1,7,8,16,18,23

ARF occurs rapidly resulting in fifty percent or more nephronsto losefunction,and as this occurs quickly the body is unable to compensate.

There are three classifications of ARF based on the location of the cause. 23

Prerenal

Renal dysfunction is largely related to systemic factors that limit blood flowand reduce glomerular filtration rate. Examples include:

Hypotension

Hypovolaemic shock- dehydration, blood loss

Cardiogenic shock post MI

Septic Shock

Bilateral renal vascular obstruction- thrombosis 1,8,9,16,18,23

Intrarenal

Renal impairment occurs secondary to damage that is sustained at the siteof the nephrons. This may be the result of a number of conditions ornephrotoxins:

Acute Tubular Necrosis (ATN)

Acute Glomerulonephritis

Acute Pyelonephritis

Acute Cortical Necrosis

Malignant Hypertension

Acute Vasculitis Rhabdomyolysis - drugs, trauma

Nephrotoxins - IV contrast, aminoglycosides 1,8,9,16,18,23

Postrenal

Renal failure secondary to obstruction that prevents excretion of urine

Prostatic Hypertrophy

Renal Calculi

Tumour

Blocked Urinary Catheter

1,8,9,16,18,23


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Signs & Symptoms

Fluid and electrolyte abnormalities

Metabolic acidosis

Anaemia

Pruritis secondary to uremic frost Nausea & vomiting

Confusion

LOC

Congestive heart failure resulting in acute pulmonary oedema1,8,16,18,23


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Self Test 2

Q1. Define Acute Renal Failure

Q2. Describe 3 forms of acute renal failure and the associated causes

Q3. List the signs and symptoms of acute renal failure


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Renal Replacement Therapy

Renal replacement therapy (RRT) is an extracorporeal technique of bloodpurification. Blood passes over a semipermeable membrane (filter) allowing

solutes and water to cross over to a collection side. There are variousmodalities included under the umbrella of RRT. 19

Continuous Modalities (CRRT)

Haemofiltration

Haemodialysis

Haemodiafiltration

Ultrafiltration

Advantages:

Better for haemodynamic instability

Readily accessible Effective fluid removal and clearance of solutes

Can be performed by ICU staff rather than specialised renal nurses2,4,5,9,17,20

Disadvantages:

Patient mobilisation is limited

Access complications

Anticoagulation

Reduced blood flow rates secondary to small filters when compared toIHD 2,4,5,9,17,20

Intermittent Haemodialysis (IHD)

Advantages:

Quick and effective

Large amounts of fluid and solutes can be removed over a shortperiod 5,9

Disadvantages:

Access Complications- formal access such as A.V. Fistula iseventually required

Requires specialised staff and is therefore not readily accessible May not be well tolerated by haemodynamically unstable patients

Intermittent fluid removal with IHD can be associated with fluidoverload and increased electrolytes between treatments 5,9

Peritoneal Dialysis

This form of dialysis utilises the peritoneum as the semipermeablemembrane.

Advantages:

Comparatively Cheaper No anticoagulation required


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No haemodynamic instability 5,9,24

Disadvantages:

High incidence of peritonitis

Slow clearance

Access Formal access required (Tenkhoff catheter) Limitations on patient as it is required frequently 5,9,24


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Continuous Renal Replacement Therapy (CRRT)

Indications

Fluid Overload, pulmonary oedema

Worsening Metabolic Acidosis

Hyperkalaemia Worsening Azotaemia

Drug overdoses

Removal of toxins 9

Basic PrinciplesThe basic principles incorporated in the function of CRRT involve:

Convection

Diffusion

Ultrafiltration

Hydrostatic Pressure

2,4,9,17,20

Terminology

DiffusionThe movement of small and middle molecule solutes from an area of high

concentration to low concentration across a semipermeable-membrane.5,9

22

OsmosisThe movement of water from an area of high water concentration to an areaof lower water concentration across a semi-permeable membrane. 5,9

22


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Ultrafiltration

The movement of water and solutes across a semipermeable membrane bysolvent drag created by convection and hydrostatic pressure. 5,9

22

ConvectionWater flow across a semi-permeable membrane by hydrostatic pressure thatdrags solutes with it (the way a waterfall moves pebbles and sand) 9

Hydrostatic Pressure

The force that pushes fluid and solutes across the membrane. Themechanical blood pump on the dialysis machine creates this.5,9

Oncotic PressurePlasma proteins including albumin, globulin and fibrinogen create the

pulling pressure that favours fluid retention and opposes hydrostaticpressure. 5,9

Counter Current

The flow of two fluids in opposing directions. The direction of dialysis flowsopposite to that of blood flow maximising the concentration differencebetween blood and dialysate.5

DialysateA synthetic solute free solution used to achieve diffusive solute clearance 5

EffluentErroneous term used to indicate the solute and solvent discarded form thepatient.9

ReplacementPre or post dilution fluid

Pre-dilutionAdministration of the replacement fluid into the circuit prior to the filter 5,9

Post-dilutionAdministration of replacement fluid into the circuit after the filter 5,9


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Modalities

Slow Continuous Ultrafiltration (SCUF)

Continuous Arterio/Venovenous Haemofiltration (CAVH/CVVH)

Continuous Arterio/Venovenous Haemodialysis (CAVHD/CVVHD)

Continuous Arterio/Venovenous Haemodiafiltration(CAVHDF/CVVHDF)

SCUFSlow Continuous Ultrafiltration is the method used when fluid removal isthe only objective. Dialysate and replacement fluids are not utilised.Maximum fluid removal is 2000ml/hr. 2,17,20

= pump

SCUF System Setup13

CAVH/CVVHContinuous Venovenous Haemofiltration uses convective clearance toremove water and solutes. Replacement is used to replace ultrafiltrate.

Maximum fluid removal is 1000ml/hr. 2,17,20

= pump

CVVH System Setup 13


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CAVHD/CVVHDContinuous Venovenous Haemodialysis uses diffusion to remove fluid andsolutes. Dialysate is pumped in a counter current to blood flow. Maximumfluid removal is 1000ml/hr. 2,17,20

= pump

CVVHD System Setup 13

CAVHDF/CVVHDFContinuous Venovenous Haemodiafiltration utilises both convection anddiffusion to remove fluid and solutes. Dialysate and replacement is used.Maximum fluid removal is 1000ml/hr. 2,17,20

= pump

CVVHDF System Setup 13


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CRRT Modality Summary 2,17,20

Mode Filtering Process Removes Indication

Slow ContinuousUltra Filtration

(SCUF)

Convection-Ultrafiltration

Fluid, Minimalsolutes

Fluid OverloadHeart failure

ContinuousArterio/Venovenous

Haemofiltration(CAVH/CVVH)

Convection-Ultrafiltration

Fluid removal.Moderate soluteremoval. Urea

clearanceapproximately 15-

17ml/min

Moderate electrolyteimbalances

Oliguria withparenteral nutrition

or bloodrequirementsSeptic Shock


Haemodialysis(CAVHD, CVVHD)

DiffusionFluid removal. More

aggressive soluteremoval. Urea


21ml/min.

Fluid overload with

haemodynamicinstabilityAzotaemiaElectrolyte

disturbance andacidosis

Parenteral nutritionaccompanying fluid

overload


Haemodiafiltration(CAVHDF/CVVHDF

Convection &Diffusion

Maximum fluid andsolute removal. Urea


26ml/min.

Fluid Overload,pulmonary oedema

Worsening Metabolic

AcidosisHyperkalaemia

Worsening AzotaemiaDrug overdoses

Removal of toxins

NB: There are other forms of CRRT however the above are mostapplicable to LHS


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Self Test 3

Q1. What is renal replacement therapy?

Q2. List advantages and disadvantages of continuous modalities comparedto other forms of RRT

Q3. List Indications for CRRT

Q4. Describe the basic principles of fluid and solute removal involved in

CRRT.

Q5. Describe the different modes of CRRT.


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Vascular Access

Good access that allows high flow rates through the circuit is one of the keyaspects in CRRT that effects blood flow, clearance and filter life.

Catheters

Blood Flow is proportional to the diameter of the catheter- i.e. the wider thetube the better the blood flow. 3,4Therefore the largest diameter cathetershould be utilised. Vascaths available in Liverpool ICU include.

Gambro- 13fr ( 15cm &20cm)

Niagra- 13.5Fr (15cm & 24cm)

Gambro- 12Fr (15cm & 20cm)

Arrow Triple Lumen- 12 Fr (20cm)Lumens are colour codedbeing red and blue. The red lumenis the arterialport also known as the access port. This lumen supplies blood from thepatient to the filter. The blue lumenis the venous port also known as thereturn port. Blood is returned via this lumen from the filter to the patient.Differentiating these lumens is necessary when troubleshooting access orreturn pressure alarms on the CRRT machines. 5

Catheter Location

Typically the vessels utilised for vascaths are the Internal Jugular, Femoraland Subclavianveins. The choice of catheter site is dependant on manyfactors including:

Skill of the accessing clinician Size of the patient

Mobility of the patient

Anticipated Duration of therapy

Presence of other intravenous lines

Coagulopathy 3,4

Internal Jugular Vein

Advantages:

Allows for patient mobility Easy to visualise insertion site

Disadvantages:

Requires Chest Xray prior to use

Kinking can occur when the patient moves their head

Sometimes attains insubstantial blood flows secondary to variations

in central filling and intrathoracic pressures. Positive pressureventilation can make this more apparent. 3,4,5


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Femoral Vein

Advantages:

Easily accessible by most clinicians

May allow greater blood flows

Disadvantages:

Prone to kinking, more so in the obese patient

Does not allow for patient mobility

Difficult to visualise and dress insertion site

Higher incidence of infection secondary to the proximity to intestinal

flora. 3,4,5

Subclavian Vein

Advantages:

Allows for patient mobility

Easy to visualise and dress insertion site

Disadvantages:


Risk of pneumothorax on insertion

Risk of subclavian stenosis, which can impair suitability for an A-Vfistula on the affected side, if renal failure becomes chronic.

Sometimes attains insubstantial blood flows secondary to variationsin central filling and intrathoracic pressures. Positive pressureventilation can make this more noticeable. 3,4,5

Nursing Care for the Access Device

Regularly inspect insertion site for signs of infection, haematoma and

bleeding

Apply standard precautions and aseptic technique wheneverconnecting or disconnecting lines to and from the catheter

Clean catheter and site with 0.5% chlorhexidine once weekly and prnusing an aseptic technique and cover with an occlusive dressing (IV3000)

When catheter is not in use lumens should be Heparin-Locked toprevent clotting within the catheter 5

NB: Form more information on care of a vas cath see policy-management of central venous access devices in appendix

Heparin-Lock for a Vas-Cath

Apply standard precautions and utilise aseptic technique

Using 3 ampoules of 5000 units heparin in 1ml (15000 units/3ml)inject the stated amount (located on each port) of this solution intothe Vas Cath port. Label lumens as Heparin Locked 9,10


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Troubleshooting Access Device

Where the CRRT machine exhibits high-pressure alarms the problem maystem from a malfunctioning catheter. Assess catheter patency as follows:

Apply standard precautions and utilise aseptic technique Aspirate and flush 10ml of blood on the effected lumen to testresistance to blood flow. Further, flush 10ml 0.9% sterile normalsaline. 22

Where resistance is present, a clot may be obstructing the catheter, butmore likely it is positioned against the vessel wall. Slightly withdrawing orrotating the catheter may overcome this problem. Where this fails to resolve

the problem the catheter must be changed. 5,9,21

NB:Swapping the lumens- i.e. attaching the access line to the return portand visa versa may also overcome this problem, however this can result in a

significant reduction in clearance and is therefore not recommended. It canbe used as a temporary measure to overcome access problems. 9


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Self Test 4

Q1. What is the importance of adequate access?

Q2. Sate the appropriate name and functions of the red and blue lumens ona vascath

Q3. What are the three possible sites for vascath insertion? State theadvantages and disadvantages of each.

Q4. How would you troubleshoot a vascath?

Q5. How would you heparin lock a vascath?


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Preparation for Therapy

Orders & Equipment

Obtain a complete and correctly filled order for CRRT using the ICU

CRRT prescription form. NB:Pre dilution or Post dilution set Obtain equipment according to ICU protocol Continuous Renal

Replacement Therapy (CRRT) using the PRISMA MACHINE. NB:equipment for the PRISMA FLEX is identical except for the requiredset, compatible warming line and one extra bag of GAMBRO orHEMOSOL solution as ordered.

Please read and become familiar with this protocol in conjunctionwith this package. (See appendix)

Preparation of Fluids

Losses in ultrafiltrate through CVVH and CVVHDF require replacing.Replacement fluid should be a balanced electrolyte solution that will offsetthe convective loss of electrolytes and plasma water during haemofiltration.As stated earlier, replacement fluid is a pre or post dilution fluid. The fluidsavailable for such purpose in Liverpool ICU include HEMOSOL andGAMBRO. These fluids are also used as dialysate in modalities wherediffusive clearance is also involved (CVVHDF, CVVHD).3To maintain acid-base balance, it is necessary for these fluids to contain base that will providea buffer. Typically lactate serves this purpose as it is converted tobicarbonate in the liver.4,GAMBRO is the fluid that contains lactate as

its buffer.

Lactate free solutions also exist where bicarbonate must be addedimmediately prior to use.4,HEMOSOL is considered lactate free and thusrequires the addition of bicarbonate prior to use. This is accomplished bybreaking the seal within the bag to mix the solutions together.

HEMOSOL is the fluid of choice where the patient is severely acidotic orsuffering liver dysfunction that would prevent the metabolism of lactate tobicarbonate. Utilising GAMBRO in this circumstance may contribute to aworsening acidosis.

Specific to Dialysate

Both GAMBRO and HEMOSOL solutions require addition of KCL when usedas dialysate. KCL is added to these fluids to reduce loss K+of throughdiffusion.NB: KCL is only added to these fluids when patients K+level is


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Procedure

GAMBRO- Add 15mmol K+ to 5L (already contains 5mmol K+/ 5L)

HEMOSOL- Add 20mmol K+ to 5L (Contains no K+ )

Addition of K+

in these quantities will make a final concentration of 4mmolK+ /L.9

Priming The Circuit

Both PRISMA and PRISMA FLEX machines contain on screen step by stepinstructions for setting up and priming the circuit. For further informationon priming the PRISMA machine consult ICU protocol, Continuous Renal

Replacement Therapy (CRRT) using the PRISMA MACHINE. Furtherinformation regarding the same processes for the PRISMA FLEX can befound in the operators manual located on the back of the machine. Failingthis, please consult a senior staff member or educator that may assist you.

Access

Once the circuit is primed and ready to connect, 5ml of blood should beaspirated and discarded to remove heparin from the line.The vascathshould then be checked for patency as described earlier in troubleshootingaccess device.It is important that therapy with a good circuit not becommenced on inadequate access. Circuits are expensive and poor accesswill significantly reduce its functional duration. Always apply aseptictechnique when accessing catheter. 9


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Commencing Therapy

Providing access is adequate, access and return lines can be connected tothe corresponding lumens of the vascath using standard precautions andaseptic technique. A full breakdown of this procedure is located in ICU

protocol Continuous Renal Replacement Therapy (CRRT) using the PRISMAMACHINE.

Connecting Patient to CRRT (Running pt on)

Once patient is connected select desired flow rates for Dialysate,Replacement, Blood Pump Speed, Ultrafiltrate/Fluid removalaccording to order (Commence blood pump at 80-100ml/hr andincrease as tolerated by patient)

Assess patients haemodynamic status

Commence therapy

Administer 2500 units heparin bolus via the red port on the accessline. Omit heparin bolus if patient is coagulopathic or has been onCRRT in the last 4 hours.

Monitor patient for haemodynamic instability for 15-30 minutes postcommencing therapy. Patient may experience a transient drop in

blood pressure, that will therefore require adjustment of pump speedto compensate, depending on the sensitivity of the patient. 9,21

Safety

CRRT Machine should be plugged into an isolated power socket

When commencing therapy, colloid on a pump giving setshould beconnected to patients intravenous access

10mg Metaraminol (Aramine) should be drawn up and readilyavailable. 10mg of Aramine is prepared in 20ml of 0.9% sodiumchloride. This in conjunction with colloid is precautionary, should thepatient become hypotensive. If the patient is on inotropes, Araminemay not be necessary as blood pressure can be controlled with theexisting inotropic drugs. 9,21

Pre-dilution or Post-dilution

Pre-dilution involves administering replacement fluid prior to the filter. Thisthereby reduces the viscosity of blood and hematocrit and in effect may aidin preventing filter clotting. Unfortunately this method also dilutes theconcentration of solute in plasma, which can negatively impact on clearance.In order to optimise clearance of solutes, replacement rate must beincreased in order to increase the rate of ultrafiltration. 3,9

Post-dilution therefore involves administering replacement fluid after thefilter. This does not dilute solutes in plasma, however the ability for optimal

clearance is lost when blood viscosity is not reduced and high flow rates arethen difficult to achieve. With reduced blood flow comes reduced

ultrafiltration. Utilising filters with larger surface areas in conjunction withthis method may improve clearance. 9


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Complications

Hypotension that may result from aggressive fluid removal

Electrolyte imbalances

Cardiac Arrhythmias

Anaemia secondary to haemolysis of red blood cells

Thrombocytopaenia secondary to platelet aggregation in filter Hypothermia secondary to extracorporeal blood circulation

Coagulopathy secondary to over heparinisation

Infection (line sepsis)

Heparin induced thrombocytopaenia 2,9,17,21


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Self Test 5

Q1. What is the purpose of dialysate and replacement fluids?

Q2. State the two fluids available at Liverpool ICU for CRRT, including themajor difference and the preparations required.

Q3. How do you prepare the vascath prior to commencing CRRT with a newcircuit?

Q4. List the safety aspects of connecting and commencing therapy.

Q5. Differentiate pre dilution from post dilution including benefits anddisadvantages.

Q6. List the complications of CRRT.


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Optimising Clearance

Regardless of which CRRT machine is being used, optimising clearance isdependant on two factors. These include improving diffusion andconvection/ultrafiltration.

Improving Diffusion

Using filters with larger surface areas is one means of improving diffusion. 6

Currently Liverpool ICU stock consists of M100 and ST 100 filter sets. TheM100 circuits incorporate an AN69 hollow fiber filter. These filters arecomprised of Acrylonitrile and sodium methallyl sulfonate copolymer andhave a surface area of 0.9m2. The ST 100 sets are similar but have a surfacearea of 1.0 m2. The filter is comprised of identical materials, however also

includes the surface treatment agent polyethylene imine. 14This surfacetreatment aims to encourage heparin binding during priming that canultimately reduce heparin requirements for anticoagulation of the circuit.

This may also benefit patients who require heparin free dialysis. 15

A second means of improving diffusion involves utilising an appropriatedialysate fluid. Eg. Withholding addition of KCL to dialysate fluid when thepatient is hyperkalaemic so that serum potassium concentration remainshigher than that in the dialysate. K+will therefore be filtered off the patientfrom an area of high to low concentration.

Improving Convection/Ultrafiltration

Improving convection/ultrafiltration is largely accomplished through high

flow rates (Dialysate, Replacement, Ultrafiltration & Blood Pump). Asmentioned earlier pre dilution assists in achieving higher flow rates byreducing the viscosity of blood and hematocrit. Location and care of thevascath is also shown to influence flow considerably. 6,9


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Prolonging Filter Life

Prolonging filter life simply refers to preventing the filter clotting andmaintaining its functional ability to remove fluid and waste. Factors thatprolong filter life include:

High blood flow rates

Pre dilution and warming of fluid

Adequate Access

Anticoagulation 3,4,9

Anticoagulation

On priming the circuit 5000 units of heparin should be added to each1L bag of warmed normal saline

Unless the patient is coagulopathic or has been on CRRT in the past 4

hours, 2500 units of heparin should be administered as a bolus, viathe red pre filter port of the access line, as therapy is commenced.

A heparin infusion of 15000 units in 50ml 0.9% sodium chloride canbe administered according to ICU HEPARIN SODIUM protocol foranticoagulation of the dialysis circuit via the designated anticoagulantline of the circuit.

Aim for a pre filter APTT (from pre filter port or arterial line/patient)between 30-40 seconds. 10

NB: If patient is coagulopathic run heparin free CRRT- refer toprotocol for further precautions.

NB:Full information for anticoagulation of the dialysis circuit is available inICU HEPARIN SODIUM protocol. Please read and become familiar with this

protocol in conjunction with this package. (See appendix)

Discontinuing CRRT (Running Patient Off)

Refers to ending therapy either temporarily or permanently

Indications

When indications for CRRT are no longer present

When return pressures are elevated associated with filter clotting When alarms are indicating poor clearance

For procedures in theatre or CT 21


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Procedure

1. Observe standard precautions and aseptic technique. Use sterile gloveswhen disconnecting lines from the Vascath.

2.

Press 'stop' and choose to end treatment. The PRISMA will then promptyou to return blood to the patient after providing the following:

Attach a secondary giving set to 500mL bag of normal saline, addthree-way tap to the end of this line and prime.

Connect the red access line of the PRISMA circuit to the three-waytap, using aseptic technique.

Return blood by following on screen prompts

Remove circuit as per onscreen prompts.3. Flush each lumen of the Vascath with 10mL normal saline.4. Heparin Lock as per protocol

NB: If only a temporary disconnection and filter is still viable then connect

both lines to a three-way tap. Circuit can then be reconnected to patient asnormal when recommencing therapy. 21


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Self Test 6

Q1. What factors need to be manipulated in order to optimise clearance?

Q2. Describe methods of optimising clearance.

Q3. List four factors that can prolong filter life.

Q4. When would anticoagulation NOT be used?

Q5. What are the indications for terminating therapy?


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Common Alarms & Troubleshooting

There are various alarms that occur on both CRRT machines available inLiverpool ICU. The most common are discussed. Troubleshooting options areavailable in operators manual and instruction cards attached to each

machine. On screen prompts are also issued when alarms are triggered.

Access Pressure High

Possible Triggers include:

Red clamps closed

Blocked or kinked vascath secondary to clot or position

Blocked or kinked access line

High blood flow rate

High airway pressures

Patient coughing 9,13

Return Pressure High


Blue clamps closed

Blocked or kinked vascath secondary to clot or position

Blocked or kinked return line

High airway pressures

Filter Clotting/Clotted 9,13

Treatment obviously involves correcting the above problems. Wherefilter clotting is a possibility blood should be returned ASAP

Access or Return Disconnect

Triggered by low pressure in either of the lines. May indicate disconnectionsomewhere in the circuit. Check that all lines are connected securely.

Air in Blood


Fluid level in bubble trap below sensor

Air in circuit

Incomplete priming

Return line not installed in Air detector

Dirty sensor

Leaking connection 9,13

NB: This alarm must not be bypassed. It is a protective mechanismagainst the possibility of air embolism. Do not override untiltroubleshooting procedures in operators manuals have been fullyfollowed. 9,13


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There are many alarms that may be triggered during CRRT. If in doubt followthe on screen prompts or refer to the operators manual for guidance. Mostalarms that occur will be related to the following:

Vascath obstruction due to position of patient Access or return lines kinking or clotting

Bag placement on scales is incorrect

Clotting of the filter/circuit

Poorly placed blood leak detector

Air in the circuit

Periodic self test failure 9,13

Diaphragm Reposition Procedure

13

13

Performed if pod is accidentallyremoved or machine alarmsindicating problem

-ve Pods (Access & Effluent)

Stop Pump

Clamp line above & belowpod

Remove pod & clean port

Inject maximum of 1ccnormal saline into pod using20 g needle

Reinstall pod

Resume therapy

+ve Pods (Filter & Return)

Same as above

Aspirate maximum of 1cc


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Summary of Nursing Care for the Patient on CRRT

Continuous monitoring of haemodynamic parameters

Pressure area care and hygiene needs

Optimise blood pressure prior to commencing therapy

Colloid and Metaraminol precautions when running patient on When anticoagulation is running an initial APTT should be checked 4

hours after commencing therapy. 6 hourly APTT is attended thereafterand heparin infusion titrated according to protocol

Electrolytes, urea and creatine (EUC) and calcium, magnesium and

phosphate (CMP) should be checked 2 hours after commencingtherapy. 6 hourly EUC/CMP thereafter. Where electrolytes needreplacing, do so in accordance with ICU electrolyte protocols.

Strict monitoring of fluid balance to prevent excessive fluid losseswhen removing fluid- this should monitored hourly and documentedon CRRT observation chart to prevent incorrect fluid removal

secondary to scale malfunction. Attend CRRT observation chart monitoring pressures in particularthat may warn of filter clotting or access problems

Monitor Vascath site for signs of infection. Clean and dress asrequired as earlier described.

Monitor patients temperature and actively warm using a bear huggerblanket if necessary

Maintain standard precautions and aseptic technique when priming,connecting, disconnecting the circuit. This also applies whenchanging fluids or disposing of ultrafiltrate

As with all intensive care patients the MFASTHUG pneumonic shouldbe followed- i.e. Mouth care, Feeding, Analgaesia, Sedation,

Thromboembolism prophylaxis, Elevated bed head, Stress ulcerprophylaxis and Glucose control + Gut- aperients etc 2,5,8,17,20


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Self Test 7

Q1. List the common triggers for alarms on the CRRT machines.

Q2.How would you reposition the diaphragms on both positive andnegative pressure pods when required?

Q3. What nursing care is necessary for the patient undergoing CRRT?


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Answers

Self Test1

Q1. State the primary and secondary functions of the kidneys.

The primary role of the kidneys is to remove metabolic wastes and maintainfluid and electrolyte balance. The kidneys also have a role in Blood PressureControl, Red Blood Cell Synthesis, Bone Metabolism and Acid- BaseBalance.

Q2. Name the functional units of the Kidneys and list theircomponents.

The functional units of the kidneys are known as nephrons. The nephronconsists of a Glomerulus, Bowman Capsule, Proximal Convoluted Tubule,Loop of Henle, Distal Convoluted Tubule and Collecting Duct.

OrGlomerulus, tubule and collecting duct.

Q3. Discuss the processes involved in urine formation

Three process involved in urine formation include Glomerular Filtration,Tubular Reabsorption and Tubular Secretion. Glomerular filtration occursas blood passes through the glomerulus being filtered of fluid and solutes.

Tubular reabsorption and secretion occurs progressively through the areasof the tubule. Fluid, electrolytes and waste products are excreted as filtratedepending on the bodys requirements.

Self Test2

Q1. Define Acute Renal Failure

Acute renal failure (ARF) is a clinical syndrome, characterised by an abruptdecline in glomerular filtration rate (GFR). There is a subsequent retention ofmetabolic waste products and an inability to maintain electrolyte and acid-base homeostasis. Regulation of fluid volume isalso affected.

Q2. Describe 3 forms of acute renal failure and the associated causes

Prerenal ARF is largely related to systemic factors that limit blood flow andreduce glomerular filtration rate. Related causes may include hypotension,hypovolaemic shock, cardiogenic shock, septic shock and thrombosis thatresults in bilateral renal vascular obstruction.

Intrarenal ARF is the result of damage sustained at the site of the nephrons.This could be secondary to a number of conditions or nephrotoxinsincluding: Acute tubular necrosis, acute glomerulonephritis, acute corticalnecrosis, malignant hypertension, acute vasculitis, rhabdomyolysis, IVcontrast and aminoglycosides.


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Post renal ARF occurs secondary to obstruction that prevents excretion ofurine. This may relate to prostatic hypertrophy, renal calculi, tumour orblocked urinary catheter.

Q3. List the signs and symptoms of acute renal failure

Fluid and electrolyte abnormalities

Metabolic acidosis

Anaemia

Pruritis secondary to uremic frost

Nausea & vomiting

Confusion

LOC

Congestive heart failure resulting in acute pulmonary oedema

Self Test 3

Q1. What is renal replacement therapy?

Renal replacement therapy (RRT) is an extracorporeal technique of bloodpurification. Blood passes over a semipermeable membrane (filter) allowingsolutes and water to cross over to a collection side. There are variousmodalities included under the umbrella of RRT.

Q2. List advantages and disadvantages of continuous modalitiescompared to other forms of RRT

Advantages:

Better for haemodynamic instability Readily accessible

Effective fluid removal and clearance of solutes

Can be performed by ICU staff rather than specialised renal nurses

Disadvantages:

Patient mobilisation is limited

Access complications

Anticoagulation

Reduced blood flow rates secondary to small filters when compared toIHD

Q3. List Indications for CRRT

Fluid Overload, pulmonary oedema

Worsening Metabolic Acidosis

Hyperkalaemia

Worsening Azotaemia

Drug overdoses

Removal of toxins


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Q4. Describe the basic principles of fluid and solute removal involved inCRRT.

Diffusion involves the movement of small and middle molecule solutes froman area of high concentration to low concentration across a semipermeable-

membrane.Convection occurs withwater flow across a semi-permeablemembrane by hydrostatic pressure that drags solutes with it (the way awaterfall moves pebbles and sand). Ultrafiltration is the movement of fluidand solutes across a semipermeable membrane secondary to convection orhydrostatic pressure. Positive pressure pushes the fluid across wherenegative pressure pulls the fluid across. The force that pushes fluid andsolutes across the membrane is known as hydrostatic pressure. Themechanical blood pump on the dialysis machine creates this.

Q5. Describe the different modes of CRRT.

Slow Continuous Ultrafiltration utilises convection and ultrafiltration toremove fluid. It is indicated for fluid overload. SCUF does not requiredialysate or replacement fluids.

Continuous Venovenous Haemofiltration incorporates convection andultrafiltration to remove fluid and moderate solutes. Replacement fluid isused. This modality is indicated for moderate electrolyte imbalances, oliguriawhilst receiving TPN or blood and for patients in septic shock.

Continuous Venovenous Haemodialysis filters via diffusion. Fluid is removed

together with more aggressive solute removal. Replacement fluid is not used.CVVHD is warranted for fluid overload with haemodynamic instability,Azotaemia, electrolyte disturbances and acidosis.

Continuous Venovenous Haemodiafiltration uses both diffusive andconvective processes. Both replacement and dialysate solutions are used formaximum fluid and solute removal. This mode of CRRT is indicated for fluidoverload, pulmonary oedema, worsening metabolic acidosis, hyperkalaemiaworsening Azotaemia, drug overdoses and removal of toxins

Self Test 4

Q1. What is the importance of adequate access?

Good access that allows high flow rates through the circuit is one of the keyaspects in CRRT that effects blood flow, clearance and filter life.

Q2. State the appropriate name and functions of the red and bluelumens on a vascath

The red lumen is the arterial port also known as the access port. This lumen

supplies blood from the patient to the filter. The blue lumen is the venous


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port also known as the return port. Blood is returned via this lumen fromthe filter to the patient.

Q3. What are the three possible sites for vascath insertion? State the

advantages and disadvantages of each.

Internal Jugular Vein

Advantages:


Easy to visualise insertion site

Disadvantages:


Kinking can occur when the patient moves their head

Sometimes attains insubstantial blood flows secondary to variationsin central filling and intrathoracic pressures. Positive pressureventilation can make this more apparent.

Femoral Vein

Advantages:

Easily accessible by most clinicians

May allow greater blood flows

Disadvantages:

Prone to kinking, more so in the obese patient

Does not allow for patient mobility Difficult to visualise and dress insertion site

Higher incidence of infection secondary to the proximity to intestinalflora.

Subclavian Vein

Advantages:


Easy to visualise and dress insertion site

Disadvantages: Requires Chest Xray prior to use

Risk of pneumothorax on insertion

Risk of subclavian stenosis, which can impair suitability for an A-Vfistula on the affected side, if renal failure becomes chronic.

Sometimes attains insubstantial blood flows secondary to variationsin central filling and intrathoracic pressures. Positive pressureventilation can make this more apparent.

Q4. How would you troubleshoot a vascath?

Using aseptic technique, assess catheter patency by aspirating and flushing10ml of blood on the effected lumen to test resistance to blood flow. Further,flush 10ml 0.9% sterile normal saline. Where resistance is present, a clot


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may be obstructing the catheter, but more likely it is positioned against thevessel wall. Slightly withdrawing or rotating the catheter may overcome thisproblem. Where this fails to resolve the problem the catheter must bechanged. The lumens may be swapped, however this is only a temporarymeasure as there is a loss in clearance.

Q5. How would you heparin lock a vascath?

Apply standard precautions and utilise aseptic technique

Using 3 ampoules of 5000 units heparin in 1ml (15000 units/3ml)inject the stated amount (located on each port) of this solution intothe Vas Cath port. Label lumens as Heparin Locked

Self Test 5

Q1. What is the purpose of dialysate and replacement fluids?

Dialysate fluid is used as a means to encourage diffusive clearance.Replacement fluid is a pre or post dilution fluid used to replace losses inultrafiltrate.

Q2. State the two fluids available at Liverpool ICU for CRRT, includingthe major difference and the preparations required.

GAMBRO is the fluid that contains lactate as its buffer. HEMOSOL isconsidered lactate free and thus requires the addition of bicarbonate prior touse. This is accomplished by breaking the seal within the bag to mix thesolutions together. Both GAMBRO and HEMOSOL solutions require addition

of KCL when used as dialysate. 15mmol K+

is added to 5L of GAMBRO.20mmol K+ is added to 5L of HEMOSOL. Both make a final concentration of4mmol K+ /L. KCL is added to these fluids to reduce loss K+of throughdiffusion.

Q3. How do you prepare the vascath prior to commencing CRRT with anew circuit?

Once the circuit is primed and ready to connect, 5ml of blood should beaspirated and discarded to remove heparin from the line. Assess catheterpatency by aspirating and flushing 10ml of blood on the effected lumen to

test resistance to blood flow. Further, flush 10ml 0.9% sterile normal saline.

Q4. List the safety aspects of connecting and commencing therapy.

CRRT Machine should be plugged into an isolated power socket

When commencing therapy, colloid on a pump giving set should beconnected to patients intravenous access

10mg Metaraminol (Aramine) should be drawn up and readilyavailable. This in conjunction with colloid is precautionary, shouldthe patient become hypotensive. Inotropes can be titrated for controlof hypotension, if the patient is on them rather than utilising

Aramine.


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Q5. Differentiate pre dilution from post dilution including benefits anddisadvantages.

Pre-dilution involves administering replacement fluid prior to the filter. Thisthereby reduces the viscosity of blood and hematocrit and in effect may aidin preventing filter clotting. Unfortunately this method also dilutes theconcentration of solute in plasma, which can negatively impact on clearanceby reducing the diffusion gradient. In order to optimise clearance of solutes,replacement rate must be increased in order to increase the rate ofultrafiltration.

Post-dilution therefore involves administering replacement fluid after thefilter. This does not dilute solutes in plasma, however the ability for optimalclearance is lost when blood viscosity is not reduced and high flow rates are

then difficult to achieve. With reduced blood flow comes reducedultrafiltration. Utilising filters with larger surface areas in conjunction withthis method may improve clearance.

Q6. List the complications of CRRT.

Hypotension that may result from aggressive fluid removal

Electrolyte imbalances

Cardiac Arrhythmias

Anaemia secondary to haemolysis of red blood cells

Thrombocytopaenia secondary to platelet aggregation in filter

Hypothermia secondary to extracorporeal blood circulation Coagulopathy secondary to over heparinisation

Infection

Heparin induced thrombocytopaenia

Self Test 6

Q1. What factors need to be manipulated in order to optimiseclearance?

Regardless of which CRRT machine is being used, optimising clearance is

dependant on two factors. These include improving diffusion andconvection/ultrafiltration.

Q2. Describe methods of optimising clearance.

Using filters with larger surface areas and appropriate dialysate fluid canoptimise diffusive clearance. Improving clearance viaconvection/ultrafiltration is largely accomplished through high flow rates(Dialysate, Replacement, Ultrafiltration & Blood Pump). Pre dilution assistsin achieving higher flow rates by reducing the viscosity of blood andhematocrit. Location and care of the vascath is also shown to influence flowconsiderably.


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Q3. List four factors that can prolong filter life.

High blood flow rates Pre dilution and warming of fluid

Adequate Access

Anticoagulation

Q4. When would anticoagulation NOT be used?

Anticoagulation is not used if the patient is coagulopathic. A heparin bolusis not given if the patient has had CRRT within the last 4 hours.

Q5. What are the indications for terminating therapy?

When indications for CRRT are no longer present

When return pressures are elevated associated with filter clotting

When alarms are indicating poor clearance

For procedures in theatre or CT

Self Test 7

Q1. List the common triggers for alarms on the CRRT machines.

Vascath obstruction due to position of patient

Access or return lines kinking or clotting Bag placement on scales is incorrect

Clotting of the filter/circuit

Poorly placed blood leak detector

Air in the circuit

Periodic self test failure

Q2. How would you reposition the diaphragms on both positive andnegative pressure pods when required?

If the pump has not stopped with an alarm, it should first be stopped. Applyclamps above and below the affected pod. Remove the pod and clean theport. If the pod is negative (Access & Effluent), inject a maximum of 1ccnormal saline using a 20g needle into the pod. Conversely, if the pod ispositive then a maximum of 1cc should be aspirated from the pod. Followingthis step the pod can be reinstalled into the appropriate port and therapyresumed.

Q3. What nursing care is necessary for the patient undergoing CRRT?

Continuous monitoring of haemodynamic parameters

Pressure area care and hygiene needs

Optimise blood pressure prior to commencing therapy


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References

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Baldwin, I., Bridge, N., Elderkin, T. (1998). Nursing issues, practicesand perspectives for the management of continuous renalreplacement therapy in the intensive care unit. In Bonett, J.,Hattley, S., & Bastick, M. Continuous renal replacementinformation package. A quick guide to CRRT.(pp1-41) Gosford:NSCCH.

4. Bellomo, R., Baldwin, I., Ronco, C. (2001). Atlas of haemofiltration. InBonett, J., Hattley, S., & Bastick, M. Continuous renal replacementinformation package. A quick guide to CRRT.(pp1-41) Gosford:NSCCH.

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Bonett, J., Hattley, S., & Bastick, M. (2005). Continuous renalreplacement information package. A quick guide to CRRT.(pp1-

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Brunet, S., Leblanc, M., Geadah, M., Parent, D., Courteau, S., &

Cardinal, J. (1999). Diffusive and convective solute clearancesduring continuous renal replacement therapy at variousdialysate and ultrafiltration flow rates. Am J Kidney Dis. 34,486-492.

7. Cannon, J.D. (2004). Recognizing chronic renal failurethe soonerthe better. Nursing, 2004, 34(1), 50-53.

8. Campbell, D. (2003). How acute renal failure puts the brakes onkidney function. Nursing 2003. 33(1), 59-64.

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Castro, P., & Shunker, S. (No date). Continuous renal replacementtherapy. Workshop handout. Liverpool: LHS.

10.Crawley, T. Shunker, S. & Edgtton-Winn, M. (2004). Heparin sodium.ICU protocol. Liverpool: LHS.


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11.Glann, J.K. (2002). Renal disorders and therapeutic management. In

Urden, L.D., Stacy K.M., Lough, M.E. (Eds). Thelans criticalcare nursing- diagnosis and management. (pp745-777). Stlouis: Mosby.

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Henke, K. (2003). Renal physiology. Dimensions of Critical CareNursing 22(3), 125-132.

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Hospal. (No date) Renal intensive care- PRISMA. Filter instructionGuide, Gambro.

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[Online]. Available: http://193.15.174.148/index.html.

16.Kaplan, A.A. (2003). Renal failure. In F.S. Bongard, & D.Y. Sue.Current critical care diagnosis & treatment(2ndEd.). [Online].Available:http://online.statref.com/TOC/TOC.aspx?FxId=5&SessionId=7

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17.Kaplow, R., & Barry, R. (2002). Continuous renal replacementtherapies: a more gentle blood filtering technique allows forfewer complications. American Journal of Nursing. 102(11), 26-

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18.Lameire, N., Van Biesen, W., & Vanholder, R. (2005). Acute renalfailure. The Lancet. 365(9457), 417.

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workbook. In Bonett, J., Hattley, S., & Bastick, M. Continuousrenal replacement information package. A quick guide to CRRT.(pp1-41) Gosford: NSCCH.

20.Paton, M. (2003). Continuous renal replacement therapy: slow butsteady. Nursing 2003. 33(6), 48-50

21.Sommer, N., Edgtton-Winn, M., & Shunker, S. (2004). Continuousrenal replacement therapy (CRRT) using the prisma machine.

ICU protocol. Liverpool: LHS


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22.Toltec International. (2006). How haemodialysis works. [online]Available: http://www.toltec.biz/how_hemodialysis_works.htm(December, 2006).

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Appendix


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