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http://ccn.aacnjournals.org/cgi/external_ref?link_type=PERMISSIONDIRECT Personal use only. For copyright permission information: Published online http://www.cconline.org © 2007 American Association of Critical-Care Nurses 2007;27:61-80 Crit Care Nurse Susan Dirkes and Kimberly Hodge History and Current Trends Continuous Renal Replacement Therapy in the Adult Intensive Care Unit: http://ccn.aacnjournals.org/subscriptions/ Subscription Information http://ccn.aacnjournals.org/misc/ifora.shtml Information for authors http://www.editorialmanager.com/ccn Submit a manuscript http://ccn.aacnjournals.org/subscriptions/etoc.shtml Email alerts by AACN. All rights reserved. © 2007 ext. 532. Fax: (949) 362-2049. Copyright 101 Columbia, Aliso Viejo, CA 92656. Telephone: (800) 899-1712, (949) 362-2050, Association of Critical-Care Nurses, published bi-monthly by The InnoVision Group Critical Care Nurse is the official peer-reviewed clinical journal of the American by guest on May 26, 2011 ccn.aacnjournals.org Downloaded from

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http://ccn.aacnjournals.org/cgi/external_ref?link_type=PERMISSIONDIRECTPersonal use only. For copyright permission information:  Published online http://www.cconline.org© 2007 American Association of Critical-Care Nurses

2007;27:61-80Crit Care Nurse Susan Dirkes and Kimberly HodgeHistory and Current TrendsContinuous Renal Replacement Therapy in the Adult Intensive Care Unit:  

http://ccn.aacnjournals.org/subscriptions/Subscription Information

http://ccn.aacnjournals.org/misc/ifora.shtmlInformation for authors

http://www.editorialmanager.com/ccnSubmit a manuscript

http://ccn.aacnjournals.org/subscriptions/etoc.shtmlEmail alerts

by AACN. All rights reserved. © 2007 ext. 532. Fax: (949) 362-2049. Copyright101 Columbia, Aliso Viejo, CA 92656. Telephone: (800) 899-1712, (949) 362-2050,Association of Critical-Care Nurses, published bi-monthly by The InnoVision Group Critical Care Nurse is the official peer-reviewed clinical journal of the American

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http://ccn.aacnjournals.org CRITICALCARENURSE Vol 27, No. 2, APRIL 2007 61

Susan Dirkes is a clinical educator at NxStage Medical, Lawrence, Mass.

Kimberly Hodge is the Advanced Cardiac Life Support and Pediatric Advanced Life Sup-port senior educator for the Emergency Response Training Institute at Clarian Health,Indianapolis, Ind.

Corresponding author: Susan Dirkes, 6326 Sterling Dr, Newport, MI 48166 (e-mail: [email protected]).

To purchase electronic or print reprints, contact The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656.Phone, (800) 809-2273 or (949) 362-2050 (ext 532); fax, (949) 362-2049; e-mail, [email protected].

focus of intermittent hemodialysis

is to replace renal function by

removing excess water and wastes.

The standard of care for patients

treated with intermittent hemodial-

ysis may not be applicable to critical

care patients because of the nature

of the latter patients’ illness and

catabolic state, the presence of sys-

temic inflammatory syndrome with

or without sepsis, and other organ

failure.5 In this article, we review

treatment of ARF in critically ill

patients, indications for intermit-

tent hemodialysis and continuous

renal replacement therapy (CRRT),

and the use of other variations of

CRRT currently under investigation.

Management of ARFMedications

ARF can be managed in some

patients by nondialytic interventions

such as loop diuretics (furosemide

and bumetanide). Recently, the effect

of diuretics in critically ill patients

Susan Dirkes, RN, MSA, CCRN

Kimberly Hodge, RN, CCRN-CMC

Acute renal failure (ARF) is a

common complication in critically

ill adult patients in critical care units.

ARF is defined as a sudden decline

or cessation of renal function. Char-

acteristics include inability of the

kidneys to excrete wastes and main-

tain fluid, electrolyte, and acid-base

balance.1,2 Despite advances in treat-

ment, data from the past several

decades continue to indicate that

ARF still is associated with high

mortality rates, ranging from 25% to

90%.3,4 Factors that may influence the

rates include the increasing age of

patients and the existence of comor-

bid conditions (eg, diabetes, preex-

isting renal disease, vascular disease).1

Historically, the treatment of ARF

has been supportive. The primary

ClinicalArticle

Authors

Continuous Renal Replacement Therapy in theAdult Intensive Care Unit

History and CurrentTrends

This article has been designated for CE credit. A closed-book, multiple-choice examination follows this article, which tests your knowledge of the following objectives:

1. Identify indications for intermittent dialysis and continuous renal replacementtherapy (CRRT)

2. Review variations and advantages and dis-advantages of CRRT

3. Examine potential complications of CRRT

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with ARF has been questioned. Mehta

et al6 and Shilliday et al7 found that

the use of diuretics in critically ill

patients with ARF was associated

with an increased risk of death and

nonrecovery of renal function. If

medications are not effective, the

choice of treatment and dialytic

therapy should ideally mimic the

efficacy of the native kidney and, at

the same time, not delay the recovery

of renal function. Therapy should be

individualized according to each

patient’s urgency and need for the

therapy and hemodynamic tolerance.

Intermittent Hemodialysis

Intermittent hemodialysis is still

a commonly used treatment for ARF

in the critical care unit for some

patients. The dialysis is typically

done 3 times a week. This timing

evolved to ensure that patients were

treated sufficiently to provide an

“adequate” state of health.8 These

treatment principles applied to

patients in chronic renal failure, not

to critically ill patients.

Intermittent hemodialysis is also

used for many patients because it is

relatively inexpensive (approxi-

mately $130 per treatment, not

including staffing) and of short

duration (typically 3-4 hours).9

Treatment of a patient 3 times a

week allows for a considerable

increase in the serum levels of urea

nitrogen and creatinine and for vari-

ations in electrolyte, water, and acid-

base balance between treatments.

Orders for intermittent hemo-

dialysis typically require, at a mini-

mum, removal of the previous 24

hours’ fluid intake during the dialy-

sis treatment. Critically ill patients

are prone to hypotension because of

the severity of their illness. Therefore,

removal of 2 to 3 L/h of fluid in a

patient in an unstable condition

may make it difficult to use conven-

tional intermittent hemodialysis.10,11

As a result, critically ill patients

with ARF will not achieve adequate

water or waste removal with tradi-

tional dialysis.12 Repeated episodes

of hypotension during intermittent

hemodialysis also can lead to

ischemia of the nephrons each time

the dialysis is performed.2,13 There-

fore, the ability of the remaining

nephrons to survive, as well as the

potentially adverse effects of aggres-

sive fluid removal, should direct the

choice of therapy.

Continuous Renal

Replacement Therapy

As the search for better treat-

ments for ARF continues, research

findings are indicating that the tech-

nique and timing as well as the type

of renal replacement therapy used

may affect patients’ survival and

recovery of renal function.14-16 The

concerns about hemodynamic sta-

bility during hemodialysis, nephron

injury, and the inability to adequately

remove excess water and solutes

have led to the development of a

slower, less aggressive renal replace-

ment therapy: continuous renal

replacement therapy (CRRT).

CRRT is an extracorporeal

process in which blood is removed

from the arterial lumen of a catheter

by a peristaltic blood pump and

pushed through a semipermeable

membrane before being pumped

back into patients via the venous

lumen of the catheter. These catheters

are typically placed in the internal

jugular or subclavian vein. When the

blood passes through the membrane

(hemofilter or dialyzer), electrolytes

and small- and medium-sized wastes

are removed from the blood by con-

vection and diffusion. Fluid removal

is achieved by ultrafiltration at an

established hourly rate and on a con-

tinuous basis.17

Types of CRRTIn 1977, Kramer et al18 described

a therapy called continuous arterio-

venous hemofiltration in which a

patient’s own blood pressure moved

the blood from an artery to a vein

through a highly porous hemofilter.

The blood flow through the hemofil-

ter was driven by the patient’s mean

arterial pressure, and ultrafiltration

was achieved by raising and lower-

ing the drain bag in relation to the

patient. The blood flow rate was

slow because of frequent hypoten-

sion experienced by critically ill

patients. It resulted in a low driving

pressure of the blood through the

circuit, much less than what a blood

pump can achieve. This slow blood

flow limited the volume of ultrafil-

trate that could be obtained, which

limited the adequacy of the dialysis.

A major drawback to continuous

arteriovenous hemofiltration was

the use of a large catheter in a major

artery, commonly the femoral

artery, a practice associated with

risks for infection, distal thrombosis

formation, disconnection, and

exsanguination.

In the 1980s, a blood pump, such

as those used in intermittent hemo-

dialysis, and a double-lumen catheter

in a large vein were used to provide a

consistent blood-flow rate without

the risks associated with the arterio-

venous approach. This method of

CRRT was called venovenous hemo-

filtration and has been adopted as

the standard for CRRT.

62 CRITICALCARENURSE Vol 27, No. 2, APRIL 2007 http://ccn.aacnjournals.org

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CRRT mimics the functions of

the kidneys in regulating water, elec-

trolytes, and wastes by continuing

24 hours a day, for several days,

slowly removing fluid and solutes.

The indications that led to the devel-

opment of CRRT include patients

who had fluid overload, diuretic

resistance, hemodynamic instability,

and azotemia.2 Because fluid removal

with CRRT is much slower than with

intermittent hemodialysis, CRRT is

an ideal therapy for critically ill

patients in unstable conditions. For

example, a net ultrafiltration rate of

12.5 mL/min is required to remove

3 L of plasma water during 4 hours

of intermittent hemodialysis. The

same amount can be removed with

CRRT in 24 hours with a net ultrafil-

tration rate of 2 mL/min.19 Removing

fluid more slowly and in smaller vol-

umes in hours or days may provide

enhanced hemodynamic stability.

Membranes in CRRT

High-efficiency membranes are

used in CRRT for maximum water

and waste removal. High-efficiency

membranes include high-flux dialyz-

ers and hemofilters. The membranes

used are synthetic and biocompati-

ble.20,21 The capability of dialysis

membranes lies in the surface area,

membrane thickness, pore size and

density, and potential to adsorb pro-

teins.22 High-efficiency membranes

have both high membrane perme-

abilities and larger pore sizes and

therefore are desirable for CCRT. In

all methods of CRRT, as blood flows

through the hemofilter, plasma

water is filtered through the pores in

the hemofilter membrane and pro-

duces the ultrafiltrate. The ultrafil-

trate produced during CRRT is

composed primarily of water, elec-

trolytes, wastes, and some dialyzable

drugs.23

High membrane permeability

and large pore size provide excellent

clearance of small-molecular-weight

solutes and larger substances, up to

the maximum pore size.24,25 Examples

of small-molecular-weight substances

(<0.5 kd) are urea, electrolytes, vita-

mins, and certain medications. Large-

molecular-weight substances such as

albumin, red and white blood cells,

and drugs bound to proteins cannot

pass through a hemofilter membrane

(typically with a maximum pore size

of 50 kd) because of the large size of

the substances.26

Another potential benefit of the

use of high-permeability dialyzers

and hemofilters is the ability to

remove cytokines, which are middle-

molecular-weight substances, or

decrease their concentration by

adsorption to the membrane.27

These inflammatory cytokines, such

as interleukin-1β, interleukin-6, and

interleukin-8, contribute to sepsis

and may be altered or removed in

CRRT.28 Although no conclusive

data confirm the link between the

beneficial clinical effects observed

in patients with sepsis who have

CRRT, the effect of cytokine removal

by adsorption and the preliminary

observations of patients’ outcomes

are encouraging.29,30

Continuous Venovenous

Hemofiltration

Continuous venovenous hemofil-

tration (CVVH, Figure 1) is defined

as “a venovenous technique where

the ultrafiltrate produced during

membrane transit is replaced in part

or completely with appropriate

replacement solutions to achieve

blood purification and volume con-

trol.”31 In CVVH, convection and

ultrafiltration are used to remove

waste products. Convection is the

movement of solutes under pressure

through a membrane along with the

movement of water. Convective ther-

apies appear to have advantages

over other continuous therapies

because of the ability to remove a

wider range of solutes with the ultra-

filtrate, including some cytokines, a

characteristic that may affect

patients’ outcomes.32,33

Figure 1 System for continuous venovenous hemofiltration.

Replacement fluid

Fluid pump

HemofilterBloodpump

Ultrafiltratepump

Airdetector

To the patient

From thepatient

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Physiological fluids termed

replacement fluid are used to replace

the majority of ultrafiltrate removed

hourly, in order to prevent instabil-

ity and to replace electrolyte losses

during CVVH. Replacement fluids

generally consist of balanced elec-

trolyte solutions that closely resemble

the composition of the ultrafiltrate

lost minus the wastes.34 Replacement

fluids are infused either into the

arterial side of the circuit before the

hemofilter, a method called “predi-

lution/prefilter,” or into the venous

side of the circuit after the hemofil-

ter, a method called “postdilution/

postfilter.” Both methods of fluid

replacement achieve the goal of

replacing ultrafiltrate volume and

electrolytes while removing wastes

by convection.23,35

The predilution method of infus-

ing replacement fluid also provides a

continuous flush for the hemofilter

that dilutes the blood flowing through

the filter, a situation that may decrease

hemofilter clotting and increase the

clearance of solutes.36 Postdilution

infusion of solutions replaces fluid

and electrolytes but does not affect

clotting in the hemofilter. Increas-

ing the volume of ultrafiltrate pro-

duced in CVVH by increasing the

infusion of replacement fluid increases

clearance of both small- and middle-

molecular-weight substances by

solute drag.23,37,38

Currently, no electrolyte solutions

have been specifically approved by the

Food and Drug Administration for

infusion as replacement fluid. Solu-

tions that are used include lactate- or

bicarbonate-based or custom phar-

macy–mixed fluids. Because of the

lack of these approved replacement

solutions in volumes greater than 1 L,

the cost of mixing custom solutions

and the ability to provide large vol-

umes for patients’ treatment, some

physicians use purchased custom-

compounded pharmacy fluids in

large volumes or may use commer-

cial solutions as an off-label pre-

scription.

Continuous Venovenous Hemodialysis

In continuous venovenous

hemodialysis (CVVHD, Figure 2),

diffusion and ultrafiltration are used

to remove waste products. The fluids

used are known as dialysate fluids.

Dialysate is infused countercurrent to

the blood flow, into the outside com-

partment of the hemofilter to provide

a diffusion of wastes from the blood.39

The dialysate fluid is not infused into

the blood as in CVVH, rather it is

infused into the outside compart-

ment of the hemofilter or dialyzer. In

diffusive therapy, small molecular

wastes and electrolytes diffuse from

the high concentration in the blood

into the sterile dialyzing fluid on the

other side of the membrane and are

removed in the ultrafiltrate.

Historically, CRRT fluids were

run at lower flow rates, approximately

1 L/h, because no research was avail-

able that indicated better treatment

efficiency with higher rates and

because many older machines lacked

the option to increase flow rates.

When dialysate is run at lower flow

rates, such as 10 to 20 mL/min, the

dialysate is almost completely satu-

rated with the wastes.19 However, if

the dialysate is run at faster rates, 30

to 60 mL/min, the amount of small

molecular waste cleared increases.

Diffusion in CVVHD does not affect

clearance of larger molecular weight

substances. Research40,41 indicates

that increasing the dialysate rate

improves the efficacy of dialysis. Most

current CRRT equipment allows fluid

rates to be prescribed at the higher

rates, often up to 150 to 200 mL/min

to improve clearance.

For CVVHD, dialysate solutions

are available from a variety of sources.

The solutions may be mixed by hos-

pital pharmacies, peritoneal dialysate

solutions may be used, or commer-

cial solutions approved by the Food

and Drug Administration may be

purchased. Disadvantages of relying

on hospital pharmacies to mix either

64 CRITICALCARENURSE Vol 27, No. 2, APRIL 2007 http://ccn.aacnjournals.org

Figure 2 System for continuous venovenous hemodialysis.

Dialysate

Dialysate pump

HemofilterBloodpump

Ultrafiltratepump

Airdetector

To the patient

From thepatient

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http://ccn.aacnjournals.org CRITICALCARENURSE Vol 27, No. 2, APRIL 2007 65

dialysate or replacement solutions

include the high cost of labor to pro-

duce multiple liters of solutions con-

sistently and safely for ongoing CRRT

treatments. Peritoneal dialysate

solutions contain large amounts of

glucose and are lactate based, mak-

ing them less suitable for CVVHD.

Lactate solutions may worsen meta-

bolic acidosis in patients with meta-

bolic derangements and hepatic

failure.42 Bicarbonate-based solutions

are preferred for patients with hepatic

failure who cannot metabolize the

lactate and are also more physiologi-

cal than are lactate solutions. Several

commercial dialysate solutions in

large volumes are currently available,

such as PrismaSate (Gambro, Lake-

wood, Colo), Baxter Premixed

Dialysate and ACCUSOL (Baxter,

Deerfield, Ill), PureFlow (NxStage

Medical, Lawrence Mass), and Duosol

(B. Braun, Bethlehem, Pa). These

solutions provide a wide choice of

electrolyte compositions and the

choice of bicarbonate- or lactate-

based solutions to meet individual

patients’ needs.

Continuous Venovenous

Hemodiafiltration

In continuous venovenous hemo-

diafiltration (CVVHDF, Figure 3),

diffusion, convection, and ultrafil-

tration are used to remove wastes

and water. In this method, dialysate

and replacement fluids are used

simultaneously in various combina-

tions of rates. The goal is to offer

both a convective therapy, for clear-

ance of middle-molecular-weight

substances, and a diffusive therapy,

for removal of smaller substances.43

This therapy was widely used to pro-

vide a more efficient dialysis when

machines were limited in the ability

to infuse large quantities of fluids.

However, current technology for

CRRT provides the ability to infuse

fluid, either replacement or dialysate,

at higher rates to provide efficient

therapy. The ability to use only a sin-

gle fluid effectively also improves the

simplicity of performing CRRT.

Slow Continuous Ultrafiltration

Slow continuous ultrafiltration

(SCUF, Figure 4) is a hemofiltration

therapy used primarily for fluid

removal.44 No dialysate or replace-

ment fluids are used because wastes,

electrolyte balance, and acid-base

status may not be as critical an issue

in patients who have SCUF and in

patients who have other CRRTs. As

it is removed from the hemofilter,

ultrafiltrate is regulated to provide a

slow, continuous removal of plasma

water for diuresis, for example, 50 to

500 mL/h to achieve fluid balance.

SCUF is a good therapy of choice when

the only goal is fluid removal and

the patient does not have azotemia.

Patients who may benefit from

SCUF include those who are refrac-

tory to diuretics or who need adjunc-

Figure 3 System for continuous venovenous hemodiafiltration.

Dialysate

Dialysate pump

HemofilterBloodpump

Ultrafiltratepump

Airdetector

To the patient

From thepatient

Fluid pump

Replacement fluid

HemofilterBloodpump

Ultrafiltratepump

Airdetector

To the patient

From thepatient

Figure 4 System for slow continuous ultrafiltration.

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tive fluid removal, such as patients

with pulmonary edema, sepsis, heart

failure, or acute respiratory distress

syndrome who need diuresis to

improve pulmonary function.

Research45,46 indicates that excess

fluid that can be effectively and slowly

removed in critically ill patients may

improve oxygenation, cardiac out-

put, and mean arterial pressure. In

infants and children, research47,48

suggests that earlier intervention

with CRRT and fluid overload is

associated with greater survival,

indicating that fluid removal may

have a beneficial effect on outcome.

Anticoagulation for CRRTDuring CRRT, a patient’s blood

is outside the body and in contact

with artificial tubing and filters. The

result is stimulation of the coagula-

tion cascade and, more important,

the complement cascade if a biocom-

patible membrane is not used. The

goal for anticoagulation in CRRT is

to reduce clotting in the hemofilter

to maximize the CRRT circuit life.

Avoiding interruptions in CRRT by

preventing clotting provides contin-

uous therapy for the patient. Although

CRRT is intended to run for 24 hours

a day, the average therapy time is

actually closer to 16 hours a day

because of interruptions.49 These

interruptions can decrease the effect

and efficacy of CRRT markedly.50

CRRT can be performed with or

without anticoagulation. The choice

of anticoagulant depends on the

physician’s preference, the patient’s

condition, and the familiarity of the

nursing staff with anticoagulation

regimens.51 At times, the choice is to

not give a patient an anticoagulant

or use an anticoagulant in the CRRT

system. Anticoagulation may not

be indicated in patients who have

recently had surgery, have sepsis or

immunosuppression, or have hepatic

failure or thrombocytopenia. Another

reason to use anticoagulants is to

maximize the CRRT circuit life so

that the therapy is continuous for

several days. This maximization can

reduce the cost of the circuit tubing

and components, which often cost

approximately $150 to $200 or more

a set, and thereby reduce the cost of

patients’ treatment.9,13

Patients receiving anticoagula-

tion for CRRT should be monitored

on a routine basis. The most com-

mon tests used to monitor coagula-

tion are activated clotting time and

activated partial thromboplastin

time (aPTT).52 Activated clotting

times can be measured at the bed-

side but require that the critical care

staff maintain competency for

point-of-care testing. Activated clot-

ting times may be maintained at 180

to 220 seconds or according to insti-

tutional protocols.53 The degree of

anticoagulation is most commonly

determined by using aPTT. The

aPTT is maintained at 1.5 to 2 times

normal to maintain patency of the

circuitry.54 The bedside nurse is

responsible for monitoring any

adverse effects of anticoagulation,

including hemorrhage, formation of

hematomas, thrombocytopenia,

and allergic reactions.

Heparin is the most widely used

anticoagulant. Other options include

citrate, direct thrombin inhibitors,

and flushes with isotonic sodium

chloride solution. Ideally, anticoagu-

lation is done without producing sys-

temic anticoagulation in the patient.

The type of therapy, the anticoagu-

lant used, and the blood-flow rates

are all key components of keeping the

CRRT system free of clots (Table 1.)

66 CRITICALCARENURSE Vol 27, No. 2, APRIL 2007 http://ccn.aacnjournals.org

Table 1 Anticoagulation options in continuous renal replacement therapy

Option

Flushes with isotonicsodium chloride solution

Heparin

Regional citrate

No anticoagulation

Regional heparinization

Direct thrombin inhibitors(eg, Argatroban, lepirudin)

Comments

Not an anticoagulantHelps flush the hemofilter, possibly prolonging filter life

Easy, inexpensiveMay cause bleeding or heparin-induced thrombocytopenia

More labor intensive than other optionsRequires diligent monitoring of results of laboratory tests,

such as serum levels of sodium, ionized calcium, andbicarbonate

Requires infusion of calcium outside the circuitProvides good anticoagulationLarge sodium load occurs when trisodium citrate usedMay cause alkalosis

Variable successNeed brisk blood-flow rates and may not prevent clottingSimplest method

Heparin infused before the filter and protamine infusedafter the filter

Requires diligent monitoring of anticoagulation to keepsystem patent

Protamine may cause adverse reactions

Good anticoagulation, but much more expensive thanother options

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68 CRITICALCARENURSE Vol 27, No. 2, APRIL 2007 http://ccn.aacnjournals.org

Heparin

Heparin is the least expensive

anticoagulant and can be used either

systemically or regionally. When

heparin is used, the hemofilter may

be flushed with a dilute heparin

solution continuously or intermit-

tently. Systemic heparinization

includes infusing heparin into a sep-

arate intravenous access or into the

arterial side of the CRRT circuit.

Infusion of the heparin into the arte-

rial side of the CRRT circuit allows

mixing of the heparin with the blood

from the patient before the blood

reaches the filter (prefilter). The

heparin can be infused via an intra-

venous pump or a syringe pump,

depending on the CRRT system

used. Systemic heparinization pro-

vides anticoagulation of the circuit

as well as for the patient.

Heparin-induced thrombocy-

topenia is a complication of heparin

therapy. This complication is well

documented and therefore has lim-

ited the popularity of heparin for

anticoagulation in recent years.55

Heparin-induced thrombocytopenia

occurs when antibodies to heparin

bind to coagulation factor IV on

platelets, causing platelet activation

and aggregation.56 These changes in

turn cause the generation of venous

and arterial thrombi and a decrease

in the platelet count. Even after

heparin is discontinued, the platelet

count may remain low. Consequently,

in patients with heparin-induced

thrombocytopenia, the concerns for

thrombi and the associated costs of

changing CRRT circuits frequently

have led to the use of other anticoag-

ulants in CRRT.

Regional heparinization involves

use of an anticoagulant in the circuit

only, not systemic heparinization in

the patient. Heparin is infused directly

via a syringe or an intravenous

pump into the circuit blood pre-

filter. Protamine, a heparin antago-

nist, is delivered via an intravenous

pump into the circuit near the

catheter on the return blood line to

deactivate the heparin.57

Anticoagulation monitoring for

regional heparinization requires

determining the aPTT of blood from

the patient (eg, blood obtained via a

peripheral site or an arterial

catheter) and the aPTT of blood in

the CRRT circuit (usually from the

postfilter preprotamine infusion

side of the CRRT circuit) regularly.

The goal in regional heparinization

is a normal aPTT for the patient and

an aPTT of approximately 100 sec-

onds for the postfilter level. Advan-

tages of monitoring of aPTT in both

the circuit and the patient include

“tight” heparinization, that is, the

heparin is not sent to the patient,

and therefore anticoagulation occurs

only in the circuit. Disadvantages

include the requirement for meticu-

lous monitoring of laboratory

results and frequent adjustment of

dosage of both the heparin and the

protamine.

Direct Thrombin Inhibitors

Argatroban (GlaxoSmithKline,

Research Triangle Park, NC) and lep-

irudin (Refludan, Berlex Pharmaceu-

ticals, Richmond, Calif ) are both

direct thrombin inhibitors. Direct

thrombin inhibitors are used for

their anticoagulant properties in

patients with heparin-induced throm-

bocytopenia who are undergoing

CRRT and require anticoagulation.

Lepirudin is cleared by the kidneys

and therefore may not be the drug of

choice for patients in ARF. Arga-

troban is eliminated by the liver and

is therefore more suitable for use in

patients with renal failure.56 Both

Argatroban and lepirudin are infused

via an intravenous pump into the

arterial or access side of the CRRT

system. Both drugs are considerably

more expensive than heparin.

Citrate

Citrate is also used in CRRT

because of the compound’s excellent

anticoagulant ability and potential to

prolong circuit life. Calcium is an

essential component of the clotting

cascade.58 Citrate binds to the calcium

in the patient’s blood within the CRRT

system and prevents clotting. Citrate

is infused prefilter into the CRRT sys-

tem, and calcium is typically infused

via another intravenous line outside

the circuit. Ionized calcium levels are

routinely monitored because the ion-

ized form of calcium is a the biologi-

cally active form of calcium and

accounts for about 50% of the calcium

in the blood in normal conditions.59

Citrate is available as a trisodium

citrate or as anticoagulant citrate

dextrose formula A. Trisodium cit-

rate has a higher sodium content

than does anticoagulant citrate dex-

trose formula A (420 mmol/L vs

112.9 mmol/L).51 Citrate is used in

CVVH, CVVHD, CVVHDF, and

SCUF. Citrate can be used as a replace-

ment fluid that contains less sodium

than normal.60 In CVVHD, a dialysate

that also has less sodium than normal

may be used to manage the sodium

in the citrate solution. Typically,

calcium-free solutions are preferred

in CRRT to prevent interaction with

the infused citrate. Some clinicians

use replacement or dialysate solu-

tions containing calcium because the

amount of calcium in these solutions

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is small and unlikely to affect the

efficacy of the citrate.61

Alkalosis is a potential complica-

tion of CRRT and, in particular, cit-

rate anticoagulation because the

body metabolizes citrate into bicar-

bonate.62,63 The resulting alkalosis

can be treated by administering

sodium chloride to provide hydro-

gen ions to produce hydrochloric

acid, infusing hydrochloric acid, or

reducing the citrate infusion rate.23,64

Citrate anticoagulation in patients

with hepatic failure or with lactic

acidosis may be contraindicated

because these patients may not be

able to metabolize citrate.54 An

essential requirement of citrate anti-

coagulation is diligent monitoring of

all laboratory values, including lev-

els of ionized calcium and sodium

and acid-base status.

Flushes With Isotonic

Sodium Chloride Solution

When a patient’s condition war-

rants that no anticoagulant be used,

the circuit may be flushed at intervals

with small boluses of isotonic sodium

chloride solution to reduce stagna-

tion of blood in the hemofilter or

dialyzer and keep the circuit free of

clots. Some protocols dictate that

when no anticoagulant is used, the

circuit should be flushed with 50 to

100 mL of isotonic sodium chloride

solution each hour to reduce stagna-

tion of the blood in the membrane

itself. Isotonic sodium chloride solu-

tion is not an anticoagulant, so this

maneuver may deter clotting in the

hemofilter, but it also increases the

volume of fluid intake for the patient.

Maintaining the patency of the

CRRT circuit for a patient who is not

given an anticoagulant may pose a

challenge. Other options to reduce

clotting in the circuit include the use

of blood tubing that minimizes the

air-blood interface, such as eliminat-

ing the arterial or venous air traps.

Tubing designs that provide methods

for air removal without using a large

air-blood interface and use of circuit

design in which the blood flow moves

in straight lines instead of around a

blood pump may reduce stagnation

and pooling of the blood as the blood

flows through the circuit. Because

replacement fluid is infused directly

into the blood prefilter in CVVH,

preventing clotting in the hemofilter

by diluting the blood may be help-

ful. Use of a well-placed, large-bore

catheter also can help streamline

blood flow from the patient and

back to the patient.

Fluid Management in CRRT

Most patients undergoing CRRT

are oliguric, anuric, and possibly

volume overloaded. The volume of

hourly ultrafiltrate removed depends

on an hourly fluid-balance calcula-

tion and an assessment of the patient’s

volume status. Fluid management in

CRRT typically involves hourly cal-

culation of the patient’s non-CRRT

system intake (eg, infusions , medica-

tions, feedings) plus fluid loss ordered

by the physician minus non-CRRT

system output (eg, urine, drainage

fluid, blood loss).23 Excess fluid vol-

ume to be removed in a patient with

fluid overload is usually termed “net

loss” and is ordered by a physician.

An example of net loss volume

ordered may be 25 to 200 mL/h

more than the hourly intake to ensure

a slow and gentle removal of the

excess fluid volume (Table 2).

The CRRT system infuses and

removes fluid after the fluid balance

is calculated and the desired volumes

are input to the system. The system

monitors the volume of the dialysate

and/or replacement fluids infused

and the volume of fluid removed on

an ongoing basis. Scales or balancing

chambers are used to manage the

administration and removal of fluid.

Any volume of fluid infused outside

the CRRT system, such as infusions,

tube feedings, boluses, and medica-

tions, is not accounted for unless the

volume is programmed into the

machine to be removed.

If a scale system is used, the

scales balance the weight of the vol-

ume of fluid programmed to be lost

on the infusion scale and the weight

gained on the output scale. In a bal-

ancing chamber system, the balance

chambers empty and fill precisely, to

balance the fluid volume programmed

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Table 2 Typical calculation of fluid balance for continuous renal replacementtherapy

Variable

A: All intake of fluid (eg, infusions, antibiotics, tube feedings, anticoagulants)

B: Desired fluid loss ordered by physician

C: Output in previous hour (eg, chest tubes, drains, nasogastric tubes)

Programmed fluid output

D: Actual fluid volume achieved

Actual net fluid lost: A – C – D

80

50

10

120

110

-40

Example, mL

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in and out, ensuring that the fluid

volume desired is accurate.

In either type of system, to verify

accuracy, a nurse can monitor the

therapy history, if available, for the

volume of actual fluid removed at

the end of each hour and compare

that volume with the volume that

was programmed. The volumes pro-

grammed to be infused and removed

by the system should be within the

manufacturer’s error specifications

of the system in use. If the volumes

are incorrect, or if the nursing assess-

ment indicates an error, additional

troubleshooting is required to achieve

the patient’s goals and to ensure the

patient’s safety. Every time an alarm

occurs, or the pumps stop on the

system, the fluid removal is also

stopped. Therefore, under certain

conditions, the programmed volume

of fluid to be removed may not be

the volume that was removed that

hour. Regardless of the type of system

used, the fluid balance should be cal-

culated hourly or according to the

institutional standard to monitor

the patient’s status and fluid balance.

Before CRRT is started, patients

should have a complete nursing

assessment (Table 3). The assessment

includes evaluation of the fluid status

and the volume of fluid the patient is

receiving each hour, the patient’s base-

line blood pressure, dosages of any

vasopressors being administered,

weight (“dry” weight before admission

and current weight), presence of

edema, central venous pressure, pul-

monary artery occlusion pressures,

cardiac index, and cardiac output if

the patient has a pulmonary artery

catheter in place. Other helpful meas-

urements include arterial blood gases,

arterial oxygen saturation, and mixed

venous oxygen saturation. Once CRRT

is started, ongoing measurements of

these parameters indicate the patient’s

tolerance of the procedure as well as

any improvement in fluid status.

Decreases in blood pressure,

central venous pressure, pulmonary

pressures, and weight may indicate

that fluid is being lost and the patient

is experiencing the benefits of CRRT.

A marked decrease in blood pressure,

mixed venous oxygen saturation, or

arterial oxygen saturation; an increase

in edema; or weight gain may indi-

cate that the therapy objectives are

not being achieved or that the circuit

is not functioning properly. In this

instance, a physician should be noti-

fied and fluid removal should be

decreased or stopped until the

patient’s condition becomes more

stable. Because one goal of CRRT is

to reduce fluid overload, the bedside

nurse should discuss the possibility

of reducing intake to minimal vol-

umes of fluids if at all possible and

concentrating medications and infu-

sions to minimize fluid intake.

Mechanical failures can occur if

alarms are ignored or bypassed

without determining the cause of the

alarms. If scales are not properly cal-

ibrated, the volumes of fluid admin-

istered and removed may not be the

programmed volumes. Bypassing

alarms without correcting the cause

of the alarm is a safety hazard.

Hypothermia in CRRTHypothermia is a complication

of CRRT.73,74 The typical blood circuit

can contain anywhere from 110 mL

to 200 mL or more of blood outside

the body at any time, a situation that

contributes to cooling of the patient.

Solutions such as replacement fluid

and dialysate are used at room tem-

perature. Infusion rates of 2 to 5 L/h

or more provide a more efficient

treatment than do slower rates; how-

ever, such large volumes of fluid can

quickly lower a patient’s temperature

if the fluids are not warmed.75,76

Effects of hypothermia include dys-

function of clotting factors and

platelets, activation of fibrinolysis,

and cardiac dysrhythmias.77 Some

CRRT manufacturers offer a blood

warmer for the blood in the circuit,

but most systems have some type

of plate or convective warmer for

warming the therapy fluids.

Before CRRT is started and once

it has begun, the patient’s tempera-

ture should be routinely monitored

and the warmer temperature

increased as necessary to keep the

patient’s temperature near normal.

If increasing the warmer temperature

does not correct the hypothermia

adequately, or fluid warming options

are not available, warming blankets

and increases in the room tempera-

ture may be used. Nursing tasks

include monitoring the patient’s

temperature, implementing warm-

ing interventions if needed, and

monitoring for signs and symptoms

of infection (eg, increased white blood

cell counts), because the patient’s

temperature is masked by the cool-

ing effect of the circuit.

Air EmbolusAir embolus can occur if a patient

receives air in the blood returned.

CRRT systems have air detectors

built in to detect even microbubbles

of air. If the system’s safety mecha-

nisms are bypassed, a patient can

receive an air embolus. Alarms can

occur if the air is not properly

removed from the blood circuit dur-

ing priming or if a port in the circuit

is loose or open. Air also can occur

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Table 3 Nursing management during continuous renal replacement therapy (CRRT)

Assessment

Overall assessment

Cardiovascular assessment

Respiratory assessment

Gastrointestinal assessment

Renal/ fluid volume assessment

Neurological assessment

CRRT fluid balance calculations

Nursing management

Obtain information on the following:Past medical illnessesCurrent diagnosesCurrent therapiesMedicationsLaboratory valuesAllergies

Determine the following:Blood pressure, heart rate, cardiac rhythm,Central venous pressure, pulmonary arterypressures, stroke volume, cardiac index/cardiacoutput, peripheral pulses

Measure or calculate the following:Oxygen saturation as measured by pulse oxime-try, fraction of inspired oxygen, carbon dioxidelevels, PaO2, ventilator settings, respiratory rateand effort, arterial blood gases, ratio of PaO2 tofraction of inspired oxygen

Assess gastrointestinal function and nutritionalstatus

Assess or determine the following:EdemaBody weightUrine output, fluid intakeFluid losses (eg, blood loss, drainage fluid)

Calculate CRRT fluid balance

Assess or obtain the following:MentationScore on Glasgow Coma ScalePainMedication effects (especially if patient is

receiving sedatives or paralytics)

Calculate fluid balance once an hour or per insti-tutional policy

Rationale/comments

Information obtained about the patient’s medicalhistory and current treatments can provideinformation about the effect of the therapy

Knowledge of the patient's normal values andcurrent status helps to follow trends, instead ofindividual values

The patient's cardiac status and pulmonary pres-sures indicate the effect of the fluid removal andthe patient's tolerance of the therapy

Too much fluid removed can decrease bloodpressure significantly65

Respiratory status and parameters can indicatepositive effects of the therapy

Unwanted changes in arterial blood gases, devel-opment of acute respiratory distress syndrome,and increases in pulmonary pressures indicateadverse effects of overhydration

Adequate nutritional balance is important to pro-mote wound healing and provide proper meta-bolic function

Ongoing assessment of fluid balance helps deter-mine the effect of the therapy and the patient'stolerance of it

Prescribed fluid-balance goals should be com-pared with achieved goals

A physician should be notified if fluid goals can-not be achieved because the patient’s conditionis unstable.

Patients undergoing dialytic therapies canbecome confused as serum urea nitrogen levelsincrease or decrease

This symptom occurs because during dialysis theosmolality of cerebral spinal fluid decreasesmore slowly than the osmolality of the blood66

Fluid gains may be indicated by increases inblood pressure, pulmonary capillary wedgepressure, and central venous pressure and adecrease in arterial oxygen saturation

Fluid losses may be indicated by decreases inblood pressure, central venous pressure, andpulmonary capillary wedge pressure

Patients’ weight often increases as fluid is gained,and an increase in edema may occur

Fluid-balance calculations are a potential sourceof error in CRRT

Incorrect calculations can cause unwanted gain orloss of fluid

Some patients do not tolerate prescribed fluidremoval

A physician should be notified about the effect ofthe prescribed fluid loss 44,65

Continued

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Table 3 Continued

Nursing management

Observe or check for the following hourly:Blood-flow rateVenous or return pressuresArterial or access pressuresFilter pressures (if applicable) Balance pressures (if applicable)Effluent pressuresColor of the blood in the circuitPresence of air

Assess for hypothermia and hyperthermiaUse a warmer for fluid or blood if indicated

Monitor catheter patency before and during CRRTand at disconnection of the CRRT system

Monitor access pressures hourly to assesscatheter flow and detect access problems

Manage catheter dressing changes according toinstitutional policy

Check for the proper solution, dialysate, orreplacement fluid and the proper infusion site

Be sure laboratory work is done routinely or perinstitutional protocol to assess the effectivenessof the therapy

Check the solutions to make sure they are thecorrect prescription and are infusing into thecorrect port on the circuit: dialysate into thedialysate compartment and replacement fluidinto the prefilter or postfilter infusion ports intothe blood

Provide proper circuit care and interventions toprevent nosocomial infection

Determine the cause of all alarms

Assessment

Ongoing circuit monitoring

Body temperature

Dialysis catheter care and patency

Monitoring of electrolytebalance and dialysis solutions

CRRT circuit care and management

Alarms

Rationale/comments

The documentation in CRRT is not individually ineach hourly value, but in the trends

Changes in pressures (ie, increases in filter, balance, and effluent pressures) can indicateclotting

Pressures can also alert nurses about disconnec-tion or catheter dysfunction

Blood-flow rates and fluid rates may have to beadjusted according to prescription

The color of the blood can indicate clotting (eg,the blood becomes very dark)

Air should be assessed continually

The patient’s blood is outside the body in a largecircuit

Hypothermia is a common complication of CRRTMaintaining body temperature promotes healing

and helps maintain normal coagulation and nor-mal laboratory values

Colder patients may experience cardiac arrhyth-mias and are prone to using more energy inaddition to increasing cardiac output67,68

Patency of the catheter can affect the effective-ness of the therapy

Patency can be quickly evaluated by flushing 10mL of isotonic sodium chloride solution intoeach lumen of the catheter and assessing resist-ance by quickly pulling back the blood into thesyringe (remove anticoagulant first if applicable);blood should quickly and easily fill the syringe

Aspiration of air bubbles or a “catch” in aspiratingblood into the syringe may indicate a problemwith the catheter69,70

The type of solution used in CRRT can have a sig-nificant effect on a patient’s electrolyte levels

Monitoring laboratory values can assist in pre-venting sudden changes in electrolyte levels andprovide for prompt intervention65,71

All circuit interventions require using precautionssuch as gloves, masks, and aseptic or steriletechniques to protect the patient from exposureto infectious agents

Patients receiving CRRT have a higher risk ofbloodstream infections than other patients do72

Nurses who provide care for patients receivingCRRT should be able to troubleshoot alarms

Overriding alarms without investigating the causeis a safety hazard

The alarms should also be distinct and loudenough to be differentiated from other alarms inthe room

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in the circuit if the access cannot

provide the blood flow programmed

on the machine. In this situation,

the blood pump will run, but a vac-

uum is created, causing air to move

through the circuit. In each of these

situations, the nurse caring for the

patient is responsible for trouble-

shooting the system to determine

the source of the air or for checking

the help screens on the system to

determine if therapy can be resumed.

After the system is primed and

brought to the bedside and before

the connection with the patient is

established, the circuit should be

checked to ensure that all air has

been removed. It is imperative to

verify that the arterial or access side

of the access tubing is securely con-

nected to the catheter and, even

more important, that the venous or

return side of the tubing is securely

attached to the catheter. If the venous

side of the blood tubing is not con-

nected securely to the catheter, an

air embolism can occur because the

blood will have traveled past the

machine’s air detector. Nurses must

continually assess the circuit tubing

for the presence of air.

Minimizing Blood Loss in CRRTMinimizing blood loss in patients

receiving CRRT is always a priority.

Prompt attention to alarms and

knowledge of troubleshooting can

prevent loss of blood in the circuit.

Nurses caring for a patient receiving

CRRT should know how to perform

an automatic or manual return of

the patient’s blood when CRRT is

discontinued or the circuit is clotted.

As mentioned earlier, some circuits

can hold 200 mL or more of blood.

Ongoing blood loss due to failure to

rinse the blood back to the patient

or to an inability to detect signs of

clotting in the hemofilter is detri-

mental to the patient and may affect

the patient’s safety. Nurses’ yearly

competency testing should include

a review of rinsing patients’ blood

back in addition to a review of

machine alarms.

Transport ProceduresAt times, a patient receiving CRRT

may need to go out of the critical

care unit for a diagnostic procedure

or test (eg, computed tomography

or angiography). Before the patient

leaves the critical care unit, the con-

nection with the CRRT system is dis-

continued, and the patient’s blood is

returned to the patient by flushing

the blood back with isotonic sodium

chloride solution. The machine is

placed in a recirculation mode while

the patient is away. When the patient

returns to the critical care unit, the

system is taken out of recirculation

mode, the connection between the

patient and the machine is reestab-

lished, and therapy is resumed.

Flushing the patient’s blood back in

this situation not only minimizes

blood loss but also allows maximum

use of the CRRT circuit if the circuit

is not clotted.

Institutions should have protocols

in place to guide the length of time

CRRT can be discontinued while the

isotonic sodium chloride solution

recirculates. Protocols can be devel-

oped by using the manufacturer’s

guidelines and recommendations

from the infection control service

and the blood bank.

Innovative Developments With CRRT

Timing of therapy, early initiation

of renal replacement therapy, and

the adequacy of dialysis (eg, “dialy-

sis dose”) may affect patients’ out-

comes.78-81 The impact of adequate

amount or dose of dialysis in ARF

has been long debated. In CRRT, an

adequate dose is considered the

amount of dialysis, with fluids, based

on the patient’s weight required to

provide a therapeutic treatment, as

opposed to conventional dialysis in

which not only the patient’s weight

but also the time on dialysis is taken

into account.35,79 Some think that the

actual dose of dialysis delivered in

ARF is low and is strongly affected

by the patient’s underlying disease

process, hypercatabolic state, hemo-

dynamic instability, and volume

overload.1,14,82

The importance of dose of dialy-

sis is being examined in a random-

ized trial83 by researchers at the

Department of Veterans Affairs and

the National Institutes of Health.

The purpose of the trial is to deter-

mine the effect of conventional dial-

ysis dose versus intensive dialysis on

patients’ outcomes. The aim is to

compare traditional methods of

dosing in CRRT and intermittent

hemodialysis, as well as in slow

extended dialysis.

Other dose-related research sug-

gests that higher blood-flow rates

(200-300 mL/min) can enhance

clearance in CRRT. These higher

blood-flow rates combined with

fluid infusion rates determined on

the basis of body weight may improve

morbidity and mortality and also

preserve renal function. Ronco et al84

studied administration of replacement

fluid at rates of 20, 35, and 45 mL/kg

per hour with use of moderate blood-

flow rates in CRRT. In patients given

fluids at rates of 20 mL/kg per hour,

survival was 41%, whereas in patients

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given fluids at 35 and 45 mL/kg per

hour, survival was 57%. In addition,

90% or more of the survivors in the

35 and 45 mL/kg per hour group

had full return of renal function. The

weight-based fluid doses used in the

study84 were higher than the smaller

volumes of fluids thought to be ben-

eficial in the past.

Slow Extended Daily Dialysis

A therapy that some think pro-

vides the same or similar benefits

of 24-hour CRRT is termed slow

extended daily dialysis (SLEDD) or

“SHIFT” therapy, because the therapy

is completed during a single nursing

shift. SLEDD is done exactly as CRRT

is but is completed in a shorter time,

such as 8 to 12 hours instead of 24

hours of continuous treatment. Com-

pared with other methods of CRRT,

SLEDD requires higher fluid-flow

rates, higher blood-flow rates, and

higher hourly volumes of fluid

removed to condense the treatment.85

The shorter duration allows patients

to be treated with renal replacement,

for example, during the night shift

but also be free for tests, rehabilita-

tion, or discontinuation of ventilator

support during the day.

Diligent assessment of patients’

hemodynamic stability and fluid-

volume status is imperative when

SLEDD is used because compared

with other CRRT methods, approxi-

mately double the amount of fluid

may need to be removed in a shorter

time. During SLEDD, anticoagulant

may not be required because of the

shorter treatment time. Some

researchers86,87 have indicated that

SLEDD or SHIFT therapy combines

excellent waste removal and supports

cardiovascular stability and is still as

efficient as a 24-hour CRRT.

Nonrenal Indications for CRRT

Novel approaches of using CRRT

to treat sepsis have been proposed.

A method of high-volume ultrafiltra-

tion of 4 to 6 L/h for 6 to 8 hours

termed pulse hemofiltration may pro-

vide benefits such as elimination of

cytokines and middle-molecular-

weight substances known to cause

sepsis.88-90 Researchers91,92 continue to

examine using continuous hemofil-

tration to remove inflammatory

mediators in patients with sepsis.

Ronco et al93 suggest that the

management of patients with multi-

organ dysfunction syndrome should

focus not only on renal replacement

but also on a multiorgan support

therapy. Multiorgan support therapy

is based on the principle that all

organs share one thing in common:

contact with blood. Therefore, blood

purification and modulation of the

blood composition may have a

potential effect on all body organs.

On the basis of this principle, CRRT

may support several organs at one

time by early detection and correc-

tion of the abnormalities that occur

in multiorgan dysfunction syndrome.

The results of other studies94-96

suggest that sepsis can be treated by

using hemoperfusion. In hemoper-

fusion, a plasma filtrate sorbent fil-

ter is used in place of a hemofilter on

a CRRT-type circuit. In hemoperfu-

sion, adsorption of the solutes is a

primary mechanism of cytokine

clearance. The sorbent filter used

can be either charcoal or a synthetic

material. The filters adsorb cytokines

and appear to improve survival in

animal models of sepsis.97

A similar treatment for sepsis is

coupled plasma filtration.98 In this

treatment, plasma is filtered to

improve blood purification; blood is

passed through a hemofilter-type

membrane with larger pores so that

the blood is separated from the

plasma water and proteins, which

are removed. The plasma is then

pumped through another filter to

remove water and smaller molecular

weight substances. Because the sub-

stances removed are larger than

those removed in CRRT alone, the

benefit of coupled plasma filtration

may be an increase in the removal of

cytokines from the plasma of patients

who have sepsis. This model is based

on the benefits of plasmapheresis in

critically ill patients.99

Treatment of decompensated

heart failure with ultrafiltration has

been studied in the past and currently

is being examined more closely.100,101

Patients who have myocardial dys-

function or congestive heart failure

are often refractory to conventional

therapy (eg, diuretics and inotropic

agents). CRRT for the removal of

excess fluid can improve myocardial

elasticity and cardiovascular stabil-

ity and optimize fluid balance for

patients who may also have some

degree of renal impairment.102 Some

applications of this therapy include

the use of traditional CRRT machines

to perform SCUF for short periods

and the use of more specialized

equipment and peripheral intra-

venous blood access for simple

removal of plasma water.

The use of a bioengineered artifi-

cial kidney is yet another exciting

area of research.103 Humes et al103

have performed research in the

treatment of patients in ARF in

which CRRT is used in tandem with

a bioartificial kidney, known as a

renal tubule assist device. CRRT can

replace some functions of the kidneys,

such as water and waste removal,

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but it does not provide the metabolic,

immunological, or endocrine func-

tions of the kidneys. This bioartifi-

cial kidney contains human renal

proximal tubule cells that are grown

and seeded inside the fibers of a con-

ventional hollow fiber dialyzer. Humes

et al postulate that when the tubule

cells are bathed in ultrafiltrate from

the CRRT circuit, the cells act similar

to a human kidney. The use of human

renal tubule cells may provide a

dynamic, interactive, and individu-

alized therapy that responds to the

pathophysiological conditions of

critically ill patients, reducing mor-

bidity and mortality by providing a

more complete renal replacement

therapy.104,105 Phase 2 clinical trials

with the bioartificial kidney have

recently been completed, and some

results are promising.

Studies106,107 to date have indi-

cated that mortality does not differ

between patients who have had

CRRT and patients who have had

intermittent hemodialysis, but criti-

cally ill patients may experience

other benefits from CRRT that are

not possible with intermittent

hemodialysis. Although CRRT has

many benefits, like any other ther-

apy, it does not guarantee survival.

Patients requiring CRRT are often in

a tenuous situation, and once CRRT

is started, the therapy may or may

not be discontinued without result-

ing in death. The decision to initiate

CRRT requires clear and explicit

understanding by patients and their

families about the indications for

the therapy and the potential that

the therapy may or may not affect

recovery. Critical care nurses have a

responsibility to advocate for

patients and patients’ families,

encourage questions, and partici-

pate in education of patients and

patients’ families about CRRT.

Recent research indicating treat-

ment with larger volumes of fluids

each hour to provide a more adequate

therapy may affect how CRRT con-

tinues to be used in critical care

units.84,88-90 Some centers have set

standards for care of patients receiv-

ing CRRT that require a ratio of 1

nurse to 1 patient, not only because

of the severity of illness of patients

receiving CRRT but also because of

the additional burden of managing

multiple liters of fluid volumes each

hour and monitoring an extracorpo-

real blood circuit.65,71 This paradigm

shift may contribute to an increased

nursing workload if containers of

therapy fluid and ultrafiltrate require

replacement and disposal several

times a shift or per hour. (Note: most

commercial fluid and disposal bags

are 2.5- to 7-L bags.) If the practice

of using higher volumes of fluids

increases, the issue of nursing time

required to replace multiple liters of

fluids for therapy and dispose of

larger volumes of ultrafiltrate more

frequently will have to be addressed.

SummaryCurrently, mortality associated

with ARF remains high, and CRRT is

becoming the therapy of choice for

the treatment of ARF in critically ill

patients. CRRT has many benefits

for patients in the critical care unit,

including improved hemodynamic

stability, excellent fluid and solute

removal, and possibly other benefits

such as enhanced cytokine removal

and prevention of sepsis. The use of

CRRT in a multicenter trial may be

necessary to validate its efficacy in the

treatment of ARF. The use of CRRT

for nonrenal indications and in con-

junction with a bioartificial kidney

will require further research and may

offer promise for patients in whom

ARF develops in the critical care unit.

Financial DisclosuresNone reported.

References1. Jorres A. Acute renal failure: extracorporeal

treatment strategies. Minerva Med.2002;93:329-394.

2. Mueller BA, Krause MA, Ronco C, Clark,WR. Considerations in the management ofpatients in acute renal failure. In: Hörl WH,Koch KM, Lindsay RM, Ronco C, Winches-ter JF, eds. Replacement for Renal Function byDialysis. 5th ed. Norwell, Mass: Kluwer Aca-demic Publishers; 2004:1181-1202.

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51. Tobe SW, Aujla P, Walele AA, et al. A novel citrate anticoagulation proto-col for CRRT using only commercially available solutions. J Crit Care.2003;18:121-129.

52. Davenport A, Mehta S. The Acute Dialysis Quality initiative, VI: accessand anticoagulation in CRRT. Adv Ren Replace Ther. 2002; 9:273-281.

53. Dorval M, Madore F, Geadeh D, LeBlanc M. Citrate anticoagulationmonitoring: postfilter ACT or ionized calcium? Blood Purif. 2002;20:305-323.

54. Oudemans-van Straaten HM, Wester JP, de Pont AC, Schetz MR. Antico-agulation strategies in continuous renal replacement therapy: can thechoice be evidence based? Intensive Care Med. 2006;32:188-202.

55. Davenport A. Management of heparin-induced thrombocytopenia dur-ing continuous renal replacement therapy. Am J Kidney Dis. 1998;32:E3.

56. Hirsch J, Heddle N, Kelton JG. Treatment of heparin-induced thrombocy-topenia: a critical review. Arch Intern Med. 2004;164:361-369.

57. Morabito S, Guzzo I, Solazzo A, Muzi L, Luciani R, Pierucci A. Continu-ous renal replacement therapies: anticoagulation in the critically ill athigh risk of bleeding. J Nephrol. 2003;16:566-571.

58. Moffett DF, Moffett SB, Scauf L. Human Physiology: Foundations andFrontiers. St. Louis, Mo: Mosby Year Book Inc; 1993:398.

59. Kraft MD, Btaiche IF, Sacks GS, Kudsk KA. Treatment of electrolyte dis-orders in adult patients in the intensive care unit. Am J Health SystPharm. 2005;62:1663-1682.

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63. Morgera S, Scholle C, Voss G, et al. Metabolic complications duringregional citrate anticoagulation in continuous venovenous hemodialysis:single-center experience. Nephron Clin Pract. 2004;97:c131-c136.

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66. Brouns R, De Deyn PP. Neurological complications in renal failure: areview. Clin Neurol Neurosurg. 2004;107:1-16.

67. Kyles DM. Coagulopathy and transfusion. In: Schell HM, Puntillo KA,eds. Critical Care Nursing Secrets. 2nd ed. St. Louis, Mo: Mosby Inc:2006:432-445.

68. Gordon P. Post-resuscitation care. In: Kinney MR, Dunbar SB, Brooks-Brunn JA, Molter N, Vitello-Cicciu JM. AACN Clinical Reference for Criti-cal Care Nursing. 4th ed. St. Louis, Mo: Mosby Inc: 1998:199-217.

69. LeBlanc M, Bosc JY, Paganini EP, Canaud B. Central venous dialysis

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72. Hoste EA, Blot SI, Lameire NH, VanholderRC, De Bacquer D, Colardyn FA. Effect ofnosocomial bloodstream infection on theoutcome of critically ill patients with acuterenal failure treated with renal replacementtherapy. J Am Soc Nephrol. 2004;15:454-462.

73. Druml W. Metabolic aspects of continuousrenal replacement therapies. Kidney IntSuppl. November 1999:S56-S61.

74. Jones SK. Loss of body heat during continu-ous venovenous hemodialysis (CVVHD) incritically ill patients. Blood Purif. 2003;21:183-207.

75. Yagi N, LeBlanc M, Sakai K, Wright EJ,Paganini EP. Cooling effect of continuousrenal replacement therapy in critically illpatients. Am J Kidney Dis. 1998;32:1023-1030.

76. Rickard CM, Couchman BA, Hughes M,McGrail MR. Preventing hypothermia dur-ing continuous veno-venous haemodiafiltra-tion: a randomized controlled trial. J AdvNurs. 2004;47:393-400.

77. Wolberg AS, Meng ZH, Monroe DM III,Hoffman M. A systemic evaluation of theeffect of temperature on coagulationenzyme activity and platelet function. J Trauma. 2004;56:1221-1228.

78. Bent P, Tan HK, Bellomo R, et al. Early andintensive continuous hemofiltration forsevere renal failure after cardiac surgery.Ann Thorac Surg. 2001;71:832-837.

79. von Bommel RF. Renal replacement therapyfor acute renal failure on the intensive careunit: coming of age? Neth J Med. 2003;61:239-248.

80. Gettings LG, Reynolds HN, Scalea T. Out-come in post-traumatic acute renal failurewhen continuous renal replacement therapyis applied early vs late. Intensive Care Med.1999;25:805-813.

81. Bouman CS, Oudemans-van Straaten HM,Tijssen JG, Zandstra DF, Kesecioglu J. Effectsof early high-volume continuous hemofiltra-tion on survival and recovery of renal func-tion in intensive care patients with acuterenal failure: a prospective, randomized trial.Crit Care Med. 2002;30:2205-2211.

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CE Test Test ID C0722: Continuous Renal Replacement Therapy in the Adult Intensive Care Unit: History and Current TrendsLearning objectives: 1. Identify indications for intermittent dialysis and continuous renal replacement therapy (CRRT) 2. Review variations and advantages anddisadvantages of CRRT 3. Examine potential complications of CRRT

Program evaluationYes No

Objective 1 was met � �Objective 2 was met � �Objective 3 was met � �Content was relevant to my

nursing practice � �My expectations were met � �This method of CE is effective

for this content � �The level of difficulty of this test was:

� easy � medium � difficultTo complete this program,

it took me hours/minutes.

Test answers: Mark only one box for your answer to each question. You may photocopy this form.

1. What is the mortality rate associated with acute renal failure?a. 0% to 15%b. 10% to 25%c. 25% to 90%d. 90% to 100%

2. What type of medication is used to manage acute renal failure?a. Loop diureticsb. Ace inhibitorsc. Angiotensin blockersd. Beta blockers

3. What is the goal of ideal treatment of acute renal failure?a. Return to adequate state of health by periodic removal of wastes and excessfluidb. Mimic efficacy of native kidney and not delay recovery of renal functionc. Return to maximum state of health by removal of previous 24-hour fluidintaked. Mimic efficacy of native bladder and urethra and not delay recovery of bladder function

4. How does intermittent dialysis af fect the kidney in a critically illpatient?a. Potential for ischemia of ureters and bladder-causing spasmb. Potential for ischemia of nephronsc. Potential for ischemia of abdominal walld. No ischemia since dialysis works effectively to safe guard nephrons

5. How are wastes removed from the blood with CRRT?a. Convection and diffusionb. Conduction and transfusionc. Convection and transfusiond. Conduction and diffusion

6. How is f luid removed from the blood with CRRT?a. Diureticsb. Transfusionc. Ultra filtrationd. Conduction

7. What was a major drawback to continuous arteriovenous hemof iltration?a. Use of large catheter in a major arteryb. Required arteriovenous fistulac. Required peritoneal catheterd. Required large catheter in major vein

8. What types of substances cannot pass through a hemof ilter (max pore size of 50kd)?a. Ureab. Electrolytesc. White blood cellsd. Vitamins

9. What is a benef it of predilution f luids?a. Removes wastesb. Provides electrolytesc. Provides ultra filtrate volumed. Provides continuous flush for hemofilter

10. How does continuous venovenous hemodialysis (CVVHD) dif ferfrom continuous venovenous hemof iltration?a. Dialysate is infused into blood in CVVHDb. Dialysate is infused into the outside compartment of the dialyzer inCVVHDc. Blood is infused into dialysate in CVVHDd. Blood is infused into the outside compartment of the dialyzer in CVVHD

11. What type of CRRT is best for f luid removal if the patient doesnot have azotemia?a. Continuous venovenous hemodiafiltrationb. Continuous venovenous hemofiltration dialysisc. Continuous venovenous hemofiltrationd. Slow continuous ultra filtration

12. What is a complication of CRRT?a. Gallstonesb. Goutc. Hypoxiad. Hypothermia

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Test ID: C0722 Form expires: April 1, 2009 Contact hours: 1.5 Fee: $11 Passing score: 9 correct (75%) Category: A Test writer: Jane Baron, RN, CS, ACNP

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The American Association of Critical-Care Nurses is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center’s Commission on Accreditation.

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