arfcrit care nurse
TRANSCRIPT
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:
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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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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.
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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
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Figure 2 System for continuous venovenous hemodialysis.
Dialysate
Dialysate pump
HemofilterBloodpump
Ultrafiltratepump
Airdetector
To the patient
From thepatient
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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.
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74. Jones SK. Loss of body heat during continu-ous venovenous hemodialysis (CVVHD) incritically ill patients. Blood Purif. 2003;21:183-207.
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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.
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79. von Bommel RF. Renal replacement therapyfor acute renal failure on the intensive careunit: coming of age? Neth J Med. 2003;61:239-248.
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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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