Transcript Document

CRRT in ICU
Overview
• Introduction
• CRRT
– CRRT in ICU
• Indications
• Clinical studies
– ATN, RENAL
• RRT in ICU: Preference
• Prescription
• Complications
• Self assessment
• Status of issues
• Conclusions
Introduction
In the past, the interaction between nephrology and intensive care
was minimal
Today,
there is
continuous
interaction
with several
moments of
high
interaction
due to
common
patients and
complex
syndromes
Contrib Nephrol. Basel, Karger, 2010 (166):1–3
Introduction (Contd)
Classification of blood purification in critical care (BPCC) technology
PMX =
polymyxinB immobilized
fiber;
PMMA =
polymethylmeth
acrylate;
PAN =
polyacrylonitrile;
PEPA =
polyether
polymer alloy
Contrib Nephrol. Basel, Karger, 2010(166):11–20
Introduction (Contd)
The calcification of terminology of blood purification in critical care
HDF = hemodiafiltration
Contrib Nephrol. Basel, Karger, 2010(166):11–20
Introduction (Contd)
• Continuous Blood Purification
• Blood purification initiated with the intention of
continuing it for 24 h/day is defined as continuous
blood purification, even if it has not been sustained for
24 h due to unavoidable circumstances
• When it is performed, the methods and circumstances
of its implementation
– Hemofilter, blood flow (QB),
– Dialysis fluid flow (QD)
– Substitution fluid flow and filtration rate (QF)] must be
recorded
CRRT
• CRRT technology
• The first CRRT treatments were performed
using circuits driven by arterial blood pressure
• However, it is in the form of roller-pumped,
venovenous therapy that CRRT became a
mature technology
• CRRT originated—and remains widely
practiced—in the form of continuous
hemofiltration
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Nomenclature
CRRT in ICU
• As a continuous therapy, CRRT can be rapidly
tailored to changes in a patient’s clinical
condition during critical illness
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CRRT in ICU (Contd)
•These perceived advantages have contributed to the widespread
uptake of CRRT as the first-choice RRT in ICUs throughout
Australia, Japan and Europe
•In these regions, CRRT is usually initiated, prescribed and
managed within the ICU, with RRT being integrated with
other aspects of the management of critical illness
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CRRT in ICU (Contd)
Blood purification treatments performed at the ICU in Chiba
University Hospital (1981–2008) in Japan
Contrib Nephrol. Basel, Karger, 2010(166):21–30
CRRT in ICU (Contd)
• In north america, however, traditional structures of ICU
management favor an ‘open-ICU’ approach
– Within this model, RRT is usually prescribed by a nephrologist in the ICU
and is initiated by a dialysis nurse
– In this environment, IHD has the advantage of requiring only daily or
alternate-day attendance by the renal team
– Conversely, the relative labor costs of providing CRRT are increased, an
effect that is compounded by the larger fixed costs and higher
consumable requirements of CRRT
• These logistic factors have led to a preference for IHD over
CRRT being maintained in ICUs that use the north american
model,
• aAstance further justified by the lack of compelling evidence from controlled
trials in favor of CRRT
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CRRT in ICU (Contd)
• Two large multicenter, randomized controlled
trials,
– The veterans affairs/ national institutes of Health
acute renal Failure trial network (ATN) study and
– The randomized evaluation of normal versus
augmented level replacement therapy (RENAL) trial,
– have now, however, examined the use of RRT in the
ICU and provided a more consistent set of clinical
data with which to answer questions concerning the
clinical application of CRRT
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CRRT in ICU: Indications
Acute blood purification in critical care currently performed in Japan
Contrib Nephrol. Basel, Karger, 2010(166):47–53
CRRT in ICU: Indications
• 1 Acute kidney injury with
–
–
–
–
Fluid overload (refractory to diuretics)
Hyperkalemia (K+ > 6.5)
Severe metabolic acidosis (pH < 7.1)
Rapidly climbing urea/creatinine (or urea >
30mmol/l)
– Symptomatic uraemia: encephalopathy, pericarditis,
bleeding, nausea, pruritus
– Oliguria/anuria
CRRT in ICU: Indications
• 2 Overdose with a dialyzable drug or toxin
• Some drugs are removed by RRT
– As a general rule, drugs are cleared by RRT if they are watersoluble and not highly protein-bound
CRRT in ICU: Indications
• 3. Severe sepsis
• There has been recent interest in the potential for
haemofiltration to remove inflammatory mediators in
patients with severe sepsis/septic shock.
• A number of small studies (with 25 subjects or less)
have suggested that high volume haemofiltration (4085ml.kg-1.hr-1) may reduce vasopressor requirements
and possibly improve survival in patients with septic
shock irrespective of whether they have an AKI
– However, strong recommendations cannot be made about
the role of RRT in this area until larger, well designed trials
address the issue
Mechanism
• Mechanism of solute removal:
• Filtration (convection) versus dialysis (diffusion)
Mechanism (Contd)
Schematic representation of CVVH and CVVHDF circuits
Mechanism (Contd)
The arrangement of
a haemofiltration and
a haemodiafiltration
circuit
CRRT in ICU
• Clinical studies of CRRT in the ICU
• The diversity of clinical approaches to the
treatment of AKI in the ICU is illustrated by the
results of the BEST Kidney study,
– The only multinational epidemiological study of
RRT practice in the ICU
– Study documented the treatment of AKI in 1,738
patients in 54 ICUs on five continents
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CRRT in ICU (Contd)
• BEST study results
– CRRT was the most common choice of initial RRT
treatment, with 80% of patients on CRRT;
– IHD use was mostly restricted to ICUs in north and south
America, where it was used as initial therapy in 30–40% of
patients, while, by contrast,
– CRRT is used first in 100% of ICUs in Australia
– Among patients receiving CRRT, however, marked variation
in the modality, intensity, timing and threshold of use was
observed,
• Making it difficult to compare outcomes between patients on CRRT
and those on IHD
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CRRT in ICU (Contd)
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CRRT in ICU (Contd)
• Timing of CRRT
• Dose or intensity of CRRT
CRRT in ICU (Contd)
• The ATN and RENAL trials
– Important to recognize that these studies differed in
methodology and patient characteristics and that
• Any comments made from their comparison can only be regarded as
inferential
– However, as the trials enrolled comparable patient
populations (all patients were critically ill, all had been
admitted to an ICU, and mean APACHE scores were
equivalent at randomization),
– The marked discrepancies in outcomes in the two trials
demand examination, even if any conclusions might be seen
as controversial
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Nat. Rev. Nephrol.
2010:6:521–529.
CRRT in ICU (Contd)
• Both the ATN and RENAL studies failed to
detect any survival benefit from more-intensive
RRT
– In addition, no significant differences in mortality
rates were observed between high-intensity and lowintensity treatment in pre-specified subgroups in
either study
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CRRT in ICU (Contd)
• ATN and RENAL studies
– These results provide definitive evidence to
recommend that escalation of CRRT intensity to
beyond conventional doses of 25 ml/kg per hour is
not beneficial for unselected ICU patients with AKI
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CRRT in ICU (Contd)
• RENAL study
• The results suggest that initial use of CRRT might be
associated with greater recovery of independent renal
function compared with use of IHD,
– but confirmation of this hypothesis in a prospective,
multicenter, randomized controlled trial would be required
for a strong recommendation for CRRT on this basis alone
• Disadvantages of CRRT include its
– Higher cost and the
– Need for greater use of anticoagulation therapy (compared to
intermittent therapy)
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CRRT in ICU (Contd)
• Authors of review in Nature reviews nephrology (2010) states
– Despite a lack of formal evidence, however, in our opinion the
clinical argument for use of CRRT in patients with hemo
dynamic instability does seem to be largely won
– Although our preference for the use of CRRT in critical illness
may be influenced by the fact that we practice in Australian
and UK environents,
• Even the ATN investigators in the US did not feel that they had
sufficient equipoise to assign hemo dynamically unstable patients to
IHD in their trial
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CRRT in ICU (Contd)
• This decision is an important point because it implies
that, in a large group of veterans affairs and other
academic hospitals in the US,
– clinicians felt that patients receiving vasopressor therapy
should receive CRRT in preference to IHD
– In the ATN trial, such patients formed the majority of
individuals with AKI in the ICU
• If facilities and training are required to provide CRRT
for the majority of patients requiring RRT, the
economic arguments against extending use of CRRT to
other patients become less important
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CRRT in ICU (Contd)
• Dose of CRRT
• The ATN and RENAL studies have now
established an upper limit of intensity for CRRT
– Given the likelihood of a dose–response relationship
at treatment intensities <20 ml/kg per hour, delivery
of doses lower than this seems to be undesirable
– Clinicians should prescribe CRRT on the basis of
patient body weight to the established effluent flow
rate target of 20–25 ml/kg per hour
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CRRT in ICU (Contd)
• Dose of CRRT (Contd)
• Equally importantly, both the ATN study and
the RENAL study demonstrated that
– The prescribed dose is 10–15% less than the
delivered dose in these patients, presumably owing
to treatment downtime
• Thus, if clinicians wish to avoid delivering a
dose <20 ml/kg per hour, they need to make
appropriate adjustments to their prescription
Nat. Rev. Nephrol. 2010:6:521–529.
RRT in ICU: Preference
• Decision about which technique to use depends on:
• 1. What we want to remove from the plasma
RRT in ICU: Preference (Contd)
• 2. The patient`s cardiovascular status
– CRRT causes less rapid fluid shifts and is the
preferred option if there is any degree of
cardiovascular instability.
• 3. The availability of resources
– CRRT is more labour intensive and more expensive
than IHD
– Availability of equipment may dictate the form of
RRT
RRT in ICU: Preference (Contd)
• 4. The clinician`s experience
– It is wise to use a form of RRT that is familiar to all the staff
involved
• 5. Other specific clinical considerations
– Convective modes of RRT may be beneficial if the patient
has septic shock
– CRRT can aid feeding regimes by improving fluid
management
– CRRT may be associated with better cerebral perfusion in
patients with an acute brain injury or fulminant hepatic failure
Prescription of CRRT
• A typical prescription for a 75kg patient
requiring CRRT for an AKI would be as
follows:
• Anticoagulation:
– Unfractionated Heparin: 5,000 IU bolus followed by
a pre-filter infusion at 500 IU.hr.-1
– Aim to anticoagulate filter but ensure APTTR<2
Prescription of CRRT (Contd)
• Fluid balance over 24 hours:
– Aim for an even balance if the patient is euvolaemic
– Aim for the appropriate negative balance if the patient is fluid
overloaded (<1500ml/24hrs)
• Type of Replacement fluid/Dialysate:
– Use solutions without potassium if serum potassium is high
but switch to potassium containing solutions as serum
potassium normalises
– Use a bicarbonate-based buffer rather than a lactate-based
buffer if there are concerns about lactate metabolism or if
serum lactate>8mmol.l.-1 [Note- An intravenous bicarbonate
infusion may be required if a lactate-based buffer is used]
Prescription of CRRT (Contd)
• Exchange rate/treatment dose:
– 1500ml.hr.-1 (75kg x 20ml.kg.-1hr-1)
– The treatment dose is usually prescribed as an hourly
“exchange rate” which is the desired hourly flow rate adjusted
for the patient`s weight
– In the case of CVVH, the exchange rate simply represents the
ultrafiltration rate whereas in
– CVVHDF it represents a combination of the ultrafiltration
rate and the dialysate flow rate
• In CVVHDF, the ratio of ultrafiltration to dialysate flow is often set
at 1:1 but it can be altered to put the emphasis on either the dialysis
or filtration component
Prescription of CRRT (Contd)
CRRT: Complications
• Complications related to the vascath (including linerelated sepsis)
• Haemodynamic instability
• Air emboli
• Platelet consumption
• Blood loss
• Electrolyte imbalances
• Hypothermia
• Effects of anticoagulation (bleeding or specific sideeffects of the anticoagulant used e.g. heparin induced
thrombocytopenia)
Self Assessment - 1
• Which of the following statements comparing Dialysis
with Filtration are true:
A Dialysis depends on diffusion whereas filtration
depends on convection
B Filtration is more effective than dialysis at removing
small molecules
C Filtration in more effective than dialysis at removing
cytokines
D Dialysis is not as effective as Filtration at removing
water
Self Assessment - 1: Answers
• Which of the following statements comparing Dialysis
with Filtration are true:
A Dialysis depends on diffusion whereas filtration
depends on convection - True
B Filtration is more effective than dialysis at removing
small molecules - False
C Filtration in more effective than dialysis at removing
cytokines - True
D Dialysis is not as effective as Filtration at removing
water - True
Self Assessment - 2
• Which of the following statements are true regarding
the differences between CRRT and IHD
A CRRT is more cost effective than IHD
B IHD is preferable to CRRT in patients who are
cardiovascularly unstable
C IHD offers an overall survival benefit when compared
with CRRT
D CRRT is preferable to IHD in patients with a
coexistent acute brain injury
Self Assessment – 2: Answers
• Which of the following statements are true regarding
the differences between CRRT and IHD
A CRRT is more cost effective than IHD - False
B IHD is preferable to CRRT in patients who are
cardiovascularly unstable - False
C IHD offers an overall survival benefit when compared
with CRRT - False
D CRRT is preferable to IHD in patients with a
coexistent acute brain injury - True
Self Assessment - 3
• Are the following statements regarding RRT True or
False:
A Poor vascular access often contributes to the clotting of
a filter
B RRT has an established role in septic shock with normal
renal function
C Protein bound drugs are not easily removed by
CRRT/IHD
D The hospital mortality of patients with AKI on RRT is
approx 60%
Self Assessment - 3: Answers
• Are the following statements regarding RRT True or
False:
A Poor vascular access often contributes to the clotting of
a filter - True
B RRT has an established role in septic shock with normal
renal function - False
C Protein bound drugs are not easily removed by
CRRT/IHD - True
D The hospital mortality of patients with AKI on RRT is
approx 60% - True
CRRT in ICU: Status of issues
Nat. Rev. Nephrol. 2010:6:521–529.
Conclusions
• Much practice variation continues to exist in the
provision of CRRT in the ICU
• Two large prospective, multicenter, randomized
controlled trials (ATN and RENAL) have now
addressed the appropriate intensity of CRRT,
but many questions remain regarding the
– Timing of therapy,
– Role of intermittent dialysis in the ICU and the
– Effect of therapy choice on renal recovery
Conclusions (Contd)
• Further examination of the results from these
two studies may shed light on some of these
issues and might guide the conception of future
clinical trials
• Devising prescriptive guidelines for the
management of all aspects of this complex and
costly therapy that are widely applicable to
differing clinical environments worldwide is
likely to remain difficult
Any Questions?