Document 6516805

Peritoneal Dialysis International, Vol. 28, pp. 591–595
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Copyright © 2008 International Society for Peritoneal Dialysis
TRANSITIONS IN CARE: WHAT IS THE ROLE OF PERITONEAL DIALYSIS?
F
PATIENT SELECTION
Is there a subpopulation of patients initiating PD that
would benefit from the formation of a preemptive arteriovenous fistula (AVF)? In other words, can we predict
early failures on PD? A recently published registry-based
analysis (2) attempted to use neural network and logistic regression to predict early failure of PD. The artificial
neural network methodology outperformed the regression technique in predictive power. The advantage of the
neural network methodology is that it allows modeling
of complex interactions between variables.
It may therefore be possible to provide a predicted
rate of failure for an individual based on demographic
and comorbid factors at the start of PD. What is then required is an understanding of the threshold failure rate
that would trigger setting in motion provision of an AVF.
The evidence base here is even thinner. For patients commencing dialysis itself, the optimal timing of AVF formation is unknown. Simply factoring in age can result in
wide variation in whether access is utilized when formed,
ranging from 5 (unused) to 1 (used) for elderly individuals to a ratio of 1:2 for younger patients (3). Yet, knowing such information does not tell a clinician when the
benefit of providing access outweighs the downside; it
is not simply that nonuse is a negative. What are required
are studies that can measure the overall healthcare benefit of a particular strategy.
PREDICTING FAILURE
In contrast to early failure, late failures perhaps, can
be more accurately predicted, at least in a proportion.
Three scenarios are proposed: emergency loss of PD, failure of the PD modality, and what could be considered
failure of the patient to sustain PD as a technique.
Clearly, the sudden unexplained loss of PD due to an
emergency, on the surface, is just that, unexpected, and
so can have no prior planning. However, this group
should not be neglected. What is it about someone who
develops, out of the blue, resistant peritonitis? Perhaps
it would be possible to generate a risk score for this type
of mechanism. For example, it has long been known that
diverticular disease is associated with enteral-related
peritonitis (4). Perhaps such patients could be considered high risk for resistant de novo severe peritonitis.
Understanding failure of the modality itself may be
more amenable to study and prediction. Peritonitis is an
important reason for technique failure in nearly 40% of
those that move to HD (5). Only 12% of moves to HD are
attributed to patient choice; the rest are due to direct
adequacy or fluid issues. The key issues here are that,
not only are these factors that are measured and tracked
in individuals, but also early recognition that the trajectory is pointed toward failure allows time to provide HD
access. However, as pointed out, work is still required to
develop the models from these types of data. The same
is true of patient-related factors, but computer simulations and neural networks may provide clinicians with
the necessary tools.
FISTULAS: OUTCOMES IN THE PD POPULATION
The authors also rightly raise the issue of fistula outcomes in PD patients. Are they the same as the general
dialysis-requiring population? The selection of an individual for PD may have been based on a relative evaluation of an individual’s access assessment. This may alter
the benefit to risk of forming a fistula, with the problem
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or patients with chronic kidney disease who are destined for renal replacement therapy, care is a continuum punctuated by fundamental shifts in the type
of care that they receive. Be it the commencement of a
dialytic therapy, a switch from one treatment to another, or a decision to commence palliative care, it is
clear that these represent, for many individuals, a discontinuity in care that can be perceived to be poorly
managed. Why such switches are a problem can be complex. What is required is a more systematic understanding of the process, with predictive tools to assist
clinicians and patients in providing timely and organized processes.
Chiarelli and co-authors (1) look at one such point in
care and explore the issues associated with it: the movement of patients from peritoneal dialysis (PD) to hemodialysis (HD). They challenge the community in four areas
where evidence and guidance are needed.
FLUCK
UNPLANNED DIALYSIS STARTS: A ROLE FOR PD?
The transition onto dialysis remains an important
milestone for patients with end-stage renal failure. A
smooth transition, with prior preparation and planning,
is associated with better short- and long-term outcomes.
It allows an individual to be both physically and psychologically readied for the potential rigors of renal replacement. For example, preparation allows the patient to
have input into the choice of modality and the location
of that modality, and to have any necessary surgery, such
as a fistula, carried out in sufficient time to allow such
access to be utilized at the start of dialysis. In addition,
complications such as anemia and mineral metabolism
may also be addressed and suitable subjects prepared
and listed for transplantation (or indeed performed
preemptively).
However, for a substantial number of people, such a
transition is far from ideal. The causes of an unplanned
start are complex. For example, they may have occult
renal disease, presenting de novo when symptomatic. It
may be that acute kidney injury fails to recover. A patient may have evidence of chronic kidney disease but
the risk of decline to established renal failure is unrecognized or underappreciated, in either primary or secondary care or even within specialist nephrologic care.
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Finally, the healthcare system may not be able to deliver
the timely surgical pathway required for adequate access. In these individuals, the default mode to dialysis
initiation is almost always to commence dialysis with a
venous catheter (either tunneled or non tunneled). Such
issues were demonstrated in the United Kingdom Vascular Access Survey, published as part of the 9th Renal Registry Report (available at www.renalregistry.org). One
third of incident patients presented within 3 months of
dialysis start, of whom 90% commenced dialysis via a
venous catheter. Of the remainder, even those under
renal specialist care were exposed to a high rate of
venous catheters, the rate being 50%. Follow-up data
confirmed that the rate of progression to definitive access was slow over the next year, and few patients
switched to domiciliary therapies such as PD (7).
Dialysis access, then, remains a key weakness in the
common approach to unplanned dialysis. The high
usage of venous catheters is associated with an increased risk of infection, increased hospital bed usage,
and poorer outcomes. Individuals are often denied the
opportunity to explore dialysis options closer to home.
Again, the reasons may be complex. The “black hole”
effect of the in-center HD facility may not allow someone to look beyond its walls, nor may healthcare professionals within that setting have the expertise to
advocate for other forms of therapy. Individuals may
have lost confidence in either themselves or the healthcare system to provide for them due to their perceived
precipitous arrival onto dialysis. This view may be enhanced by terminology such as “crash landing” onto
dialysis, adding to the aura of crisis. Renal centers
themselves may lack the pathways or resources to fasttrack the education and preparation of unplanned starters. Finally, one may be harsh on the specialists and
say we have become too accepting of poor planning,
too comfortable with venous catheters, and lacking in
vision to change our processes. Such a challenge was
laid down in the National Service Framework for Renal
Services (England), which stated,
“All children, young people and adults with established renal failure are to have timely and appropriate surgery for permanent vascular or
peritoneal dialysis access, which is monitored and
maintained to achieve its maximum longevity” (8)
[italics added for emphasis].
Clearly there is scope for improving care. It is therefore appropriate to explore the potential merits of the
early use of continuous ambulatory PD in the context of
unplanned dialysis starts.
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that a valuable access may fail before use. Again, this is
a fertile area for research, exploring the overall benefit
of a particular clinical strategy.
How should such an approach be utilized? First, for
incident patients, a score might be useful to determine
what subgroup requires a fistula at the outset of PD. This
paper clearly indicates that not all patients would benefit from a preemptive fistula (1). However, PD failure
might be predictable in a small population (2). Second,
ongoing assessment of the probability of PD failure is
required. What that assessment would look like requires
research. Finally, and just as crucially, thresholds need
to be defined; in other words, at what level of probability of PD failure does fistula placement become of benefit to an individual and to the overall care of a
population? Given the potential rate of complications
seen — Chui et al. (6) demonstrated a rate of 22.8%, with
nearly 50% not using the access over 2 years — this is of
great import.
Can we take this approach and generalize it to other
points in the patient pathway? One area that is of interest to all nephrologists is the initiation onto dialysis. As
a way of balance, it might be useful to consider how the
use of PD could be configured at the start of unplanned
dialytic therapy.
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OUTLINE OF CONSIDERATIONS
FEASIBILITY
The first aspect to consider is that of feasibility. The
key component to delivering HD is the ability to access
the circulation. Is it possible to access the peritoneum
with the same (or at least comparable) ease? Is it then
possible to initiate PD within an appropriate time frame?
Essentially, this is an issue of providing an access into
the peritoneum that is available for rapid or timely use.
Available techniques include percutaneous insertion at
the bedside, use of a peritoneoscope, and more formal
surgical methods, such as open or laparoscopic placement. With appropriate provision and training, any
method could, in theory, provide ready access to allow
PD to be performed. One must consider whether PD is to
be utilized as the very first method of renal replacement
therapy or, alternatively, could PD be employed at an
early stage, perhaps after a short period of HD. Have such
systems been tried?
First, can PD be utilized as the first therapy, taking
advantage of modern technology? Gabriel et al. (9) explored the use of high volume automated PD in the setting of acute kidney injury. Using bedside percutaneous
insertion, 30 patients with acute kidney injury received
236 sessions. The reported incidence of mechanical complications was 6.7% and peritonitis 16.7%. Such risks
compare favorably with the risks of a venous catheter
inserted acutely. For example, the French Catheter Study
Group in Intensive Care (10) reported rates of complications of about 18%, and infection rates of up to 19.8%,
including sepsis rates of 4.4%.
Alternatively, PD might be utilized rapidly, but not
necessarily as the first renal replacement therapy. In
other words, take those people commencing dialysis via
a venous catheter and convert them rapidly onto PD.
Lobbedez et al. (11) reported on this approach recently,
describing short-term outcomes similar to those patients
converted to venous catheters. Of interest, they noted
that hospitalization was not different between unplanned and planned PD starters.
It is clearly possible then to provide a patient with a
PD catheter rapidly and safely, with initial safety rates
as good as those of a temporary venous line.
SAFETY
Two questions need to be considered when debating
safety. First, is the complication rate for the early use of
PD comparable to that of late use for a planned starter?
Second, compared to conventional unplanned starts with
a venous catheter, how does early use of PD fare?
Povlsen and Ivarsen (12) described their experience
comparing planned versus unplanned PD starts. In a
comparison of outcomes for 52 late-referred PD starts
and 52 matched planned PD starts, what was apparent
was a higher rate of mechanical complications in those
referred late. Catheter insertion, however, was by an
open surgical approach. Mechanical issues in this group
were related to leaks and dysfunction. Censoring for
death and transplantation, technique survival was identical (86.7% vs 90%) and infection rates were identical.
It is therefore likely that the mechanical issue was related to the insertion technique chosen. Using the percutaneous method, Gabriel et al. (9) reported a lower
mechanical complication rate of 6.7%.
Clearly, a second consideration is the comparison between a PD catheter start and HD via a venous catheter,
but there are fewer comparative data available. Infection remains a principle concern and relative rates of
bacteremia for HD have been well described in many studies. For venous catheters, rates of 4 – 6/1000 patientdays have been reported [e.g., Marr et al. (13)]. Not only
are absolute numbers of septicemia high, but complications related to bacteremia are common. This study
reported a 22% rate, with cases of osteomyelitis, endocarditis, and septic arthritis, all related to gram-positive species. Aslam (14) described relative rates of
infection comparing HD and PD in an incident cohort.
While total infection rates (including peritonitis) were
equivalent, bacteremia was restricted solely to the HD
cohort, and largely to those patients reliant on venous
catheters. It was also noted that this risk was largely
restricted to the first 90 days. They concluded, “Patients
should be informed that there is a high risk for bacteremia when starting dialysis using an HD catheter….”
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Peritoneal dialysis was commonly used for acute renal
failure up until the late 1970s, until HD became more
readily available. The use of rigid PD catheters was associated with considerable technical issues, such as malfunction, displacement, leakage, and infection, not to
mention insertion-related complications. To routinely
reintroduce the use of PD there are a number of considerations. One needs to understand whether early use is
feasible, safe, and effective; then a judgment needs to
be made about the desirability of such a strategy and
what are the potential advantages it brings in comparison to current practice. Finally, it is useful to consider
scenarios for such a strategy. For example, PD may be
the definitive modality choice for a starter, but it may
also act as a bridge to a definitive start on HD via a
fistula.
TRANSITIONS IN CARE: WHAT IS THE ROLE OF PD?
FLUCK
DESIRABILITY AND ADVANTAGES
PRACTICALITY
What remains a barrier are the practicalities of such
an approach. Junior medical staff members are confident in the techniques of venous catheterization and
units have ready access to HD staff to carry out the treatment. The technical aspects of HD provide a reassurance
that therapy can be effective, with good and rapid control of metabolic abnormalities. The same is not always
true for PD. For example, the ability to insert a PD cath594
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eter is not a competency that many renal physicians in
the UK have, and few trainees currently acquire those
skills. There is the perception that PD is not appropriate
for a metabolic crisis, yet Gabriel et al. (9) demonstrate
its role in acute renal failure and equivalence against
continuous venovenous hemofiltration in metabolic control. Centers may have emergency systems to call staff
in to perform HD, but the same is not true for PD.
The realities are that percutaneous insertion of a PD
catheter is a safe well-tolerated technique that can
readily be taught. Even in the absence of such training,
surgical support can be developed to provide a catheter
(12). The performance of PD, using automated PD, can
be delivered by protocol, with programs set up easily by
in-patient staff. What are required then, are training of
staff, some modest equipment and supplies, and policies to ensure safe application. Is this achievable?
A case scenario may illustrate the potential. A 27-yearold male presented after a blood test performed for malaise. He was admitted as an emergency with a serum
creatinine of 1870 µmol/L, urea 32.3 µmol/L, and potassium 5.3 mmol/L. An ultrasound performed on the
day of admission diagnosed polycystic kidney disease,
confirmed with a family history. After seeing a nurse
counselor and nephrologist on the day of admission, he
was offered PD as a bridge to a definitive decision. There
were no urgent indications for dialysis, so, on the following day, a PD catheter was inserted by a nephrologist by Seldinger technique with radiological screening.
Seven days later, as an outpatient, training commenced
on automated PD. It transpired that he was due to get
married 7 weeks later, abroad. He was also referred and
listed for transplantation within 1 week. Despite late
presentation, a definitive solution was achieved that
maintained choice and a return to work, and allowed him
to go through with his wedding. Safe and appropriate
therapy has been delivered, and while HD would have
achieved a medical solution in the short term, his social
and work life would have been severely disrupted.
Peritoneal dialysis remains an effective therapy for
renal replacement therapy. Current practice for unplanned dialysis starts overemphasizes the benefits of
HD while underestimating the complications associated
with commencing dialysis with a venous catheter. In
“playing safe,” we do in fact subject patients to potential greater harm while at the same time denying individual choice and undermining conf idence. In its
essence, the initiation of PD offers a definitive bridge to
a robust long-term plan, reducing risk. Superficial arguments about feasibility, safety, and desirability against
its use are not borne out in the literature. Consequently,
one could argue strongly that PD should be more widely
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A case can be made for the use of PD in an unplanned
dialysis start being as good as a start on HD with a catheter. The argument has been made that, in terms of infection, PD may well be superior, in terms of both
frequency and consequence. Are there any other potential benefits?
For patients that commence dialysis in an unplanned
way, there is a tendency for physicians to use the language of crisis: “crash landing” is a common phrase. Such
a message will create a perception that dialysis is an
emergency, that it requires hospitalization or at least
hospital-based therapy, and potentially close down discussion of self-care models. Clinicians will commonly
then focus on the direct medical issues and opt for HD.
Patients are then denied choice at a critical stage of their
arrival on dialysis. Such an individual has a low chance
of moving from in-center HD to a domiciliary therapy.
The UK Renal Registry Vascular Access Survey (7) demonstrated that just 10% of patients that commenced HD
via a catheter were on PD at 1 year. The reasons are multiple but lack of initial choice, lack of a reevaluation of a
patient’s options, poor linkage between in-center HD
programs and community PD services, and patient reluctance all contribute. So, the advantage of adding PD
to the menu of unplanned start options is just that: patients have choice.
Renal physicians are very comfortable with the use of
a tunneled line as a bridge to a fistula. Perhaps PD could
be viewed in a similar vein: a bridge to a definitive solution for renal replacement therapy. It may be that an
individual is trained and becomes independent on PD. It
may be that PD is not the preferred long-term option. In
such a scenario, a fistula could be created, mature, and
be readied for use while PD is continued; access is preserved and risk reduced. Lobbedez et al. (11) reported a
median time of 4.4 months to the use of a fistula in unplanned starts with a venous catheter, confirming data
from the UK survey (7). Use of PD could reduce this period of risk.
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TRANSITIONS IN CARE: WHAT IS THE ROLE OF PD?
available for unplanned starts onto dialysis. Such an
approach requires thought, training, and a change in
attitude, but the techniques required to carry it out are
already there.
5.
6.
CONCLUSION
Richard Fluck
Nephrology
Derby City General Hospital
Derby, United Kingdom
7.
8.
9.
10.
e-mail: [email protected]
11.
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