In-service Training Manual Section 2: Theory Crit-Line III

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In-service Training ManualSection 2
TheoryCrit-Line III TQA
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Managing the Vicious Cycle of Fluid Removal The
CRIT-LINE Monitor is a CQI Outcome Management
Tool that allows clinicians to safely and
consistently dialyze their patients to their
ideal dry weights. The CRIT-LINE Monitor
provides a window into the intravascular
compartment of the body by monitoring a patients
blood volume change in real time during dialysis.
 Now for the first time, the clinician can
accurately determine how well a patients plasma
refilling rate is keeping up with the ultra
filtration rate of the dialysis machine. Having
this information in real time enables proactive
intervention based on the amount of fluid the
patients body is able shift into the
intravascular space during any given treatment
session. If the fluid removal is too rapid the
clinician can intervene before hypovolemic or
hypotensive symptoms occur. If the fluid removal
rate is too slow, the clinician can intervene by
increasing the ultra filtration rate to
successfully achieve the patients dry weight.
The CRIT-LINE Monitor can help clinicians
determine the effectiveness of an intervention
based on the instantaneous feedback it gives.
 The CRIT-LINE Monitor is a tool the clinician
can utilize to improve the clinical outcome of
every dialysis patient giving them increased
accuracy and control of the fluid removal
process.  The case studies towards the back of
this manual are printouts from actual patient
runs monitored with the CRIT-LINE Monitor. These
are common scenarios found in dialysis centers
across the country, but because each patient and
each dialysis treatment session is unique they
should not be considered as protocols for
intervention. The CRIT-LINE Monitor provides
additional insight about the dialysis process,
which should be used to supplement the
information already known about the patient in
establishing the most beneficial care plan. The
CRIT-LINE Monitor must always be used in
conjunction with the patients existing clinical
information before altering a dialysis treatment.
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HEMATOCRIT AND BLOOD VOLUME RELATIONSHIP
The test tube represents the volume of blood in
the intravascular compartment as broken down into
its two major components the red cell volume and
the plasma volume. Total blood volume is the sum
of these two. Hct is defined as the ratio of the
red cell volume to the total blood volume and is
a fundamental vascular marker. Because red blood
cells are too large to pass through the dialyzer
they remain constant during dialysis.
UF MIN
UF MIN
UF MIN
Because red blood cell volume remains constant, a
rise in hematocrit during dialysis represents a
reduction in plasma volume. Therefore,
hematocrit and blood volume have an inverse
relationship as illustrated by these profiles.
The top profile illustrates the change in
hematocrit during a dialysis treatment session.
Below is the BV profile that indicates the
corresponding change that occurs in the blood
volume of a patient. By monitoring the hematocrit
in real time, the CRIT-LINE calculates the
percent change in blood volume in the
intravascular space and then displays this
information graphically.
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FLUID DYNAMICS OF THE BODY
The dialysis process removes fluid directly from
the intravascular space, this space is then
refilled with fluid from the extracellular space
(the tissue). Prior to the CRIT-LINE Monitor
there was no way to measure how well the
patients plasma refilling rate kept up with the
ultrafiltration rate of the dialysis machine. The
plasma refilling rate (PRR) is the bodys ability
to shift fluid from the extracellular space into
the blood (intravascular space). Now, with
CRIT-LINE one can directly measure the blood
volume change in the intravascular space, and
thereby determine how well the body is refilling
this compartment during dialysis. If dialysis
progresses faster than the bodies ability to
refill (the ultra-filtration rate is greater than
the plasma refilling rate), the volume of the
intravascular space will be reduced and will be
displayed on the CRIT-LINE as a reduction in
blood volume.
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THE GUYTON CURVE
The Guyton curve illustrates the approximate
relationship between extracellular fluid volume
and blood volume, and demonstrates a limit to
blood volume as fluid levels continue to increase
past a normal range. The average 70 kg adult has
approximately 5 liters of blood volume in his/her
intravascular space. This corresponds to a
normal extracellular fluid level of about 17
liters on Guytons curve. According to Guyton,
as fluid volume is added or removed, the body
will distribute its fluid load according to this
curve. In the case of fluid being added and not
removed (as is the case with pre-dialysis
patients), once a maximum vascular capacity of
approximately 7 liters is reached, all additional
fluid expands into the extracellular space.
Note Guytons curve is an approximation of fluid
dynamics and is patient specific.
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THE A PROFILE
On the far right , the curve describes Edema as a
region with as much as 40 liters of extracellular
fluid. If the pre-dialysis fluid status of an
ESRD patient falls within this region it is
possible to remove a significant amount of fluid
from the patient and still be in the edematous
region on the Guyton curve. In this case the
patient would leave still having two extra liters
of fluid in their vascular space (blood volume).
A patient who is fluid Overloaded or in the
edematous region on the Guyton curve will
typically display a positive blood volume slope,
a flat-line, or a BV profile slower than -3
per hour an A profile. Accordingly, this
region on the Guyton curve is called the A
region.
An A profile suggests that the patient is not
at the correct dry weight and that excess fluid
must be removed before the correct dry weight is
reached. It also illustrates that
ultrafiltration and plasma refilling were
equivalent during treatment. Patients who
remains in the A region will eventually
experience complications such as CHF, LVH,
pulmonary edema and hypertension.
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THE B PROFILE
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THE C PROFILE
As shown here, the fluid removal falls below the
Guyton curve into the C region of the graph as
the vascular compartment alone sustains the fluid
removal. The corresponding BV profile slope
becomes quite steep (greater than -8 BV
change per hour) as the vascular volume is
depleted too rapidly.
A C profile, which can begin anywhere along the
Guyton curve, describes a dialysis session in
which the patient ultimately experiences some
type of intradialytic morbidity such as
lightheadedness, nausea, vomiting, cramping or
hypotension a condition often called crashing.
This usually requires intervention and
discontinuation of the dialysis session. Most
C profiles are characterized by trace
discontinuities. The three profiles below show
C profiles at different stages during a
treatment.
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Treatment to Treatment Stability
Once the staff has established a B profile for a
patient, it is important to continue to use the
Crit Line monitor on the patient to ensure that
they get the same profile consistently treatment
to treatment. The graph above represents a
patient who was followed for 21 treatment
sessions with no intervention based upon
information from the CRIT-LINE . It also
illustrates how patients can present themselves
differently from treatment to treatment. There
are several reasons why patients do present
themselves differently such as sodium intake,
their general diet, fluid intake, and blood
pressure medication, to name a few. The
CRIT-LINE provides a real-time window into the
vascular space to assist the clinician in
achieving optimal fluid removal each treatment
regardless of patient presentation.
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HYPOVOLEMIA AND THE HCT THRESHOLD (CRASH CRIT)
Each dialysis patient has a critical blood volume
level where symptoms begin. This illustration
depicts a patient who had a starting hematocrit
of 34 on Thursday. After a weekend of fluid
intake they presented themselves with a starting
hematocrit of 30, yet their Crash CRIT was 39
during both dialysis sessions.
The critical blood volume level in a patient can
be identified at the absolute hematocrit at
which the symptoms occur in the patient. This is
called the HCT Threshold or crash-crit. The
HCT Threshold, which marks the onset of
hypovolemia and related morbidity, is very
patient specific. But once this level has been
identified for any individual patient, it can
serve as a marker where the symptoms will occur
in subsequent treatments. By setting a HCT LIMIT
(or alarm line called the crit-line) on the
Crit-Line Monitor 1-2 HCT units below the
identified HCT Threshold, and reducing the UFR to
minimum at this point, intradialytic morbid
events can be prevented. If the HCT Threshold
is unknown, the HCT LIMIT should be set
approximately 15 above the starting HCT.
This profile depicts a patient who began dialysis
with a 33 hematocrit and became symptomatic at a
hematocrit of approximately 40.7 three
consecutive times during the treatment. Now the
staff will know in subsequent treatment that
whenever the hematocrit reaches 40.7 this patient
will become symptomatic.
Three consecutive Crashes at a Hct of 40.7
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FLYING THE CURVE

• The HCT Threshold is independent of UFR, time of
  dialysis, and session to session patient and
  treatment variations (i.e. weight gains/losses,
  inaccurate weight assessment, temperature,
  constipation, blood glucose or sodium levels,
  etc.). The slope of the profile does not predict
  when morbidity may occur. Conversely, the
  absolute HCT can be used to define a singular
  endpoint-a patient specific threshold value.
  Bringing blood volume down to a safe minimum
  early (avoiding the HCT Threshold) , and keeping
  it there throughout the session creates the
  highest possible mobilization of tissue fluid
  possible over the longest period. By setting a
  HCT Limit on the Crit-Line Monitor, 1-2 HCT units
  below the identified HCT Threshold and reducing
  the UFR to minimum ( at or below 400 mls per
  hour) , intradialytic morbid events may be
  prevented. The HCT Threshold will remain
  constant as long as the patients RBC mass
  remains relatively constant between treatments
  and should be reassessed approximately every 3-4
  weeks.
• The picture above depicts a BV change of
  approximately -18 in the first hour of
  treatment. Subsequently, when the patients HCT
  reached the HCT Limit, the UFR was reduced to
  minimum and was maintained at this level. No
  refill was noted indicating that the patient is
  at or near their ideal dry weight.

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TRACKING AND ACHIEVING DRY WEIGHTS
Refill An Indicator of Over-Hydration
10
0
-10
BV Change ()
1
-20
2
-30
0
1
2
3
4
Time (hours)
Evaluating and adjusting a patients dry weight
is difficult because there is no way to look
into the extracellular space to see just how much
fluid is there. Although Crit-Line monitoring
gives no indication of extracellular fluid
status, it does provide a window into the
intravascular space. With the ability to
determine the change in blood volume, the
clinician can determine how effective the
patients body is transferring fluid from the
extracellular space to the intravascular space.
Knowing this can assist the clinician in
achieving ideal dry weights gradually over
several treatments. This is done by using what
Hema Metrics refers to as a dry weight check.
Near the end of treatment or when the fluid
removal goal is achieved, the clinician can turn
the UFR to minimum (at or below 400 mls per hour)
for 15 to 20 minutes to determine if extra fluid
from the extracellular space will transfer into
the intravascular space. The CRIT-LINE blood
volume profile will then display either refill
as shown by the number 1 profile above or,
display little or no refill as shown by the
number 2 profile. If there is a pronounced
refill, this is an indication that the patient
is still over-hydrated, that more fluid could be
removed and that the patient is not at their
ideal dry weight. It is important to conduct
several dry weight checks on the same patient
over several treatments to gradually dialyze the
patient to their ideal dry weight. If a
patient crashes, and after turning the UFR on
minimum there is a pronounced refill as in 1,
this is an indicator that the UF rate was too
high and that more fluid could be removed. If a
patient crashes and there is little or no refill,
as in 2, after turning the UF to minimum, this is
an indicator that the patient is at or near an
ideal dry weight.
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BLOOD VOLUME PROFILES REVIEW
Blood Volume Profiles A-C display the effect of
hemodialysis on the intravascular space, measured
in BVD change over a typical 3-4 hour dialysis
treatment session.
BV Profile A, associated with segment A of the
Guyton Curve, is typical of the fluid overloaded
patient
BV Profile B, associated with segment B of the
Guyton Curve, illustrates a gradual decrease in
blood volume with no required nurse intervention.
BV Profile C, associated with segment C of the
Guyton Curve, illustrates a very rapid depletion
in blood volume resulting in an early sign-off
or Crash, with nurse intervention.
There are three basic types of blood volume
profiles, A profiles, B profiles and C
profiles. The A or the fluid overloaded
profile indicates no change in blood volume and
no change in hematocrit during dialysis. This
indicates a patient is still on the right side of
the Guyton Curve and not at their correct dry
weight. The plasma refilling rate (PRR) was the
same as the ultrafiltration rate (UFR). The B
or ideal profile has a 5 per hour decline in
blood volume while experiencing no morbidity.
This indicates the patient is moving down the
knee of the Guyton curve approaching a normal
blood volume level. The C or crash profile
indicates that the BV level in the intravascular
space was reduced to an unsafe level. The
patient experienced hypovolemic symptoms due to
this volume depletion in his intravascular space.
In this instance, even though the patient
experienced a crash or intradialytic morbidity,
the refill noted suggests that more fluid could
be removed. Just because a patient crashes, it
does not mean they are at their dry weight.
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HYPOXEMIA DURING HEMODIALYSIS

• Hypoxemia can be a significant complication of
  hemodialysis causing intradialytic morbid events
  such as hypotension, cramping, as well as periods
  of tissue ischemia. This has been attributed to
  the release of adenosine. Tissue ischemia causes
  the release of adenosine which subsequently
  blocks the release of norepinephrine from the
  sympathetic nerve terminals and has intrinsic
  vasodilator properties. Thus, hypotension can
  perpetuate itself through the release of
  adenosine and its effects.
• (See diagram below)

Figure 7 Tissue Ischemia

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HYPOXEMIA DURING HEMODIALYSIS

• As many as 26 of patients drop their O2
  Sat 2-8 in the first hour of dialysis 56 of
  patients experience at least one episode of
  hypoxemia. Sleep apnea occurs in approximately 50
  to 70 of all treatments. With the chronic
  hemodialysis cardiac mortality rate of
  approximately 50, any additional cardiac stress
  has to be viewed as detrimental. The incidence
  of intradialytic hypoxic events may be
  underestimated as an additional causal factor of
  chronic deterioration of the cardiovascular
  system. (See Sleep Apnea profile below)
• The Crit-Line Monitor provides a continuous,
  real time O2 Sat that is insensitive to poor skin
  perfusion, peripheral vasoconstriction,
  hypotension, hypovolemia, multiple previous
  accesses, low body temperature, and other
  dialysis related factors that cause errors in
  pulse oximeters. The Crit-Line Monitor measures
  the true arterial saturation (SaO2 ) via the
  fistula/ graft or a mixed venous saturation
  (SvO2) via a CVC line.
• Hypoxemia generally occurs at SaO2 levels of lt90
  (COPD patients may exhibit readings in the 80s).
  Acceptable SvO2 ranges between 60-80.
  Hypoxemia may present with a drop of 5-10
  below the patients previous value. Hypoxemia may
  also occur with severe anemia (HCT lt25). Oxygen
  Saturation is the percent to which hemoglobin
  (HGB) is filled with O2. The more anemic the
  patient is, (the lower the HCT) the fewer total
  HGB molecules they have. This causes the total
  amount of O2 available to the tissues to be low,
  even though the O2 sat appears normal. O2
  saturation must be interpreted in relationship to
  the degree of anemia.
• If the O2 saturation or HCT fall below the
  above parameters, suggesting hypoxemia, clinical
  protocol for administering oxygen should be
  followed.

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HYPOTENSION-- NOT PREDICTED BY BP CUFF
Currently, clinicians are relying on symptoms
like a drop in blood pressure to determine when a
patient has had a potentially dangerous reduction
in their vascular volume. There are two inherent
problems with relying on blood pressure as an
indicator of hypotension and hypovolemia. The
two graphs above illustrate these problems. The
dots represent systolic blood pressure
measurements that were taken every fifteen
minutes, and the profile represents change in
blood volume. In figure 1 the blood pressure
did not drop until after the patient had
experienced symptoms. Not allowing the clinician
a chance for prevention. However, the blood
volume profile did show a rapid decrease in the
blood volume and that the patient could no longer
tolerate the current Ultrafiltration rate. In
the second figure, the patient experienced
hypovolemic symptoms with no corresponding change
in blood pressure again not allowing for
detection or prevention by the clinician. As
illustrated the blood pressure may not drop until
after symptoms occur, or the blood pressure may
not drop at all. Using the information on the
Crit-Line, the clinician can now see how well a
patient is plasma refilling and can take
proactive steps to prevent crashing.
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CASE STUDY - A OVERLOADED PATIENT PROFILE
BVD
The graph above is a blood volume profile printed
from a CRIT-LINE Monitor after monitoring a
patient on dialysis for 4 hours 20 minutes.
During treatment, 4 liters of fluid were removed,
however, the patients PRR was slightly faster
than the UFR, as depicted by the positive trend
in blood volume. This is an indication that at
the completion of dialysis the patient still had
extra fluid in the intravascular space and extra
fluid in the extracellular space. This graph
represents an A or fluid overloaded profile,
which is typical of a patient who is not at their
ideal dry weight.
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CASE STUDY - B OR IDEAL PATIENT PROFILE
In this treatment the nurse removed 3.5 liters.
There is a gentle decline in blood volume
(recommended blood volume change is approximately
minus 5 per hour), and the patient was
asymptomatic. This profile indicates that the
prescribed fluid removal not only removed
extracellular fluid but also dipped into the
patients intravascular space reducing the blood
volume in the intravascular space to the normal
level on the Guyton Curve. Dialyzing a patient to
their ideal dry weight reduces the risk of CHF,
LVH, and hypertension. The ultrafiltration rate
(UFR) was slightly faster than the patients
plasma refilling rate (PRR). This is the ideal
profile for this patient.
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CASE STUDY - INTERVENING USING THE CRIT-LINE
This patient run demonstrates how the CRIT-LINE
Monitor is typically used to guide nurse
intervention during a dialysis treatment. The
patients original goal was 3.2 liters. Using
feedback from the CRIT-LINE Monitor, the UFR was
increased from 800 ml/hour to 1500 ml/hr to
obtain a gradual (5 per hour) decrease in blood
volume. After 2 hours 20 minutes the original
goal of 3.2 liters was reached. A dry weight
check was performed to see if the patients blood
volume would rebound. As shown in the above
graph, refill occurred indicating there was
additional fluid in the extracellular space. The
nurse then decided to challenge the patients dry
weight by turning the UFR back to 500 ml/hr and
placing the patient in Trendelenberg. The nurse
removed an additional liter of fluid and turned
the UFR to minimum again, resulting in another
plasma refill. The UFR was turned back on to 800
ml/hr and an additional 0.5 liters were removed.
The ability to see how the intravascular space is
being refilled is critical during aggressive or
challenging treatments.
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CASE STUDY - VOLUME OVERLOADED/HYPOTENSIVE PATIENT
A volume overloaded, hypotensive patient can be
difficult to dialyze. Additional fluid in the
intravascular space of a dialysis patient can be
one of the primary causes of elevated blood
pressure. However, if the patient becomes too
overloaded the extra volume may overcome the
bodies compensatory mechanisms and cause the
patient to have a low pre-dialysis blood pressure
and/or pressure drop during dialysis. The patient
in the example above had a low starting blood
pressure due to extreme volume overload. In
addition, the patient would consistently
experience a blood pressure drop 10 to 15 minutes
into the treatment. In response to the pressure
dropping the staff was forced to discontinue
ultrafiltration and infuse saline. These
measures would fail to bring the blood pressure
up and as a result the fluid removal goal was
never achieved. Monitoring the patient with the
CRIT-LINE Monitor the nurse could see the
patients blood volume level was actually
increasing during dialysis. Realizing that a
positive trend in blood volume would cause a
further drop in blood pressure, the nurse
increased the fluid foal from 7 liters to 8.8
liters. This caused the blood volume to
gradually decrease to a normal level allowing the
compensatory mechanisms of the body to return the
blood pressure to a more normal level. The
original fluid goal was exceeded by 1 liter.
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CASE STUDY - INTERVENING WITH TRENDELENBERG
Due to the rapid decrease in blood volume (minus
15 in the first hour), the nurse intervened by
placing the patient in Trendelenberg. Without
changing the ultrafiltration rate, this caused a
rebound effect , helping the body plasma refill
more quickly. The refill suggests that there is
additional extracellular fluid, however the
patients body was unable to transfer this fluid
into the intravascular space fast enough to
compensate for the UFR. Trendelenberg assisted
the patient in shifting fluids to the
intravascular space. Upon returning to sitting
position, the graph began to drop off rapidly
again. As the graph started to rapidly drop
again, the nurse put the patient back in
Trendelenberg position. This action flattened
the blood volume profile. The nurse was able to
manipulate this treatment using only
Trendelenberg position to achieve the UF goal
with no symptoms.
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CASE STUDY - MORE FLUID REMOVED/DRY WEIGHT CHECK
In this treatment the original fluid removal goal
was 2.4 liters. Using the CRIT-LINE instrument
as a guide to increase the ultrafiltration rate,
an additional 2.8 liters of fluid were removed.
By seeing the blood volume change in real time
the nurse was able to challenge the patient
safely. If the patient had been unable to keep
up with the more aggressive fluid removal the
blood volume profile would have started to drop
off dramatically (PRR was less than the UFR) and
the nurse would have reduced the goal before the
patient experienced hypovolemic symptoms. At the
end of the treatment she performed a Dry Weight
Check by reducing the UFR to minimum. If fluid
is no longer being ultrafiltrated, any fluid
above normal that is left in the extracellular
space will refill the intravascular space. As
stated previously, an ideal dialysis session
would remove any fluid in the extracellular space
that is above the normal point on the Guyton
curve. It would also bring the intravascular
volume to normal levels. However, as shown in
the above graph, there is a rebound in blood
volume, refill, which indicated there is more
fluid to be removed. A patient is typically not
at their ideal dry weight if their fluid removal
goal was achieved and a dry weight check
indicates more fluid could have been removed.