Transcript Hemodialysis Prescription

Hemodialysis Prescription
Shahram Taheri M.D.
Associate of Prof.
Isfahan School of Medicine
Principle of Hemodialysis
Vein
Artery
Dialysis Rx:
 Time: 2-5 hours
 Bath
 Blood flow rate: 400-450cc/min
 Dialysate flow rate: 500-800cc/min
 Anticoagulant
 Additives:
◦ Anemia (EPO, blood)
◦ Bone metabolism (vit D, calcitriol, etc)
◦ Meds (antibiotics)
ADEQUACY OF DIALYSIS
• The higher mortality rate in the United States was thought to
be related at least in part to inadequate dialysis.
• The weekly dialysis times declined progressively in the
United States from 25 to 40 hours in the 1960s to 12 to 15
hours in the 1970s and 1980s to as low as seven to eight
hours in the 1990s.
Dialysis adequacy
5
• Studies in both Germany and the United
States have documented the relationship
between shorter dialysis time and poorer
outcome.
• Patients dialyzed fewer than 3.5 hours three
times per week have approximately twice
the mortality risk compared to patients
dialyzed four or more hours three times per
week.
Dialysis adequacy
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• These patients, who were dialyzed very
intensively (Kt/V of 1.67), also had a high
incidence of full rehabilitation and almost all
patients were rendered normotensive on no
antihypertensive medications.
Dialysis adequacy
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How is dialysis adequacy
calculated
1. Prescribed KT/V
2. Measured KT/V
Dialysis adequacy
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 Kt/V
is defined as the dialyzer
clearance of urea (K, obtained from
the manufacturer in mL/min, and
periodically measured and verified
by the dialysis team) multiplied by
the duration of the dialysis
treatment (t, in minutes) divided
by the volume of distribution of
urea in the body (V, in mL), which
is approximately equal to the total
body water.
Dialysis adequacy
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Prescribed KT/V
CLEARANCE
In ml/min
Distribution
Volume of urea
In ml
K T / V
Dialysis adequacy
10
Measured KT/V
Kt/V = -ln (R - 0.03) + [(4 - 3.5R) x (UF ÷ W)]
URR = (1 - [postdialysis BUN ÷ predialysis BUN])
Dialysis adequacy
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Dialysis adequacy
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 Cognizant
of the results from the HEMO
study, we continue to aim for a singlepool Kt/V of approximately 1.4 to 1.6
Dialysis adequacy
13
A number of factors contribute to Kt/V
including:
The size of the dialysis membrane, since
larger surface area membranes can remove
more urea per unit time.
 The blood flow rate to the dialyzer (Qb),
since presenting new plasma with a high
urea concentration maintains the favorable
gradient for urea removal.
 The dialysate flow rate (Qd), since delivering
new fluid containing no urea also maintains
the urea concentration gradient.

Dialysis adequacy
14
Ultrafiltration, which removes urea by
convection in a concentration similar to
that in the plasma, also plays a
contributory role.
 Convective loss of small solutes is of
minor importance with standard
dialysis, but is the primary route of urea
removal with continuous dialytic
therapies for acute renal failure.

Dialysis adequacy
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Hemodialysis Filter (Dialyzer)
Hemodialysis Filter (Dialyzer)
Hemodialysis Vascular Access
Polytetrafluoroethylene
Arteriovenous (AV) Fistula
Question 1
• Which type of vascular access is associated
with better outcomes in hemodialysis
patients? (choose one answer):
1.
2.
3.
4.
Central venous cuffed catheter
Arteriovenous graft
Arteriovenous fistula
Temporary central venous catheter
Which Vascular Access and
When Should It Be Placed?
Initial presentation:
HTN, CKD, proteinuria
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eGFR cc/min/1.73m
CKD Progression
Vascular
Access
(AVF)
Dates
HD
SODIUM



Ideally, dialysate sodium should be slightly lower, than
the patient’s sodium level
Currently, sodium is viewed more as a way to stabilize
intra-dialytic blood pressure rather than a way to
“ultrafiltrate” and reduce circulating volume
Traditional “sodium modeling” results in a gain of sodium,
an increase in post-dialytic thirst, resulting in increased
interdialytic wt gain
Sodium

The choice of dialysate sodium concentration for
individual patients depends upon the predialysis
serum sodium concentration and the hemodynamic
status of the patient
Patients with normal serum sodium

For most patients with normal or near-normal serum
sodium levels, we use a sodium dialysate
concentration of approximately 137 mEq/L.
Hypernatremia

If the serum sodium concentration is only mildly
elevated, we use a dialysate sodium concentration
that is within 2 mEq/L of the plasma sodium
concentration for the first dialysis session.
Hypernatremia

The use of dialysate sodium concentrations more than
3 to 5 mEq/L below the plasma sodium concentration
is associated with hypotension, muscle cramps, and,
most importantly, disequilibrium syndrome.
Subsequently, correction of the hypernatremia is
performed with the administration of hypotonic
solutions.
TEMPERATURE



Normal dialysate temperature (37° C) results in
positive thermal gain, resulting in vasodilation and
drop in B/P
Lower temperature dialysate prevents the thermal
gain and results in greater stability of B/P
Lowering dialysate temperature should be one of the
first considerations in improving intra-dialytic stability
Potassium

Patients with severe hyperkalemia are often treated
medically prior to dialysis.
Patients with potassium <4.0 mEq/L


If the predialysis serum potassium level is <4.0
mEq/L, we use a dialysate potassium concentration of
4.0 mEq/L.
This concentration prevents the development of
hypokalemia and its complications.
Patients with potassium between 4.0 and 5.5 mEq/L


If the predialysis serum potassium level is between 4.0 and 5.5 mEq/L,
the typical dialysate potassium concentration ranges from 2.0 to 4.0
mEq/L.
We generally use a dialysate potassium of 3.0 mEq/L if the predialysis
serum potassium is between 4.5 to 5.5 mEq/L.
Patients with potassium between 5.5 and 8.0 mEq/L


If the predialysis potassium level is between 5.5
mEq/L and 8.0 mEq/L, then we generally use a 2.0
mEq/L dialysate potassium bath.
An exception may be made for patients who are at
risk for arrhythmias related to potassium removal, for
whom some nephrologists do not use a dialysate
potassium <3.0 mEq/L
Buffer solutions


The main dialysate buffer used in intermittent
hemodialysis is bicarbonate.
Bicarbonate is inexpensive and generally well
tolerated, without the hemodynamic problems that
may be observed with acetate.
Buffer solutions

A disadvantage of bicarbonate is that it precipitates as
an insoluble salt when stored together with the
divalent cations, calcium and magnesium, thereby
requiring the buffer and electrolytes to be stored
separately prior to hemodialysis.
Buffer solutions


The dialysate bicarbonate concentration varies based
upon the acid-base status of the patient.
The acid-base status should be assessed using both
the serum bicarbonate and pH.
Buffer solutions

In addition, possible side effects of bicarbonate
include hypoxemia due to decreased respiratory drive
related to the higher pH, and altered mental status,
weakness, cramping, and lethargy due to acute
metabolic alkalosis.
Mild or moderate metabolic acidosis

For patients with mild or moderate metabolic acidosis
(ie, serum bicarbonate 10 to 23 mEq/L and an
acidemic pH), we generally use dialysate bicarbonate
concentration of approximately 30 to 35 mEq/L.
Severe metabolic acidosis


For patients with severe metabolic acidosis (ie, serum
bicarbonate <10 mEq/L and a severely acidemic pH),
the concentration of the bicarbonate solution may be
increased to approximately 35 to 40 mEq/L.
For such patients, an extended duration of
hemodialysis may be necessary.
Calcium


For patients with significant hypocalcemia (total
plasma calcium level <8.0 mg/dL [<2.0 mmol/L],
corrected for hypoalbuminemia), particularly if the
patient is symptomatic, we use a dialysate calcium
concentration of 3.0 to 3.5 mEq/L.
For patients with severe hypercalcemia (total plasma
calcium level >12.0 mg/dL [>3.0 mmol/L]), we use a
dialysate calcium concentration of 2.0 to 2.5 mEq/L.
Calcium

For patients with mild hypocalcemia, normocalcemia,
or mild hypercalcemia (total plasma calcium level
between 8.0 to 12.0 mg/dL [2.0 to 3.0 mmol/L]), we
use a dialysate calcium concentration of 2.5 mEq/L.
Magnesium

The usual dialysate magnesium concentration is 0.5 to
1.0 mEq/L.
Chloride

The amount of dialysate chloride is dependent upon
the dialysate sodium and bicarbonate concentrations.
Glucose

The standard dialysate glucose concentration is
generally either 100 mg/dL (5.5 mmol/L) or 200
mg/dL (11.1 mmol/L).
BLOOD FLOW RATE

We select the blood flow rate based, at least initially,
by the duration of significant azotemia (ie, blood urea
nitrogen [BUN] >100 mg/dL) prior to starting dialysis.
BLOOD FLOW RATE

Among patients with severe, longstanding azotemia,
the rapid reduction of solute should be avoided, in
order to prevent dialysis dysequilibrium syndrome.
BLOOD FLOW RATE


If the BUN has been >100 mg/dL for at least three
days in the patient with acute kidney injury (AKI), we
use a blood flow rate less than 200 mL/min for the
first treatment.
If the BUN has not been >100 mg/dL for at least
three days, we use a dialysis blood flow rate of 300350 mL/min.
ULTRAFILTRATION

The approach to volume overload is different for endstage renal disease (ESRD) patients undergoing
chronic maintenance dialysis and for critically ill AKI
patients.
ULTRAFILTRATION

The target weight of a chronic dialysis patient is
usually determined empirically as the weight at which
clinical signs of extracellular fluid expansion are
absent and below which clinical signs of extracellular
depletion arise.
ULTRAFILTRATION

In contrast, in critically ill acute renal failure (ARF)
patients, the volume expansion that is frequently
observed is often necessary to maintain optimal
circulatory and oxygen transport status.
ULTRAFILTRATION

In hemodynamically stable patients, the estimation of
target intravascular volume can be made in the usual
fashion utilized for ESRD patients.
ULTRAFILTRATION

In hemodynamically unstable patients, target
intravascular volume should be titrated to invasive or
noninvasive monitoring (such as bioimpedance
analysis, pulse contour analysis [PiCCO], or
echocardiography), which should guide the UF goals
for a given intermittent hemodialysis session.
Hemodialysis anticoagulation


Hemodialysis and continuous renal replacement
therapies require extracorporeal blood flow.
Some form of anticoagulation, usually with heparin, is
required to prevent thrombosis in the blood circuit.
STANDARD ANTICOAGULATION


Anticoagulation in routine hemodialysis consists of a
standard dose of heparin given as a bolus at the start
of the dialysis treatment, with a mid-treatment dose
to maintain suitable anticoagulation.
Heparin modeling can be performed using an initial
bolus followed by a constant fixed infusion of heparin
to maintain an activated clotting time (ACT) of 200 to
250 seconds (normal = 90 to 140 seconds).
No-heparin hemodialysis

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No-heparin hemodialysis was developed for use in the
patient at high risk of bleeding.
The protocol requires pretreating both the dialyzer
and blood lines with 2000 to 5000 units of heparin
contained in a liter of normal saline.
The heparinized saline is flushed from the
extracorporeal lines prior to the start of the dialysis
treatment so that heparin is not administered to the
patient.
No-heparin hemodialysis

Extracorporeal blood flows are rapidly increased to
250 to 500 mL/min and maintained throughout the
treatment, and 25 to 30 mL saline flushes are
administered every 15 to 30 minutes into the arterial
(predialyzer) limb to minimize hemoconcentration and
to wash fibrin strands from the kidney into the bubble
trap.
No-heparin hemodialysis


The volume of saline administered with such frequent
flushing must be removed during the dialysis to
prevent hypervolemia.
One-to-one nursing is required, with careful
monitoring of the arterial and venous pressure alarms
to detect early clotting.
Minimum-dose heparin


The use of minimum-dose heparin has been shown to
reduce bleeding complications in high-risk patients
when compared with regional heparinization with
protamine neutralization (10 versus 19 percent).
The protocol usually involves boluses of 500 units of
heparin every 30 minutes to keep the activated
clotting time >150 but <200 seconds.
Minimum-dose heparin

Alternately, a continuous infusion of heparin with
frequent activated clotting time (ACT) monitoring can
be used to achieve the same degree of
anticoagulation.