Anemia in Kidney Disease and
Dialysis
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If
your blood is low in red blood cells,
you have anemia. Red blood cells carry
oxygen (O2)
to tissues and organs throughout your
body and enable them to use the energy
from food. Without oxygen, these tissues
and organs?particularly the heart and
brain?may not do their jobs as well as
they should. For this reason, if you
have anemia, you may tire easily and
look pale. Anemia may also contribute to
heart problems.
Anemia is common in people with kidney
disease. Healthy kidneys produce a
hormone called erythropoietin, or EPO,
which stimulates the bone marrow to
produce the proper number of red blood
cells needed to carry oxygen to vital
organs. Diseased kidneys, however, often
don't make enough EPO. As a result, the
bone marrow makes fewer red blood cells.
Other common causes of anemia include
loss of blood from hemodialysis and low
levels of iron and folic acid. These
nutrients from food help young red blood
cells make hemoglobin (Hgb), their main
oxygen-carrying protein.
|
Healthy kidneys produce a hormone called erythropoietin, or
EPO, which stimulates the bone
marrow to make red blood cells
needed to carry oxygen (O2)
throughout the body. |
Diseased kidneys don't make enough EPO, and bone marrow then
makes fewer red blood cells. |
Laboratory Tests
A
complete blood count (CBC), a laboratory
test performed on a sample of your
blood, includes a determination of your
hematocrit (Hct), the percentage of the
blood that consists of red blood cells.
The CBC also measures the amount of Hgb
in your blood. The range of normal Hct
and Hgb in women who menstruate is
slightly lower than for healthy men or
healthy postmenopausal women. The Hgb is
usually about one-third the value of the
Hct.
When Anemia Begins
Anemia may begin to develop in the early
stages of kidney disease, when you still
have 20 percent to 50 percent of your
normal kidney function. This partial
loss of kidney function is often called
chronic renal insufficiency. Anemia
tends to worsen as kidney disease
progresses. End-stage kidney failure,
the point at which dialysis or kidney
transplantation becomes necessary,
doesn't occur until you have only about
10 percent of your kidney function
remaining. Nearly everyone with
end-stage kidney failure has anemia.
Diagnosis
If
you have lost at least half of normal
kidney function (based on your
glomerular filtration rate calculated
using your serum creatinine measurement)
and have a low Hct, the most likely
cause of anemia is decreased EPO
production. The National Kidney
Foundation's Dialysis Outcomes Quality
Initiative (DOQI) recommends that
doctors begin a detailed evaluation of
anemia in men and postmenopausal women
on dialysis when the Hct value falls
below 37 percent. For women of
childbearing age, evaluation should
begin when the Hct falls below 33
percent. The evaluation will include
tests for iron deficiency and blood loss
in the stool to be certain there are no
other reasons for the anemia.
|
When to Evaluate Dialysis
Patients for Anemia |
|
|
Hematocrit (Hct) |
Hemoglobin (Hgb) |
|
Women who menstruate |
less than 33% |
less than 11 g/dL |
|
All men and postmenopausal women |
less than 37% |
less than 12 g/dL |
Source: The
National Kidney Foundation's Dialysis
Outcomes Quality Initiative.
Treatment
EPO
If
no other cause for EPO deficiency is
found, it can be treated with a
genetically engineered form of the
hormone, which is usually injected under
the skin two or three times a week.
Hemodialysis patients who can't tolerate
EPO shots may receive the hormone
intravenously during treatment, but this
method requires a larger, more expensive
dose and may not be as effective. DOQI
recommends that patients treated with
EPO therapy should achieve a target Hgb
of 11 to 12 g/dL.
Iron
Many people with kidney disease need
both EPO and iron supplements to raise
their Hct to a satisfactory level. If
your iron levels are too low, EPO won't
help and you'll continue to experience
the effects of anemia. You may be able
to take an iron pill, but many studies
show that iron pills don't work as well
in people with kidney failure as iron
given intravenously. Iron is injected
directly into an arm or into the tube
that returns blood to your body during
hemodialysis.
A
nurse or doctor will give you a test
dose because a very small number of
people (less than 1 percent) have a bad
reaction to iron injections. If you
begin to wheeze or have trouble
breathing, your health care provider can
administer epinephrine or
corticosteroids to counter the reaction.
Even though the risk is small, you'll be
asked to sign a form stating that you
understand the possible reaction and
that you agree to have the treatment.
Talk with your health care provider if
you have any questions.
In
addition to measuring your Hct and Hgb,
your tests will also include two
measurements to show whether you have
enough iron.
-
Your ferritin level indicates the amount of iron stored in your
body. According to DOQI guidelines,
your ferritin score should be no
less than 100 micrograms per liter
(mcg/L) and no more than 800 mcg/L.
-
TSAT stands for transferrin saturation, a score that indicates how
much iron is available to make red
blood cells. DOQI guidelines call
for a TSAT score between 20 percent
and 50 percent.
Other Causes of
Anemia
In
addition to EPO and iron, a few people
may also need vitamin B12
and folic acid supplements.
If
EPO, iron, vitamin B12,
and folic acid all fail, your doctor
should look for other causes such as
sickle cell disease or an inflammatory
problem. At one time, aluminum poisoning
contributed to anemia in people with
kidney failure because many phosphate
binders used to treat bone disease
caused by kidney failure were antacids
that contained aluminum. But
aluminum-free alternatives are now
widely available. Be sure your phosphate
binder and your other drugs are free of
aluminum.
Anemia keeps many people with kidney
disease from feeling their best. But EPO
treatments help most patients raise
their Hgb, feel better, live longer, and
have more energy.
Hope Through
Research
The National Institute of Diabetes and
Digestive and Kidney Diseases (NIDDK),
through its Division of Kidney,
Urologic, and Hematologic Diseases,
supports several programs and studies
devoted to improving treatment for
patients with progressive kidney disease
and end-stage kidney failure, which is
sometimes called end-stage renal disease
or ESRD, including patients on
hemodialysis:
-
The End-Stage Renal Disease Program.
This program promotes research to
reduce medical problems from bone,
blood, nervous system, metabolic,
gastrointestinal, cardiovascular,
and endocrine abnormalities in
end-stage kidney failure and to
improve the effectiveness of
dialysis and transplantation. The
research focuses on reuse of
hemodialysis membranes and on using
alternative dialyzer sterilization
methods; on devising more efficient,
biocompatible membranes; on refining
high-flux hemodialysis; and on
developing criteria for dialysis
adequacy. The program also seeks to
increase kidney graft and patient
survival and to maximize quality of
life.
-
The Frequent Hemodialysis Network.
This multicenter clinical trial will
test whether receiving hemodialysis
more than three times a week
provides better outcomes than the
normal schedule of three sessions
per week.
-
The U.S. Renal Data System (USRDS).
This
national data system collects,
analyzes, and distributes
information about the use of
dialysis and transplantation to
treat kidney failure in the United
States. The USRDS is funded directly
by the NIDDK in conjunction with the
Centers for Medicare & Medicaid
Services. The USRDS publishes an Annual Data Report, which
characterizes the total population
of people being treated for kidney
failure; reports on incidence,
prevalence, mortality rates, and
trends over time; and develops data
on the effects of various treatment
modalities. The report also helps
identify problems and opportunities
for more focused special studies of
renal research issues.
-
The Hemodialysis Vascular Access Clinical Trials Consortium
is conducting a series of
multicenter, randomized,
placebo-controlled clinical trials
of drug therapies to reduce the
failure and complication rate of
arteriovenous grafts and fistulas in
hemodialysis. Recently developed
antithrombotic agents and drugs to
inhibit cytokines are being
evaluated in these large clinical
trials.
