C H A P T E R 4 8
Drugs affecting blood coagulation
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CRITICAL THINKING
What care interventions should be done at this point?
Why do people with mitral valve disease frequently develop
AF?
Think about why emboli formwhen the atria fibrillate.
Stabilising G.R. on warfarin may take several weeks of blood
tests and dose adjustments.
How can this process be
made easier?
What teaching points should be covered with G.R. to
ensure that she is protected from emboli and does not
experience excessive bleeding?
DISCUSSION
G.R.’s situation is complex. She has a progressive
degenerative valve disease that usually leads to heart failure
(HF) and frequently to other complications, such as AF and
emboli formation. Her digoxin and potassium levels should
be checked to determine whether her HF has stabilised or
the digoxin is causing the AF because of excessive doses
or potassium imbalance. If these tests are within normal
limits, G.R. may be experiencing AF because of irritation
to the atrial cells caused by the damaged mitral valve
and associated swelling and scarring. If this is the case, an
anticoagulant will help protect G.R. against emboli, which
form in the auricles when blood pools there while the atria
are fibrillating. There is less chance of emboli formation if
clotting is slowed.
G.R. will need extensive teaching about warfarin,
including the need for frequent blood tests, the list of
potential drug–drug interactions, the importance of
being alert to the many factors that can affect dose needs
(including illness and diet) and how to monitor for subtle
blood loss. This can also be a good opportunity to review
teaching about valvular disease and HF and to answer any
questions that she might have about how all of these things
interrelate. If possible, it would be useful to teach G.R. or a
responsible caregiver how to take a pulse so that G.R. can be
alerted to potential arrhythmias and avert problems before
they begin. It also would be a good idea to check on support
services for G.R. to ensure that her blood tests can be done
and that her response to the drug is monitored carefully.
CARE GUIDE FOR G.R.: WARFARIN
Assessment: History and examination
Assess G.R.’s health history for allergies to warfarin, subacute
bacterial endocarditis (SBE), haemorrhagic disorders,
tuberculosis, renal or hepatic dysfunction, gastric ulcers,
thyroid disease, uncontrolled hypertension, severe
trauma or a long-term indwelling catheter (which
increases the risk of bleeding). Also assess concurrent use
of numerous drugs and herbal therapies.
Focus the physical examination on the following areas:
Cardiovascular: blood pressure, pulse, perfusion, baseline
electrocardiogram (ECG)
Neurological (CNS): orientation, affect, reflexes, vision
Skin: colour, lesions, texture
Respiratory system: respiratory rate and character,
adventitious sounds
GI: abdominal examination, guaiac stool test results (for
occult blood)
Laboratory tests: liver and renal function tests, prothrombin
time (PT), International Normalised Ratio (INR)
Implementation
Ensure proper administration of the drug.
Provide comfort and safety measures, such as small
meals, protection from injury during invasive and
other procedures, bowel program as needed, standby
antidotes (e.g. vitamin K) and careful skin care.
Provide support and reassurance to deal with drug effects.
Provide teaching regarding drug, dosage, adverse effects,
what to report and safety precautions.
Evaluation
Evaluate drug effects: increased bleeding times,
PT 1.5–2.5 times control or PT/INR ratio of 2:3.
Monitor for adverse effects: bleeding, alopecia, rash,
GI upset, excessive bleeding.
Monitor for drug–drug interactions (numerous).
Evaluate the effectiveness of the teaching program and
comfort and safety measures.
TEACHING FOR G.R.
• An anticoagulant slows the body’s normal blood clotting
processes to prevent harmful blood clots from forming.
This type of drug is often called a “blood thinner”;
however, it cannot dissolve any clots that have already
formed.
•
Never
change any medication that you are taking—such
as adding or stopping another drug, taking a new over-
the-counter medication, or stopping one that you have
been taking regularly—without consulting with your
healthcare provider. Many other drugs affect the way that
your anticoagulant works; starting or stopping another
drug can cause excessive bleeding or interfere with the
desired effects of the drug.
• Some of the following adverse effects may occur:
•
Stomach bloating, cramps:
These problems often pass
with time; consult your healthcare provider if they
persist or become too uncomfortable.
•
Loss of hair, skin rash:
These problems can be very
frustrating; you may wish to discuss these with your
healthcare provider.
•
Orange-yellow discolouration of the urine:
This can be
frightening, but it may just be an effect of the drug. If
you are concerned that this might be blood, simply add
vinegar to your urine; the colour should disappear. If the
colour does not disappear, it may be caused by blood,
and you should contact your healthcare provider.
