C H A P T E R 4 4
Cardiotonic agents
693
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The cardiac glycoside digoxin increases the movement
of calcium into the heart muscle. This results in
increased force of contraction, which increases blood
flow to the kidneys (causing a diuretic effect), slows
the heart rate and slows conduction through the
atrioventricular node. All of these effects decrease the
heart’s workload.
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Phosphodiesterase inhibitors block the breakdown
of cAMP in the cardiac muscle. This allows more
calcium to enter the cell (leading to more intense
contraction) and increases the effects of sympathetic
stimulation (which can lead to vasodilation but also
can increase pulse, blood pressure and workload on
the heart).
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Phosphodiesterase inhibitors are associated with
severe effects. They are reserved for use in extreme
situations. They are only available for IV use.
CHAPTER SUMMARY
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HF, a condition in which the heart muscle fails to
effectively pump blood through the cardiovascular
system, can be the result of a damaged heart muscle
and increased demand to work harder.
KEY POINTS
to avoid hypersensitivity reactions
; acute aortic
or pulmonic valvular disease, acute MI or fluid
volume deficit and ventricular arrhythmias,
which
could be exacerbated by these drugs
; and current
status of pregnancy and breastfeeding
to prevent
potential adverse effects to the fetus or baby.
■
■
Perform a physical assessment
to establish baseline
status before beginning therapy, determine the
effectiveness of therapy and evaluate for any
potential adverse effects.
■
■
Assess cardiac status closely, including pulse and
blood pressure,
to identify changes or the presence
of adverse effects
; auscultate heart sounds, noting
any evidence of abnormal sounds.
■
■
Obtain the person’s weight, noting any recent
increases or decreases,
to determine the fluid status.
■
■
Inspect skin and mucous membranes for colour,
and check nail beds and capillary refill
for evidence
of perfusion.
■
■
Examine the abdomen for distension; auscultate
bowel sounds
to evaluate GI motility.
■
■
Assess voiding patterns and urinary output
to
provide a gross indication of renal function.
■
■
Obtain a baseline ECG
to identify rate and rhythm
and evaluate for possible changes.
■
■
Monitor the results of laboratory tests, including
serum electrolyte levels, full blood count, and renal
and hepatic function tests,
to determine the need
for possible dose adjustment.
Implementation with rationale
■
■
Protect the drug from light
to prevent drug
degradation
.
■
■
Ensure that the person has a patent intravenous
access site available
to allow for intravenous
administration of the drug.
■
■
Monitor pulse and blood pressure frequently during
administration
to monitor for adverse effects so that
the dose can be altered if needed to avoid toxicity.
■
■
Monitor input and output and record daily weight
to evaluate the resolution of HF.
■
■
Monitor platelet counts before and regularly during
therapy
to ensure that the dose is appropriate
;
inspect the skin for bruising or petechiae
to detect
early signs of thrombocytopenia
; consult with the
prescriber about the need to decrease the dose at
the first sign of thrombocytopenia.
■
■
Monitor intravenous injection sites and provide
comfort measures
if infusion is causing irritation.
■
■
Provide life support equipment on standby
in case
of severe reaction to the drug or development of
ventricular arrhythmias.
■
■
Provide comfort measures
to help the person
tolerate drug effects.
These include small, frequent
meals
to alleviate GI upset and anorexia
; access to
bathroom facilities to provide needed facilities if GI
upset is severe and when increased urination occurs
secondary to increased cardiac output; safety
precautions
to protect the person if visual changes,
dizziness or weakness occur
s; and orientation to
surroundings
to support the person if CNS changes
occur.
■
■
Offer support and encouragement
to help the person
deal with the diagnosis and the drug regimen.
■
■
Provide thorough teaching, including the name
of the drug, dosage prescribed, measures to avoid
adverse effects, warning signs of problems and
the need for periodic monitoring and evaluation,
to enhance knowledge about drug therapy and to
promote compliance.
Evaluation
■
■
Monitor response to the drug (alleviation of signs
and symptoms of HF).
■
■
Monitor for adverse effects (hypotension, cardiac
arrhythmias, GI upset, thrombocytopenia).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage, adverse effects to
watch for, specific measures to avoid them and the
importance of continued follow-up).
