764
P A R T 8
Drugs acting on the cardiovascular system
T
hrombolytic agents
Thrombolytic agents
break down the thrombus that
has been formed by stimulating the plasmin system.
This process is called clot resolution. Thrombolytic
agents include alteplase (
Actilyse
), reteplase (
Rapilysin
),
streptokinase (
Streptase
[not available in Australia]) and
tenecteplase (
Metalyse
)
.
Therapeutic actions and indications
If a thrombus has already formed in a vessel (e.g. during
an acute MI), it may be necessary to dissolve that clot to
open the vessel and restore blood flow to the dependent
tissue. All of the drugs that are available for this purpose
work to activate the natural anticlotting system—con
version of plasminogen to plasmin. The activation of
indwelling catheters and threatened abortion.
Also screen for pregnancy
to ensure that benefits
outweigh any potential risks (contraindicated with
warfarin)
; breastfeeding,
because of the potential
for risks to the baby
(use of heparin is suggested if
an anticoagulant is needed during breastfeeding);
renal or hepatic disease,
which could interfere with
the metabolism and effectiveness of these drugs
;
HF; thyrotoxicosis; senility or psychosis
because of
the potential for unexpected effects
; and diarrhoea
or fever,
which could alter the normal clotting
process.
■
■
Assess baseline status before beginning therapy
to determine any potential adverse effects.
This
includes body temperature; skin colour, lesions
and temperature; affect, orientation and reflexes;
pulse, blood pressure and perfusion; respirations
and adventitious sounds; clotting studies, renal and
hepatic function tests, FBC and stool guaiac; and
electrocardiogram (ECG), if appropriate.
Implementation with rationale
■
■
Evaluate for therapeutic effects of warfarin—
prothrombin time (PT) 1.5 to 2.5 times the
control value or ratio of PT to INR (International
Normalised Ratio) of 2 to 3—
to evaluate the
effectiveness of the drug dose.
■
■
Evaluate for therapeutic effects of heparin—whole
blood clotting time (WBCT) 2.5 to 3 times control
or activated partial thromboplastin time (APTT)
1.5 to 3 times the control value—
to evaluate the
effectiveness of the drug dose.
■
■
Evaluate the person regularly for any sign of blood
loss (petechiae, bleeding gums, bruises, dark-
coloured stools, dark-coloured urine)
to evaluate
the effectiveness of the drug dose and to determine
the need to consult with the prescriber if bleeding
becomes apparent.
■
■
Establish safety precautions
to protect the person
from injury.
■
■
Provide safety measures, such as use of an electric
razor and avoidance of contact sports,
to decrease
the risk of bleeding.
■
■
Provide increased precautions against bleeding
during invasive procedures; use pressure dressings;
avoid intramuscular injections; and do not rub SC
injection sites
because the state of anticoagulation
increases the risk of blood loss.
■
■
Mark the chart of any individual receiving this
drug
to alert the medical staff that there is a
potential for increased bleeding.
■
■
Maintain antidotes on standby (protamine sulfate
for heparin, vitamin K for warfarin)
in case of
overdose.
■
■
Monitor the person carefully when any drug is
added to or withdrawn from the drug regimen
of a person taking warfarin
because of the risk
of drug–drug interactions that would change the
effectiveness of the anticoagulant.
■
■
Make sure that the person receives regular
follow-up and monitoring, including measurement
of clotting times,
to ensure maximum therapeutic
effects.
■
■
Provide thorough teaching, including the name
of the drug, dosage prescribed, measures to avoid
adverse effects, warning signs of problems, the
need for periodic monitoring and evaluation,
and the need to wear or carry a MedicAlert
notification,
to enhance knowledge about drug
therapy and to promote compliance with the drug
regimen.
■
■
Offer support and encouragement
to help the
person deal with the diagnosis and the drug
regimen.
Evaluation
■
■
Monitor response to the drug: increased bleeding
time (warfarin, PT 1.5 to 2.5 times the control
value or PT/INR ratio of 2 to 3; heparin, WBCT of
2.5 to 3 times the control value or APTT of 1.5 to
3 times the control value).
■
■
Monitor for adverse effects (bleeding, bone marrow
depression, alopecia, GI upset, rash).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage, adverse effects
to watch for and specific measures to avoid them;
the individual understands the importance of
continued follow-up).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
