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P A R T 8
Drugs acting on the cardiovascular system
O
ther drugs affecting clot
formation
Other drugs that affect clot formation are also effective
in preventing thromboembolic episodes. These drugs
include the low-molecular-weight heparins, adjunctive
agents used to help alleviate adverse reactions to these
drugs and a haemorrheologic agent.
Low-molecular-weight heparins
In the late 1990s, a series of low-molecular-weight
heparins were developed. These drugs inhibit thrombus
and clot formation by blocking factors Xa and IIa.
Because of the size and nature of the molecules, these
drugs do not greatly affect thrombin, clotting or the
PT; therefore, they cause fewer systemic adverse effects.
They have also been found to block angiogenesis, the
process that allows cancer cells to develop new blood
vessels. They are being studied as possible adjuncts to
cancer chemotherapy. These drugs are indicated for very
specific uses in the prevention of clots and emboli for
mation after certain surgeries or prolonged bed rest. The
care of a person receiving one of these drugs is similar
to that of a person receiving heparin. The drug is given
just before (or just after) the surgery and then is con
tinued for 7 to 14 days during the postoperative recovery
process. Caution must be used to avoid combining these
drugs with standard heparin therapy; serious bleeding
episodes and deaths have been reported when this com
bination was inadvertently used. Low-molecular-weight
heparins include dalteparin (
Fragmin
), enoxaparin
(
Clexane
) and tinzaparin (
Innohep
[not available in
Australia]). See Table 48.1 for additional information
about these agents.
Anticoagulant adjunctive therapy
Agents used in anticoagulant adjunctive therapy include
lepirudin, protamine sulfate and vitamin K. See Focus
on safe medication administration under Adverse effects
for anticoagulants for additional information about
vitamin K and protamine sulfate. See also Table 48.1 for
additional information for each of these agents.
Lepirudin (
Refludan
[an unapproved drug in New
Zealand]) is an IV drug developed to treat a rare allergic
reaction to heparin. In some people, an allergy to heparin
precipitates a heparin-induced thrombocythaemia with
associated thromboembolic disease. Lepirudin directly
inhibits thrombin, blocking the thromboembolic effects
of this reaction. A 0.4-mg/kg initial IV bolus followed
by a continuous infusion of 0.15 mg/kg for 2 to 10 days
is the usual treatment. The individual needs to be moni
tored for bleeding from any site and for the development
of direct hepatic injury.
because the timing for the administration of
tenecteplase or streptokinase is critical to resolve
the clot before permanent damage occurs to the
myocardial cells.
■
■
Discontinue heparin if it is being given before
administration of a thrombolytic agent, unless
specifically ordered for coronary artery infusion,
to prevent excessive loss of blood.
■
■
Evaluate the person regularly for any sign of blood
loss (petechiae, bleeding gums, bruises, dark-
coloured stools, dark-coloured urine)
to evaluate
drug effectiveness and for the need to consult with
the prescriber if blood loss becomes apparent.
■
■
Monitor coagulation studies regularly; consult
with the prescriber
to adjust the drug dose
appropriately.
■
■
Institute treatment within 6 hours after the onset
of symptoms of acute MI
to achieve optimum
therapeutic effectiveness.
■
■
Arrange to type and cross-match blood
in case
of serious blood loss that requires whole-blood
transfusion.
■
■
Monitor cardiac rhythm continuously if the drug
is being given for acute MI
because of the risk of
alteration in cardiac function;
have life support
equipment on standby as needed.
■
■
Provide increased precautions against bleeding
during invasive procedures, use pressure dressings
and ice, avoid intramuscular injections and do
not rub SC injection sites
because of the risk of
increased blood loss in the anticoagulated state.
■
■
Mark the chart of any person receiving this drug
to alert medical staff that there is a potential for
increased bleeding.
■
■
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 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 (dissolution of the
clot and return of blood flow to the area).
■
■
Monitor for adverse effects (bleeding, arrhythmias,
hypotension, hypersensitivity reaction).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, adverse effects to watch
for and specific measures to avoid them).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
