C H A P T E R 4 8
Drugs affecting blood coagulation
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Haemostatic agents are used to stop bleeding from
occurring. They are used in situations that result in a
fibrinolytic state with excessive plasminogen activity
and the risk of bleeding from clot dissolution. For
example, people undergoing repeat coronary artery
bypass graft surgery are especially prone to excessive
bleeding and may require blood transfusion.
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Aminocaproic acid is a systemic haemostatic agent
used to treat conditions resulting from systemic
hyperfibrinolysis. Several topical agents are also
available for local use on active bleeding sites, often
during surgery or with severe injury.
CHAPTER SUMMARY
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Coagulation is the transformation of fluid blood into
a solid state to plug up breaks in the vascular system.
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Coagulation involves several processes, including
vasoconstriction, platelet aggregation to form a plug,
and intrinsic and extrinsic clot formation initiated by
Hageman factor to plug any breaks in the system.
KEY POINTS
■■
The final step of clot formation is the conversion
of prothrombin to thrombin, which breaks down
fibrinogen to form insoluble fibrin threads.
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Once a clot is formed, it must be dissolved to prevent
the occlusion of blood vessels and loss of blood
supply to tissues.
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Plasminogen is the basis of the clot-dissolving system.
It is converted to plasmin (fibrinolysin) by several
factors, including Hageman factor. Plasmin dissolves
fibrin threads and resolves the clot.
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Anticoagulants block blood coagulation by
interfering with one or more of the steps involved,
such as blocking platelet aggregation or inhibiting the
intrinsic or extrinsic pathways to clot formation.
■■
Thrombolytic drugs dissolve clots or thrombi that
have formed. They activate the plasminogen system
to stimulate natural clot dissolution.
■■
Haemostatic drugs are used to stop bleeding. They
may replace missing clotting factors or prevent the
plasminogen system from dissolving formed clots.
■■
Haemophilia, a genetic lack of essential clotting
factors, results in excessive bleeding. It is treated by
replacing missing clotting factors.
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ONLINE RESOURCES
An extensive range of additional resources to enhance teaching
and learning and to facilitate understanding of this chapter may
be found online at the text’s accompanying website, located on
thePoint at
These include Watch and
Learn videos, Concepts in Action animations, journal articles,
review questions, case studies, discussion topics and quizzes.
WEB LINKS
Healthcare providers and students may want to explore
the following Internet sources:
Home page of the Haemophilia Foundation Australia.
Health_Problems/HP8948_warfarin_B.pdf
Department of Health Western Australia publication
“Living with Warfarin”.
bleeding%20management.pdf
Guidelines for management of bleeding with
dabigatran—for possible inclusion into local
management protocols. PHARMAC New Zealand.
Safer Use of High Risk Medicines—Waitemata District
Health Board New Zealand.
as needed (e.g. support hose, positioning,
ambulation, exercise).
■
■
Orient the person and offer support and safety
measures if hallucinations or psychoses occur
to
prevent injury.
■
■
Offer comfort measures
to help the person deal
with the effects of the drug.
These include small,
frequent meals; mouth care; environmental
controls; and safety measures.
■
■
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 (control of bleeding
episodes).
■
■
Monitor for adverse effects (thrombosis, CNS
effects, nausea, hypersensitivity reaction).
■
■
Evaluate the effectiveness of the teaching plan
(person can name drug, dosage of drug, adverse
effects to watch for, specific measures to avoid
them and warning signs to report).
■
■
Monitor the effectiveness of comfort measures and
compliance with the regimen.
