McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 4 8 Drugs affecting blood coagulation

■■ The final step of clot formation is the conversion of prothrombin to thrombin, which breaks down fibrinogen to form insoluble fibrin threads. ■■ Once a clot is formed, it must be dissolved to prevent the occlusion of blood vessels and loss of blood supply to tissues. ■■ 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. ■■ 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. Knowing your strengths and weaknesses helps you to study more effectively. Take a PrepU Practice Quiz to find out how you measure up! 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 http://thepoint.lww.com. These include Watch and Learn videos, Concepts in Action animations, journal articles, review questions, case studies, discussion topics and quizzes. Healthcare providers and students may want to explore the following Internet sources: www.haemophilia.org.au Home page of the Haemophilia Foundation Australia. www.health.wa.gov.au/docreg/Education/Population/ Health_Problems/HP8948_warfarin_B.pdf Department of Health Western Australia publication “Living with Warfarin”. www.pharmac.govt.nz/2011/06/10/Dabigatran%20 bleeding%20management.pdf Guidelines for management of bleeding with dabigatran—for possible inclusion into local management protocols. PHARMAC New Zealand. www.saferx.co.nz/full/dabigatran.pdf Safer Use of High Risk Medicines—Waitemata District Health Board New Zealand. WEB LINKS

as needed (e.g. support hose, positioning, ambulation, exercise).

■■ 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. ■■ 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 ■■ Coagulation is the transformation of fluid blood into a solid state to plug up breaks in the vascular system. ■■ 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. ■ ■ 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. KEY POINTS