McKenna's Pharmacology for Nursing, 2e

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Drugs affecting blood coagulation

Learning objectives Upon completion of this chapter, you should be able to: 1. Outline the mechanisms by which blood clots dissolve in the body, correlating this information with the actions of drugs used to affect blood clotting. 2. Describe the therapeutic actions, indications, pharmacokinetics, contraindications, most common adverse reactions and important drug–drug interactions associated with drugs affecting blood coagulation. 3. Discuss the use of drugs that affect blood coagulation across the lifespan. 4. Compare and contrast the prototype drugs aspirin, heparin and antihaemophilic factor with other agents used to affect blood coagulation. 5. Outline the care considerations, including important teaching points, for people receiving drugs used to affect blood coagulation.

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Glossary of key terms anticoagulants: drugs that block or inhibit any step of the coagulation process, preventing or slowing clot formation antiplatelet agents: drugs that interfere with the aggregation or clumping of platelets to form the platelet plug clotting factors: substances formed in the liver—many requiring vitamin K—that react in a cascading sequence to cause the formation of thrombin from prothrombin; thrombin then breaks down fibrin threads from fibrinogen to form a clot coagulation: the process of blood changing from a fluid state to a solid state to plug injuries to the vascular system extrinsic pathway: cascade of clotting factors in blood that has escaped the vascular system to form a clot on the outside of the injured vessel haemorrhagic disorders: disorders characterised by a lack of clot-forming substances, leading to states of excessive bleeding haemostatic agents: drugs that stop blood loss, usually by blocking the plasminogen mechanism and preventing clot dissolution Hageman factor: first factor activated when a blood vessel or cell is injured; starts the cascading reaction of the clotting factors, activates the conversion of plasminogen to plasmin to dissolve clots and activates the kinin system responsible for the activation of the inflammatory response intrinsic pathway: cascade of clotting factors leading to the formation of a clot within an injured vessel plasminogen: natural clot-dissolving system; converted to plasmin (also called fibrinolysin) by many substances to dissolve clots that have formed and to maintain the patency of injured vessels platelet aggregation: property of platelets to adhere to an injured surface and then attract other platelets, which clump together or aggregate at the area, plugging up an injury to the vascular system thromboembolic disorders: disorders characterised by the formation of clots or thrombi on injured blood vessels with potential breaking of the clot to form emboli that can travel to smaller vessels, where they become lodged and occlude the vessel thrombolytic agents: drugs that lyse, or break down, a clot that has formed; these drugs activate the plasminogen mechanism to dissolve fibrin threads Simulation-based learning On completion of the chapter, consider the scenario of Carl Shapiro (Part 1) who arrives in the emergency department. Consider the medication management of Carl’s condition, as it relates to your learning in this chapter. Then, work through the second scenario of Vernon Watkins (Part 2) who underwent a hemicolectomy 5 days ago and now has abdominal and leg pain. Consider how the concepts learnt in this chapter relating to medication management apply to his case.