McKenna's Pharmacology for Nursing, 2e

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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. ■ ■ 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. Evaluation