McKenna's Pharmacology for Nursing, 2e

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

CRITICAL THINKING What care interventions should be done at this point? Why do people with mitral valve disease frequently develop AF? Think about why emboli formwhen the atria fibrillate. Stabilising G.R. on warfarin may take several weeks of blood tests and dose adjustments. How can this process be made easier? What teaching points should be covered with G.R. to ensure that she is protected from emboli and does not experience excessive bleeding? degenerative valve disease that usually leads to heart failure (HF) and frequently to other complications, such as AF and emboli formation. Her digoxin and potassium levels should be checked to determine whether her HF has stabilised or the digoxin is causing the AF because of excessive doses or potassium imbalance. If these tests are within normal limits, G.R. may be experiencing AF because of irritation to the atrial cells caused by the damaged mitral valve and associated swelling and scarring. If this is the case, an anticoagulant will help protect G.R. against emboli, which form in the auricles when blood pools there while the atria are fibrillating. There is less chance of emboli formation if clotting is slowed. G.R. will need extensive teaching about warfarin, including the need for frequent blood tests, the list of potential drug–drug interactions, the importance of being alert to the many factors that can affect dose needs (including illness and diet) and how to monitor for subtle blood loss. This can also be a good opportunity to review teaching about valvular disease and HF and to answer any questions that she might have about how all of these things interrelate. If possible, it would be useful to teach G.R. or a responsible caregiver how to take a pulse so that G.R. can be alerted to potential arrhythmias and avert problems before they begin. It also would be a good idea to check on support services for G.R. to ensure that her blood tests can be done and that her response to the drug is monitored carefully. CARE GUIDE FOR G.R.: WARFARIN Assessment: History and examination Assess G.R.’s health history for allergies to warfarin, subacute bacterial endocarditis (SBE), haemorrhagic disorders, tuberculosis, renal or hepatic dysfunction, gastric ulcers, thyroid disease, uncontrolled hypertension, severe trauma or a long-term indwelling catheter (which increases the risk of bleeding). Also assess concurrent use of numerous drugs and herbal therapies. Focus the physical examination on the following areas: Cardiovascular: blood pressure, pulse, perfusion, baseline electrocardiogram (ECG) DISCUSSION G.R.’s situation is complex. She has a progressive

Neurological (CNS): orientation, affect, reflexes, vision Skin: colour, lesions, texture Respiratory system: respiratory rate and character, adventitious sounds GI: abdominal examination, guaiac stool test results (for occult blood) Laboratory tests: liver and renal function tests, prothrombin time (PT), International Normalised Ratio (INR) Implementation Ensure proper administration of the drug. Provide comfort and safety measures, such as small meals, protection from injury during invasive and other procedures, bowel program as needed, standby antidotes (e.g. vitamin K) and careful skin care. Provide support and reassurance to deal with drug effects. Provide teaching regarding drug, dosage, adverse effects, what to report and safety precautions. Evaluation Evaluate drug effects: increased bleeding times, PT 1.5–2.5 times control or PT/INR ratio of 2:3. Monitor for adverse effects: bleeding, alopecia, rash, GI upset, excessive bleeding. Monitor for drug–drug interactions (numerous). Evaluate the effectiveness of the teaching program and comfort and safety measures. TEACHING FOR G.R. • An anticoagulant slows the body’s normal blood clotting processes to prevent harmful blood clots from forming. This type of drug is often called a “blood thinner”; however, it cannot dissolve any clots that have already formed. • Never change any medication that you are taking—such as adding or stopping another drug, taking a new over- the-counter medication, or stopping one that you have been taking regularly—without consulting with your healthcare provider. Many other drugs affect the way that your anticoagulant works; starting or stopping another drug can cause excessive bleeding or interfere with the desired effects of the drug. • Some of the following adverse effects may occur: • Stomach bloating, cramps: These problems often pass with time; consult your healthcare provider if they persist or become too uncomfortable. • Loss of hair, skin rash: These problems can be very frustrating; you may wish to discuss these with your healthcare provider. • Orange-yellow discolouration of the urine: This can be frightening, but it may just be an effect of the drug. If you are concerned that this might be blood, simply add vinegar to your urine; the colour should disappear. If the colour does not disappear, it may be caused by blood, and you should contact your healthcare provider.