McKenna's Pharmacology for Nursing, 2e

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P A R T 9  Drugs acting on the renal system

CRITICAL THINKING SCENARIO Using frusemide (Lasix) in heart failure

THE SITUATION M.R. is a 68-year-old woman with rheumatic mitral valve heart disease. She has refused any surgical intervention and has developed progressively worsening heart failure (HF). Recently frusemide ( Lasix ), 40 mg/day PO, was prescribed for her along with digoxin. After 10 days with the new prescription, M.R. calls to tell you that she is allergic to the new medicine and cannot take it anymore. She reports extensive ankle swelling and difficulty breathing. You refer her to a cardiologist for immediate review. CRITICAL THINKING Think about the physiology of mitral valve disease and the progression of HF in this person. How does frusemide work in the body? What additional activities will be important to help maintain some balance in this person’s cardiac status? What is the nature of M.R.’s reported allergy and what other options could be tried? DISCUSSION Over time, an incompetent mitral valve leads to an enlarged and overworked left ventricle as the backup of blood “waiting to be pumped” continues to progress. Drug therapy for a person with this disorder is usually aimed at decreasing the workload of the heart as much as possible to maintain cardiac output. Digoxin increases the contractility of the heart muscle, which should lead to better perfusion of the kidneys. Frusemide—a loop diuretic—acts on the loop of Henle to block the reabsorption of sodium and water, and lead to a diuresis, which decreases the volume of blood the heart needs to pump and makes the blood that is pumped more efficient. This blood then has an oncotic pull to move fluid from the tissue into circulation, where it can be acted on by the kidney, leading to further diuresis. M.R. should be encouraged to maintain fluid intake and to engage in activity as much as possible but to take frequent rest periods. Her potassium level should be monitored regularly (this is especially important because she is also taking digoxin, which is very sensitive to potassium levels), her oedematous limbs should be elevated periodically during the day, and she should monitor her sodium intake. When M.R. was questioned about her reported allergy, it was discovered that her “allergic reaction” was actually increased urination (a therapeutic effect). M.R. needs to learn about the actions of the drug. She also needs information about the timing of administration

so that the resultant diuresis will not interfere with rest or with her daily activities. HF is a progressive, incurable disease, so education is a very important part of the overall management regimen. CARE GUIDE FOR M.R.: DIURETIC AGENTS Assessment: History and examination Assess M.R.’s health history, including allergies to diuretics, fluid or electrolyte disturbances, gout, glucose tolerance abnormalities, liver disease, systemic lupus erythematosus, pregnancy and breastfeeding. Focus the physical examination on the following areas: Neurological: orientation, reflexes, strength Skin: colour, texture, oedema Cardiovascular: blood pressure, pulse, cardiac auscultation Gastrointestinal: liver evaluation Genitourinary: urinary output Laboratory tests: haematology; serum electrolytes, glucose, uric acid; liver function tests Implementation Obtain daily weight and monitor urine output. Provide comfort and safety measures: sugarless lozenges, mouth care, safety precautions, skin care, nutrition. Administer the drug with food early in the day. Provide support and reassurance to deal with drug effects and lifestyle changes. Provide teaching regarding drug name, dosage, side effects, precautions, warnings to report, daily weighing and recording dietary changes as needed. Evaluation Evaluate drug effects: urinary output, weight changes, status of oedema, blood pressure changes. Monitor for adverse effects: hypotension, hypokalaemia, hyperkalaemia, hypocalcaemia, hypercalcaemia, hyperglycaemia, increased uric acid levels. Monitor for drug–drug interactions as indicated. Evaluate the effectiveness of the teaching program and comfort and safety measures. TEACHING FOR M.R. • A diuretic, or “water pill”, such as frusemide ( Lasix ) will help to reduce the amount of fluid that is in your body by causing the kidneys to pass larger amounts of water and salt into your urine. By removing this fluid, the diuretic helps to decrease the work of the heart, lower blood pressure, and get rid of oedema or swelling in your tissues. • This drug can be taken with food, which may eliminate possible stomach upset. When taking a diuretic, you