McKenna's Pharmacology for Nursing, 2e

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P A R T 9  Drugs acting on the renal system

and pulmonary oedema, liver failure, cirrhosis and various types of renal disease, and as adjuncts in the treatment of hypertension. ■■ Classes of diuretics differ in their site of action and intensity of effects. Thiazide diuretics work to block the chloride pump in the distal convoluted tubule. This effect leads to a loss of sodium and potassium and a minor loss of water. Thiazides are frequently used alone or in combination with other drugs to treat hypertension. They are considered to be mild diuretics. ■■ Loop diuretics work in the loop of Henle and have a powerful diuretic effect, leading to the loss of water, sodium and potassium. These drugs are the most potent diuretics and are used in acute situations, as well as in chronic conditions not responsive to milder diuretics. ■■ Carbonic anhydrase inhibitors work to block the formation of carbonic acid and bicarbonate in the renal tubule. These drugs can cause an alkaline urine and loss of the bicarbonate buffer. Carbonic anhydrase inhibitors are used in combination with other diuretics when a stronger diuresis is needed, and they are frequently used to treat glaucoma because they decrease the amount of aqueous humour produced in the eye. ■■ Potassium-sparing diuretics are mild diuretics that act to spare potassium in exchange for the loss of sodium and water in the urine. These diuretics are preferable if potassium loss could be detrimental to a person’s cardiac or neuromuscular condition. People must be careful not to become hyperkalaemic while taking these drugs. ■■ Osmotic diuretics use hypertonic pull to remove fluid from the intravascular spaces and to deliver large amounts of water into the renal tubule. There is a danger of sudden change of fluid volume and massive fluid loss with some of these drugs. These drugs are used to decrease intracranial pressure, to treat glaucoma and to help push toxic substances through the kidney.

■ ■ Provide thorough teaching, including the name of the drug and dosage prescribed, to enhance knowledge about drug therapy and to promote compliance. Additional teaching includes the following: –– Importance of taking the diuretic early in the day to avoid interference with sleep. –– Administration of the drug with food or meals if GI upset occurs. –– Need to weigh self daily and report any increase in weight of 2 kg or more in 1 day. –– Importance of maintaining an adequate fluid intake to prevent fluid rebound (see Focus on safe medication administration in this chapter’s introduction to diuretic agents). –– Need to have readily available access to bathroom facilities after taking the prescribed dose. –– Signs and symptoms of adverse effects, including hypo- and hyperkalaemia and hypocalcaemia, and the need to notify the healthcare provider should any occur. –– Danger signs and symptoms to be reported immediately. –– Safety measures, such as moving slowly if dizziness is an issue and avoiding very hot environments and other situations potentially leading to extra loss of fluid. –– Dietary sources of foods high in potassium, with an emphasis on the need for intake of these foods or the need to avoid these foods. –– Need for compliance with therapy to achieve intended results. –– Importance of continued follow-up and monitoring, including laboratory testing to determine the effectiveness of therapy. Evaluation ■ ■ Monitor response to the drug (weight, urinary output, oedema changes, blood pressure). ■ ■ Monitor for adverse effects (electrolyte imbalance, orthostatic hypotension, rebound oedema, hyperglycaemia, increased uric acid levels, acid– base disturbances, dizziness). ■ ■ Monitor the effectiveness of comfort measures and compliance with the regimen. ■ ■ Evaluate the effectiveness of the teaching plan (person can name drug, dosage, adverse effects to watch for and specific measures to avoid them).

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CHAPTER SUMMARY

■■ Diuretics—drugs that increase the excretion of sodium, and therefore water, from the kidneys—are used in the treatment of oedema associated with HF