6.9 Diuretics
Diuretics are used to decrease blood pressure and to decrease symptoms of fluid overload such as edema. There are many classifications of diuretics. We will discuss loop, thiazide, and potassium-sparing diuretics. Other diuretics, such as osmotic diuretics, are used to decrease fluid from cerebrospinal fluid and the brain.
Diuretics cause diuresis (increased urine flow) by inhibiting sodium and water reabsorption from the kidney tubules. By eliminating excess water, blood volume and blood pressure, as well as preload, are decreased. Diuretic medications can have a significant impact on renal function; therefore, laboratory monitoring of renal function tests may be required. Common tests that are ordered to assess side effects of diuretic medications include blood urea nitrogen (BUN), creatinine, and creatinine clearance. Clients with abnormal BUN and creatinine levels may require a lower dosage of diuretics or a different medication regimen. Creatinine clearance is then calculated based on the amount of creatinine in the urine and the blood, as well as the client‘s age, gender, and weight. The results of the test can help health care providers monitor kidney function in clients who are taking diuretics, as well as adjust dosages or medications if necessary to prevent further kidney damage.
Diuretics are often used in combination with other antihypertensive agents to reduce a client’s blood pressure. Cients on diuretics often require dietary medications. Clients should follow a low-sodium diet to prevent fluid retention and hypertension. However, some clients may substitute salt with high-potassium salt substitutes, which can increase potassium levels and cause hyperkalemia. Health care providers should educate clients regarding the risks of using salt substitutes and provide guidance on dietary recommendations.
Furosemide
Mechanism of Action: Loop diuretics inhibit absorption of sodium and chloride in the loop of Henle and proximal and distal tubules, thus causing fluid loss, along with sodium, potassium, calcium, and magnesium losses. Loop diuretics are very potent diuretics and are used when a client has an exacerbation of fluid overload.
Indications: Furosemide is used to treat clients with edema and is also used to treat hypertension. IV furosemide is used to urgently treat pulmonary edema in conditions such as congestive heart failure.
Nursing Considerations: The onset of diuresis following oral administration is within 1 hour. The peak effect occurs within the first or second hour. The duration of diuretic effect is 6 to 8 hours. When possible, loop diuretics should be administered in the morning, and evening doses should be avoided (unless urgent) so that sleep is not disturbed.
Nurses should continually monitor for dehydration and electrolyte imbalances that can occur with excessive diuresis, such as dryness of mouth, thirst, weakness, lethargy, drowsiness, restlessness, muscle pains or cramps, muscular fatigue, hypotension,