Thiazide Diuretics

• Diuretics increase urine flow, or diuresis
• They achieve this by inhibiting sodium and water reabsorption in kidney tubules

Main Purposes of Diuretics

• Lowering blood pressure
• Reducing edema, which is typically peripheral/pulmonary
• Edema is associated with heart failure (HF) as well as renal or liver disorders

Five Categories of Diuretics

• Thiazide and thiazide-like diuretics
• Loop or high-ceiling diuretics
• Osmotic diuretics
• Carbonic anhydrase inhibitors
• Potassium-sparing diuretics

Thiazide and Thiazide-Like Diuretics

• Benzothiadiazides are commonly called thiazides.
• Thiazides have been used since the 1960s as diuretics and antihypertensive agents
• Chlorothiazide, the first thiazide, was introduced in 1957
• Hydrochlorothiazide was introduced a year after chlorothiazide
• Numerous thiazide and thiazide-like preparations are available

Thiazide Action

• Thiazides act on the distal convoluted renal tubule, beyond the loop of Henle
• Thiazides promote excretion of sodium, chloride, and water
• Sodium and chloride ions that are not reabsorbed are passed into the collecting ducts
• This causes water molecules to be carried with them to result in diuresis

Thiazide Uses

• Treat hypertension and peripheral edema
• Thiazides are not effective for immediate diuresis
• Thiazides should not be used to promote fluid loss in cases of severe renal dysfunction
• Thiazide diuretics are primarily used in patients with normal renal function
• Thiazide effectiveness decreases greatly with renal disorder and creatinine clearance less than 30 mL/min.
• Thiazides cause a loss of sodium, potassium, and magnesium
• They promote calcium reabsorption

Thiazide Therapeutic Outcome

• Diuresis with reduced edema
• Improvement in symptoms from excessive fluid accumulation
• Reduction in elevated blood pressure

Thiazide Nursing Implications

• Assess vital signs as well as weight, urine output, and serum chemistry values to get baseline levels
• Check peripheral extremities for edema and note pitting edema if present
• Obtain a history of drugs and herbal supplements taken daily
• Review possible drug interactions, especially with digoxin, corticosteroids, antidiabetics, ginkgo, and licorice
• Monitor for risks of deficient fluid volume
• Address urinary elimination impairments related to kidney dysfunction
• Address excess fluid volume related to body fluid retention
• Plan to see a decrease in blood pressure or return to a normal value
• The patients edema should decrease
• The patients serum chemistry levels will need to remain within normal ranges

###Loop (High Ceiling) Diuretics

• Ethacrynic acid was the first loop diuretic marketed
• Furosemide and bumetanide followed
• Bumetanide is more potent than furosemide on a milligram basis
• High diuretic potential causes them to be called high-ceiling diuretics or potassium-wasting diuretics

Loop Diuretics Action

• Loop diuretics act on the thick ascending loop of Henle
• They inhibit chloride transport of sodium into the circulation
• They inhibit passive reabsorption of sodium
• Sodium and water are lost along with potassium, calcium, and magnesium
• Drugs in this group are extremely potent, and cause marked depletion of water and electrolytes

Loop Diuretics Uses

• Treat edema from heart failure, liver cirrhosis, and renal disease including nephrotic syndrome, using bumetanide, furosemide, and torsemide
• Used alone or combined with other antihypertensive therapy for hypertension, using furosemide and torsemide
• Furosemide is combined with 0.9% sodium chloride infusions to enhance calcium excretion in hypercalcemia and to treat edema/heart failure

Loop Therapeutic Outcome

• Achieving diuresis to reduce edema
• Improving symptoms related to excessive fluid accumulation by using sulfonamide loop diuretic therapy
• Furosemide and torsemide are expected to reduce blood pressure

Loop Nursing Implications

• Focus on identifying what medications the patient is already taking to catch any possible interactions with loop diuretics
• Alcohol, aminoglycosides, anticoagulants, corticosteroids, lithium, amphotericin B, or digitalis are possible interactions
• Furosemide is highly protein bound and can displace other protein-bound drugs like warfarin
• Track vital signs, serum electrolytes, weight, and urine output for baselines levels
• Track patients drug dose and recommended dose, and report any discrepancy
• Check whether or not the patient is hypersensitive to sulfonamides
• Address the risk for deficient Fluid Volume
• Address the risk for Electrolyte Imbalance
• Hypertension or edema should decline
• Serum chemistry levels will need to remain within normal ranges

Osmotic Diuretics

• Mannitol is the most frequently prescribed osmotic diuretic
• Urea follows next

Use of Osmotic Diuretics

• Preventing kidney failure
• Decreasing intracranial pressure (ICP), such as in cerebral edema
• Decreasing intraocular pressure (IOP), such as in glaucoma
• Frequently used in emergency situations such as ICP and IOP because mannitol is a potent osmotic, potassium-wasting diuretic
• Inducing frank diuresis with cisplatin and carboplatin in cancer chemotherapy because mannitol decreases side effects of treatment

Action of Osmotic Diuretics

• Osmotic diuretics increase osmolality (concentration)
• They increase sodium reabsorption in the proximal tubule and loop of Henle.
• Sodium, chloride, potassium, and water are excreted.

Therapeutic Outcome of Osmotic Diuretics

• Mannitol pulls large amounts of fluid into the urine due to its osmotic pull
• It is a sugar not well reabsorbed by the tubules
• Fluid will also pull into the vascular system from extravascular spaces like aqueous humor

Nursing Implications of Osmotic Diuretics

• Check vital signs prior to administrations
• Assess urinary output, hydration status, and electrolytes
• Assess BUN, renap, and hepatic panels
• Look for S/S CHF and pulmonary edema
• Warm the IV medication

Carbonic Anhydrase Inhibitors

• Acetazolamide and methazolamide block carbonic anhydrase
• Carbonic anhydrase inhibitors are needed to maintain the body's acid-base or hydrogen/bicarbonate ion balance

Carbonic Anhydrase Inhibitors Action

• Acetazolamide inhibits carbonic anhydrase
• The enzyme is located in the kidneys, brain, and eyes
• As a weak diuretic, it promotes excretion of sodium, potassium, water, and bicarbonate

Carbonic Anhydrase Inhibitors Uses

• Acetazolamide is not used frequently as a diuretic because more effective medications are available
• It is used to reduce intraocular pressure in patients with glaucoma
• Lowering IOP in patients with open-angle (chronic) glaucoma
• Diuresis, management of epilepsy, and treatment of high-altitude or acute mountain sickness for other uses

Carbonic Anhydrase Inhibitors Therapeutic Outcome

• Carbonic anhydrase inhibition reduces sodium bicarbonate stored as alkaline reserve in the renal tubules
• Carbonic anhydrase is a catalyst for the formation of sodium bicarbonate
• Sodium and bicarbonate will be greater in quantity and be lost in urine, as hydrogen ions slow down movement

Carbonic Anhydrase Inhibitors Nursing Implications

• Observe for signs of hypersensitivity, especially sulfa allergy
• Monitor laboratory values and vital signs like blood pressure

Potassium-Sparing Diuretics

• Weaker than thiazides and loop diuretics
• Used as mild diuretics, or combined with another diuretic like hydrochlorothiazide
• Can be used as an antihypertensive drug
• Spironolactone, discovered in 1958, was the first potassium-sparing diuretic.
• Aldosterone is a mineralocorticoid hormone that typically promotes sodium retention and potassium excretion

Potassium-Sparing Diuretics Action

• Spironolactone blocks the sodium-retaining
• It also blocks the potassium-excreting properties of aldosterone
• It also blocks the magnesium-excreting properties of aldosterone
• The result is a loss of water with increased sodium excretion

Potassium-Sparing Diuretics Uses

• Relieving edema and ascites that do not respond to the usual diuretics
• Given with thiazide diuretics to increase its effect and reduce the hypokalemia often induced by thiazides
• Reduce further morbidity and mortality for patients with heart failure
• Heart Failure patients must also be treated with an ACE inhibitor and a loop diuretic

Potassium Sparing Therapeutic Outcome

• Diuresis to reduce edema
• Improvement in the symptoms of excessive fluid accumulation
• Relief for Heart Failure symptoms

Nursing implications of Potassium-Sparing Diuretics

• Assess if patient is taking potassium supplement or using salt substitute
• Assess vital signs, serum electrolytes, weight, urinary output
• Compare patient's drug dose with the recommended dose
• Plan will need to include fluid retention being decreased and electrolyte levels need to remain within normal ranges