Chapter 41: Diuretics

What is a normal potassium level?

3.5-5.0 mEq/L

hydrochlorothiazide (HydroDIURIL) peak time

4-6 hours (doesn't work immediately like loop diuretics)

Proximal convoluted tubule (PCT)

65% of sedum is absorbed here (along with water and chloride)

What is the normal range for pH?

7.35-7.45

Which of the following statements about mannitol [Osmitrol] are correct? (Select all that apply.) A. Mannitol cannot be given orally. B. Mannitol can cause edema. C. Mannitol can cause renal failure. D. Diuresis begins in 30 to 60 minutes after administration. E. Mannitol is a loop diuretic

A, B, and D Rationale: Mannitol does not diffuse across the GI epithelium and cannot be transported by the uptake systems that absorb dietary sugars. Accordingly, to reach the circulation, the drug must be given parenterally. Diuresis begins in 30 to 60 minutes and persists 6 to 8 hours. Mannitol can leave the vascular system at all capillary beds except those of the brain. When the drug exits capillaries, it draws water along, causing edema. Mannitol is used in prophylaxis of renal failure. Mannitol is an osmotic diuretic, not a loop diuretic.

The nurse knows that diuretics mostly affect which function of the kidneys? A. Cleansing and maintenance of extracellular fluid volume B. Maintenance of acid-base balance C. Excretion of metabolic waste D. Elimination of foreign substances

A. Cleansing and maintenance of extracellular fluid volume Rationale: Most diuretics block sodium and chloride reabsorption, thus affecting the maintenance of extracellular fluid volume.

The nurse should monitor for which adverse effect after administering hydrochlorothiazide [HydroDIURIL] and digoxin [Lanoxin] to a patient? A. Digoxin toxicity B. Decreased diuretic effect C. Dehydration D. Heart failure

A. Digoxin toxicity Rationale: Digoxin levels have an inverse relationship with potassium levels. Because hydrochlorothiazide can lower potassium levels, combined use of hydrochlorothiazide and digoxin poses a risk for elevated digoxin levels and ensuing digoxin toxicity. Decreased diuretic effect

The nurse is reviewing the home medication list with the patient. The nurse recognizes that hydrochlorothiazide is used primarily for which condition? A. Hypertension B. Edema C. Diabetes insipidus D. Protection against postmenopausal osteoporosis

A. hypertension Rationale: The primary indication for hydrochlorothiazide is hypertension, a condition for which thiazides are often the drugs of first choice. Hydrochlorothiazides are used for other conditions, but the primary indication is hypertension.

When providing discharge teaching for a pt who has been prescribed furosemide (Lasix), it is most important for the nurse to include which dietary items to prevent adverse effects of this drug therapy? A. oranges, spinach, and potatoes B. baked fish, chicken, and cauliflower C. tomato juice, skim milk, and cottage cheese D. oatmeal, cabbage, and bran flakes

A. oranges, spinach, and potatoes Rationale: furosemide may have an adverse effect of hypokalemia which can be reduced by eating foods high in potassium like nuts, dried fruits, spinach, citrus fruits, potatoes, and bananas.

The nurse is caring for a patient with heart failure who needs a diuretic. Which agent is likely to be chosen, because it has been shown to greatly reduce mortality in patients with heart failure? A. Furosemide [Lasix] B. Hydrochlorothiazide [HydroDIURIL] C. Spironolactone [Aldactone] D. Mannitol [Osmitrol]

C. Spironolactone [Aldactone] Rationale: Spironolactone is a potassium-sparing diuretic used to treat both hypertension and edema. It is a preferred drug in heart failure, because it has been shown to have a cardioprotective effect, reducing mortality in patients with heart failure.

A pt is prescribed spironolactone (Aldactone) for treatment of hypertension. Which foods should the nurse teach the pt to avoid? A. baked fish B. low-fat milk C. salt substitues D. green beans

C. salt-substitutes Rationale: spironolactone (Aldactone) is a potassium-sparing diuretic and with these potassium supplements, and salt substitutes should be avoided as well as foods high in potassium

The nurse cares for a pt who is prescribed oral bumetanide twice daily. It is most important for the nurse to take which action? A. monitor the pt for signs and symptoms of hyperkalemia B. insert a urinary catheter and assess the hourly urine output C. weight the pt before administering each dose D. schedule the medication to be given at 0800 and 1400.

D. Rationale: giving this drug at these times can reduce nocturemia and the incidence of falls. Daily weights should be obtained in the morning before eating. Pts receiving this drug IV are more likely to need hourly monitoring of urine output with a catheter, and this drug may cause hypokalemia

The nurse caring for a patient taking furosemide [Lasix] is reviewing the patient's most recent laboratory results, which are: sodium, 136 mEq/L; potassium, 3.2 mEq/L; chloride, 100 mEq/L; blood urea nitrogen, 15 mg/dL. What is the nurse's best action? A. Administer Lasix as ordered. B. Place the patient on a cardiac monitor. C. Begin a 24-hour urine collection. D. Hold the Lasix and notify the physician.

D. Hold the Lasix and notify the physician. Rationale: The nurse's best action is to hold the Lasix and notify the physician. Loop diuretics, such as furosemide, can cause significant potassium loss. The normal potassium level is 3.5 to 5 mEq/L. The remaining electrolyte levels are normal. Administering the Lasix could result in a critically low potassium level. Effects of low potassium include cardiac dysrhythmias. Placing a patient on a cardiac monitor requires a physician's order and would warrant further assessment first, such as taking vital signs and asking the patient whether he or she is having any cardiac-related symptoms. Collecting a 24-hour urine specimen is not appropriate in this case.

Other loop diuretics

Ethacrynic acid (Edecrin) Bumetanide (Bumex) Torsemide (Demadex); all are similar to furosemide and have similar side effects

hydrochlorothiazide (HydroDIURIL) adverse effects (same as furosemide- Lasix)

Hyponatremia, hypchloremia, dehydration Hypokalemia - lowers potassium Hyperglycemia, Hyperuricemia, Impact on calcium and magnesium (causes levels to decrease)

A pt with heart failure who takes furosemide (Lasix) is diagnosed with bacterial pneumonia. Which medication, if ordered by the physician, should the nurse question? A. ciprofloxacin (Cipro) B. gentamicin (Garamycin) C. amoxicillin (Amoxcil) D. erythromycin (E-Mycin)

B. gentamicin Rationale: high-ceiling loop diuretics can cause hearing impairment and furosemide may result in deafness that is transient. Because of this risk, when these high ceiling diuretics are used, they should be used with caution with other ototoxic drugs like aminoglycosides.

The healthcare provider orders furosemide [Lasix] 20 mg IV twice daily. The medication available is furosemide [Lasix] 10 mg/mL. How many mL will the nurse administer with each dose? A. 0.5 mL B. 1 mL C. 2 mL D. 4 mL

C.

Site of action of diuretics

Proximal tubule produces greatest diuresis

Example of aldosterone antagonist

Spironolactone

The nurse is teaching a patient who has a new prescription for spironolactone [Aldactone]. Which statement by the patient indicates that the teaching was effective? A. "I will use salt substitutes to lower my sodium intake." B. "I will increase my intake of foods that are high in potassium." C. "I will call my doctor if I begin having menstrual irregularities." D. "I will take this medication at bedtime each evening."

C. "I will call my doctor if I begin having menstrual irregularities." Rationale:Spironolactone is a potassium-sparing, aldosterone-blocking diuretic. As such, it can cause endocrine effects, such as gynecomastia, menstrual irregularities, impotence, hirsutism, and deepening of the voice. Patients taking spironolactone should avoid salt substitutes because they contain potassium, and high-potassium foods should be avoided with this drug. Ideally, all diuretics should be taken in the morning to prevent nocturia.

The healthcare provider orders mannitol 72 gm infusion over 24 hours. The nurse plans to set the infusion pump for how many grams per hour? A. 1 gm B. 2 gm C. 3 gm D. 4 gm

C. 3gm

The nurse plans to closely monitor for which clinical manifestation after administering furosemide [Lasix]? A. Decreased pulse B. Decreased temperature C. Decreased blood pressure D. Decreased respiratory rate

C. Decreased blood pressure Rationale: High-ceiling loop diuretics, such as furosemide, are the most effective diuretic agents. They produce more loss of fluid and electrolytes than any others. A sudden loss of fluid can result in decreased blood pressure. When blood pressure drops, the pulse probably will increase rather than decrease. Lasix should not affect respiration or temperature. The nurse should also closely monitor the patient's potassium level.

Examples of nonaldosterone antagonists

Triamtrene and Amiloride

Thiazide diuretics and related drugs

also called hydrochlorothiazide; effects are similar to loop diuretics; increase secretion of sodium, chloride, potassium, and water and elevate levels of uric acid and glucose

Furosemide (Lasix) works in the...

ascending loop of henle and is VERY rapid

Which ion is secreted by the kidneys when the body is in acidosis?

bicarbonate; this ion is an alkali so it buffers the amount of acid and maintains a normal pH

Mechanism of action of diuretics

blocking sodium and chloride reabsorption (if the sodium and water are not being reabsorbed, more potassium and water are being excreted to produce urine)

Spironolactone (Aldactone) MOA

blocks aldosterone in the distal nephron (which retains potassium), retains potassium, and increases excretion of sodium

Dose and route for furosemide (Lasix)

can be given PO or IV and the doses are the same for both (onsets differ between both; IV- 5 minutes, PO- 60min)

Fifth group of diuretics

carbonic anhydrase inhibitors

Loop of Henle (ascending and descending)

descending is where most of the sodium and potassium is reabsorbed (pulls fluid into the glomerulus)

Furosemide (Lasix) drug interaction

digoxin (must have potassium to be effective), ototoxic drugs (like aminoglycosides), potassium sparing diuretics, lithium, antihypertensives, and NSAIDs (because they reduce renal blood flow)

hydrochlorothiazide (HydroDIURIL) drug interactions

digoxin, enhances effects of antihypertensives (increases drop in BP), reduces renal excretion of lithium causing a toxicity), NSAIDs can blunt diuretic effect, and can be combined with ototoxic drugs without risk of hearing loss

What is the best time of day to give diuretics?

early in the morning when the pt is waking up and down give the second dose after 4pm because they'll wake up to urinate and be at risk for falls.

Adverse effects of mannitol (Osmitrol)

edema, headache, nausea, vomiting, and fluid and electrolyte imbalance

Therapeutic uses of hydrochlorothiazide (HydroDIURIL)

essential hypertension (has no true cause), edema, and diabetes insipidus (pituitary malfunction- not enough anti-diuretic hormone so they urinate a lot)

Filtration

first part of urine formation where the small molecules will be filtered out and the large molecules like proteins will stay in the kidneys and the bloodstream

Extracellular fluid

fluid outside of the cell in the plasma of the blood stream

Intracellular fluid

fluids/electrolytes inside of the cell

Which is the most frequently prescribed loop diuretic?

furosemide (Lasix)

Reabsorption occurs at the...

glomerulus

Filtration occurs at the...

glomerulus; which is a network of capillaries

What does the buffer system in the kidneys do?

helps the body stay within a normal pH

Aldosterone

hormone that helps to reabsorb potassium

What is the most commonly used thiazide diuretic?

hydrochlorothiazide (HydroDIURIL) also called HCTZ

Adverse effects of Spironolactone (Aldactone)

hyperkalmia (monitor electrolyte panels), benign and malignant tumors, and endocrine effects

Therapeutic uses of Spironolactone (Aldactone)

hypertension, edema, heart failure (helps decrease fluid in the heart and reduce work), primary hyperaldosteronism, premenstrual syndrome, PCOS, and acne in young women

Adverse effects of furosemide (Lasix):

hyponatremia, hypochloremia, dehydration, hypotension (because of loss of volume, and relaxation of smooth muscle), hypokalemia (can have lots of cardiac dysrhythmias, and ototoxicity (pt may complain of tinnitus if IV infusion is too quick), hyperglycemia (may need to increase insulin dose), hyperuricemia,

Adverse effects of diuretics

hypovolemia (deficit in fluid volume), acid-base imbalance, and electrolyte imbalances

Where are sodium and water exchanged in the kidneys?

in the proximal and distal convoluted tubules (part of the loop of henley)

Why do we need to be careful giving diuretics to pts with gout?

it will cause uric acid to build up and will cause pain

4 classes of diuretics

loop, thiazide, osmotic, and potassium-sparing (2 subcategories: aldosterone antagonists and non-aldosterone antagonists)

Potassium-sparing diuretics uses

modest increase in urine production, substantial decrease in potassium excretion (good to give with furosemide because diuresis is already occurring and the major potassium loss can be prohibited)

The basic functional unit of the kidneys is...

nephrons

Are potassium-sparing diuretics used alone?

no because they don't increase urine output very much

Ascending limb of loop of henle

only 20% of water and chloride is absorbed here (sodium and potassium also exchange across here through the aldosterone)

Route of administration of mannitol (Osmitrol)

parenterally (IV)

Which is the primary intracellular electrolyte?

potassium (levels in the serum of the blood will be low)

Which ions do the kidneys absorb and reabsorb?

potassium and sodium chloride

mannitol (Osmitrol)

promotes diuresis by creating osmotic force within the lumen of the nephron

Therapeutic uses of mannitol (Osmitrol)

prophylaxis of renal failure, reduction of ICP, and reduction of intraocular pressure

mannitol (Osmitrol) MOA

pulls fluid from the interstitial and goes through the renal system to be excreted (can pull fluid from brain and eyes to reduce pressure)

Loop diuretics are primarily used for:

pulmonary edema- (effect seen because of heart failure and the heart can't get the blood out of the systemic circulation fast enough so it builds up in the lungs) and hypertension

Which is the primary extracellular electrolyte?

sodium (levels will be higher in the serum of the blood than in the intracellular fluid)

Why is mannitol (Osmitrol) used for head injuries?

the brain swells and the cavity can't expand sot the blood flow to the cerebral tissues is restricted and this drug helps pull fluid and help the body excrete it through the renal system

Osmosis

the movement of fluid from a lesser to greater concentration which is how the kidneys maintain water balance

Where is most of the sodium chloride reabsorbed in the kidneys?

the proximal convoluted tubule

Spironolactone (Aldactone) drug interactions

thiazide and loop diuretics (enhances the effects of these) and agents that raise potassium levels

Thiazides compared to loop diuretics

thiazides don't work as well because they aren't effective when urine flow is low where as furosemide and loop diuretics will make urine regardless of urine output

How do the kidneys maintain fluid volume?

through filtration and reabsorption which cleans out the fluid in the cell (osmosis)

Descending limb of loop of henle

very water permeable and is permeable to some sodium (this is where the urine becomes more concentrated because the water is being reabsorbed back into the body)

Glomerulus:

where most of the filtration occurs in the kidneys