Diuretics: Navigating the Waters (FL INITIAL Autonomous Practice -Pharmacology)

We look at the heart as if it were a pump to pump blood to the rest of the body. In CHF, the pump is not working as effectively as it should be for a multitude of reasons. When the blood is not being pumped effectively, blood backs up in the vascular and cardiovascular systems. It causes signs and symptoms, including swelling in the lower extremities, difficulty breathing, abnormal lung sounds, coughing up frothy pink sputum, and even orthopnea, which all could require sleeping with many pillows to breathe when sleeping. The reason behind why a patient has CHF can be from a myocardial infarction (MI), atrial fibrillation, or other disease processes (Drugs.com, 2018). The reason for prescribing a diuretic for a patient with CHF is to reduce the amount of circulating fluid in the system so that the heart pump can function more effectively (Drugs.com, 2018).

Renal impairment, whether it be complete renal failure, renal insufficiency, chronic kidney disease, or acute kidney injury, results in the renal system not being able to excrete the wastes and excess water from the body. Renal impairment can result from a hypotensive episode where the organs themselves did not get enough perfusion, a complication from diabetes, or damage from high blood pressure, just to name a few. Using a diuretic in a patient with renal impairment will help rid the body of excess fluid and waste products that it cannot do on its own.

High blood pressure, or hypertension, is a condition where the vasculature force, more so the arteries, makes it more challenging to get the blood out to the rest of the body. The reasons for high blood pressure can range anywhere from genetics to lifestyle choices, and the complications from high blood pressure can include issues such as renal failure, impotence, stroke, vision damage, and heart damage (Drugs.com, 2018). The rationale behind using a diuretic in a patient with hypertension is to reduce the amount of circulating blood volume in the arterial pressure part of the vascular system so that the heart does not need to work so hard to pump the blood out to the rest of the body.

The first class, the carbonic anhydrase inhibitors, works by inhibiting bicarbonate in the kidney's proximal tubule, resulting in a diuretic effect.

According to Aslam and Gupta (2020), carbonic anhydrase inhibitors work to block carbonic anhydrase, which is produced in the body to convert carbonic acid to water and carbon dioxide. By blocking the action of this enzyme, the urine becomes more alkaline, and blood becomes more acidic. When this happens, the body rids itself of more urine to compensate due to the acid-base balance change.

Examples of medications in this class include (Drugs.com, 2021):

• Acetazolamide
• Dichlorphenamide
• Methazolamide

The next main class of diuretics is called loop diuretics. Loop diuretics work by binding the reabsorption of sodium chloride (NaCl) in the ascending Loop of Henle, which helps in the excretion of free water.

Examples of this type of diuretic include (Huxel et al., 2020):

• Furosemide (*Most common; Trade name: Lasix)
• Torsemide
• Bumetanide
• Ethacrynic acid

The next class of diuretics is called potassium-sparing diuretics. As the name implies, potassium-sparing diuretics leave behind the potassium in the system. This reduces the possibility of hypokalemia or potassium deficiency for the patient. Other types of diuretics typically have the action of removing fluid as well as electrolytes. These electrolytes generally include potassium.

Examples of potassium-sparing diuretics include (Knott, 2020):

• Amiloride
• Triamterene
• Eplerenone
• Spironolactone

The fourth and last primary class of diuretics is called thiazide diuretics.

According to Akbari and Khorasani-Zadeh (2020), this class of diuretics works by inhibiting the reabsorption of anywhere from three to five percent of luminal sodium in the distal convoluted tubule within the nephron, which promotes both natriuresis and a diuretic effect.

The three most common medications used in this class of drugs include (Akbari & Khorasani-Zadeh, 2020):

• Hydrochlorothiazide
• Chlorthalidone
• Indapamide

The main side effects of carbonic anhydrase inhibitors include (Mandal, 2019):

• Allergic reactions
• Hypokalemia
• Drowsiness
• Neurotoxicity
• Kidney stones
• Metabolic acidosis

The side effects of loop diuretics include (Mandal, 2019):

• Hypokalemia
• Metabolic alkalosis
• Ototoxicity
• Increased uric acid levels
• Decreased magnesium levels
• Dehydration
• Allergic reactions

Potassium-sparing diuretics' side effects include that of (Mandal, 2019):

• Erectile dysfunction
• Metabolic acidosis
• Hyperkalemia
• Breast enlargement in males
• Acute renal failure
• Benign Prostatic Hypertrophy (BPH)

Thiazide diuretics' side effects include (Mandal, 2019):

• Hypokalemia
• Increased uric acid levels
• Impaired glucose tolerance
• Increased blood lipid levels
• Hyponatremia
• Allergic reactions
• Fatigue
• Weakness in the limbs
• Impotence in males

As noted earlier, the physician may already be aware of the possible side effects of diuretics. It is also the nurses' responsibility to be mindful of these potential side effects and report them to the physician if there are any concerns.

Vital signs, especially the blood pressure, need to be considered before administering the diuretic because certain diuretics may cause a drop in blood pressure, some more than others. A perfect example of this is Furosemide or Lasix. This is especially true if you must give the medication via the intravenous route. In addition, while it is not considered one of the main vital signs, it is always a good idea to evaluate the patient's intake and output. The reason to assess intake and output is to determine if and how well the diuretic works to get rid of the extra fluid.

The lab considerations are essential for any medication. Still, in giving a diuretic, especially Lasix, it is vital to check the patient’s electrolytes, focusing on the potassium and magnesium levels. If the patient has serum potassium less than the low normal of 3.4-3.5 and Lasix is given, the patient may become more prone to arrhythmias, such as ventricular tachycardia or ventricular fibrillation, due to the serum potassium level. If the serum potassium drops or stays below the normal limits, the nurse will have to notify the physician to order potassium replacement.

The other electrolyte to monitor is serum magnesium, which, if the levels fall less than 1.8 mg/dl, may also predispose the patient to arrhythmias (Lewis, 2020). The other lab considerations to look out for are the blood urea nitrogen or BUN and creatinine, especially the creatinine. The reason to look at the creatinine is that if the patient is getting too much diuretic, it may harm the kidneys, and the diuretic dose will have to be reduced or stopped.

The medication's timing is very important for nurses to consider. The diuretic timing first depends on how many times a patient is taking the medication. It is usually only taken once or twice daily. If given once a day, it should be given in the morning to work throughout the day.

If given twice daily, the second dose should be given early enough in the afternoon or early evening so that the patient may have a chance to sleep without waking up and making multiple trips to the bathroom.

Another aspect of timing, especially when in the hospital, is that the nurse may need to adjust times or hold the diuretic if the patient has a test or procedure done. During a procedure or test, it can be very embarrassing for a patient to have to go to the bathroom or be incontinent if unable to reach the bathroom in time, so it is a good idea to keep that in mind.