Question

Case Scenario:

            JQ, a 58-year-old patient, has been recently diagnosed with hypertension. His resting blood pressure is 158/92. He is prescribed hydrochlorothiazide 50 mg/day and told to eat foods rich in potassium.

            After 1 month on hydrochlorothiazide therapy,JQbecomes weak and complains of nausea and vomiting. His muscles are “soft.” His serum potassium level is 3.3 mEq/L.

Questions:

1. Why is it necessary for JQ to eat foods rich in potassium when taking hydrochlorothiazide? Explain your answer.
2. Should JQ receive a potassium supplement? Explain your answer.

Answer 1

answer 1:

It is necessary for JQ to eat Potassium rich foods when taking hydrochlorothiazide because of the following reasons;

JQ is receiving Hydrochlorothiazide for his hypertension. This is a diuretic drug which works by causing the decreased absorption of sodium and chloride into the body and increasing the excretion of potassium. This causes a state of hypokalemia. He must have a diet which is rich in potassium in order to compensate for the increase in the loss of potassium from his body on account of hydrochlorothiazide therapy and protect himself from suffering the dangerous effects of the electrolyte imbalance,hypokalemia.

Explanation:

Mechanism of action of hydrochlorothiazide and hypokalemia.

1.Hydrochlorothiazide is a diuretic .It acts by inhibiting the sodium-chloride co-transport pump in the distal tubule of the nephron.It decreases the absorption of sodium and chloride into the body and increases their excretion into the urine. This action causes decrease in the blood sodium levels and blood volume , thereby decreasing the hypertension.

2.As higher concentrations of sodium are presented to the distal tubule, there is an activation of Sodium Potassium pump in the distal tubule for sodium reabsorption(aldosterone mediated) to decrease the natriuresis .As a result. the sodium is reabsorbed and potassium is excreted in the later part of the distal tubule. The Potassium excretion is directly related to the the sodium retained by the inhibition of the sodium chloride co transport.

3. Due to the decrease in the blood volume and in the blood pressure action of the hydrochlorothiazide, there is a stimulation of the renin angiotensin aldosterone mechanism to retain the Sodium and the blood volume. This activates the aldosterone mediated sodium reabsorption and potassium and hydrogen excretion in the distal tubule and is partly responsible for the hypokalemia. Aldosterone activation is due to a)decrease in the sodium reaching the distal tubules b)decrease in blood pressure and renal perfusion (effect of hydrochlorothiazide.)

This explains the reason for hypokalemia in patients taking hydrochlorothiazide and the need for its supplementation.

4..As hydrochlorothiazide causes a loss of potassium from the body by increasing its excretion, it predisposes the person to Hypokalemia. Potassium is an important mineral that is required for normal functioning of the body. Its normal levels are 3.6-5.3mEq/L. It is required for normal muscle contraction, nerve conduction, brain normal electrical activity and cardiac contraction.The normal levels of potassium have to be maintained within this range.Any derangement of potassium levels of the body to either high or low causes severe disturbances in the body function.Hypokalemia can be life threatening . A person who is a started on hydrochlorothiazide diuretic has to supplement the diet with foods which are rich in potassium like bananas and oranges ,sweet potatoes ,beets,beans.spinach to compensate for the potassium loss from the body{replenishment} caused by hydrochlorothiazide.

answer2:

Yes JQ should receive a potassium supplementation because he is experiencing symptoms of hypokalemia (muscle weakness,nausea,vomiting,soft muscles) and his serum K levels are 3.3meq/L; less than 3.5 meq/L.

Explanation: Potassium is an important electrolyte required for muscle contraction,nerve conduction,normal electrical impulses of the brain and heart.Hypokalemia can be life threatening as it affects functions of vital organs of the body.

Potassium is an important mineral that is required for normal functioning of the body. Its normal levels are 3.6-5.3mEq/L. It is required for normal muscle contraction, nerve conduction, brain normal electrical activity and cardiac contraction.Decrease in the levels of potassium causes skeletal muscle weakness.Hpyokalemia affects the respiratory muscles causing flaccid paralysis of the respiratory muscles.It alters the electrical rhythm of the heart  predisposing to bradycardias and arrythmias.It causes intestinal ileus and affects brain function.Hypokalemia deranges the normal physiology of the body cells and the organ systems.

The goal of therapy in hypokalemia is to

1.decrease the losses by replacing the drug(here K sparing diuretic or other antihypertensive can be used).use of antiemetics to decrease the potassium loss in the vomitus.

2.replenish the stores of potassium by oral or iv supplementation

3.careful monitoring of the potassium levels till restored to normalcy.

4.monitor for toxicity.

The general guidelines for the restoration of serum potassium levels followed in hypokalemia are as follows.

.2.5-3.5 meq/l===oral supplementation.

<2.5meq/l====intravenous potassium supplementation.

If the normal potassium levels are not restored urgently by potassium supplementation,it can be dangerous for JQ as hypokalemia can cause increasing muscle weakness, respiratory muscle paralysis,bradycardia and life threatening arrhythmias.hence JQ should receive a potassium supplement.(He is symptomatic for hypokalemia and his serum potassium levels are lower than normal)