TRC: Diuretics in CHF

Diuretics in CHF

Diuretics increase excretion of Na+ ions from the kidney. As a result, water is excreted as well, which lowers plasma volume, extracellular fluid, cardiac output, and hence blood pressure. Two classes of diuretics are applied in the treatment of the symptoms of heart failure.

Loop diuretics act in the ascending loop of Henle and block the Na+/K+/2Cl–-co-transporter.

Example: Furosemide is an efficacious drug mainly acting in the ascending limb of the loop of Henle.

It almost completely inhibits reabsorption of Na+ and Cl– in the ascending loop by blocking the Na+/K+/2Cl– co-transporter. Neither Na+ nor K+ are reabsorbed. As a result, the NaCl concentration drops, which leads to decreased reabsorption of water and thus more diuresis.

Thiazide diuretics act in the distal tubule by inhibiting the Na⁺/Cl^– co-transporter. These diuretics are used in the treatment of heart failure in order to decrease symptoms of oedema and dyspnoea by the mechanism of lowering preload.

Why is a diuretic benefial for treatment of heart failure? Choose the most correct answer.

Option explanation:

It lowers the arterial pressure, which results in a decrease in cardiac output.

It lowers edema, which results in decreased blood pressure and decreased work load of the left ventricle.

It lowers the venous pressure, which results in a decreased preload and decreased work load of the right ventricle.

It lowers the blood pressure, which results in a decreased afterload and an improved contractility of the heart.

Diuretics in CHF

Diuretics in CHF

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