Hypertensive patient is given diuretics because it lowers blood pressure by?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2015

Pharmacology

Hard

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2015

Explanation

Diuretics primarily lower blood pressure by inhibiting the reabsorption of sodium (Na+) in the renal tubules.
Due to osmosis, water follows the excreted sodium, leading to an increase in urine output (diuresis).
This process, known as natriuresis, depletes the body's sodium and water stores.
The resulting reduction in blood volume and cardiac output is the main reason for the decrease in blood pressure.
While some diuretics affect potassium, the core antihypertensive mechanism for the entire class is the excretion of sodium and water.

Option A: This option incorrectly omits sodium. The primary driver for water excretion (diuresis) is the inhibition of sodium reabsorption (natriuresis).
Option B: This is a close distractor, but it's not the most accurate answer. While many diuretics (like thiazides and loop diuretics) do cause potassium excretion, this is a side effect, not the fundamental mechanism. Potassium-sparing diuretics lower blood pressure without this effect.
Option D: This option incorrectly omits water. The reduction in blood volume from water loss (diuresis) is a critical component of how blood pressure is lowered.

Clinical Relevance

Nursing practice connection: Use the key finding related to Mechanism of action of diuretic drugs in hypertension to guide bedside assessment, documentation, and the next nursing action.
Nurses must monitor patients on diuretics for electrolyte imbalances, particularly hypokalemia with thiazide/loop diuretics and hyperkalemia with potassium-sparing diuretics.
Patient education is crucial. Instruct patients to take their diuretic in the morning to prevent sleep disruption from nocturia (nighttime urination).
Monitoring for orthostatic hypotension is a key safety measure. Due to volume depletion, patients may feel dizzy when standing, increasing their risk of falls.

How to Approach the Question

First, identify the core of the question: it asks for the primary mechanism by which diuretics lower blood pressure.
Recall the main function of diuretics, which is to increase urine output.
Think about the physiological principle that governs water movement in the kidneys: osmosis. Water follows solutes, primarily sodium.
Therefore, to increase water excretion, the drug must first increase sodium excretion. This is called natriuresis.
Evaluate the options based on this core mechanism. The correct option must include both sodium and water.
Differentiate between the primary mechanism and common side effects. Potassium loss is a well-known side effect of many diuretics but not the reason they lower blood pressure, which helps eliminate distractors that include potassium as part of the core mechanism.

Concept Tested & Keywords

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E6 Pharmacology Katzung 16e p. 271-273

E6 Physiology Guyton 4SAE Part 2B p. 88-90