The principle of hemodialysis in which the water is moving under high pressure to an area of lower pressure i… - AIIMS Raipur NO - 2019 (Shift-1)

AIIMS Raipur NO - 2019 (Shift-1)

Medical & Surgical Nursing

Easy

Appeared in: AIIMS Raipur NO - 2019 (Shift-1)

Explanation

Ultrafiltration is the process where fluid (water) is moved across a semipermeable membrane due to a pressure gradient.
In hemodialysis, this is achieved by applying positive hydrostatic pressure to the blood side and/or negative pressure (suction) to the dialysate side of the dialyzer.
This pressure difference, called transmembrane pressure, forces excess water and some waste products out of the blood and into the dialysate, effectively removing excess fluid from the patient's body.
This mechanism is distinct from diffusion and osmosis, which are driven by concentration gradients.

Option B: Osmosis is the movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. It is driven by an osmotic gradient, not a pressure gradient.
Option C: Diffusion is the movement of solutes (like urea, creatinine, and potassium) from an area of higher concentration (the blood) to an area of lower concentration (the dialysate). It is the primary principle for removing metabolic waste products, not for removing water via pressure.
Option D: Perfusion refers to the flow of blood through the vessels of an organ or tissue. While adequate blood perfusion through the dialyzer is necessary for hemodialysis to be effective, it is not a principle of transport across the dialysis membrane itself.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Principles of Hemodialysis as background academic context rather than a clinical decision trigger.
The nurse's role during hemodialysis includes carefully monitoring the rate of ultrafiltration to prevent complications. Removing fluid too quickly can lead to intradialytic hypotension, muscle cramps, and dizziness.
The prescribed amount of fluid to be removed (the ultrafiltration goal) is calculated based on the patient's interdialytic weight gain (the amount of fluid gained between dialysis sessions).
Accurate pre- and post-dialysis weight measurement is a critical nursing responsibility to ensure the correct amount of fluid is removed.

How to Approach the Question

First, identify the key terms in the question: 'hemodialysis', 'water moving', 'high pressure', and 'lower pressure'.
The core of the question is about the mechanism of water removal driven by a pressure difference.
Recall the fundamental principles of transport across a semipermeable membrane: diffusion, osmosis, and ultrafiltration.
Define each principle: Diffusion is solute movement down a concentration gradient. Osmosis is water movement down a water concentration gradient (or towards a higher solute concentration). Ultrafiltration is water movement down a pressure gradient.
Match the question's description ('water moving under high pressure') with the correct definition. This directly corresponds to ultrafiltration.
Eliminate the other options based on their definitions. Perfusion is blood flow to tissue, not a membrane transport principle.

Concept Tested & Keywords

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