In hypertonic dehydration fluid moves from-

RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

Applied Physiology

Medium

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2022

Explanation

In hypertonic dehydration, the body loses more water than electrolytes, which increases the solute concentration (osmolarity) of the extracellular fluid (ECF).
The ECF, which includes the interstitial space, becomes hypertonic (more concentrated) compared to the fluid inside the cells (intracellular fluid or ICF).
Following the principle of osmosis, water moves from an area of lower solute concentration (the cells) to an area of higher solute concentration (the interstitial space) to restore equilibrium.
This movement of water out of the cells results in cellular shrinkage and is the hallmark of hypertonic dehydration.

Option A: This describes the fluid shift in hypotonic dehydration, where the extracellular fluid is less concentrated than the intracellular fluid, causing water to move into the cells.
Option C: This is not a primary fluid shift in dehydration. The main fluid exchange occurs between the intracellular and extracellular (interstitial and intravascular) compartments based on osmotic gradients.
Option D: This describes 'third-spacing' or effusion, where fluid moves from the intravascular space into potential body cavities like the peritoneal or pleural space, often due to inflammation or decreased plasma proteins.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Fluid and Electrolyte Balance: Hypertonic Dehydration as background academic context rather than a clinical decision trigger.
Hypertonic dehydration is particularly dangerous because cellular shrinkage in the brain can lead to significant neurological symptoms, including irritability, confusion, lethargy, seizures, and coma.
Nurses must carefully monitor the neurological status, serum sodium levels, and urine output of patients at risk for hypertonic dehydration, such as the elderly, infants, or individuals with impaired thirst mechanisms.
What if? If a patient with hypertonic dehydration were incorrectly treated with a hypertonic IV solution (e.g., 3% saline), it would worsen the osmolarity imbalance, pull even more water from the cells, and could lead to severe neurological damage or death. The correct treatment involves hypotonic or isotonic fluids to gradually rehydrate the cells.

How to Approach the Question

First, identify the key term in the question: 'hypertonic dehydration'.
Recall the definition: 'Hyper-' means high concentration. This signifies that the extracellular fluid has a high concentration of solutes because more water has been lost than solutes.
Apply the fundamental principle of osmosis: Water always moves from a region of lower solute concentration to a region of higher solute concentration across a semipermeable membrane.
Connect the concepts: Since the cells have a lower solute concentration and the interstitial space has a higher concentration, fluid must move out of the cells and into the interstitial space.
Evaluate the options to find the one that accurately describes this fluid shift from the intracellular to the extracellular compartment.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 1 pp. 90-92, 96-98