The nurse is aware that to maintain fluid balance between the intracellular and extracellular ...

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The proportions of extracellular and intracellular fluid vary with age. The balance of fluid between plasma and interstitial fluid is regulated by hydrostatic pressure (blood pressure) and osmotic pressure. If the intracellular fluid becomes hypertonic in relation to the extracellular fluid, water moves by osmosis from the extracellular fluid into the cell to restore balance. If the intracellular fluid becomes hypotonic in relation to the extracellular fluid, the process just described is reversed, resulting in a constant exchange between the compartments.