Disorders of ECF Volume: Volume Contraction Flashcards
What is the primary factor affecting extracellular fluid (ECF) volume?
Extracellular concentration of Na⁺
An increase in total body Na⁺ causes an expansion in ECF volume, while a decrease reduces ECF volume.
What happens to blood pressure during sudden loss of Na⁺?
Marked reduction in blood pressure
Sudden loss of Na⁺ leads to a significant decrease in cardiac output.
How does pure water loss affect serum Na⁺ levels?
High serum [Na⁺]
Pure water loss results in hypertonicity.
What is the difference between dehydration and volume depletion?
Dehydration is pure water loss; volume depletion involves loss of Na⁺ and water
Dehydration results in high serum [Na⁺], while volume depletion affects the intravascular compartment.
What characterizes hypotonic volume contraction?
Electrolyte loss exceeds water loss
This results in decreased plasma osmolality and expansion of the intracellular fluid (ICF) compartment.
What is isotonic volume contraction?
Loss of salt and water in proportionate amounts
Results in no change in plasma osmolality and contraction of the ECF compartment.
What causes hypertonic contraction?
Water loss exceeds salt loss
This leads to increased plasma [Na⁺] and osmolality.
Name a cause of extrarenal Na⁺ loss.
Gastrointestinal losses
Other causes include vomiting, diarrhea, and excessive sweating.
What laboratory finding indicates dehydration?
High serum [Na⁺]
Serum osmolality is also high in dehydration.
What is the goal of therapy in volume-contracted patients?
Improve perfusion pressure and alleviate symptoms
Vital organs such as the brain, kidney, and liver are prioritized.
What type of fluid should be given for dehydration?
Water or 5% dextrose in water
This should be administered slowly to correct the water deficit.
What fluid is recommended for treating volume depletion?
Normal (0.9%) saline
This fluid can be given rapidly to restore intravascular volume.
True or False: Dehydration and volume depletion are synonymous.
False
They differ in their pathophysiology and clinical presentation.
Fill in the blank: In isotonic volume contraction, plasma osmolality _______.
does not change
This is due to equal loss of salt and water.
What is a common clinical sign of volume depletion?
Orthostatic blood pressure changes
This occurs due to loss of Na⁺ and water from the ECF compartment.
What does a urinary Na⁺ level <10 mEq/L indicate?
Dehydration
This suggests that the kidneys are conserving Na⁺ in response to low volume.
What condition is characterized by hyponatremia, hyperkalemia, and acute kidney injury?
Addison disease
This is related to glucocorticoid and mineralocorticoid deficiency.
What happens if a patient with volume depletion receives D5W?
It does not improve volume status or blood pressure
D5W can lead to hypokalemia due to glucose-induced insulin release.
