Fluids and Electrolytes | Complete Nursing Exam Review & Practice Questions | 2026-2027
What is the water distribution in the body? 2/3 intracellular:
- major cations: K+ and Mg++
- anions: proteins, phosphates, ATP
1/3 extracellular:
- major cations: Na+
- anions Cl- and HCO3-
- plasma: 1/4 of ECF (1/12 TBW)
- interstitial fluid: 3/4 of ECF (1/4 of TBW) -> where edema comes from
How does the kidney regulate hemostasis? ADH - regulates water balance
RAAS - regulates sodium and ECF (volume)
ANP - promotes sodium excretion (opposite of aldosterone and ADH)
Thirst - restores water deficits
Big Takeaway:
Kidneys regulate ECF volume by controlling sodium and regulate osmolality by
controlling water.
What happens when there is water loss (sweating, fever, - serum Na+ and plasma osmolality rises
diarrhea, diabetes insipidus, hyperventilation)? - hypothalamic osmoreceptors shrink which stimulates thirst
- ADH secretion
- aquaporin channels inserted and water reabsorbed in collecting duct
- plasma osmolality returns to normal
How do people become hypernatremic? Healthy people rarely become hypernatremic
- requires BOTH impaired thirst and lack of access to water
Who is at highest risk of hypernatremia? - infants
- elderly
- intubated patients
- dementia
- stroke
- AMS
These people require maintenance IVF
, Fluids and Electrolytes | Complete Nursing Exam Review & Practice Questions | 2026-2027
What happens when there is a positive sodium balance - ECF expansion
(too much taken in stays in the system)? - edema
- hypertension
What happens when there is a negative sodium balance volume depletion and hypotension
(sodium depleted)?
What is the obligatory minimum urine volume per day? 500 mL/day
Why?
kidneys need to excrete urea, sodium, potassium, sulfate, and phosphate which
require water for elimination
If kidneys cannot eliminate metabolic waste - toxic buildup occurs
3 main sources of water intake 1. Drinking fluids
2. Water in food (fruits, veggies, soups)
3. Metabolic water = 300-400 mL/day produced during aerobic metabolism
What are insensible "hidden" water losses? primarily pure water loss (not electrolytes) from respiratory loss and skin loss (not
sweat, but transepidermal water loss)
these losses occur continuously and contribute significantly to daily fluid
requirements, however we cannot measure them
What happens to insensible water loss in patients with more air enters lungs and must be humidified, so more water evaporates and
higher minute ventilation (increased respiratory rate)? greater water loss
When are additional fluids for insensible respiratory water anxiety, pain, sepsis, DKA, PE, mechanical ventilation -> all create higher
loss needed? respiratory water los
How do fever and pain affect insensible water loss? increase by 10-15% d/t increased RR, skin evap, and metabolic rate
Why do we humidify ventilators? - reduces respiratory water loss
- decreases airway driving and protects mucosa
- improves secretory cleaerance
What is the water distribution in the body? 2/3 intracellular:
- major cations: K+ and Mg++
- anions: proteins, phosphates, ATP
1/3 extracellular:
- major cations: Na+
- anions Cl- and HCO3-
- plasma: 1/4 of ECF (1/12 TBW)
- interstitial fluid: 3/4 of ECF (1/4 of TBW) -> where edema comes from
How does the kidney regulate hemostasis? ADH - regulates water balance
RAAS - regulates sodium and ECF (volume)
ANP - promotes sodium excretion (opposite of aldosterone and ADH)
Thirst - restores water deficits
Big Takeaway:
Kidneys regulate ECF volume by controlling sodium and regulate osmolality by
controlling water.
What happens when there is water loss (sweating, fever, - serum Na+ and plasma osmolality rises
diarrhea, diabetes insipidus, hyperventilation)? - hypothalamic osmoreceptors shrink which stimulates thirst
- ADH secretion
- aquaporin channels inserted and water reabsorbed in collecting duct
- plasma osmolality returns to normal
How do people become hypernatremic? Healthy people rarely become hypernatremic
- requires BOTH impaired thirst and lack of access to water
Who is at highest risk of hypernatremia? - infants
- elderly
- intubated patients
- dementia
- stroke
- AMS
These people require maintenance IVF
, Fluids and Electrolytes | Complete Nursing Exam Review & Practice Questions | 2026-2027
What happens when there is a positive sodium balance - ECF expansion
(too much taken in stays in the system)? - edema
- hypertension
What happens when there is a negative sodium balance volume depletion and hypotension
(sodium depleted)?
What is the obligatory minimum urine volume per day? 500 mL/day
Why?
kidneys need to excrete urea, sodium, potassium, sulfate, and phosphate which
require water for elimination
If kidneys cannot eliminate metabolic waste - toxic buildup occurs
3 main sources of water intake 1. Drinking fluids
2. Water in food (fruits, veggies, soups)
3. Metabolic water = 300-400 mL/day produced during aerobic metabolism
What are insensible "hidden" water losses? primarily pure water loss (not electrolytes) from respiratory loss and skin loss (not
sweat, but transepidermal water loss)
these losses occur continuously and contribute significantly to daily fluid
requirements, however we cannot measure them
What happens to insensible water loss in patients with more air enters lungs and must be humidified, so more water evaporates and
higher minute ventilation (increased respiratory rate)? greater water loss
When are additional fluids for insensible respiratory water anxiety, pain, sepsis, DKA, PE, mechanical ventilation -> all create higher
loss needed? respiratory water los
How do fever and pain affect insensible water loss? increase by 10-15% d/t increased RR, skin evap, and metabolic rate
Why do we humidify ventilators? - reduces respiratory water loss
- decreases airway driving and protects mucosa
- improves secretory cleaerance
