Intracellular And Extracellular Fluid Compartments And Edema Flashcards
Edema
Presence of excess fluid in the body tissues
Hyponatremia
Plasma sodium concentration being reduced below normal (about 142mEq/L)
Hypernatremia
Plasma sodium concentration being elevated above normal
hyperosmotic
Solution that have a higher osmolarity compared with the normal extracellular fluid
Hypoosmotic
Solution that have a low osmolality compared with the normal extracellular fluid
Isosmotic
Solutions with an osmolarity the same as the cell
Frequent problems in treating seriously ill patients
maintaining adequate fluids in one or both of the intracellular and extracellular compartments
amount of extracellular fluid distributed between the plasma and interstitial spaces are determined by
The balance of hydrostatic and colloid osmotic forces across the capillary membrane
Distribution of fluid between intracellular and extracellular compartments is determined by
The osmotic effect of the smallest reduced especially sodium chloride and other electrolytes acting across the cell membrane
Rate of osmosis
is the rate of diffusion of water across the membrane from a region of high concentration to a region of low concentration
80% of the total osmolarity of interstitial fluid and plasma is due to
Sodium and chloride ions
Almost half of the osmolarity of intracellular fluid is due to
Potassium ions endo is divided among many other intercellular substances
Total osmolality of each of the three compartments is
About 300mOsm /L
Slight difference in osmolarity between plasma and interstitial fluid is caused by
The osmotic effect of the plasma proteins
Why is there corrected osmolar activities of plasma, interstitial fluid and intracellular fluid
The reason for these corrections is that cations and anions exert inter ionic attraction which cause a slight decrease in osmotic activity of the dissolved substance
Tonicity of solution depends on
The concentration of impermeant solutes
if a cell is place in a hyper tonic solution
Water will flow out of the cell into the extracellular fluid causing it to shrink
If a cell is placed into a hypotonic solution
Waterway diffuse into the cell causing it to swell (<282 mOsm/L)
How long does it take to achieve osmotic equilibrium everywhere in the body
Fluid usually enters the body through the gut and must be transported by the blood to all the tissues before complete osmotic equilibrium can occur. it usually takes about 30 minutes to achieve osmotic equilibrium everywhere in the body after drinking water
Basic principles in order to calculate intracellular and extracellular fluid
- Water moves rapidly across the cell membrane therefore the osmolarity of the two fluid compartments is almost equal
- Cell membranes i almost completely into mobile too many solutes
Effect of isotonic saline being added to extracellular fluid
- Extracellular osmolality does not change
- no osmosis occurs
- increase in extracellular fluid volume
Effect on extracellular fluid if hypertonic solution is added
- Rise in osmolarity of both compartments
- osmosis of water out of the cell occurs
- increase in extracellular volume
Effect on extracellular fluid if hypotonic solution is added to it
- Osmolarity of extracellular fluid decreases
- osmosis of water into the cell occurs
- intracellular and extracellular volumes are increased
Why is plasma sodium concentration used to measure patients fluid status
sodium and its associated and anions account for more than 90% of the solute in the extracellular fluid therefore used sales an indicator of plasma osmolarity
Cause of hyponatremia
- Loss of sodium chloride from extracellular fluid
2. addition of excess water to extracellular fluid
Conditions that cause hyponatremia due to loss of sodium chloride from extracellular fluid
- Diarrhea
- vomiting
- overuse of diuretics
- certain types of sodium wasting kidney diseases
- addison disease
Addison disease
Decreased secretion of hormone almost erode impairs ability of kidneys to reabsorb Sodium
Hyponatremia- overhydration
Hyponatremia caused by excess water retention which dilutes the sodium in the extracellular fluid
Conditions that cause hyponatremia water retention
Excessive secretion of antidiuretic hormone can cause the kidney tubules to reabsorb more water
Consequences of a rapid reduction in plasma sodium concentration
- Brain cell edema
- neurological symptoms like headache nausea lethargy and disorientation
- if concentration rapidly falls below 115-120 mmol/L swelling leads to seizures, coma, permanent brain damage and death
- herniation of the brain down the neck
consequences of Hyponatremia as it evolves slowly over several days
Tissues respond by transporting Sodium, Chloride, potassium, and organic solutes such as glutamate from the cell into extracellular compartments this reduces osmotic flow of water into the cells and swelling of tissues