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
Transport of solutes during slowly developing hyponatremia makes dublin 12 injury if hyponatremia is corrected to rapidly
If hypertonic solution are added too rapidly to correct hyponatremia this can outspace the brain’s ability to recapture the solutes lost from the cell and may lead to osmotic injuries that is associated with demyelination
How is osmotic- mediated demyelination avoided
By limiting the correction of chronic hyponatremia to less than 10 - 12mmol/L in 24 hours and 18mmol/L in 48 hours, which permits the brain to recover the lost osmoles
Causes of hypernatremia
- Loss of water from the extracellular fluid which concentrates sodium ions
- excess sodium in extracellular fluid
Conditions that cause hyponatremia due to water loss
- Central diabetes insipidus
- nephrogenic diabetes insipidus
- dehydration
Central diabetes insipidus
Lack of antidiuretic hormone causes the kidneys to excrete large amounts of dilute urine causing dehydration and increase concentration of sodium chloride in extracellular fluid
Nephrogenic diabetes insipidus
Kidneys cannot respond to antidiuretic hormone
Hypernatremia - overhydration
Hyponatremia occurs when excess sodium chloride is added to the extracellular fluid which is associated with at least some degree of water retention by the kidneys
Conditions that cause hyponatremia due to excessive sodium chloride retention
Excessive secretion of sodium retaining hormone aldosterone
why is hyponatremia not that severe
Sodium retention caused by increased secretion of aldosterone hormone also increases the secretion of antidiuretic hormone and causes kidneys to absorb greater amounts of water
Hyponatremia is less common than hyponatremia
Hyponatremia promotes intense thirst and stimulates secretion of antidiuretic hormone which protects against a large increase in the plasma and extracellular fluid Sodium.
When can severe hyponatremia occur
- Patients with hypothalamic lesion that impairs the sense of thirst
- infants who may not have ready access to water
- Elderly patients with altered mental status
- persons with diabetes insipidus
How is hyponatremia corrected
By administrating hypoosmotic sodium chloride or dextrose solution
Hyponatremia should be corrected slowly in patients with had chronic increase in plasma sodium concentration
Hyponatremia activates defense mechanisms that protect the cell from changes in volume that is increase the intracellular concentration of sodium and other solutes which need to be brought back to normal concentrations
Conditions that cause intracellular edema
- Hyponatremia
- depression of the metabolic system of tissues
- lack of adequate nutrition to the cells
Normonatremia
When a concentration of sodium and water inside and outside the cell is normal
How does decrease in blood flow lead to intracellular edema
Blood flow to a tissue is decreased the delivery of oxygen and nutrients is reduced if blood flow becomes too low to maintain normal tissue metabolism the cell membrane ionic pumps become depressed sodium ions that normally leak into the interior of the cell can no longer be pumped out and the excess intracellular sodium ions cause Osmosis of water into the cell which can sometimes lead to death of the tissue
How is intracellular edema caused by inflammation
Inflammation usually increases cell membrane permeability allowing sodium and other ions you diffuse into the interior of the cell with subsequent osmosis of water into the cell causing edema
Cause of extracellular edema
Abnormal leakage of fluid from the plasma to interstitial spaces across the capillaries failure of the lymphatics to return fluid from the insterstitium back into the blood often called lymphedema
How is capillary filtration rate increase
Based on the capillary filtration rate equation any one of the following changes can increase the capillary filtration rate:
- increased capillary filtration coefficient
- increased capillary hydrostatic pressure
- decreased plasma colloid osmotic pressure
conditions that cause extras cellular edema by the two types of all of abnormalities
- Increased capillary pressure
- decreased plasma protein
- increased capillary permeability
- blockage of lymph return
Cause of increased capillary pressure
1.Excessive kidney retention of salt and water 2.high venous pressure and venous constriction 3.decreased arteriolar resistance
cause of excessive kidney retention of salt and water
- acute or chronic kidney failure
2. mineralocorticoid excess (aldosterone)
Cause of high venous pressure and venous constriction
- Heart failure
- venous obstruction
- Failure of venous pump
Cause of failure of venous pump
- Paralysis of muscles
- immobilization of parts of the body
- failure of venous valves
Cause of decreased arteriolar resistance
- Excessive body heat
2. insufficiency of sympathetic nervous system 3.vasodilator drugs
Cause of decreased plasma protein
- loss of protein in urine (nephrotic syndrome)
- loss of protein from denuded skin areas
- Failure to produce protein
Cause of loss of protein from denuded skin areas
- burns
2. wounds
cause of failure to produce protein
- Liver disease (cirrhosis)
2. serious protein or caloric malnutrition
cause of increased capillary permeability
- immune reaction that causes release of histamine and other immune products
- toxins
- bacterial infections
- vitamin deficiency especially vit C
- prolonged ischemia
- burns
Cause of blockage of lymph
- Cancer
- infection(filarial nematodes)
- surgery
- congenital absence or abnormality of lymphatic vessels
How does heart failure cause edema
- fails to pump blood from the veins into the Arteries which increases Venous pressure and capillary pressure causing increased capillary filtration.
- arterial pressure falls causing retention of salt and water by the kidneys causes edema
- Reduced blood flow to the kidneys stimulate secretion of renin causing increased formation of angiotensin II and increases secretion of aldosterone which causes salt and water retention
cause of pulmonary edema
Patients with left sided heart failure, blood is pumped normally into the lungs by the right side of the heart but cannot escape easily from the pulmonary veins to the left side because it is weekend. Consequently Pulmonary capillary pressure rises which causes pulmonary edema, fluid accumulation in the lungs can cause death within a few hours.
Main effect of decrease kidney excretion of salt and water
Large amount of salt and water added to extracellular fluid most of this is released into the interstitial space some remains in the blood effects are :
- extracellular edema
- hypertension because of increase in blood volume
Why does decreased plasma protein cause edema
Decreased plasma protein due to failure to produce normal amount or leakage of proteins from the plasma causes plasma colloid osmotic pressure to fall leading to increased capillary filtration and extracellular edema. Edema occurs when Plasma protein conc falls below 2.5g/100ml
Edema occurs when Plasma protein falls below
2.5g/100ml
How does cirrhosis of the liver lead to extra cellular edema
- failure to produce sufficient plasma protein
- fibrosis compresses the abdominal portal venous drainage vessels which rises capillary hydrostatic pressure increasing filtration of fluid out of the plasma into intra-abdominal areas condition called hydriperitoneal or ascites
What is cirrhosis of the liver
Cirrhosis means development of large amount of fibrous tissue among the liver parenchymal cells
Safety factors that prevent edema
- Low tissue compliance in negative pressure range is about 3 mm Hg
- Ability to increase lymph flow is about 7 mmhg 3. washdown of proteins from interstitial spaces is about 7 mmhg
What is compliance of the tissue
Define as a change in volume per mm of mercury pressure change
How is Luke appliance of infestation in the negative pressure range a safety Factor
Invitation hydro static pressure is less than atmospheric pressure about -3 mmHg as long as interstitial fluid hydrostatic pressure is in the negative pressure range a small increase in Interstitial fluid volume causes a relatively large increase in hydrostatic pressure opposing filtration of fluid into the tissue. If hydrostatic pressure increase about 3mmHg, fluid will begin to accumulate.
How does increases lymph flow act as safety factor
Major function of the lymphatics system is to return fluid and protein filtered by capillaries back to the blood without this edema would occur. Lymph flow can increase 10-50 folds when fluid begins to accumulate this allows lymphatics to carry large amounts of fluid and protein in response to increased capillary filtration preventing intestinal pressure from rising into positive rage. Increased lymph flow calculated to be 7mmHg
How is washing down of intestinal fluid protein a safety Factor
Increased amount of fluid are filed into the insterstitium the interstitial pressure increases causing increased lymph flow which carries away large amounts of proteins, decreasing the interstitial fluid colloid osmotic pressure which lowers net filtration and prevent fluid accumulation. The safety factor from this effect calculated to be 7mmHg
Total safety factor against the edema
About 17 mmhg which means capillary pressure in peripheral tissue could theoretical rise to 17mmHg or approximately double the normal amount before marked edema.
How good is collected from potential spaces
Proteins collect in potential spaces and these are removed through lymphatics or other channels and return to the circulation each potential spaces is either directly or indirectly connected with Lymphatic vessels
what is effusion
When edema in subcutaneous tissue adjacent to potential spaces edema fluid collects in the potential space as well and this fluid is called effusion
Interstitial fluid hydrostatic pressure in Pleural cavities
About -7 to -8mmHg
Interstitial fluid hydrostatic pressure in joint spaces
-3to - 5 mmHg
Interstitial fluid hydrostatic pressure in pericardial cavity
-5 to -6mmHg
