body fluid compartments Flashcards
what is interstitual fluid
water that lies between blood circulation and cells
what is transcellular fluid
CSF, pleural, synovial etc
what is included in extracellular fluid
- plasma
- interstitial
- transcellular
how does cellular movement occur between the lumen and the intersitium
- absorbing sodium, chloride and potassium creates osmotic gradient
- is paracellular
why is high sodium, glucose and potassium solutions needed
to maximise water translocation
how does sodium movement occur
- across basolateral membrane
- sodium potassium atpase
- build up make positive electrochemical gradient
- helps chloride movement
what is colloid osmotic pressure
osmotic gradient created by the differential distribution of protein across this barrier
how does movement between cappilaries occur
hydrostatic pressure in capillary and extracellular fluid hydrostatic pressure makes net outward force
what is starlings force
determines the ratee of plasma filtration from blood to intersitium
what are the effects of right sided heart failure
- hard for blood to be pumped back into heart from veins
- blood build up makes backlog increasing pressure
how does right sided heart failure affect fluid
- increased net filtration out of capillaries
- pressure is greatest at feet
what are the effects of left sided heart failure
- pressure build up until excessive build up of blood into the pulmonary interstitial fluid
how is there stable levels of plasma nd interstitial fluid
blood filtration is equal to drainage rate of the liver of the lymph
what causes lymphedema
blockage to the lymphatic system
what causes pitting oedema
- no blockage to the lymph system
- there is a change in starling forces
how does water move intracellularly and extracellularly
- difference in osmolarity
- water soluble membrane
- aquaporins
- move from low to high
how do solutes exert an osmotic force
- differential distribution across a membrane
- increased permeability will decrease the osmotic force
how do you have effective osmoles
- cell impermeant to solute
- low permeability
what occurs in an isotonic solution
- cell volume remains constant
- no net movement of water
- impermeable so osmotic forces
what occurs in a hypotonic solution
- movement from low effective osmolarity to high effective osmolarity
- cell swells
what is a hypertonic solution
the solution outside of the cell is more concentrated than inside the cell
what are the main differences between the composition of the intracellular and extracellular fluids
-intra = higher potassium
- extra = high sodium
- similar osmolarity
what are signs of increased extracellular volume
- hypoxia
- high BP
- periorbital oedema
- raised JVP
- bi-basal crackles
- leg oedema (pitting)
what are signs of decreased extracellular volume
- tachycardia
- hypotension
- dry mouth
- reduced JVP
- cool peripherals
- oliguria
what is hypertonic dehydration
- lose more water then sodium
- excessive water loss or not enough intake
what is isotonic dehydration
- lose same amount of water as sodium
- trauma, vomiting, burns, sweating
what is hypotonic dehydration
- lose more sodium than water
- Addison’s, diuretics
why is dehydration more common in the elderly
- decreased total body water
- reduce urine concentration
- reduced thirst
how does a decreased heart volume affect MAP
- decreases venous pressure
- decreases venous return
- decrease in edv
- decrease cardiac output
- decreased MAP
how does an increase in blood volume affect MAP
- increase venous pressure
- increase venous return
- increase EDV
- increase cardiac output
- increase MAP
what mechanisms do the kidneys use to regulate Na
- decreased blood volume triggers baroreceptors
- cause the sympathetic nervous system to fire for more sodium reabsorption
- release renin starting RAAS
- retains more sodium
stages of RAAS
- angiotensinogen
- renin release
- cleave angiotensin I
- angiotensin I and ACE
- angiotensin II into kidney
- release aldosterone
what are the effects on an increase in angiotensin II
- increase arteriolar vasoconstriction
- increase thirst and Na appetite
- increased aldosterone secretion
how is the feeling of thirst triggered
- stimulation of subfornical organ and organum vasculosum of the lamina terminals
- modulated by GI afferents and baroreceptor inputs
what are the stages of response to a decrease in extracellular fluid volume
- stabilise arterial blood pressure with baroreflex
- neuroendocrine reflexes increase plasma - vasoconstriction
- reduced starlings force, net reabsorption
- stable circulating volume, increasing reabsorption
- increase thirst and Na appetites
- increase albumin, platelets and erythrocytes
what are the changes in starlings force in decreased capillary hydrostatic pressure
- loss of gradient
- limited net filtration out
- albumin levels are ok
- force exceeds that of capillary hydrostatic pressure so increase water reabsorption
what are the short term effects of decrease blood volume
- reduced arterial and cardiopulmonary baroreceptors firing
- increased CO
- arterial vasoconstriction + venoconstriction
what are the long term effects of blood volume
- increase thirst
- decrease urinary loss of water and sodium
what is the long term aim in blood volume loss
restore the blood volume
what is the short term aim in blood volume loss
stabilise the MAP
what are the different types of fluid for IV fluid resucitation
- crystalloid
- colloid
what is a risk of using crystalloid IV fluid therpay
risk of exacerbating oedema
what are the risks of using colloid IV therapy
- risk of anaphylactic reactions
- expand intravascular volume
- infused can cause haemodilution impacting coagulation
