IV Fluids Flashcards
What is diffusion?
Movement of SOLUTE from high concentration to low concentration
What feature must the membrane have for diffusion?
Must be solute permeable
What is osmosis?
Movement of water from high concentration to low concentration
What feature must the membrane have for osmosis?
Solute impermeable
What is osmolarity?
The measure of the solute concentration per unit VOLUME of solute
What does osmolarity take into account?
ALL of the solute concentrations, not just the ones that cant cross the semipermeable membrane
What would be the concentrations of H20 and solute be in the hyperosmotic side?
Higher solute concentration
Lower free H20 concentration
What concentrations of H20 and solute be in the hypoosmotic side?
Lower solute concentration
higher free H20 concentration
What is osmolality?
Measure of solute concentration per unit MASS of solvent
Osmolality in the ICF and ECF
It is the same in the ICF and ECF
What is tonicity?
The measure of the osmotic pressure gradient between two solutions
What is tonicity influenced by?
Only influenced by solutes that cannot cross the semipermeable membrane, because these are the solutes influencing the osmotic pressure gradient
How much water is in the body of a average 70kg male?
42 litres
Distribution of water in the body
42 L in total 2/3 (28L) INTRACELLULAR - 66% 1/3 (14L) EXTRACELLULAR - 20% plasma (3L) - 80% interstitial
How much water is needed per day?
25 - 30 ml / kg/ day
How much sodium is needed per day?
1 mmol / kg / day
How much potassium is needed per day?
1 mmol / kg / day
How much glucose is needed per day?
50-100g / day
How much of fat is water?
10%
How much of muscle is water?
75%
How much does our water content change with age?
Babies = 70%
Child = 60%
Old person = 50%
Questions to ask about fluids
- What is my patients volume status?
- Does my patient need IV fluids?
- How much fluid do they need?
- What types of fluid do they need?
What is euvolaemia?
The right amount of fluid in the body
Presentation of euvolaemia
Feels well Not thirsty Veins well filled Warm extremities Mild sweat Normal BP and HR Normal urine
Needs of euvolaemia
No fluids (unless electrolyte deplete or low BP)
Presentation of hypovolaemia
nausea thirsty flat veins cool peripheries no sweat low or postural BP and high HR Concentrate oliguria Responds to SLR
Needs of hypovolaemia
Resuscitation fluids (if low BP)
Rehydration fluids
“plug the leak”
Presentation of hypervolaemia
Feels breathless Not thirsty Veins distended Warm and oedematous extremities sweaty high BP and high HR Dilute urine (could be oliguric or polyruic)
Needs of hypervolaemia
No more fluids
Possibly diuretics (if resp compromise)
Hemofiltration (if anuric)
Low oncotic pressure (low protein/albumin) can present as what?
Oedema in dehydrated patients due to loss of intracapillary fluid
Tends to be odematous, but behave hypovolaemic (low BP, high HR, thirsty)
What can heart failure present as?
Oedema
Low BP
but still require diuresis due to high circulating volume causing increased RVP
Things to look at to work out the water deficit
Catheters Drains Input charts Vomit bowels Sputum pots Stool charts and stoma losses
What are the insensibles?
Transepidermal diffusion
Open wounds
Burns
Bleeding
What is Transepidermal diffusion?
Water that passes through the skin and is lost by evaporation AND water loss from the resp tract.
Sepsis (sweat)
ventilation
How much loss of fluid occurs daily in adults by Transepidermal diffusion?
400-800mls
The 5 Rs
Resuscitation Routine maintenance Replacement Redistribution Reassessment
What are IV fluids used?
If cannot take orally
Urgently to restore circulation with hypovolaemia
Enterally to meet patient maintenance requirements
If dont need IV fluids for resuscitation, when is another scenario you may need for IV fluids?
If need IV additional to maintenance to correct existing deficit OR
ongoing abnormal external losses e.g. diarrhoea, fever
Where can dextrose move in the body?
Through all compartments
Dextrose is useful in …..
Chronic dehydration
Hypernatraemia
When is dextrose not useful?
Resuscitation
Low albumin
Where do crystalloids remain?
In ECF
Crystalloids are useful in …..
Acute dehydration
AKI
resuscitation
When are crystalloids not useful?
Long term maintenance
Hypernaetraemic patient
Plasma expanders are useful in …..
liver patients
select intra-operative
What are plasma expanders not useful in?
much else
What are plasma expanders and where are they found in the body?
Colloids
Exclusively stay in IVS
