Intravenous Fluids Flashcards
Define diffusion
movement of solute from high concentration to low concentration. Membrane has to be solute permeable
Define osmosis
movement of water from high concentration to low concentration. membrane has to be solute impermeable
Define osmolarity
the measure of solute concentration per unit volume of solvent
Define osmolality
the measure of solute concentration per unit mass of solvent
Define tonicity
the measure of the osmotic pressure gradient between two solutions
Describe the fluid components of a 70kg man
42 l water
2/3 28l intracellular
1/3 14l extracellular - 3l is intravascular
what solutes are found in plasma
HPO4^2- Cl- protein bilirubin Mg2+ K+ Na+ urea
daily requirement of water
25-30ml/kg
daily requirement of sodium
1mmol/kg
daily requirement of potassium
1mmol/kg
daily requirement of glucose
50-100g
what questions do you need to ask before prescribing fluids?
patients volume status
do they need IV fluids
how much
type of fluid
describe a euvolaemic patient
feels well, not thirsty veins well filled warm extremities mild sweat normal BP and HR normal urine
describe a hypovolaemic patient
feels nauseous, thirsty flat veins cool peripheries no sweat low or postural BP and high HR concentrate oliguria responds to SLR
what are the fluid needs in a hypovolaemic patient?
low BP - resus fluids
rehydration fluids
describe a hypervolaemic patient
feels breathless, not thirsty veins distended warm and oedematous extremities sweaty high BP and HR dilute urine - may be oliguric or polyuric
what are the fluid needs in a hypervolaemic patient?
no more fluids
possibly diuretics if resp compromise
haemofiltration (if anuric)
how can you work out the water deficit of a patient?
catheters, drains input charts vomit bowls sputum pots stool charts and stoma losses
how do you work out the insensible losses?
sepsis - sweat ventilation open wounds burns bleeding
what is a resuscitation fluid?
IV fluids urgently to restore circulation with hypovolaemia
what are routine maintenance fluids?
IV fluids if cannot take orally or enterally to meet patient maintenance requirements
what are replacement fluids?
some don’t need IV resus but do need IV additional to maintenance to correct existing deficit or ongoing abnormal external losses e.g. diarrhoea, fever
what are redistribution fluids?
some patients have abnormal internal fluid redistribution or abnormal fluid handling, particularly with sepsis, or major illness, cardiac, liver or renal disease e.g. tissue oedema, GIT/thoracic/peritoneal collection
describe dextrose and its uses
total body water
moves through all compartments - not useful for blood volume expansion
0 Na load, isotonic
useful - chronic dehydration, hypernatraemia
when is dextrose NOT useful?
resus
low albumin
describe crystalloids and their uses
utilitarian, comes in various combinations
remain in ECF
usually high Na load - can cause problems over time
uses - acute dehydration, AKI, resus
when are crystalloids NOT useful?
long term maintenance,
hypernatraemia
decribe the colloids (plasma expanders) and their uses
stay in IVS Blood and TPN are colloids IV albulin sometimes used in cirrhosis liver patients select intraoperative
