IV fluids Flashcards
Why is it important to learn about IV fluids?
up to 20% patients receiving IV fluids experiencing complications or morbidity
Diffusion
movement of solute from high to low concentration
membrane must be solute permeable
osmosis
movement of water from high to low concentration
membrane must be solute impermeable
osmolarity
all solute concentrations
solute concentration per unit volume of solvent
osmolality
solute concentration per unit mass of solvent
tonicity
osmotic pressure gradient
solute unable to cross membrane
Fluid physiology - 70kg male
42L
2/3 ICF = 28L
1/3 ICF = 14L - 20% (3l) intravascular
osmolality in ECF and ICF
285-290mOsm/kg - the same
water requirements a day
25-30ml/kg
glucose requirement a day
50-100g
potassium requirement a day
1mmol/kg
sodium requirement a day
1mmol/kg
water content of fat
10% water
water content of muscle
75%
4 main questions with fluid balance
- patients volume status
- need IV fluids?
- how much fluid?
- what kind of fluid?
assessing patients volume status
age, gender, muscle mass, insensible loss, physiology
ABCD
ventilation, SOB (pulmonary oedema)
circulation - raised JVP
mucous membranes, reduced skin turgor, sweat
Hypovolaemia characteristics
nauseous - thirsty - flat veins - cool peripheries - low bp - low HR - no sweat - concentrated oliguria
Hypovolaemic patient needs?
resuscitation fluids - low bp
rehydration fluids
plug the leak
Euvolaemia characteristics
feels well, not thirsty, normal bp and HR, veins well fixed, mild sweat
Euvolaemic patient needs?
no fluids unless low bp or electrolyte deplete
hypervolaemia characteristics
SOB, veins distended, sweaty, warm and oedematous extremities, high bp and HR, dilute urine
hypervolaemic patient needs?
no more fluids
diuretics
haemofiltration if anuric
particularly tricky situations
low oncotic pressure - low albumin (oedema)
heart failure
How to work out water deficit
catheters - drains - input charts - stool and stoma - sputum pots - vomit bowls
Insensible losses volume and areas
400-800ml
sepsis (sweat), ventilation, burns, bleeding, open wounds
3 main types of fluids given and what membranes they cross
dextrose - all membranes, crystalloids - stays in ECF, plasma expanders
D5W good for
hypernatraemia
D5W not good for
resuscitation, low albumin
Crystalloids good for
AKI, acute dehydration, resuscitation, sepsis
crystalloids not good for
hypernatraemia
colloids good for
liver patients, bleeding, intra-op
blood, TPN
Resuscitation fluids
IV fluids urgently to restore circulation with hypovolaemia
routine maintenance fluids
IV fluids if not taken orally or enterally
Replacement fluids
IV additional to maintenance or correct existing deficit or ongoing abnormal external losses eg diarrhoea
redistribution fluids
abnormal internal fluid redistribution or fluid handling eg sepsis, liver or renal patients, tissue oedema
5th R
reassessment
