Fluid Therapy

Question 1

What is osmolarity

Answer 1

Measure of solute concentration per unit volume of solvent (all solute, not just those that can’t cross membrane)

Question 2

What is osmolality

Answer 2

Measure of solute concentration per unit mass of solvent

Same in ICF and ECF

Question 3

What is tonicity

Answer 3

Measure of osmotic pressure gradient between two solutions

Only solutes that cannot cross membrane

Question 4

Split of fluid in average 70kg male

Answer 4

2/3 intracellular (28L)

1/3 extracellular (14L) (3L intravascular)

Question 5

General intake values for water, sodium, potassium and glucose

Answer 5

W - 25-30ml/kg/day
Na - 1mmol/kg/day
K - 1mmol/kg/day
Glucose - 50-100g/day

Question 6

Features of euvolaemia

Answer 6

Feels well, not thirsty
Veins well filled
Warm extremities
Mild sweat
Normal BP and HR 
Normal urine
Does not need fluids

Question 7

Features of hypovolaemia

Answer 7

Feels nauseous, thirsty
Flat veins
Cool peripheries
No sweat
Low or postural BP and high HR
Concentrate oliguria
Responds to SLR 
Needs resuscitation fluids if low BP, rehydration fluids

Question 8

Features of hypervolaemia

Answer 8

Feels breathless, not thirsty 
Veins distended
Warm and oedematous extremities
Sweaty
High BP and HR
Dilute urine 
Needs no more fluids, possibly diuretics, haemofiltration

Question 9

Features of dextrose fluid

Answer 9

Total body water
Moves through all compartments (not useful for blood volume expansion)
Zero sodium load, isotonic
Useful in chronic dehydration, hypernatraemia
Not useful in resuscitation and low albumin

Question 10

Features of crystalloid fluid

Answer 10

Utilitiarian - come in various combinations
Remain in ECF
Usually high Na load
Used in acute dehydration, AKI, resuscitation
Not useful in long term maintenance, hypernatraemic patient

Question 11

Features of plasma expanders

Answer 11

Colloid - stays in IVS

Used in liver patients, select inraoperative patients