IV Fluids

Question 1

Define osmolarity

Answer 1

Measure of solute concentration per unit VOLUME of solvent

Question 2

Define osmolality

Answer 2

Measure of solute concentration per MASS of solvent

Is the same in the ICF and ECF

Question 3

Define tonicity

Answer 3

The measure of osmotic pressure gradient between two solutions

Is only influenced by solutes that cannot cross semipermeable membrane as these are the only ones influencing osmotic pressure gradient

Question 4

Describe basic body fluid distribution

Answer 4

Average 70kg male; 42L water

2/3 IC
1/3 EC

Question 5

What do we need fluidwise?

Answer 5

No-one exactly the same

Water 25-30ml/kg/day

Sodium 1mmol/kg/day

Potassium 1mmol/kg/day

Glucose 50-100g/day

Question 6

Questions to ask when prescribing fluids

Answer 6

1. What is my patient’s volume status? - ABCDE
2. Does my patient need IV fluids?
3. How much fluid do they need?
4. What types of fluid do they need?

Question 7

Describe euvolaemia

Answer 7

Patient feels well, not thirsty

Veins well filled

Warm extremities

Mild sweat

Normal BP and HR

Normal urine

NEEDS no fluids (unless electrolyte deplete or low BP)

Question 8

Describe hypovolaemia

Answer 8

Feels nauseous, thirsty

Flat veins

Cool peripheries

No sweat

Low or postural BP and high HR

Concentrate oliguria

Responds to SLR

NEEDS fluid resus if low bp, rehydration fluids, “plug the leak”

Question 9

Describe hypervolaemia

Answer 9

Feels breathless not thirsty

Veins distended

Warm and oedematous extremities

Sweaty

High BP and HR

Dilute urine; may be oliguric or polyuric

NEEDS; no more fluids, possibly diuretics, haemofiltration if anuric

Question 10

How to work out how much fluid a patient needs

Answer 10

Work out water deficit

• catheters, drains
• input charts
• vomit bowl
• sputum pots
• stool charts and stoma losses

Sepsis (sweat)
Ventilation
Open wounds
Burns
Bleeding

Question 11

Describe resuscitation fluids

Answer 11

IV fluisd urgently restore circulation with hypovolaemia

Question 12

Describe routine maintenance fluids

Answer 12

IV fluids if cannot take orally or enterally to meet patient maintenance requirements

Question 13

Describe replacement fluids

Answer 13

Some don’t need urgent IV resus but do need IV additional maintenance to correct existing deficits or ongoing abnormal EXTERNAL losses e.g. diarrhoea or fever

Question 14

Describe redistribution fluids

Answer 14

Some patients have abnormal INTERNAL fluid redistribution or fluid handling e.g. sepsis or major illness; cardiac, liver or renal disease

Question 15

Describe dextrose as an IV fluid

Answer 15

Moves through all compartments; not useful for blood volume expansion

Zero sodium load, isotonic

Useful in; chronic dehydration, hypernatraemia

Not useful in; resuscitation, low albumin

Question 16

Describe crystalloids as an IV fluid

Answer 16

Utilitarian, come in various combinations

Remain in ECF

Usually high Na load; can cause problems over time

Useful in; acute dehydration, AKI, resuscitation

Not useful in; long term maintenance, hypernatraemic patient

Question 17

Describe plasma expanders as an IV fluid

Answer 17

Colloid, stays exclusively in IVS

Trials show no better than crystalloid in resus

IV albumin sometimes used in cirrhosis

Remember blood and TPN are also colloids

Useful in; liver patients, selected intra-operative

Not useful in much else