IV fluids

Question 1

What is a colloid and what is it used for?

Answer 1

Fluid

1. Used to expand circulating volume in states of impaired tissue perfusion (inc shock). However, compound sodium lactate and NaCl 0.9% are usually preferable
2. In cirrhotic liver disease, albumin is used to prevent effective hypovolaemia in large-volume paracentesis (ascitic fluid drainage)

Question 2

Name some examples of colloids?

Answer 2

Gelatins, albumin

Question 3

How do colloids work?

Answer 3

The IV fluid contains large molecules of albumin or gelatin. These modules cannot cross a semipermeable membrane, and their osmotic effect ‘holds’ the infused volume in the intravascular compartment
They therefore act to expand circulating volume

however in sepsis capillaries become “leaky” so they don’t work as well

They aren’t used as often as crystalloids such as sodium chloride 0.9% as there’s is no convincing evidence they work better

Question 4

What are the importantly adverse effects of colloids?

Answer 4

Colloids contain sodium, diffusion of which into the interstitium produces oedema, including pulmonary oedema

Question 5

What are the warnings about colloids?

Answer 5

They should undertaken in caution in patients with heart failure, due to the risk of pulmonary oedema
This is solved by doing reduced volume fluid challenges, to prevent fluid overload

Warned in renal impairment

Question 6

How are colloids prescribed and administered?

Answer 6

E.g shock- 250mL of Gelofusine to be given over 5 minutes
E.g. Paracentesis- consult with specialists about the need for albumin, commonly give 100ml albumin 20% solution for every 2L of ascitic fluid drained

Give through an infusion, use warmed fluids if possible to avoid hypothermia

Question 7

What is Hartmann’s solution?

Answer 7

Compound sodium lactate

Contains sodium, chloride, potassium, calcium and lactate

Question 8

What is Hartmann’s solution used for?

Answer 8

1. To provide sodium and water in patients unable to take enough orally
2. To expand circulating volume in states of impaired tissue perfusion (inc shock)

Question 9

What are the adverse effects of Hartmann’s solution?

Answer 9

Oedema

Pulmonary oedema

Question 10

How is Hartmann’s solution prescribed?

Answer 10

For patients unable to tolerate fluid- 500ml at 100ml/hour and glucose 5% 2L at 100ml/hour
Together these would provide 65mmol/day of sodium and 2400ml of water- a reasonable maintenance fluid regime

To expand circulating volume, you might prescribe 500ml over 5 mins

Question 11

what are the different fluid compartments?

Answer 11

intracellular and extracellular

within extracellular is interstitial and intravascular

Question 12

how many litres of water is in the average 70kg man?

Answer 12

42 litres
65% (28L)- intracellular
35% (14L)- extracellular

Question 13

what are levels of sodium and potassium in intra and extracellular fluids?

Answer 13

The intracellular fluid has:
A high potassium concentration.
A low sodium concentration.
Intracellular solute concentrations remain more or less constant.

Extracellular fluid has:
A high sodium concentration.
A low potassium concentration.

Question 14

what are oncotic and hydrostatic pressures?

Answer 14

oncotic- low proteins to high protein conc gradient

hydrostatic- high pressure volume to low pressure volume gradient

Question 15

what is the recommended fluid, electrolyte and glucose intake for a person?

Answer 15

25-30 ml/kg/day of water
Approximately 1 mmol/kg/day each of sodium, chloride and potassium
50 - 100 g/day of glucose to limit starvation ketosis

Question 16

why might someone with severe hypovolaemia have a normal BP and how should you further investigate it?

Answer 16

compensation due to peripheral vasoconstriction

should check for postural drop

Question 17

what things do you need to assess before prescribing fluids?

Answer 17

Blood pressure
 Capillary refill time
 Fluid balance charts
 Response to straight leg raise
 Skin turgor
 Weight

Question 18

name some examples of hypo, iso and hypertonic crystalloids?

Answer 18

iso- sodium chloride 0.9% (most commonly used)
hypo- sodium chloride 0.45%.
hyper- sodium chloride 3%, mannitol.

Question 19

how much sodium and chloride does 1L of 0.9% saline contain?

Answer 19

Contains 154 mmol/litre of sodium and chloride

Stays in the extracellular fluid compartment-> 25% into intravascular compartment

Question 20

When you give 1 litre (1000 ml) of glucose 5%, do you know how it distributes in the various fluid compartments?

Answer 20

Contains 50 grams/litre of glucose
Two thirds goes to the intracellular fluid.
One third goes to the extracellular fluid.
Of the one third in the extracellular fluid, only approximately 80 ml of the 1000 ml administered will stay in the intravascular compartment

This explains why glucose 5% is not commonly used in resuscitation situations secondary to blood loss.

Question 21

what are the different types of shock?

Answer 21

1. Distributive shock- relative hypovolaemia e.g. sepsis, anaphylaxis and neurogenic shock
2. Hypovolaemic shock e.g. haemorrhage, burns
3. Cardiogenic shock- a relative or absolute reduction in cardiac output due to a primary cardiac disorder. causes inc ischaemia, heart failure and arrhythmias
4. Obstructive shock e.g. massive PE and cardiac tamponade

Question 22

indicators that a patient may need urgent fluid resuscitation?

Answer 22

Systolic blood pressure less than 100 mmHg

Heart rate is more than 90 beats per minute

Capillary refill time more than 2 seconds or peripheries are cold to touch

Respiratory rate more than 20 breaths per minute

NEWS2 is 5 or more

Passive leg raising suggests fluid responsiveness

Question 23

what is the minimum aim for urine output?

Answer 23

0.5ml/kg/hour

Question 24

how much fluid per day is estimated to be gained from metabolism?

Answer 24

400ml