IV fluids Flashcards
What is a colloid and what is it used for?
Fluid
- Used to expand circulating volume in states of impaired tissue perfusion (inc shock). However, compound sodium lactate and NaCl 0.9% are usually preferable
- In cirrhotic liver disease, albumin is used to prevent effective hypovolaemia in large-volume paracentesis (ascitic fluid drainage)
Name some examples of colloids?
Gelatins, albumin
How do colloids work?
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
What are the importantly adverse effects of colloids?
Colloids contain sodium, diffusion of which into the interstitium produces oedema, including pulmonary oedema
What are the warnings about colloids?
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
How are colloids prescribed and administered?
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
What is Hartmann’s solution?
Compound sodium lactate
Contains sodium, chloride, potassium, calcium and lactate
What is Hartmann’s solution used for?
- To provide sodium and water in patients unable to take enough orally
- To expand circulating volume in states of impaired tissue perfusion (inc shock)
What are the adverse effects of Hartmann’s solution?
Oedema
Pulmonary oedema
How is Hartmann’s solution prescribed?
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
what are the different fluid compartments?
intracellular and extracellular
within extracellular is interstitial and intravascular
how many litres of water is in the average 70kg man?
42 litres
65% (28L)- intracellular
35% (14L)- extracellular
what are levels of sodium and potassium in intra and extracellular fluids?
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.
what are oncotic and hydrostatic pressures?
oncotic- low proteins to high protein conc gradient
hydrostatic- high pressure volume to low pressure volume gradient
what is the recommended fluid, electrolyte and glucose intake for a person?
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
why might someone with severe hypovolaemia have a normal BP and how should you further investigate it?
compensation due to peripheral vasoconstriction
should check for postural drop
what things do you need to assess before prescribing fluids?
Blood pressure Capillary refill time Fluid balance charts Response to straight leg raise Skin turgor Weight
name some examples of hypo, iso and hypertonic crystalloids?
iso- sodium chloride 0.9% (most commonly used)
hypo- sodium chloride 0.45%.
hyper- sodium chloride 3%, mannitol.
how much sodium and chloride does 1L of 0.9% saline contain?
Contains 154 mmol/litre of sodium and chloride
Stays in the extracellular fluid compartment-> 25% into intravascular compartment
When you give 1 litre (1000 ml) of glucose 5%, do you know how it distributes in the various fluid compartments?
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.
what are the different types of shock?
- Distributive shock- relative hypovolaemia e.g. sepsis, anaphylaxis and neurogenic shock
- Hypovolaemic shock e.g. haemorrhage, burns
- Cardiogenic shock- a relative or absolute reduction in cardiac output due to a primary cardiac disorder. causes inc ischaemia, heart failure and arrhythmias
- Obstructive shock e.g. massive PE and cardiac tamponade
indicators that a patient may need urgent fluid resuscitation?
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
what is the minimum aim for urine output?
0.5ml/kg/hour
how much fluid per day is estimated to be gained from metabolism?
400ml
