Fluids

Question 1

3 areas to consider when prescribing fluids?

Answer 1

1. basal requirements
2. existing deficit (before admission, intraoperative loss and replacement, fasting, type of sugery
3. predicted losses (vomiting, diarrhoea, wound drains)

Question 2

bowel and intraabdominal vascular surgery are associated with ‘third space’ losses - what does this mean?

Question 3

fluids move from plasma volume into interstitial fluid after acute injury

Question 4

T/F: examination is a useful tool in assessing dehydration

Answer 4

false

• classical signs (dry mouth, loss of skin elasticity and cold peripheries) can have other causes
• look at CVS and op site too
• tachycardia often late sign
• hypotension often v late sin

Question 5

Investigations for dehydration?

Answer 5

Fluid balance chart

• input: IV fluids, oral intake
• output: urine output, NG tube aspirate, vomit, drain fluid, diarrhoea

Bloods

• raised urea and creatinine can indicate dehydration or prerenal faiulre to to hypovolaemia

Question 6

normal UO?

Answer 6

>0.5ml/kg/hour

Question 7

basal requirements for 70kg man?

(water and electrolytes)

Answer 7

• 2-2.5L water
• 80mmol Na (1-2mmol/kg)
• 60mmol K (1-2mmol/kg)

Question 8

examples of crystalloids

Answer 8

sodium chloride

Hartmann’s

Question 9

how does sodium chloride affect fluid balance in body and why

Answer 9

• contains more Na and lots more Cl than plasma
• because of the electrolytes it doesn’t enter cells and equilibrates with ECF (i.e. plasma and interstitial fluid)

Question 10

hazard associated with use of NaCl?

Answer 10

the lare conc of Cl means H ions come out of cells to maintain electrical neutrality of the plasma > can cause a metabolic acidosis

Question 11

NaCl

1. good for
2. beware of

Answer 11

1. resuscitation, maintenance, cheap and widely available
2. hypernatraemia and metabolic acidosis if infused in large quantities

Question 12

what is 5% glucose good for and why

Answer 12

replacement of water (i.e. pure dehydration) and maintenance

it contains no electrolytes and is metabolised by the liver leaving only water

it equilibrates with everything

Question 13

why is 5% glucose bad for?

Answer 13

resuscitation (equilibrates with everything)

Question 14

What is Hartmann’s solution

Answer 14

crystalloid containing Na, Cl, K (so is close to normal plasma composition)

As it contains electrolytes it equlibrates ith ECF same as NaCl

Question 15

what is Hartmann’s good for

Answer 15

resuscitation

maintenance

Question 16

what kind of fluid is gelofusine?

Answer 16

colloid

Question 17

composition and mechanism of colloids?

Answer 17

contain

• big molecules (exert oncotic pressure)
• 0.9% saline

big molecules stay in intravascular space for longer than simple crystalloid would and theoretically attract water due to their oncotic pressure (can draw in water from ECF - volume expanders)

Question 18

hazard with colloids?

Answer 18

contain 0.9% NaCl so same issue with acidosis

Question 19

T/F: studies have shown colloids are better than crystalloid for resus in patients with haemorrhage

Answer 19

false - sound better but studies have shown no diff

Question 20

total body water (approx 42L for 70kg man) is made up of 2/3 ___ and 1/3 ___

Answer 20

2/3 ICF

1/3 ECF

Question 21

components of the ECF?

Answer 21

interstitial fluid

plasma

Question 22

What is this showing

1. hypovolaemia
2. dehydration
3. vomiting or diarrhoea

Answer 22

dehydration i.e. pure water deficiency

all compartments will be depleted

Question 23

What is this showing

1. hypovolaemia
2. dehydration
3. vomiting or diarrhoea

Answer 23

in hypovolaemia caused by acute blood loss plasma is the only compartment initially depleted, before fluid begins to move in from elsewhere

Question 24

What is this showing

1. hypovolaemia
2. dehydration
3. vomiting or diarrhoea

Answer 24

loss of electrolyte rich fluid e.g. in vomiting or diarrhoea, causes depletion of ECF (interstitial + plasma)

Question 25

this is showing infusion of 1L of:

1. 1L crystalloid (0.9% saline or Hartmann’s)
2. glucose
3. colloid (gelofusine)

Answer 25

1L crystalloid

increase in ECF i.e. interstitial and plasma

Question 26

this is showing infusion of 1L of:

1. 1L crystalloid (0.9% saline or Hartmann’s)
2. glucose
3. colloid (gelofusine)

Answer 26

1L colloid

not only does plasma increase in volume but the big colloid osmotic particles actually draw water in from the interstitial compartment

Question 27

this is showing infusion of 1L of:

1. 1L crystalloid (0.9% saline or Hartmann’s)
2. glucose
3. colloid (gelofusine)

Answer 27

1L 5% glucose

The water equilibrates with all fluid compartments

Question 28

Choose your weapon

• 82 y/o lady who broke her ankle and was found lying on the floor a day later. Drowsy with dry mucous membranes. Urea and creatinine raised

Answer 28

5% glucose (she is dehydrated and needs water)

Question 29

Choose your weapon

• 22y/o male with T1DM who has come in vomiting and drowsy. BM 29

Answer 29

• Crystalloid (Hartmann’s or 0.9% saline)
• He probably has DKA and will be profoundly dehydrated and hypovolaemic due to osmotic diuresis
• He needs crystalloid which will stay in his ECF

Question 30

Choose your weapon

• 16 y/o female involve in RTA. Has an open femoral fracture which is bleeding profusely. She is pale, tachycardic but normotensive

Answer 30

• Crystalloid (Hartmann’s or 0.9% saline)
• she is hypovolaemic due to blood loss and needs a fluid that will restore her circulating volume
• colloid would also be acceptable
• this patient may ultimately require blood