Fluids

Question 1

What is the definition of osmolality?

Answer 1

The number of osmoles in a kilogram of a solvent

Question 2

What is osmolarity?

Answer 2

The number of osmoles in a litre of a solvent

Question 3

How much of our body is water?

Answer 3

60%

Question 4

Of this 60%, how much is in ECF and ICF?

Answer 4

1. Intracellular fluid is inside of the cells and comprises of 2/3’s of the 60%
2. extracellular fluid is outside of the cells and is 1/3 of the 60%

Question 5

The ECF is comprised of two components, namely:

Answer 5

1. plasma(fluid in circulation) 20%

2. interstitial fluid(fluid between cells) 80%

Question 6

What is normal plasma osmolality?

Answer 6

275-295mmOsm/kg

Question 7

What is the plasma osmolality equation?

Answer 7

1. 2[NA] plus urea plus glucose

Question 8

What is pulsus paradoxus?

Question 9

What causes pulsus paradoxus?

Answer 9

• negative pressure intrathoracically on ispiration which causes pooling in the lungs
• decreased filling of the left heart and decreased stroke volume

Question 10

What do we use for maintenance?

Answer 10

crystalloid

Question 11

What do we use for bolus?

Answer 11

colloid

Question 12

What are the static parameters?

Answer 12

1. HR
2. BP
3. CVP
4. urine output

Question 13

What are the dynamic parameters?

Answer 13

1. stroke volume variation
2. pulse pressure variation
3. passive leg raise test

Question 14

What is tonicity?

Answer 14

It is the difference in osmotic activity between two compartments

Question 15

What is the mechanism for low plasma osmolarity?

Answer 15

This means that there is increased water in the plasma and so the water will diffuse intracellularly where there is less water

Question 16

High plasma osmolarity >195 means?

Answer 16

That there is not enough water extracellularly and so the water will travel from the inside of the cell extracellularly

Question 17

What does the hydrostatic pressure consist of?

Answer 17

It is at the arteriolar end of the capillary and forces the blood outside of the capillary

Question 18

What does the osmotic pressure consist of?

Answer 18

It is in the venous side and forces the blood back into the capillary

Question 19

What will cause tissue oedema?

Answer 19

1. increased hydrostatic pressure
2. decreased oncotic colloid pressure
3. endothelial damage of the capillary

Question 20

What are some mechanisms of the renal system to cope with fluid loss?

Answer 20

With the renin, angiotensin. aldosterone system which subsequently increases aldosterone which will cause reabsorption of water and sodium at the distal tubule

Question 21

What is the cause of a patient presenting with fluid deficit?

Answer 21

• vomiting
• perspiration
• diarrhea

Question 22

What are crystalloids?

Answer 22

1. hypotonic-maintenance 5 and 10% maintelyte

2. isotonic- replacement fluids-ringers lacate,0,9% Na chloride

Question 23

Why are colloids great as fluid replacements?

Answer 23

1. They do not contain infective agents
2. They are cheaper
3. They are good volume replacers

Question 24

What must you do pre-operatively if there’s a fluid deficit?

Answer 24

If the patient is fluid deficit, then give isotonic balanced solutions that will be sufficient to maintain HR, ventricullar filling pressure, and mean arterial pressure

Question 25

Does administering anaesthesia cause vasoconstriction or vasodilation?

Answer 25

1. vasodilation and can cause a decrease in preloading of the heart

Question 26

What amount of fluid do you give prior to elective surgery?

Answer 26

2 ml.kg/hour nil per mouth

Question 27

What amount of fluid do you give to patients that could require more fluid?

Answer 27

6ml.kg of a balanced salt solution prior to anaesthetic induction

Question 28

When is blood loss enough for a blood transfusion?

Answer 28

When it is more than 20%

Question 29

What is the urine output we expect post-operatively?

Answer 29

0,4-0,5ml.kg

Question 30

Which fluid has the risk of causing metabolic acidosis?

Answer 30

-0,9% saline

Question 31

Intra-operative fluids is broken up into 3 categories:

Answer 31

1. Rehydration
2. Maintenance
3. Replacement of ongoing losses

Question 32

How do you replace blood loss intra-operatively?

Answer 32

• start with isotonic crystalloids

- then move tocolloids if more than 1 L is lost, then start replacing with blood