Fluid Therapy

Question 1

When is fluid therapy needed at a fundamental level?

Answer 1

When there is a loss of fluids and when there is a need to maintain fluid levels.

Question 2

What is the ‘third space’?

Answer 2

It is when fluid is sequestered in the wrong places e.g. peritoneal cavity/lungs.

The ‘first’ and ‘second’ spaces are the ECF and ICF compartments.

Question 3

How is total body fluid distributed in the body?

Answer 3

1/3 ECF 2/3 ICF

• plasma (1/4)
• tissue fluid (3/4)

Question 4

Why is blood loss so severe in its consequences?

Answer 4

Only a very small portion of total body fluid is circulating in the plasma therefore the room for loss is very small.

Question 5

How can a fluid defect be identified? Which is the best way?

Answer 5

History
Physical Exam
Lab testing.

The best way is from the history and physical exam. Blood results are useful for showing a metabolic disturbance but don’t give a clear picture of the hydration status of an animal.

Question 6

Why is the rate of fluid therapy important?

Answer 6

If given fast then the fluid will distribute less evenly => a bolus is good for shock.

If given slow it will distribute more evenly => drip is good for dehydration.

Question 7

Why does skin turgor indicate hydration status? If an animal has ‘gelatinous’ skin, what will this indicate?

Answer 7

The fat under the skin absorbs water. Gelatinous would indicate water retention. (specifically ECF retention)

Question 8

Does dehydration commonly progress to shock?

Answer 8

Not in adult/larger animals. It is more likely in puppies and other young animals

Question 9

Other than hypovolaemia or dehydration, what is fluid therapy indicated for? Give reasons why.

Answer 9

Animals under GA - many homeostatic systems are suppressed

Flushing things out - increases GFR, water soluble toxins may also benefit from fluid therapy

Question 10

What can make up a fluid bag?

Answer 10

-Water
-Electrolytes
Sodium
Chloride
Potassium
(Magnesium)
(Calcium)
-Buffers
lactate
citrate
-Dextrose

Question 11

Why is fluid therapy used?

Answer 11

Correct electrolyte imbalance
Correct acid-base problems
Delivery of drugs (dilution/constant infusion)
Parenteral nutrition.
Diuresis

Question 12

How are fluids classified?

Answer 12

Crystalloid or colloid

By tonicity

Question 13

What is a disadvantage of crystalloid fluids?

Answer 13

They have a very even distribution once administered. Only a 1/3 will remain intravascularly so may need quite a bit when treating for hypovolaemia.

Question 14

How do colloids differ from crystalloids?

Answer 14

They generate vascular oncotic pressure as they have synthetic protein/starch based components so are useful for intravascular resuscitation.

Question 15

What are the side effects of colloids?

Answer 15

Fluid overload and coagulopathy. n.b. there is no indication that they have more benefit than crystalloids.

Question 16

What natural colloids are available?

Answer 16

Fresh blood
Packed RBCs
Frozen plasma

Human albumin - have side effects in animal use
(Canine albumin) - these are not really available commercially.
(feline albumin) - these are not really available commercially.

Question 17

Are parenteral nutrition bags crystalloid or colloid and what goes into them?

Answer 17

Crystalloid. Amino acids, lipids and dextrose go into them

Question 18

What are the indications for use of a hypertonic solution and a hypotonic solution.

Answer 18

Hyper - can inject to ‘borrow’ fluid from other compartments for intravascular resuscitation

Hypo - only in animals with very high sodium. USE WITH CARE

Question 19

Give examples of hypertonic solution.

Answer 19

3/7% saline
20% mannitol
50% dextrose

Question 20

Why is mannitol useful?

Answer 20

It is a sugar alcohol so is not absorbed by the body and is only excreted by the kidney so will help animals with oedema as water will follow it out. (Osmotic diuretic)

Question 21

When should colloid use be considered?

Answer 21

Need rapid resuscitation or the effect needs to last longer than 1hr. Need to increase COP or in oedematous animals.

Question 22

Are ready-made parentally nutrition solutions useful?

Answer 22

They are ok but depending on the case will only meet 40-70% of the requirement of the patient. The best thing is to have them made up specially - however, this is time consuming and requires expertise.