Fluid Therapy

Question 1

Define hypovolaemia.

Answer 1

Lots of vascular fluid loss in a small amount of time (e.g RTA).
A rapid response is required.

Question 2

Define dehydration.

Answer 2

Fluid loss that occurs over a longer time period.
Probably more fluid is lost but the body is able to shift and distribute so the vascular system is not comprimised.
A more gradual treatment is required.

Question 3

What is seen with <5% dehydration?

Answer 3

Nothing: it is clinically undetectable.

Question 4

What is seen with 5% dehydration?

Answer 4

dry/pale MM, skin becomes to feel ‘doughy’

Question 5

What is seen with 6-8% dehydration?

Answer 5

mild-moderate skin tugor, eyes become sunken in orbit

Question 6

What is seen at 10-12% dehydration?

Answer 6

marked decrease in skin tugours
signs of hypovolaemic shock
weak rapid pulse
prolonged CRT
mental depression

Question 7

What is seen at 12-15% dehydration?

Answer 7

Moribund

Question 8

Why would you use fluid therapy in the peri-operative period?

Answer 8

• to establish and maintain venous access
• to counter the physiological changes associated with anaesthetics.
• to replace fluid lost during surgery
• to replace on going losses attributed to surgery

Question 9

What is a crystalloid solution? (not looking for names, more properties and indications)

Answer 9

Primarily water with a glucose or sodium base.
They diffuse rapidly out of the vascular component.
Main indication:
-replace lost electrolytes
-acidify/alkalosis
-substitute normal drinking (only for a short time period!)

Question 10

What is a colloid solution? (properties and indications not names)

Answer 10

Contain macromolecules
Retained in vascular component for longer.
Main indications:
-rapid expansion of vascular component is required
-to replace protein loss
-to replace blood loss

Question 11

Name 6 crystalloid solutions

Answer 11

• 0.9% sodium chlorids (normal saline)
• Ringer’s solution
• Hartmann’s solution
• 5% Dextrose
• 0.18% NaCl and 4% Dextrose
• Hypertonic solution

Question 12

What are the properties of normal saline?

Answer 12

Isotonic crystalloid
Na 154, Cl 154
-an unbalanced ion composition that is way higher than normal ECF

Question 13

What is normal saline used for?

Answer 13

• Provides rapid expansion of ECF without adding bicarbonate

- Good treatment for metabolic alkalosis as it promotes the excretion of bicarbonate from the kidneys

Question 14

What are the properties of Ringer’s solution?

Answer 14

Isotonic crystalloid
Na 147, Cl, 155, K 4, Ca 2
- a little bit more balanced than normal saline; more like body’s ECF

Question 15

What is Ringer’s used for?

Answer 15

K and Ca are useful for an animal that has be alkalotic for a prolonged time.
Promotes bicarbonate excretion.

Question 16

What are the properties of Hartmann’s?

Answer 16

Isotonic, crystalloid
Na 131, Cl 111, K 5, Ca 2, Lactate 29
Very similar for body’s ECF

Question 17

What is Hartmann’s used for?

Answer 17

Lactate provides bicarbonate (as is a precursor) but is not high enough to cause alkalosis.
Useful ECF replacer; due to it being very similar to body’s ECF.

Question 18

Are there any contraindications to Hartmanns?

Answer 18

YES.
Take care in hyperkalemic patients and in cats.
It has phenol in it to increase half life but cats can not metabolise this.

Question 19

What are the properties and uses of 5% Dextrose?

Answer 19

Isotonic, crystalloid
Basic simple sugar solution (188 cal/L)
Used to replace primary water loss
Indication for Na restricted animals.

Question 20

What are the properties and indications for 0.18% NaCl and 4% Dextrose?

Answer 20

Isotonic, cytstalloid
NaCl 31, 150 cal/L
Useful to meet maintenance daily requirements for fluid (but deficient in K)

Question 21

What is Hypertonic saline used for and how does it act?

Answer 21

Hypovolaemia; provides an immediate improvement in circulation
Draws water into intravascular space form interstitial fluid.
Offsets swollen epithelial cells which will prevent perfusion.
Debt must be repayed or it will just return to interstitial space.
(normally 7.3-7.5%)

Question 22

What are the 2 ways to treat hypovolaemia?

Answer 22

Hypertonic saline or colloid solution.

Question 23

Name all colloid solutions.

Answer 23

Gelatin solution
Hydroxyerthyl-starch solutions
Dextrans

Question 24

What are the pharmacokinetic properties of Gelatin solution?

Answer 24

Contains molecules of varying weight: average is 35, 000.
Osmotic pressure and viscosity is similar to plasma
Persists in circulation for 2-3 hours.
Relatively little effect on coagulation.
Although treated to reduce antigenicity, it can induce a histamine response.

Question 25

What are the properties of hydroxyethyl-starch solutions?

Answer 25

They contain synthetic polymers of glucose (chains of glucose with different number of substitutions and at different sites)
Hetastarch:
-50-70% substituted
-Mw= 450,000
-38% remains in plasma after 24 hrs
Pentastarch:
-45% substituted
-Mw- 200,00
- less remains after 24hrs
Tetrastarch
-40 substituted
-Mw= 130,000
-even less remains after 24 hrs

Question 26

What are the properties of Dextrans?

Answer 26

Artificial CHOs presented in a variety of Mw.
Dextrans 40 contains more macromolecules per given weight so is more osmotically active than Dextrans 70.
Generally 6% solution.
Draws fluid into vascular compartment as well as acting as plasma replacer.

Question 27

What are concentrated additives?

Answer 27

Things that can be added to fluid solutions:

• sodium lactate
• sodium bicarbonate
• potassium chloride

Question 28

Can anything else be used as a fluid replacer?

Answer 28

YES in specific circumstances:

• whole blood: haemorrhagic shock, acute anaemia
• plasma: sever hypoproteinaemia, clotting defects
• packed red cells: chronic anaemia
• platelets: thrombocytopaenia
• cyroprecipitate plasma: von willebrand’s disease