Fluid therapy

Question 1

What is the normal fluid intake for an animal?

Answer 1

2ml/kg/hr

Question 2

What is sensible loss? How much is lost?

Answer 2

Water lost via the kidneys

1ml/kg/hr

Question 3

What is insensible loss?

Answer 3

Water lost via evaporation of skin, exhalation from lungs and faeces

Question 4

Do receptors respond directly to electrolyte balance?

Answer 4

No

Respond to changes in osmolarity, plasma volume and blood pressure

Question 5

What homeostatic mechanisms does dehydration cause that lead to increased fluid intake?

Answer 5

Decreased saliva –> dry mouth and pharynx
Increased blood osmolarity stimulates osmoreceptors in hypothalamus
Decreased blood volume an and pressure causes increased renin production from juxtaglomerular cells and increased ANG II
All leads to stimulating thirst centre in hypothalamus

Question 6

Dehydration leads to a drop in blood volume and pressure. What does this stimulate?

Answer 6

Baroreceptor reflex and RAAS
Baroreceptors cause increased sympathetic activity via medulla oblongata
Increased renin released from JG cells

Question 7

What does Ang II act on? What does it cause?

Answer 7

Arterioles - vasoconstriction
CV control centre in medulla - increased CV response
Hypothalamus -increased thirst and ADH
Adrenal cortex and proximal tubule - aldosterone and sodium reabsorption

Question 8

How are fluids given?

Answer 8

Enteral route 
Parenteral route (IV, IO, IP, SC)

Question 9

When are fluids given orally?

Answer 9

If GI tract is functional

For mild moderate disturbances

Question 10

Why are fluids not given orally for severe dehydration?

Answer 10

Severe drop in blood pressure causes vasoconstriction of the GI tract

Question 11

What type of Na/Glucose transport is used for oral fluid therapy? What ratio should they be in?

Answer 11

Active sodium glucose co transport

Give equimolar sodium and glucose

Question 12

What are the 4 generations of oral fluids?

Answer 12

1st - sodium and equimolar glucose
2nd - adds alkalising agent to prevent metabolic acidosis
3rd - high glucose for additional nutrition
4th generation - contains glutamine - promotes villi repair and regeneration

Question 13

What are the 2 types of parenteral fluids?

Answer 13

Crystalloids

Colloids

Question 14

What are crystalloid solutions?

Answer 14

Salt solutions that move freely across capillary walls

Question 15

What are colloid solutions?

Answer 15

Non-crstalline solutions

Large molecules diluted in crystalloids

Question 16

Are capillary endothelium permeable to crystalloids and colloids?

Answer 16

Crystalloids yes

Colloids -no as molecules too large

Question 17

What percent sodium chloride can crystalloids be?

Answer 17

Hypotonic 0.9% - similar to plasma but chloride rich and unbalanced
Isotonic - mimic plasma
Hypertonic - 7.2% NaCl

Question 18

Crystalloids can be buffered or balanced. What do these mean?

Answer 18

Buffered - contain HCO3- or molecules that are metabolised in liver to produce HCO3-
Balanced - contain electrolytes in addition to Na/Cl (K, Ca, Mg) to make similar to plasma

Question 19

Crystalloids can also be isotonic, hypotonic and hypertonic. Describe hypotonic crystalloids

Answer 19

Lower concentration of electrolytes than plasma

High water conc

Question 20

Describe hypertonic crystalloids

Answer 20

Plasma expanders

Cause water to move from interstitial and intracellular sites into blood vessels

Question 21

Why may it not be appropriate to give high Na concentrated solutions over a long period of time?

Answer 21

Sodium accumulation

Must balance - cannot be solution too hypotonic (water into vessels)

Question 22

Describe how tonicity of fluids affect fluid movement in and out of vessels

Answer 22

Isotonic - fluid distributed into ECF
Hypotonic - fluid moves out of vessel into cells
Hypertonic - fluid drawn into vessels

Question 23

What are colloids

Answer 23

Water based replacement solutions

Molecules too large to pass across a capillary membrane

Question 24

What are the types of colloids?

Answer 24

Natural = blood, plasma, albumin 
Synthetic = starches, gelatins, dextrans

Question 25

When might natural colloids be given?

Answer 25

If animal needs RBCs, clotting factors or albumin

Question 26

How do colloids cause plasma expansion?

Answer 26

Large molecules can’t pass out of blood endothelium

Increase colloidal osmotic pressure and pull water in from interstitial space

Question 27

What are the adverse effects of colloids?

Answer 27

Anaphylactic reactions
Coagulopathies
Oedema (also risk with crystalloids)