Fluid Therapy

Question 1

What is the 60-40-20 rule?

Answer 1

body fluid composition
60 % of body weight is water:
40% bw is intracellular fluid
20% of bw is extracellular fluid

Question 2

ICF is a solution containing what? homogeneity? pH?

Answer 2

– Primarily a solution of potassium, organic anions (phosphate, sulfate), proteins
– ICF is not homogeneous in the body
– pH is close to 7.0

Question 3

ECF contains what molecules in solution primarily

Answer 3

NaCl and NaHCO3

Question 4

– ECF is subdivided into three subcompartments:

Answer 4

• Interstitial Fluid (ISF) surrounds the cells, but does not
  circulate. It comprises about 3/4 of the ECF.
• Plasma circulates as the extracellular component of blood. It makes up about 1/4 of the ECF.
• Transcellular fluid is a set of fluids that are outside of the normal compartments (CSF, Digestive Juices, Mucus, etc.)

Question 5

pH of extracellular fluid

Answer 5

– pH is 7.40-7.45

Question 6

Dog plasma and blood volume based on BW

Answer 6

– Plasma volume- 49 mL/kg
– Blood volume- 80 mL/kg (8% bw)

Question 7

Cat blood volume based on BW

Answer 7

– Blood volume- 50-70 mL/kg (5-7%)

Question 8

Horse blood volume based on BW

Answer 8

– Blood volume- 100 mL/kg (10%)

Question 9

Ruminant blood volume based on BW

Answer 9

– Blood volume- 60 mL/kg (6%)

Question 10

Pigs blood volume based on BW

Answer 10

– Blood volume- 65-75 mL/kg (6.5-7.5%)

Question 11

what fraction of blood volume is plasma vs PCV?

Answer 11

Plasma: 55-65%
PCV: 35-45%

Question 12

blood volume for 20Kg dog:

Answer 12

– 20 kg x 80 mL/kg = 1600 mL

Question 13

blood volume for 4 Kg cat

Answer 13

– 4 kg x 65 mL/kg = 260 mL

Question 14

blood volume for 500 kg horse

Answer 14

– 500 kg x 100 mL/kg = 50 L

Question 15

blood volume for 600 kg cow

Answer 15

– 600 kg x 60 mL/kg = 36 L

Question 16

Osmolality mathematical definition, and how calculate it

Answer 16

Ratio of Solute/Volume

Osmolality = 2*Na+ + Glu/18 + BUN/2.8 (mg/dL)

Osmolality= 2 x Na+ + Glu + BUN (mOsm/L)

Question 17

normal osmolality value in the body

Answer 17

• Normal value = 290 +/- 10 mOsm/liter

Question 18

how do the osmolalities of ICF, ECF, and Plasma compare?

Answer 18

• Osm of ICF=ECF=Plasma
• Fluid compartments are in osmotic equilibrium
• Water moves freely

Question 19

what is starling’s equation and what does it tell us?

Answer 19

J = k (Pc - Pi) – σ (Πc – Πi) – Qlymph

=> flow rate is a balance between hydrostatic pressures (P) and oncotic pressures (pi)

Pc is higher for arteries than veins, so generally we see more filtration on the arterial end, and reabsorption on the venule end
>lymph term is required because on balance fluid is being pushed out of circulation and the body must handle that

Question 20

broad categories of crystalloids

Answer 20

maintenance and replacement solutions

Question 21

what are maintenance solutions? what are some examples and their purpose?

Answer 21

– Plasmalyte-56, Normosol-M
– NaCl 0.45% (+ KCl)
– Replacement + KCl

– To maintain volume and electrolyte composition
– A.) Sensible losses
* urine production (1-2 mL/kg/h)
– B.) Insensible losses
* Breathing, faeces, sweating (1 mL/kg/h)

– A + B = 2-4 mL/kg/h

Question 22

what are sensible and insensible losses? how are these relevant for calculating a maintenance rate?

Answer 22

– To maintain volume and electrolyte composition

– A.) Sensible losses
* urine production (1-2 mL/kg/h)
– B.) Insensible losses
* Breathing, faeces, sweating (1 mL/kg/h)

– A + B = 2-4 mL/kg/h

Question 23

what are replacement solutions? what are examples and what is their purpose? what is a normal replacement rate?

Answer 23

– Lactated Ringer Solution, Plasmalyte-A, Plasmalyte 148, Normosol-R
– NaCl 0.9% (± KCl)

– To replace volume without altering the electrolyte
composition of plasma
– Maintenance requirements + Blood/Fluid loss

– 5-10 mL/kg/h

Question 24

properties of replacement solutions: what types do we have generally?

Answer 24

• Isotonic, polyionic (LRS, N-R, PLA, NaCl 0.9%)

Question 25

do replacement solutions result in oncotic pressure? how much remains in the vascular space after 1-2h and what does this mean practically?

Answer 25

• No oncotic pressure
• 20-30% remain in vascular space after 1-2 h
  – Rule: To replace the amount of blood loss with 3 times the amount of crystalloids

Question 26

large volumes of replacement solutions given at once can cause what?

Answer 26

• Large volumes can cause excessive extravasation

Question 27

Blood loss of less than ____% blood volume can be effectively treated with crystalloids
Why can’t we treat greater losses with crystalloids?

Answer 27

10%
* Higher losses would require too much time and fluid

Question 28

If a 20kg dog has 10% blood loss, what volume of crystalloids should we give? how long will this take at the normal replacement rate

Answer 28

20 kg dog
– 10% blood loss
* 8% blood volume: 1.6 L
* 10% blood loss: 160 mL

• Effective replacement:
  – 3 x blood loss with crystalloids
  – 480 mL of crystalloids

Replacement rate
– 5-10 mL/kg/h
– 10 mL/kg/h- will require 2 1⁄2 hours

– 60 mL/kg/h (shock rate)- will require 25 min
* Safety
* Effect on PCV, TP

Question 29

what is hypertonic saline? what are its properties? what does it do and how should we administer it?

Answer 29

– 5 – 7.5% solutions
– Volume expansion lasts less than 60 min

– Small volume- 2-6 mL/kg
* 20 kg: 40-120 mL
* 1-2 mL/kg/min- Volume can be injected in 1-6 min

– Monitor electrolytes

Question 30

what is the purpose of lactate 28 in ringer’s lactate solution? what substances filfil this role in other replacement solutions?

Answer 30

body uses it as a substrate to create bicarbonate
>lactate is a bicarbonate precursor (as are acetate and gluconate that are used in plasmalte-A and normosol-R)

Question 31

what is an isotonic solution?

Answer 31

resembles plasma - has a similar concentration of electrolytes
plasma osmolality = 290, isotonic ~275-310

Question 32

if a negative ion is increased in the blood, how do we deal with this?

Answer 32

decrease concentration of one of the other negatives

Question 33

we can equate high chloride with what state

Answer 33

acidosis
low chloride = alkaline

Question 34

if we give a maintenance solution in excess, what effect will this have on ion concentrations in the body?

Answer 34

hypo Na+
hyper K+
hypo Cl-

=>only if given in rates that are significant

Question 35

can a maintenance solution be used as a replacement solution or vice versa?

Answer 35

a maintenance solution CANNOT be used as a replacement solution
BUT
a replacement solution CAN be used as a maintenance solution

Question 36

our normal losses of electrolytes throughout the day resemble what?

Answer 36

concentration of ions in a maintenance solution
ie
40 Na+
13 K+
40 Cl-