Chapter 187 - colloid osmotic pressure and osmolality monitoring

Question 1

goal COP to reduce the risk of oedema formation in dogs and cats?

Answer 1

15 mm Hg

Question 2

which term is redundant?
colloid osmotic pressure
colloid oncotic pressure
oncotic pressure

Answer 2

colloid oncotic pressure

Question 3

what is the percentage contribution of albumin (and associated cations) to COP?

Answer 3

60-70%

Question 4

what is the percentage contribution of globulins to COP?

Answer 4

30-40%

Question 5

state Starling’s principal

Answer 5

net rate of capillary filtration = the difference between capillary and interstitial hydrostatic pressure minus the osmotic reflection coefficient outside the difference between the plasma and interstitial oncotic pressure

Question 6

which variable(s) in Starling’s principal can be manipulated clinically?

Answer 6

plasma oncotic pressure

capillary hydrostatic pressure

Question 7

in the revised Starling’s principal, which variable is changed?

Answer 7

COP of the subglycocalyx space is used instead of the COP of the interstitium

Question 8

to what level will the total solids (by refractometer) trend towards in patients receiving artificial colloids?

Answer 8

4-4.2mg/dL

Question 9

published normal COP for canine and feline plasma?

Answer 9

dogs: 21-25mmHg
cats: 23-25mmHg

Question 10

published normal COP for canine and feline whole blood?

Answer 10

dogs: 17.85-22.05mmHg
cats: 21-28.4mmHg

Question 11

indications for COP measurement

Answer 11

1. patients receiving artificial colloids
2. patients with oedema
3. patients treated with aggressive crystalloid therapy with with low serum albumin

Question 12

3 strategies for treatment of low COP?

Answer 12

plasma
human/canine albumin solutions
artificial colloids

Question 13

osmolarity v osmolality

Answer 13

osmolality: number of osmotically active particles/kg of solution
osmolarity: number of particles/L volume of solution

Question 14

normal osmolality?

Answer 14

dogs: 290-310mOsm/kg
cats: 290-330mOsm/kg

Question 15

formula for calculation of osmolality

Answer 15

2(Na+) + (BUN/2.8) + (glucose/18)

Question 16

common causes of increased osmolality can be due to increases in effective and ineffective osmoles. name 7 effective osmoles

Answer 16

sodium, glucose, mannitol, ketoacids, lactic acids, phosphate & sulfates (ie- w/ renal failure), radiopaque contrast solutions

Question 17

common causes of increased osmolality can be due to increases in effective and ineffective osmoles. name 7 ineffective osmoles

Answer 17

BUN, ethylene glycol & metabolites, ethanol & methanol, acetylsalicylic acid, isopropyl alcohol

Question 18

most common cause of hypoosmolality?

Answer 18

hyponatremia

Question 19

most common 3 causes of hyperosmolality?

Answer 19

hypernatremia, DM, azotemia

Question 20

define osmolal gap

Answer 20

measured plasma osmolality - estimated plasma osmolality

Question 21

normal osmolal gap?

Answer 21

dogs: -5 - 2mOsm/kg
cats: -3 - 6mOsm/kg

Question 22

cut-off osmolal gap above which unmeasured solutes are present in large quantities?

Answer 22

10mOsm/kg

Question 23

calculation for effective osmolality or tonicity?

Answer 23

2 (Na+) + (glucose/18)

Question 24

difference between USG and urine osmolality

Answer 24

USG measures a ratio of the density of a substance compared to water (affected by the number of molecules and their molecular weight)
urine osmolality measures the number of molecules/kg of water

Question 25

name 4 indications for measurement of urine osmolality

Answer 25

differentiating sodium disorders
identifying SIADH
differentiating renal from pre-renal azotaemia
diagnosing diabetes insipidus