A&E 107 Hypovolaemia

Question 1

What is osmolality?

Answer 1

The number of moles of osmotically active solute particles (osmoles) per kg of solvent. Depends on the concentration of solute particles in solution

Question 2

What is osmolarity?

Answer 2

The number of osmoles per litre of solution

Question 3

What does isosmotic mean?

Answer 3

Same osmolality as plasma

Question 4

How is the body’s water and weight distributed throughout the compartments?

Answer 4

20% ECF, 40% ICF therefore 60% body weight is water

Question 5

In what order do the body compartments fall based on how much they contain?

Answer 5

ICF>ECF

Within ECF ISF> Plasm

Question 6

Which body fluid compartment contains more potassium and calcium but less sodium

Answer 6

ICF

Question 7

What does the osmolality of ECF determine?

Answer 7

The volume of ICF in cells

Question 8

If there is increased osmolality what does this mean?

Answer 8

Increased concentration of solute

Question 9

What receptors in the hypothalamus monitor osmolality?

Answer 9

Osmoreceptors

Question 10

What would increased plasma osmolality result in?

Answer 10

Increased ADH secretion from the pituitary

Question 11

What does ADH do?

Answer 11

Increased water reabsorption by aquaporin insertion in DCT
Vasoconstriction - direct and via RAAS
Thirst

Question 12

Describe isosmotic contraction of ECF

Answer 12

Decreased ECF but osmolality the same therefore so is ICF

Question 13

Describe hyperosmotic contraction of ECF

Answer 13

Decreased ECF but increased osmolality as there is more water lost than solute (e.g. sweating) so ICF and therefore cells, shrink

Question 14

Describe hyposmotic contraction of ECF

Answer 14

Decreased ECF but decreased osmolality so ICF and cells swell

Question 15

What is capilliary filtration rate proportional to?

Answer 15

Net hydrostatic pressure - net osmotic pressure

Question 16

What blood loss is defined as hypovolaemia?

Answer 16

20%

apporximately one litre

Question 17

How would you recognise a patient with shock?

Answer 17

Collapse/prostration
Conscious level alterations
rapid breathing
hypotension
poor peripheral perfusion
low urine flow