Water Balance

Question 1

Osmolality

Answer 1

Solute per kilogram of Solvent

Question 2

Osmolarity

Answer 2

Solute per liter of solution

Question 3

Effective Osmole

Answer 3

Osmotically active - a molecule/ion that can cause water to move toward it

Question 4

Calculation of Plasma Osmolality

Answer 4

2{Na} + [Glu]/18 + [BUN]/3

Question 5

Osmole Gap

Answer 5

measured osmolality -calculated osmolality

Question 6

What does an increased osmole gap indicate?

Answer 6

An increase in an osmotically active molecule in blood that is not measured on the serum biochemical profile

Question 7

What are some things that can increase the osmole gap?

Answer 7

Ethylene glycol 
methanol 
Paraldehyde
Mannitol
Radiographic contract medium

Question 8

If the osmole gap is greater than 30….

Answer 8

there is an unaccounted osmole

Question 9

What if there is no difference between calculated osmolarity and measured osmolality… but there is an increase in measured osmolality?

Answer 9

Increased Sodium or markedly increased urea or glucose

Question 10

What if there is no difference between calculated osmolarity and measured osmolality… but there is a decreases in measured osmolality?

Answer 10

decrease in Sodium

Question 11

What if there is a difference between calculated and measured osmolality with an increase in measured osmolality?

Answer 11

Increased osmole gap - signifies the presence of an unmeasured osmole such as Ethylene glycol or toxins

Question 12

What is plasma Hyperosmolality associated with?

Answer 12

Hypernatremia
Hyperglycemia
Ketoacidosis
Uremia
Presence of exogenous toxins

Question 13

Hyperosmolality with NO fluid shifts

Answer 13

Increased plasma concentration of ineffective solutes intracellular osmolality = extracellular osmolality

Question 14

Hyperosmolality with Fluid Shifts

Answer 14

Increased plasma concentration of effective solutes intracellular osmolality > extracellular osmolality