Lecture 5: TBL

Question 1

List the assumptions made when deriving the equations that commonly are used to predict the effects of fluid and electrolyte perturbations on P(Na) and P(osm)

Answer 1

1) iso-osmolality principle
2) ignore Pi (and gibbs-donnan effect)

3) Na, K and accompanying anions are the only effective osmoles
Na = exclusively EC
Na and anions = all EC osmoles
K = exclusively IC
K and anions = all IC osmoles

Question 2

Why can different interventions have the same effect on P(Na) and P(osm)?

Answer 2

P(Na) and P(osm) are determined by the ratio of TB solutes to TBW