Formulas

Question 1

Serum osmolarity and normal value

Answer 1

(2 x San + serum glucose/18) + BUN/2.8

Normal 275-295

Question 2

Winter’s formula

Answer 2

PaCO2 = 1.5xbicarb + 8 (+/-) 2

Question 3

Stool osmotic gap

Answer 3

SOG = plasma osm - 2 x (stool Na + stool K)

Question 4

Corrected Ca

Answer 4

measured total Ca + 0.8(4-albumin)

Question 5

Anion gap

Answer 5

Na - (Cl + bicarb), 8-12 is normal

Question 6

A-a gradient

Answer 6

PAO2 = 150 - PaCO2/0.8; normal is <15

Question 7

Plasma osmolality

Answer 7

?? same as osmolarity?

Question 8

Appropriate compensation for primary metabolic acidosis

Answer 8

PaCO2 = 1.5(bicarb) + 8 +/- 2

Question 9

Appropriate compensation for primary metabolic alkalosis

Answer 9

Increase in PaCO2 of 0.7mmHg for every 1mEq/L rise in serum bicarb. PaCO2 = 0.9xbicarb + 16 +/- 2

Question 10

Appropriate compensation for primary acute respiratory acidosis

Answer 10

Increase in serum bicarb by 1mEq/L for every 10mmHg rise in PaCO2

Question 11

Appropriate compensation for primary acute respiratory alkalosis

Answer 11

Drop in bicarb of 2mEq/L for every 10mmHg decrease in PaCO2