Formulae

Question 1

Anion gap

Answer 1

Anion gap: Na – (Cl + Hc03)

Question 2

Osm Gap

Answer 2

Osm Gap: (2 x Na) + (BUN/2.8) +( Glu/18) + (EtOH/4.6) = 290

Question 3

Total body water

Answer 3

Total body water(L): Wt (kg) X 0.6

*deficit = Total body water x (serum Na-140)/ (140)

Question 4

Parkland

Answer 4

Parkland: 4ml x Kg x %TBSA (first ½ over 8h)

Question 5

MAP

Answer 5

MAP: DBP + (SBP – DBP) /3

Question 6

Peds ETT

Answer 6

Peds ETT: (age + 16)/4, depth = 3 x size

Question 7

A-a gradient

Answer 7

A-a gradient: 140 – (PaO2 + PaCO2)

Question 8

Compensation numbers for respiratory acidosis

Answer 8

Acute increase PCO2: 10= inc HCO3: 1

Chronic increase PCO2: 10 = inc HCO3: 3

Question 9

Compensation numbers for respiratory alkalosis

Answer 9

Acute decrease PC02: 10 = dec HC03: 2

Chronic decrease PC02: 10 = dec HC03: 5

Question 10

Compensation numbers for metabolic alkalosis

Answer 10

Alkalosis: inc HC03: 1 = inc PC02: .7

Question 11

Compensation numbers for metabolic acidosis

Answer 11

acidosis = rule of 15s
Take HCO3 and add 15
should = PC02 and last 2 digits of pH
If not, mixed DO

Question 12

Formula for pseudohyponatremia

Answer 12

Na = +1.6 for each 100 glucose over 100

Question 13

Formula for hemophilia factor repletement

Answer 13

KG * 1/2 * % change

Question 14

Pediatric ETT size and distance

Answer 14

Endotracheal tube inner diameter (mm) = (>1 year) = Age/4 + 4 (for Croup or subglottic stenosis use 0.5 to 1 size smaller than above)
Endotracheal tube length at lip (cm): 12 + age/2