ABGs

Question 1

What is the A-a gradient?

Answer 1

PAO2-PaO2

Question 2

How do you calculate the PAO2?

Answer 2

PAO2 = 150-(PCO2/0.8)

Question 3

What is the normal A-a for age?

Answer 3

gradient = (age/4)+4

Question 4

FiO2 for 4L via nasal specs?

Answer 4

0.36

Question 5

FiO2 for 2L via nasal specs?

Answer 5

0.28

Question 6

FiO2 for room air?

Answer 6

0.20

Question 7

FiO2 for 8L CIG?

Answer 7

0.55

Question 8

FiO2 for 10L via CIG?

Answer 8

0.60

Question 9

FiO2 for 6L via CIG?

Answer 9

0.50

Question 10

How is PaO2/FiO2 useful to do?

Answer 10

This is the P/F ratio. Normal is 286- lower indicates a shunt.

Question 11

Draw the 1-2-3-4-5 rule for calculating HCO3 compensation for respiratory disorder-

Answer 11

Question 13

What is the compensation rule for when you have a metabolic acidosis?

Answer 13

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

Question 14

What is the compensation rule for when you have a metabolic alkalosis?

Answer 14

Expected PaCO2 = 0.7 x HCO3 + 20 (+/-5)

Question 16

HAGMA- MUDPILES?

Answer 16

Methanol

Uraemia

DKA

Paraldehyde

Isoniazid

Lactic acidosis

Ethanol/ethylene glycol

Salicylates

Question 17

NAGMA- HARDUPS?

Answer 17

Hyperalimentation

Acetazolamide

RTA

Diarrhoea

Ureteropelvic fistula

Post hypercapnoea

Spironolactone

Question 18

Causes of metabolic alkalosis?

Answer 18

CLEVER PD

Contraction

Liquorice

Endo-Cushings, Conns, Barters

Vomiting

Excess alkali

Reefeeding alkalosis

Post hypercapnoea

Diuretics

Question 19

What is the delta ratio and how is it useful?

Answer 19

In a metabolic acidosis, to assess if mixed or pure HAGMA/NAGMA.

Calculate as AG-12/24-Bicarb

<0.4–>Pure NAGMA

0. 4-0.8–> Consider Mixed or uraemia
1. 8-2 –> pure HAGMA

Over 2–>consider pre-existing source of bicarb like metabolic alkalosis or previously compensated resp acidosis