ABG/ metabolic

Question 1

Compensation - Acute resp acidosis

Answer 1

1:10

Bicarb increases 1 for every 10 increase in CO2 above 40

Question 2

Compensation - Chronic resp acidosis

Answer 2

4:10

Bicarb increases 4 for every 10 increase in CO2 above 40

Question 3

Compensation - Acute resp alkalosis

Answer 3

2:10

Bicarb reduces 2 for every 10 decrease CO2 from 40

Question 4

Compensation - Chronic resp alkalosis

Answer 4

5:10

Bicarb reduces 5 for every 10 decrease CO2 from 40

Question 5

Metabolic acidosis

Answer 5

(1.5x bicarb) +8 +/-2

Question 6

Metabolic alkalosis

Answer 6

1:0.7

For every increase in bicarb by 1, Expect PaCO2 to increase by 0.7

Question 7

Anion gap calculation

normal value

Answer 7

AG = Na - (Cl + HCO3)

= 12

Question 8

AG corrected for albumin

Answer 8

With low albumin, N AG value will be lower. Masks a high AG.

For every 10 decrease in albumin, normal AG for the patient reduces by 2.5

Question 9

NAGMA causes

Answer 9

A - Addisons
B - Bicarb loss - GI/ renal
C - Cl excess
D - Diretics - acetazolamide

GI diarrhoea/ fistulas/ NG tubes/ laxative use/ ureteral diversion
Renal RTA 1,2,4

Question 10

Low AGMA causes

Answer 10

increased unmeasured cations - Ca, Mg, K, lithium
decreased unmeasured antions - PO4, albumin
Multiple myeloma

Question 11

most common causes high AGMA

Answer 11

K - ketoacidosis
U - Uraemia
L - lactic acidosis
T - toxins

Question 12

Delta ratio

Answer 12

Change in AG / change in bicarb
Should be 1:1

<0.8 = HAGMA and NAGMA

0.8 - 2 = HAGMA

> 2 = HAGMA and metabolic alkalosis or chronic resp acidosis

Question 13

Aa gradient
normal value

corrected for supplemental O2

Answer 13

= PA02 - PaO2

Normal - (age/4) +4

Correct for supplemental O2
= (age/4) +4 +50(FiO2-0.21)

Question 14

PAO2 calculation

Answer 14

PAO2 = (FiO2 x 713) - (PaCO2/0.8)

(150 air sea level)

Question 15

Osmolar gap

Answer 15

OG = measured osmolality - calculated osmolality
(n = 270-290) (2Na + Ur + gluc + ETOH)

Normal OG = -4 to +10

Question 16

Correct Na for glucose

Answer 16

Na + ( (glucose - 5) /3)

Question 17

Correct K for pH

Answer 17

For every 0.1 decrease in pH, 0.5 increase in K

For every 0.1 increase in pH, decrease K 0.5