Flashcards in Arterial Blood Gas Interpretation Deck (13):

1

## What is the expected respiratory compensation for metabolic acidosis?

###
PaCO2 = 40 - 1.2 x change in bicarbonate

(approximately 1:1 decrease in paCO2 for drop in bicarb)

2

## What is the expected respiratory compensation for metabolic alkalosis?

### PaCO2 = 40 + 0.6 x change in bicarbonate

3

## What is the expected metabolic compensation for acute respiratory acidosis?

### HCO3 = 24 + Change in PaCO2/10

4

## What is the expected metabolic compensation for chronic respiratory acidosis?

### HCO3 = 24 + 4 x (change in PaCO2/10)

5

## What is the expected metabolic compensation for acute respiratory alkalosis?

### HCO3 = 24 - 2 x (change in PaCO2/10)

6

## What is the expected metabolic compensation for chronic respiratory alkalosis?

### HCO3 = 24 - 5 x (change in PaCO2/10)

7

## What is the effect of hypoalbuminemia on the interpretation of acid/base status?

###
In a metabolic acidosis, expected anion gap is decreased for hypoalbuminemia.

Normal AG = 12-14

AG in metabolic acidosis = 12- 0.25 x (change in albumin)

8

## What is the 1-2-3-4-5 Rule?

###
Rule to predict changes in HCO3 based on PaCO2:

For every 10 change in PaCO2:

Increase - acute = 1:10 +

Decrease - acute = 2:10 -

Increase - chronic = 4:10 +

Decrease - chronic = 5:10 -

i.e. For chronic resp acidosis with a PaCO2 of 60, HCO3 = 24 + 8 = 32

9

## What is the equation for the A-gradient?

###
A-a gradient = FiO2(Patm - PH2O) - PaCO2/RQ - PaO2

Where...

Patm = 760

PH2O = 47

RQ = 0.8

10

## What is the normal A-a gradient adjusted for age?

### A-a gradient = 4 + (age/4)

11

## What is the differential diagnosis for hypoxemia with a normal A-a gradient?

###
1. Hypoventilation

2. Low PiO2

12

## What is the differential diagnosis for hypoxemia with an elevated A-a gradient?

###
1. Diffusion deficit

2. V/Q mismatch

3. R to L shunt

4. Increased O2 usage, i.e. low SvO2

13