Pitfalls of ABG

Question 1

Name the 5 potential sampling errors?

Answer 1

Air in blood sample
Venous sampling or admixture
Excessive or improper anti-coagulant
Rate of metabolism (must put on ice immediately)
Temperature disparities between patient and machine

Question 2

What happens when your PaO2 is less than 160 and sample has an air bubble or was exposed to air, how does it affect your PaO2?

Answer 2

PaO2 will be falsely high because the PO2 of air is 160; due to pressure gradients;

Question 3

If your PaO2 is greater than 160 mmHg and the sample is exposed to air what will happen to your PaO2?

Answer 3

The PaO2 will then fall if it was exposed to air and greater than 160

Question 4

What happens to your CO2 level if your sample has air bubble and why?

Answer 4

Since air our contains no CO2; if your sample is exposed to air then CO2 level blood will fall.

Question 5

If your sample is exposed to air and your CO2 falls what will happen to your pH?

Answer 5

The pH in your sample will rise to counterbalance the falling CO2.

Question 6

What happens if your sample is not placed on ice? How will it effect your PaO2?

Answer 6

If not placed on ice then the metabolizing blood cells will alter the blood gas values. It will cause the PaO2 to fall dramatically

Question 7

How long is a sample good on ice?

Answer 7

1 hour if sample placed on ice

Question 8

How long is a sample good if not iced?

Answer 8

About 5 minutes max

Question 9

If a patent has leukemia or an increased WBC about 100,000 what effect will that have on your ABG?

Answer 9

It will cause a decrease in your PaO2

Question 10

What is a normal PvO2?

Answer 10

Less than 40 mm Hg

Question 11

What is the normal venous saturation level?

Answer 11

Less than 75%

Question 12

How long does it take for a change of FIO2 to register on a normally healthy patient?

Answer 12

3 minutes to achieve a steady state. Or in chronic obstructive state it may take up to 20 minutes.

Question 13

If your patient has a fever and your do not adjust in your Istat what happens to both the PaO2 and PaCO2?

Answer 13

If your patient has a fever and the sample is not adjusted to temperature of 37 then your results will be falsely low

Question 14

If you fail to correct your patient’s body temperature n the PaO2 what happens to gas molecules in the sample?
A. They will be falsely high
B. They will be falsely low
C. Nothing, as the machine can sense temperature differences and make appropriate calibration
D. Gases will be higher in the sample than in the patient

Answer 14

If a patients temperature is not corrected for than the PaO2 and PaCO2 will be falsely low;

Question 15

For each degree about 37 the PaO2 change is _____ mmHg

Answer 15

5 mmHg

Question 16

For each degree change above/below 37 the change to PaCO2 is _____ mmHg

Answer 16

2 mmHg

Question 17

What are your critical values to be aware of?

Answer 17

Ph = 7.2 - 7.55
PaCO2 < 20 or > 70
PaO2 < 55
SaO2 < 85%

Question 18

Heparin is acidic/basic?

Answer 18

Acidic

Question 19

When heparin enters your blood sample what happens

Answer 19

Heparin in the sample will cause a drop in PaCo2

Question 20

How do metabolizing blood cells alter your sample?

Answer 20

Falsely low PaO2

Question 21

If a patient is hypothermic what happens to their PaO2 and PaCO2?

Answer 21

Your readings in the sample are falsely high;

Question 22

Why are readings affected by hypothermia if temperature not corrected?

Answer 22

Because gas are speeded up by the higher temperature of machine causing falsely high readings

Question 23

Normally, the last 2 digits of pH are equal to?

Answer 23

About the same as the CO2, if it is not means another disorder is present