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TeresahRN
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Arterial Blood Gas Interpretation | for Nurses and Nursing Students
Being able to interpret Arterial Blood Gases (ABGs) as a nurse is very important. Many new nurses feel they are not comfortable with interpreting Arterial Blood Gases after they graduate. Some of these nurses feel they will never use it in their job and feel it is the respiratory therapist job or find it too confusing to understand.
However, as the nurse taking care of the patient with abnormal Arterial Blood Gases (ABGs) it is your responsibility to know what to report to the doctor and how to properly oxygenate your patient based on their ABGs.
For example, patient’s with COPD are known as “CO2 retainers” and their pCO2 levels will be higher than someone who does not have COPD. However, patients with COPD can experience abnormally high pCO2 levels which can cause confusion, dizziness, unconsciousness, increased heart rate/blood pressure, etc. So it is very important a nurse knows how to interpret ABGS.
Luckily there is a super easy way to help you interpret ABGs. It is known as the tic tac toe method. It is a quick and simple way to help you interpret ABGS.
First we need to lay the foundation and talk about what three lab values you need to look when trying to figure out ABGs, how to determine if that value is consider normal, an acid, or basic (alkalotic), and what fancy terms are used once the ABG is figured out.
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TeresahRN
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Below are the terms used to label abnormal ABG results:
Respiratory Acidosis (uncompensated, partially compensated, compensated)
Respiratory Alkalosis (uncompensated, partially compensated, compensated)
Metabolic Acidosis (uncompensated, partially compensated, compensated)
Metabolic Alkalosis (uncompensated, partially compensated, compensated)
When you are analyzing ABG results there are three things to look for when trying to find out if your patient is in respiratory or metabolic acidosis or alkalosis. Here they are and their normal numeric values:
pH: 7.35-7.45
CO2: 35-45 (CO2 lab value ALWAYS indicates a RESPIRATORY issue)
HCO3: 22-26 (HCO3 lab value ALWAYS indicates a METABOLIC issue)
Now to determine when these values are considered an acid or base. For pH anything less than 7.35 is an acid and anything greater than 7.45 is a base. For CO2 (NOTE: it is the opposite) anything less than 35 is a base and anything greater than 45 is an acid. For HCO3 anything less than 22 is an acid and anything greater than 26 is a base. Here is a guide to help you understand it:
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TeresahRN
25424 posts
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TeresahRN
25424 posts
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In order to use the tic tac toe method you must first get a sheet of paper and set up a “tic tac toe” grid. Then label each “column” as “acid”, “pH”, and “base”. It should look like this:
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TeresahRN
25424 posts
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Now lets solve a problem using the tic tac toe method: ABG results are the following…..pH7.24, PCO2 75, HCO3 28
1.Draw your tic tac toe lay out.
2.Analyze your pH. Ask yourself is it normal, basic, or acidic? Since the pH is less than 7.35 making it an acid, place it under the acid column.
3.Analyze your PCO2. Ask yourself is it normal, basic, or acidic? Since the PCO2 is greater than 45 making it an acid, place it under the acid column along with pH. Remember PCO2 is the opposite and the normal is 35-45.
4.Analyze your HCO3. Ask yourself is it normal, basic, or acidic? Since HCO3 is greater than 26 making it basic, place it under the base column because the value is considered basic.
5.Your tic tac toe lay out should look like this:
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TeresahRN
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Now that you have your tic tac toe grid set up. You need to figured out what you have. Since your pH is acidic you know that you have acidosis going on but is it respiratory or metabolic acidosis. Since CO2 represent respiratory and it is under the acid column with your pH you have respiratory acidosis going on.
But is it fully compensated, partially compensated, or uncompensated respiratory acidosis? Look at your HCO3! Since your HCO3 is under basic, the metabolic system is trying to balance the body’s system out by becoming basic so it is partially compensating. So the answer is Partially Compensated Respiratory Acidosis. Note: If HCO3 was under the normal column it would not be trying to compensated and therefore it would be considered uncompensated respiratory acidosis.
Let’s try another one: ABG results are: pH 7.50, PCO2 36, HCO3 32. Here is what your tic tac toe grid should look like:
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TeresahRN
25424 posts
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1. Analyze your pH. Ask yourself is it normal, basic, or acidic? Since the pH is greater than 7.45 making it a basic, place it under the base column.
2.Analyze your PCO2. Ask yourself is it normal, basic, or acidic? Since the PCO2 is between 35-45 it is normal, place it under the normal column.
3.Analyze your HCO3. Ask yourself is it normal, basic, or acidic? Since HCO3 is greater than 26 making it basic, place it under the base column because the value is considered basic.
4.Since your pH is basic you know you have some alkalosis going on. But is it respiratory or metabolic? Since the HCO3 (which represents metabolic) is under you basic column with pH it is a metabolic issue. So your patient is in: Metabolic Alkalosis.
5.Now is it fully compensated, partially compensated, or uncompensated metabolic alkalosis? Look at the CO2! Since it is under the normal column that means the CO2 has NOT tried to help out the body’s system by making itself acidic. So the body is not compensating.
6.Answer: Uncompensated Metabolic Alkalosis
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