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ABGs in Nursing: What Are They? How Do We Read Them?

  • Arterial Blood Gas (ABG) tests are an extremely useful tool in nursing.
  • ABGs are able to determine various medical conditions that may not recognizable to the naked eye.
  • Whether you are new to the world of nursing, or a pro, check out Nursing CE Central’s guide to everything you need to know about interpretting ABGs in nursing!
Morgan Curry, RN/BSN

Morgan Curry, BSN / RN

Intensive Care, Outpatient Surgery, Aesthetics, Education, and Nursing Leadership

May 04, 2021
Simmons University

What are ABGs in Nursing?  

The University of Michigan’s College of Medicine defines an arterial blood gas (ABG) test as form that measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood from an artery.”  

Although these tests are performed in various healthcare facilities across the U.S., you are most likely to see them used regularly in both critical care and emergency department units.  

Whether you are fresh out of nursing school, or have been working in the field for years, the ability to recognize the need for an ABG test, conduct it, and interpret the results is an extremely useful skill to have under your belt – you never know when you might need it.  

Although they may seem tricky at first, once you brush up on your ABGs in nursing, you will be a pro before you know it!

Correct and timely ABG interpretation can lead to faster interventions, changes in the plan of care, and improved patient outcomes.

A study from the National Center for Biotechnology Information outlines the six key components of an ABG test. These include:

ph = measured acid-based balance of the blood

PaO2 = measured the partial pressure of oxygen in arterial blood

PaCO2 = measured the partial pressure of carbon dioxide in the aterial blood

abgs in nursingHCO3 = calculated relative excess or deficit of base in arterial blood

SaO2 = calculated arterial oxygen saturation unless a co-oximetry is obtained, in which case it is measured

                    

Why Do We Need ABGs in Nursing? 

An ABG is one of the most commonly used tests to measure oxygenation and blood acid levels. These two components are easy determinants of a patient’s clinical status.

Correct and timely ABG interpretation can lead to faster interventions, changes in the plan of care, and improved patient outcomes.  

For this reason, ABGs in nursing are the gold standard in monitoring blood levels, especially in patients that are high risk for decompensation or whose sickness has any sort of respiratory component.

Additionally, it is important to not only understand what ABGs in nursing are, but how they differ from a Venous Blood Gas (VBG) test.

VBGs determine an accurate and reliable reading for the pH and CO2 levels of a patient but cannot accurately determine the oxygenation status due to the level being drawn directly from the vein.  

Following, Rachel Nall, MSN, CRNA, with HealthLine.com, outlines a few medical conditions that are detected through ABGs in nursing, these include:

  • Kidney failure
  • Heart failure
  • Uncontrolled diabetes
  • Hemorrhage
  • Chemical poisoning
  • Drug overdose
  • Shock

                    

How Do We Interpret Them? 

First, things first…  

You should always know what values are considered normal for ABGs in nursing.  By determining these values from the baseline, you can begin to decipher any potential variations in the patient’s results, which could be indicative of sudden deterioration.

You might be wondering, “So, what are some of the ‘normal’ values?” Let’s take a look!

 – pH: determines if the blood is acideic or alkalotic.

– PaCO2: Carbon dioxide levels will indicate if the problem is a respiratory issue, since CO2 is regulated by the lungs.

– HCO3: Bicarbonate (or bicarb) levels will indicate if the problem is related to a metabolic change referring to the patient’s renal system.

pHAcid/Base7.35 – 7.45
PaCO2Carbon Dioxide: Respiratory35 – 45 mmHg
HCO3Bicarb: Renal22 – 26 mmol/L

Now, that we have covered some of the normal values for ABGs in nursing, let’s talk about how we interpret these values to determine what direction our patient care plan should go!

Step One: pH, Is It Acidotic or Alkalotic?

If the ABGs values are not within the normal range, the pH level is either acidotic or alkalotic.  

  • The LOWER the number = MORE acidotic (ex. 7.1 pH)

     

  • The HIGHER the number = MORE alkalotic (ex. 7.6 pH)

Step Two: Respiratory or Metabolic?

Once you have identified if the sample is acidotic or alkalotic, you must determine if it’s due to respiratory or metabolic issues.  

If Acidotic:

  • Bicarb is Low= Metabolic 
  • PaCO2 is High = Respiratory  

Remember to consider your patient’s condition. If you have a COPD patient, they are most likely in respiratory acidosis, and if they are in septic shock, they are most likely in metabolic acidosis. 

If Alkalotic:

  • Bicarb is High = Metabolic  
  • PaCO2 is Low = Respiratory  

Step Three: PaCO2 Compensated or Uncompensated?

Stayed tuned for an upcoming blog covering how to understand compensation on an ABG test result! 

                    

At first glance, navigating ABGs in nursing can seem daunting and overwhelming, but don’t stress –  you got this!

Although it takes a thorough understanding of how to read each level and an ability to interpret the results to help direct your patient care plan, I have full confiedence that you can master this skill. Good luck!

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