Hi. I'm Cathy, and in this video series, I will be covering arterial
blood gas interpretation, or ABG interpretation. I'll be covering a number of topics, including
the ABG components and what the normal expected ranges of each component are.
We'll talk about buffers in the body that help maintain acid-base balance.
We'll go through the steps on how to interpret an ABG result, and we will
also talk about the causes, the symptoms, and treatment for different acid-base imbalances.
And then finally, I'll go through a number of practice problems to really get you comfortable
with interpreting ABG results. So as I go through this video series, I will be following along with
my cards that are available on leveluprn.com. It's kind of a mini-deck. You don't need to
have these cards to find value in this video series. However, it is really helpful to have
the information on these cards for reference, whether you're a nursing student or a nurse.
So what is an ABG? An ABG is an arterial blood sample that is used to assess the acid-base
balance, the ventilation, and the oxygenation of a patient. These are often critical-care patients,
but I also had patients when I worked on the Med-Surg/Tele floor who would get ABG tests done
routinely. So like I said, it's an arterial blood sample. So this is not a venous blood sample.
We need to get it from an artery. So we're not pulling it out of a PICC line.
We either need to take that arterial blood sample out of a functioning arterial line - and patients
who have arterial lines are typically in the ICU - or we can get it through a puncture. So
at my hospital and at many hospital systems, the respiratory therapist is the one who actually
comes and does the blood draw for an ABG. So they will typically get that blood sample from
the radial artery. Before they do the puncture, however, they do what's called an Allen's test. So
an Allen's test is done to make sure that we can get adequate blood flow through the ulnar artery
while we're messing with that radial artery. So with the Allen's test, we're compressing
both of those arteries. And the hand will get kind of pale and cool. We'll let go of the ulnar
artery but keep compressing the radial artery to make sure we get blood flow back to that hand
and that that artery can supply that blood flow while we're getting the blood sample out of the
radial artery. So that's an Allen's test. So with ABGs, it's all As, right? We're
getting our Arterial blood sample and we're using an Allen's test.
After we get the sample - and we want to get just about one milliliter of blood - we're
going to need to hold prolonged pressure over that artery. If we don't, then probably the respiratory
therapist or whoever is doing the blood draw is going to get squirted with blood, right,
because this is your arterial system. It's your high-pressure system, and we're going to need
to stop that bleeding, so we're going to have to hold prolonged pressure for at least five minutes.
If the patient is on anticoagulants, it may be a lot longer,
but we want to make sure they're not going to bleed out.
Alright. So you have your blood sample, it gets sent to lab, and then you get your ABG results
back, which will have the following components here, which we'll go into more detail now.
So the first thing you'll get is the pH, which is essentially telling you the acid-base balance
of the blood, whether acidosis is present or alkalosis is present. It measures the hydrogen
ion concentration in the blood, and we would expect a value somewhere between 7.35 and 7.45.
Then we have PaO2, which is the partial pressure of oxygen in the arterial blood
that should be somewhere between 80 and 100 mmHg.
Then we have the partial pressure of carbon dioxide in the arterial blood, which is PaCO2.
We would expect to have a value for PaCO2 somewhere within the range of 35 to 45 mmHg.
Then we have bicarb which is HCO3. So bicarbonate, it's an important buffer in the blood. It's
regulated by the kidneys. And we would expect a value somewhere in the range between 22 and 26.
Some textbooks and instructors use a slightly different range, and if your book or instructor
uses a slightly different range, feel free to cross this off on your card and put that
specific range in. However, it shouldn't vary too much. And when you're given a bicarbonate level
that is out of range, it will likely be very out of range, so it shouldn't trip you up too much.
Then we have SaO2 which is oxygen saturation. It basically measures the amount of oxygen
that is bound to hemoglobin in the arterial blood. And we would expect
that to be somewhere between 95 and 100%. So when we are doing ABG interpretation,
the key things we're going to be looking at are the pH, PaCO2, and HCO3.
Those are the three key components that will help us to interpret our ABGs.
So in my next video, we will talk about the different buffers that are in our body that
help to maintain acid-base balance, and then we'll get into the details of the different acid-base
imbalances such as respiratory acidosis, respiratory alkalosis, metabolic acidosis,
and metabolic alkalosis. So stay tuned!