Healthcare and Medicine Reference
Figure 6.6 Step-by-step guide: sampling the arterial blood gas. (a) Palpating
the radial pulse to identify the point of maximal pulsation. (b) Sterilising
the area using 2% chlorhexidine in 70% isopropyl alcohol. (c) The skin is
punctured at a 45° angle in a proximal direction with the syringe held like a
pencil. (d) Flashback followed by syringe fi lling as the artery is punctured.
Information from a blood gas machine
topical local anaesthetic is benefi cial. Subcutaneous infi ltration of
a local anaesthetic agent can sting and may distort the anatomy if
performed immediately before the procedure.
Firstly, learn where the blood gas machines are in your hospital.
Reliable places where they can be found are:
intensive and high-dependency care areas
Natural elasticity of the arterial wall will prevent this, but increas-
ing age and anticoagulant therapy make patients more susceptible.
Ensure pressure is applied quickly and check bleeding has stopped
before leaving the patient. If necessary ask someone to continue
pressure over the puncture site whilst you deal with the sample.
emergency medicine departments
medical admission wards.
All blood gas analysers should provide the following data set:
Refl ex constriction of the artery caused by irritation from the nee-
dle can make it diffi cult to obtain a sample.
Other machines may include electrolytes, haemoglobin, glucose
and lactate. Make sure you know which machines do what; there is
no point taking an ABG to get a rapid potassium or haemoglobin
result and taking it to the wrong machine!
Infection and sepsis
This is unlikely if skin is prepared properly. Avoid areas of skin that
are infl amed, infected or broken down.
Pain and discomfort
ABG sampling is painful. The pain is minimised by the practitioner
acquiring skill and experience. Patient anxiety is reduced through
explanation and reassurance. There is no evidence to suggest
Interpretation of the ABG result
Now you have your sample, you need to be able to interpret the
fi ndings. For the normal values of an arterial blood gas see Box 6.3