Section Two:
Arterial Pressure Monitoring
Indications
An arterial line is indicated for blood pressure
monitoring for the patient with any medical or
surgical condition that compromises cardiac
output, tissue perfusion, or fluid volume status.
It is also helpful in the management of patients
with acute respiratory failure who require
frequent arterial blood gas measurements. With
an arterial line in place, continuous
measurement of the systolic, diastolic and mean
arterial blood pressure is possible with alarms
set to warn of change in patient status.
Insertion Sites
The most frequently used site is the radial
artery. The major advantage of the radial artery
is that collateral circulation to the hand is
provided by the ulnar artery, in the event the
radial artery becomes occluded due to the
presence of the catheter. The patency of the
ulnar artery should be assessed prior to
cannulation of the radial artery, either with a
Doppler flowmeter or by doing the Allen test. In
the Allen’s test the patient’s hand is elevated
with fist clenched, and both radial and ulnar
arteries are compressed to block arterial flow
(A). The hand is then lowered (B) and opened
(C). Pressure is released over the ulnar artery
only (D). Color should return to the hand within
6 seconds, indicating a patent ulnar artery and
adequate collateral blood flow to the hand.
(See diagram above.)
Regardless of the site of insertion, insertion is
done with sterile technique. The monitoring
system is prepared as described in Section One
and attached to the catheter. After the catheter
is attached to the monitoring system the
waveform and a dynamic response test are run
and documented on a strip in the patient’s
record.
Arterial Pressure Waveform
The normal arterial waveform should have a
rapid upstroke (systole), a clear dicrotic notch
(closure of the aortic valve), and a definite
downstroke (diastole). When compared with a
simultaneous ECG recording, the peak of
systole on the arterial waveform follows the QRS
on the ECG (Fig 5).
If the radial artery is not available, the
femoral, brachial, or dorsalis-pedis arteries
may be used. The advantage of the femoral
artery is that it is large and easy to
cannulate. The disadvantage is that the site is
difficult to maintain, more susceptible to
contamination, and difficult to assess for loose
connections and blood loss.
Figure 5. Arterial pressure waveform. 1=systole,
2=dicrotic notch, 3=diastole. B/P = 142/70
Section Two – Arterial Pressure Monitoring
13
system or when the bag is empty. The CDC
has not specified recommendations related to
tubing change frequency of hemodynamic
monitoring systems. Label bag and tubing.
Cuff Blood Pressure vs. Arterial Line
Pressure
Differences in pressure between cuff and
a-line are expected because the arterial catheter
measures pressure within the artery, while the
cuff pressure measures flow from the outside.
In the normovolemic patient, differences of 5 to
10 mm Hg in the same arm are expected, with
the arterial line value normally higher than the
cuff pressure. If the patient has an abnormally
large difference in blood pressure from one arm
to the other due to arterial obstruction (rare), the
arterial line should be on the side of the higher
pressure to prevent false assumption of a
hypotensive state. Accuracy of arterial line
pressures should be assessed by checking
leveling, zeroing and performance of a square
wave test, not by comparing with the cuff
pressure.
In low cardiac output states and/or shock, the
cuff pressure is less reliable than the arterial line
pressure due to systemic vasoconstriction.
Nursing Management

Practice measures to ensure accuracy
(zeroing, leveling, dynamic response test).

Use sterile technique at all times during
insertion and whenever entering the system.



Document waveform and dynamic response
test every shift or when there is a change in
patient condition or waveform morphology.

Avoid flushing system with a syringe.

Do not infuse medication or IV solution
through the arterial line.
Blood Sampling
Ensure that sterile technique is used
whenever entering the system. Determine what
the deadspace volume of the catheter/flush
system is. The deadspace volume is how many
mL of fluid is needed to flush from the stopcock
used to draw blood to the tip of the catheter.
When obtaining blood for routine labs or ABGs,
use a discard volume of two times the deadspace volume of the catheter and tubing to the
site of sampling, then draw the amount of blood
needed for the sample.
When obtaining coagulation studies through
a heparinized system, use a discard volume of
six times the dead-space volume of the catheter
and tubing to the site of sampling and then draw
the amount of blood needed for the test.
Removal of Arterial Catheter
Apply sterile dressing.
Set alarm parameters based on individual
patient status.

Record pressures according to policy.

Monitor motor and sensory function to
identify possible nerve damage.

Monitor pulses, color, temperature, capillary
refill of limb distal to the insertion site at least
every 4 hours in order to identify ischemia or
arterial spasm.

Monitor insertion site for signs of infection
and patency of dressing.

Change flush bag and tubing according to
policy. Current research recommendations for
changing of tubing and flush solution are every
96 hours for arterial systems or with every
change of the catheter. The flush solution
should be changed only with the entire tubing
Immediately apply firm, continuous pressure
just proximal to the insertion site after the
catheter is removed. Continue to apply pressure
until hemostasis is obtained. This is for a
minimum of 5 minutes for a radial catheter site
and > 15 minutes for a femoral catheter site. Do
not release pressure to frequently assess for
hemostasis because pressure must be
continuous in order to be effective.
Apply a pressure dressing and frequently
check and document the pulses, color,
temperature, capillary refill and monitor for
bleeding at the site as specified in hospital
policy. Standards may vary depending on
insertion site and patient’s coagulation status.
(No research-based standard is currently
available for how frequent checks should be
after catheter removal.)
Section Two – Arterial Pressure Monitoring
14
The table on page 73 of the workbook
summarizes the AACN recommendations
regarding protocols for arterial line use.
Complications of Arterial Lines
Complications are primarily infection,
accidental blood loss, and impaired circulation to
the extremity. Adherence to guidelines outlined
above will help prevent complications.
Complete the Self-Test that follows.
Section Two – Arterial Pressure Monitoring
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Section Two – Arterial Pressure Monitoring
16
Section Two: Arterial Pressure Monitoring
Self-Test
Match the following:
1. _____ Less reliable measurement in low cardiac
output states.
a) Allen’s test
b) Dicrotic notch
2. _____ Minimal frequency of extremity assessments
when a-line is in place.
3. _____ Recommended frequency of tubing/flush solution
c) Cuff pressure
d) Every 96 hours
e) Every 4 hours
changes according to some studies.
4. _____ Used to assess ulnar artery patency.
5. _____ Caused by closure of aortic valve.
Review the following a-line strips and write in the pressure (systolic/diastolic) below each:
Pressure = _______________________
Pressure = _______________________
Section Two – Arterial Pressure Monitoring
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Section Two: Arterial Pressure Monitoring
Self-Test - Answers
Match the following:
1. C
Less reliable measurement in low cardiac
output states.
2. E
b) Dicrotic notch
Minimal frequency of extremity assessments
when a-line is in place.
3. D
a) Allen’s test
Recommended frequency of tubing/flush solution
c) Cuff pressure
d) Every 96 hours
e) Every 4 hours
changes according to some studies.
4. A
Used to assess ulnar artery patency.
5. B
Caused by closure of aortic valve.
Review the following a-line strips and write in the pressure (systolic/diastolic) below each:
Pressure = 195/120 1box=7.5mm Hg
Pressure = 156/60
Section Two – Arterial Pressure Monitoring
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Section Two – Arterial Pressure Monitoring
19