12. Arterial Lines Flashcards
what can happen if the art line tubing becomes disconnected?
the pt could rapidly bleed to death
2 purposes for arterial lines
- real time blood pressure
- blood samples
how often does an art line provide blood pressure
every time the heart beats
why cant you draw blood out of an IV?
pressure in veins is too low (7mmHg)
vein would flatten
adult art line sizing
20ga
18ga
radial/brachial catheter size
20ga
femoral catheter size
18ga
peds art line sizing
20-22ga
neonates art line sizing
22-24ga
NIBP reading vs art line
NIBP under-reads systolic
NIBP over-reads diastolic
Art line vs NIBP
Art systolic is higher than NIBP
Art diastolic is lower than NIBP
gold std for BP monitoring
arterial lines
pressure transducer
senses BP inside artery
why do some providers use heparinized saline?
less chance of art line system clotting
why do some providers not use heparinized saline?
eliminates possiblity of HIT
2 purposes of pressure bag
prevents blood from backing into tubing
allows fluid flush of artery
when the 500mL bag of N/S is pressurized, it allows
the pressure in the tubing to be higher than the pressure in the blood
when do you fluid flush an art line into the pt
after labs are drawn to flush the blood back into the pt
can you give drugs through an arterial line
no
why should you not give drugs via art line
cause vasoconstriction and ischemia
what should never be flushed into artery
air bubbles
which direction should the stopcock be turned in order to flush?
off to air
4 reasons an art line wont flush
- stopcock turned off to the line
- closed roller clamp
- “under pressurized” pressure bag
- clotted off catheter
how to fix a clotted off art line?
try to aspirate clot w/syringe
flush line
materials required to insert art line
chloraprep
guaze
tegadern
tape
lidocaine
arrow/angiocath
wrist support/roll
2 catheter types for art lines
20ga arrow catheter
regular 20ga catheter
what pressure do you inflate the N/S bag to?
250-300mmHg
what rate will the fluid drip into the artery with a correctly pressurized bag?
3-6mL per hour
when can the transducer be exposed to the atmosphere?
- if the stopcock if off to the pt, the stopcock will be open to air
- before the link is hooked up to the catheter in the artery
how do you zero the art line?
open the system to the atmosphere
press “zero”
steps to zeroing transducer
- change monitor to 8 wave
- turn stopcock OFF to pt (OPEN to air) and remove cap
- push zero
- turn stopcock OFF to atmosphere
- replace cap
what direction is the stopcock off to pt
away from transducer
towards noncompliant tubing
MAP
area under the curve
upstroke
systole
cardiac contractilioty
sharp vertical upstroke
good contractility
sloped sluggish upstroke
poorer contractility
downstroke
diastole
SVR
slow fall downstroke
vasoconstriction
high SVR
shar fall downstroke
vasodilation
low SVR
dicrotic notch
diastolic blood hits the aortic valve
overdamped waveform
smoother/lower amplitude
underestimates systolic
overestimates diastolic
no change to MAP
are overdamped waveforms accurate?
overdamped waveforms are inaccurate
causes of damping in waveform
- partially clotted catheter
- kinked catheter from wrist flexion
- compliance in tubing
- low pressure in system
- air bubbles
why is art line tubing non-compliant?
to reduce dampning
increase pressure accuracy
how to fix dampened wave form?
- aspirate blood/flush tubing
- extend wrist
- ensure adequate pressure (250-300 mmHg)
- aspirate air bubbles
underdamped waveform AKA
hyperresonant waveform
waveform w/overshoot
underdamped waveform BP effects
overestimated systolic
underestimated diastolic
MAP unchanged
underdamped waveform characteristics
too much detail
causes of underdamped waveform
- defective transducer
- tachycardia
most likely cause of underdamped waveform
defective transducer
just replace it
square wave high pressure test
flush of system and evaluate waveform
optimally damped
flush system
wave returns to baseline after 1 oscillation
underdamped
flush system
wave oscillates multiple times before returning to baseline
overdamped
flush system
wave does not oscillate
wave returns to baseline immediately
constructive interference of waves
waves of similar frequencies are additive
combine to form higher peak amplitude
natural (resonant) frequency of art line
20Hz
fundamental frequency of art line
1-2 Hz
what is the fundamental frequency derived from
pulse rate
fundamental frequency of 60bpm HR
1 Hz
fundamental frequency of 120bpm HR
2 Hz
at what frequency ratio can the wave from become distorted/inaccurate?
if natural freq < 10x fundamental freq
what is the most common cause of constructive interference?
tachycardia
what can tachycardia cause in a art line
resonance
underdamping
– artificially high systolic
resonance occurs when
a wave gets bigger because external force w/similar frequency was applied to it
what can counteract resonance
damping
an optimally damped system has a damping coefficient of
0.6-0.7
high damping coefficient
ovedamped waveform
low damping coefficient
underdamped waveform
most common arterial line insertion sites
radial
the radial is commonly used because
superficial location
low complication rates
radial artery controls blood supply to
digits
ulnar arterial line
more difficult
deeper
increased chance of nerve damage
when do you avoid ulnar placement
if ipsilateral radial attempt has failed
you could lose all blood supply to hand
brachial arterial line
only used if other sites are not available
limited collateral circulation
hemorrhage risk
axillary arterial line
high risk of nerve damage to brachial plexus
highest risk of cerebral emboli
why is the axillary artery the highest risk of cerebral emboli
most proximal to the brain
left is slightly safer than right axillary
where is the highest risk of cerebral emboli
right side axillary artery
what is the largest arterial line site
femoral artery
where do you palpate for femoral pulse
inner thigh
mid-inguinal point
when do you place a femoral line
emergency only
when are femoral lines contraindicated
if pt has a femoral central line on same side
(leads to arteriovenous malformation)
femoral art line complications
- hole in femoral artery
- possible femoral nerve damage
- higher infection rates
NAVEL
Nerve
Artery
Vein
Empty
Lymphatics
femoral line placement
most distal art line sites
dorsalis pedis
posterior tibial
art line waveforms at distal sites
- waveform becomes more dampened (loses detail)
- higher systolic
- lower diastolic
4, unchanged/slight lower MAP
why is the waveform more dampened at distal sites
proximal arteries absorb pressure
more compliance loss by the time the blood reaches distal site
Arteries: Proximal to Distal
aortic root
subclavian
axiallary
brachial
radial
femoral
dorsalis pedis
BP reading in distal arteries
higher resonance = higher BP
allen’s test
- exsanguinate hand (make fist)
- occlude radial/ulnar
- relax hand
- release ulnar pressure
positive allen test
adequate collateral circulation
<7 seconds
uncertain allen test
8-15 seconds
negative allen test
inadequate collateral circulation
>15 seconds
allen’s test indicates what
whether or not ulnar collateral circulation to hand is adequate
do we use allens test
not really
its nonspecific
what is a replacement for allens test
monitor pulse ox during occlusion of radial artery
art line complications
- limb ischemia
- neurologic injury
- infection
- hemorrhage
- data misinterpretation
causes of limb ischemia
thrombosis
too small of vessel for catheter
medication injection into artery
vasospasm
causes of neurologic injury
needle injury
hematoma adjacent to nerve
prolonged wrist extension
stroke
why do you not perform continuous flush of art line
risk of thrombus or air emboli
which has a higher infection rate, arterial line or central line?
central lines are more likely to be infected
arterial line transducer should be leveled to…
the phlebostatic axis
for every ____ the transducer is below the catheter, the fluid pressure increases by ______
for every 1 inch the transducer is below the catheter, the fluid pressure increases by 1.87 mmHg
transducer below level of heart
overestimates BP
transducer above level of heart
underestimates BP
transducers in sitting pts should be leveled
transducers should be leveled to the external auditory meatus in sitting pts to know the BP at the brain
in sitting pts, transducers at the level of the heart will _______ BP at the level of the head
overestimate BP
actual BP will be lower than reading
in sitting pt, if you level the transducer at the external auditory meatus, you will ________ pressures.
understimate CVP
underestimate PAP
will art line BP change if pt moves their arm with the cather inserted?
no
the pressure reading is based off of transducer location, not cather location.
pulsus bisferians
2 dicrotic notches
causes of pulsus bisferians
- hypertropic cardiomyopathy
- severe aortic regurgiation
hypertrophic cardiomyopathy
enlarged interventricular septum
narrows left ventricular outflow tract
severe aortic regurge
blood reenters LV during diastole
temporaroly decreases blood flow during mid-systole
