Arterial Lines COPY Flashcards
arterial line definition
like an IV but catheter inside artery
why are arterial lines more dangerous
if tubing is disconnected the patient could rapidly bleed to death
2 purposes for arterial lines
provide real time blood pressure
provide constant acess to blood samples for labs
catheter size used for adults arterial line
radial/brachial & femoral
20ga radial/brachial
18ga femoral
catheter size for pediatrics
20-22ga
catheter size for neonates
22-24ga
NIBP vs arterial line
NIBP tend to underread systolic and overread diastolic in comparison
what is the gold standard for BP?
arterial line
5 parts of a transducer system?
500mL bag of N/S arterial line tubing with pressure transducer pressure transducer cable pressure bag for the N/S transducer holder
what does the transducer do?
tells us how many mmHg are generated with each pulse
why use N/S vs why use heparinized saline?
N/S: less possibility of heparin induced thrombocytopenia
heparinized: less chance for aline to clot off
purpose of the pressure bag
prevent blood backup into the tubing bc arterial blood pressures are high
allows us to flush fluid into artery
how to flush arterial line
compressing the two doodads (or tail) on the transducer and opening roller clamp
Why should drugs/air bubbles never be given via the arterial route?
they can cause intense vasoconstriction and ischemia
what are the 4 reasons that an arterial line will not flush?
stopcocks turned off to the line
pressure bag underpressurized
roller clamp could be closed
aline clotted off
what should be done if an aline clots off?
try to aspirate the clot
then try to flush
4 steps of setting up an aline
1-set up bag and pressurize to 300mmHg
2- flush to remove air
3-connect the cable to the monitor
4-zero the a line
Why do you inflate the pressure bag to 300mmHg?
no backflow of blood
3-6mL/hr drip into artery to prevent clot
when we zero an aline what are we eliminating?
the effect of atmospheric pressure
4 steps to zeroing an aline
1-change monitor to from standard to 8 wave
2-turn stopsock nearest to transducer OFF to the patient and open to air (cap removed)
3- touch the ABP and push zero on monitor
4- after it shows zero turn stopcock off to atmosphere THEN put cap back on
why does caution need to be taken with where the stopcock is turned?
if it is off to the transducer then the patient could bleed to death
why do you put the cap on the stopcock after you turn the stopcock?
putting it on before could introduce pressure into the system
What are the materials needed for cannulating the artery?
chloraprep 4x4 tegaderm tape wrist support lidocaine (if awake) angiocath (biopatch??)
2 catheter options for cannulating artery
20ga arrow catheter
regular 20ga catheter
2 options for wrist extenders
rolled up towel
plastic support
6 steps to aline placement
1- set up system and zero 2- position and prep 3- numb the area (if awake) 4-puncture artery and advance catheter 5- remove needle and attach 6- secure with tegaderm and tape
upstroke of a line
systole
correlates with cardiac contractility
downstroke of a line
diastole
correlates with SVR
how is MAP calculated aline
integrating the area under the pressure curve
sloped upstroke vs sharp upstroke
SLOPED: poorer contractility
SHARP: good contractility
slow fall downstroke vs sharp fall downstroke
SLOW: vasoconstriction (high SVR)
SHARP: vasodilation (low SVR)
dichrotic notch
blood slams into the aortic valve and then is projected forward
dampened waveform definition
smoother waveform that has lower amplitude and less detail
what does a dampened waveform do to systolic BP, diastolic BP, and MAP?
sys: underestimates
dia: overestimates
MAP: unchanged
5 causes of dampened waveform
1- compliance in tubing 2- clotted off catheter 3- kinked catheter from flexed wrist 4- low pressure in the system 5- air bubbles (they are a source of compliance)
4 ways to fix dampened aline
1-aspirate/flush clot
2- extend wrist
3- make sure pressurized
4- aspirate air bubbles
Before treating a low BP what things should you check?
low BP isnt due to damened wave
transducer is at the correct level
underdampened waveform definition
RESONANCE
too much waveform detail
“hyperresonant”
“overshoot”
what does a underdamped waveform do to systolic BP, diastolic BP, and MAP?
systolic: overestimatino
diastolic: underestimation
MAP: unchanged
6 causes of underdamped waveform (or resonance)
1-defective transducer 2- tachycardia 3- long tubing 4- movement of catheter 5- catheter thats too large 6- increased vascular resistance
what test do you use to test the accuracy of the aline waveform
square wave (high pressure) test flush system
optimally damped waveform after square test
after flush returns to baseline after one oscillation
underdamped waveform after square test
wave oscillates multiple times before return to baseline
overdamped waveform after square test
wave returns to baseline without any oscillations
natural (resonant) frequency of aline
when pressurized system it oscillates at 20Hz natural frequency
fundamental frequency of aline
arterial waveform has frequency that is equal to the pulse rate
60 bpm = ____ Hz?
1Hz
120bpm= ____ Hz?
2hz
how much greater is the resonant frequency supposed to be than the fundamental frequency?
10x
if the natural frequency <10x fundamental frequency what happens?
waveform become distorted/inaccurate
constructive interference
two or more waves of similar frequency coincide to produce wave with higher peak amplitude
resonance waveform
similar to constructive interference but
bc of external FORCE with similar frequency applied
when can resonance occur with a lines?
bc pressurized tubing is external force if the natural frequency and fundamental frequency are similar then resonance possible
what could happen if the natural frequency decreases below 20Hz or increases fundamental frequency above 2Hz?
resonance more likely
where are the largest errors most likely to occur with resonance?
systolic pressure
how can the amount of damping be measured?
damping coefficient
damping ratio
what does damping counteract
resonance
high damping coefficient
dampened waveform
low damping coefficient
underdamping waveform
what is the optimally damped coefficient?
0.6-0.7
what is the most common aline cannulation site?
radial artery
superficial location and low complication rate
ulnar artery aline placement
- deeper and more difficult
- increased likelihood of nerve damage
if you have failed to place an aline in the radial artery should you try to place an ulnar aline on the same arm?
no
bc hematoma may disrupt bloodflow to hand
allens test (4)
1-pt makes fist
2- radial and ulnar arteries compressed
3- pt relaxes hand
4- pressure on ulnar released and observes how long it takes for blood to return
<7 sec allen test
positive (adequate circulation)
8-15 sec allen test
uncertain/ questionable
> 15sec allen test
negative (inadequate circulation)
brachial artery aline
limited collateral circulation
only use when other sites are not available
axillary artery aline
has significant collateral flow
high risk of nerve damange
highest risk of cerebral emboli
is the right or left axillary artery more likely to cause cerebral emboli?
right axillary artery
what is the largest arterial line cannulation site?
femoral artery
when is a femoral artery contraindicated?
femoral central line on same side
what are the 3 complications unique to femoral aline placement?
1-hole in back of femoral artery lead to retroperitoneal bleed
2-femoral nerve damage
3- potentially higher infxn rate
femoral aline placement pneumonic
NAVEL lateral>medial nerve artery vein empty lymphatic
what is the most distal a line site?
dorsalis pedis and posterior tibial
what two things happen as the cannulation site becomes more distal?
loses detail (more dampened) higher systolic, lower diastolic and lower BP
why does the systolic BP read higher the more distal you go?
pulse wave from previous pulse reflected from arterioles and added (similar to resonance)
what are the 5 aline complications?
limb ischemia neurologic injury infection hemorrhage (disconnection) misinterpretation of data
what are the 4 causes of limb ischemia
thrombosis from multiple attempts
small vessel compared to catheter
accidental medication injection
vasospasm
what are the 4 causes of neurologic injury?
needle
hematoma near nerve
prolonged wrist extension
stroke because of thrombus or air emboli when flushing
why shouldnt we perform a continuous flush?
stroke because of thrombus or air emboli when flushing
misinterpretation of data acute hypertension
transducer falls to floor
misinterpretation of data acute hypotension
transducer raised above phlebostatic axis
hydrostatic pressure
effect of gravity on blood pressure
supine BP
only force effecting pressure is flow
standing pt BP
BP at base of foot is 133mmHg higher than artery at top of head (6ft tall)
phlebostatic axis
4th intercostal space mid axillary line
represents external location of RA
“zero point”
what height should the transducer be at?
phlebostatic axis
if the transducer is below the phlebostatic axis what will be the BP
falsely high BP
if the transducer is above the phlebostatic axis what will be the BP
falsely low BP
for every inch the transducer is below the tip of the catheter how much fluid pressure increases?
1.87mmHg
in sitting patients what will the height of the transducer estimate?
height on the body
you want it to be at the head
when placing the transducer at the brain where do you want it?
external auditory meatus
alternative to leveling at phlebostatic axis
taping to pt arm (not recommended esp. in sitting pts)
arm height effect on BP
as long as the transducer is leveled at the phlebostatic axis it has no influence on BP
do you have to zero the transducer at the level of the heart?
no
