Arterial Lines Flashcards
2 purposes of arterial lines
- provide a real time blood pressure
2. arterial lines provide constant access blood samples to send for lab results
what is the catheter size for radial/brachial used for adults?
20 ga
what is the catheter size for femoral used for adults?
18 ga
what is the catheter size for pediatrics
20-22 ga
what is the catheter size for used for neonates?
22-24 ga
automatic bp machines tend to __(under read or over read) systolic bp and tend to ___ (under read or over read) diastolic bp
under read; over read
arterial lines which is most likely to be elevated?
systolic bp
Name the 5 materials for the pressure transducer system
- 500 ml NS bag
- arterial line tubing (noncompliant tubing) that contains a pressure transducer
- pressure transducer cable
- pressure bag for 500 ml NS bag
- transducer holder
what does the transducer do?
tells you how many mm Hg are generated with each pulse
why use heparinized saline?
system less likely to clot
what would happen if you did not use a pressurized bag ?
blood from the artery would back up into the tubing
what is the purpose of pressurized bag?
when the 500 mL NS is pressurized it exceeds arterial pressure and ALLOWS TO FLUSH FLUID INTO ARTERY
how do you flush an arterial line?
open the roller clamp and compressing the wings on the transducer
when should you flush fluids into an artery?
immediately after drawing blood labs from arterial line
what could happen if drugs are given the arterial route?
intense vasoconstriction and ischemia
what are the 4 possible reasons an arterial line wont flush?
- the stopcocks could be turned off to the line
- the pressure bag is under pressurized
- the roller clamp on the aline tubing could be closed
- the aline catheter could be clotted off
what pressure should the bag be pressurized?
300 mm Hg
how much fluid per hour will drip into the artery?
3-6 mL
what is the purpose of zeroing the arterial line?
eliminating the effect of atmospheric pressure has on bp reading
what should you change on the monitor for zeroing the transducer?
change from standard to arterial line tracing 8 wave
what could happen if the stopcock is turned the wrong direction off towards the transducer instead of patient?
it will bleed back and the pt could bleed to death
what should you do once the monitor shows a 0?
turn the stopcock off to the atmosphere again THEN put cap back on stopcock
7 things required for cannulating the artery
- chloraprep
- gauze
- tegaderm
- tape
- plastic “wrist support”
- lidocaine “skin wheel”
- angiocath
what are the two catheter options for cannulating the artery?
- 20 ga arrow catheter
2. 20 ga regular catheter
2 options for an Aline wrist extender
- plastic “wrist support”
2. rolled up towel under the wrist
how do you calculate MAP with a line waveform?
area under the pressure curve
correlates with cardiac contractility
upstroke
what indicates good cardiac contractility?
sharp vertical upstroke
correlates with SVR
downstroke
a slow fall or high SVR indicates ___
vasoconstriction
a sharp fall or low SVR indicates ____
vasodilation
why do you see a dichrotic notch on the A line waveform?
closing of AORTIC valve
more sluggish upstroke and downstroke indicates ___ and ___
lower contractility and higher SVR
steeper upstroke and downstroke indicate ____ and ____
higher contractility and lower SVR
what does a dampened waveform mean?
gives inaccurate bp; underestimates the systolic BP (makes you think systolic bp is lower than it really is) and overestimates the diastolic bp while the MAP is unchanged
5 causes of dampened waveform
- compliance in the tubing
- a partially clotted off catheter
- a kinked catheter from a flexed wrist
- low pressure in the system
how do you fix a dampened a line waveform ? (4)
- try to aspirate the blood and/or flush the tubing
- try extending the wrist
- make sure the system is pressurized to 300 mm Hg
- look for air and aspirate any air bubbles
before treating hypotension you have to make sure of what two things?
- the low bp reading is not due to a dampened waveform
2. the transducer is appropriately leveled
3 effects of underdamped waveform
- an overestimation of systolic bp
- an underestimation of diastolic bp
- MAP is unchanged
6 causes of an underdamped waveform
- a defective transducer
- tachycardia
- long tubing
- movement of catheter inside the artery
- a catheter that is too large for vessel
- increased vascular resistance
in an optimally damped waveform when does the wave return to baseline?
after one oscillation
in an underdamped waveform how often does the wave oscillate before returning to baseline?
oscillated multiple times
when the wave returns to baseline without any oscillations what waveform is this characteristic of?
overdamped waveform
term used when an arterial line system is pressurized it oscillates at a certain frequency
natural or resonant frequency
the fundamental frequency is equal to __
pulse rate
what is the fundamental frequency when the heart rate is 60 beats per minute?
1 Hz
what is the fundamental frequency when the heart rate is 120 beats per minute?
2 Hz
the fundamental frequency of an a line waveform should normally be between ___ and ___ Hz
1 and 2
the natural frequency is how much more than the fundamental frequency?
10 x
when two or more waves of similar frequency coincide to produce a single wave with a higher peak amplitude
constructive interference
when the wave gets bigger because b/c external FORCE with a similar frequency was applied to it
resonance
what becomes a factor if the natural frequency and fundamental frequency are similar?
resonance
when is resonance more likely?
decrease in natural frequency or increase in fundamental frequency
what can counteract resonance?
damping
how can you measure the amount of damping?
damping coefficient or damping ratio
a high damping coefficient= ___ waveform
dampened
name the arterial line cannulation sites
- radial arterial line
- ulnar arterial line
- brachial arterial line
- axillary arterial line
- femoral arterial line
- dorsalis pedis and posterior tibial (most distal)
what is the most common and preferred arterial cannulation site?
radial arterial line
<7 seconds time for blood to return to hand
positive allen’s test; adequate collateral circulation
8-15 seconds time for blood to return to hand
uncertain; questionable allen’s test
> 15 seconds time for blood to return to hand
negative allen’s test; inadequate collateral circulation
carries the highest risk of cerebral emboli
axillary arterial line
an embolus from an axillary arterial line is more likely to enter cerebral circulation through what side?
RIGHT
What are the complications for femoral lines? (3)
- a hole in the back of the femoral artery
- possible femoral nerve damage
- potentially higher infection rates
which arterial site gives the highest systolic BP, lower diastolic, and lower mean BP readings and dampened wave form ?
distal; dorsalis pedia/posterior tibial
5 complications from arterial line complications
- limb ischemia
- neurologic injury
- infection
- hemorrhage
- misinterpretation of data
the pressure of the artery at the base of the foot in a person who is standing is how much higher than the top of the head?
133 mm Hg
when will gravity or hydrostatic pressure affect blood pressure readings?
anytime pt is NOT lying flat
located at the 4th intercostal space along the mid axillary line
phlebostatic axis
phlebostatic axis represents the external location of ___
right atrium
where is central venous pressures not influences by hydrostatic pressures?
phlebostatic axis
where should bp readings be taken?
at the level of the heart
what will happen if the transducer is below the level of the heart?
overestimates blood pressure
what will happen if the transducer is above the level of the heart?
underestimates the blood pressure
how much does the fluid pressure increase if the transducer is below the tip of the catheter?
1.87 mm Hg
for sitting pts where should the transducer be placed ?
external auditory meatus
how much does the pressure in the transducer increase when raising the arm? what is unchanged?
15 cm H20; overall bp reading at the transducer unchanged