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Patient Monitoring/Instrumentation & SIM > Arterial Lines > Flashcards

Arterial Lines Flashcards

1
Q

Why are arterial lines dangerous?

A

If it becomes disconnected, the patient could bleed to death

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2
Q

Purpose of arterial lines

A
  1. Beat to beat blood pressure

2. Constant blood sample access for labs (ABG, Hgb/Hct)

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3
Q

Catheter size for adults

A

20ga for radial/bronchial

18ga for femoral

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4
Q

Catheter size for pediatrics

A

20-22ga

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5
Q

Catheter size for neonates

A

22-24ga

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6
Q

NIBP tends to (overestimate/underestimate) systolic and (overestimate/underestimate) diastolic readings

A

Underestimate systolic

Overestimate diastolic

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7
Q

Gold standard for BP monitoring

A

Arterial lines

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8
Q

Components of the pressure transducer system

A
  1. Pressure bag
  2. Pressure transducer
  3. A-line cable
  4. Saline filled, non-compressible tubing (non-compliant tubing)
  5. Catheter
  6. 500 ml bag of NS
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9
Q

Purpose of the pressure bag

A

To prevent blood from backing up in the tubing and allows us to flush fluids into the arteries

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10
Q

Why flush fluids into an artery?

A

After drawing labs to flush the non-compliant tubing of blood

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11
Q

Why are drugs never given through the arterial line?

A

They can cause vasoconstriction and ischemia

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12
Q

Why should air bubbles always be aspirated?

A

They can go into the distal artery and cause ischemia

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13
Q

Why would an A-line not flush?

A
  1. The stopcocks are turned off to the line
  2. The pressure bag is low/under pressurized
  3. The roller clamp on the tubing is closed
  4. The catheter could be clotted off
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14
Q

How do you set up the art line? (include steps for zeroing)

A
  1. Spike 500ml NS with non-compliant tubing and place inside pressure bag (300mmHg)
  2. The tubing is flushed to remove air
  3. Connect the transducer cable to the transducer and monitor
  4. Zero the transducer
    4a. Change monitor from standard to 8 wave to show A-line
    4b. Turn the stopcock nearest to the transducer OFF to the patient and open to air (remove stopcock cap)
    4c. Touch ABP on the monitor and hit “zero”
    4d. When the monitor reads 0, turn the stopcock off towards the atmosphere and replace the cap
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15
Q

At a pressure of 300mmHg, how fast will fluid drip into the artery? (assuming the roller clamp is open) and why is it important?

A

3-6 ml/hour

It helps prevent the catheter from clotting off

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16
Q

What is the point of zeroing the transducer?

A

To eliminate the effect that atmospheric pressure has on blood pressure readings

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17
Q

What happens if the stopcock is turned off towards the transducer instead of the patient?

A

It will bleed back and the patient could bleed out

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18
Q

What happens if the stopcock cap is replaced prior to turning it off to air?

A

It can introduce pressure into the system

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19
Q

The 2 catheter options for cannulating an artery

A
  1. 20 ga “arrow” catheter

2. Regular 20 ga catheter

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20
Q

2 options for wrist extenders

A
  1. Plastic “wrist support”

2. Rolled up towel under wrist

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21
Q

Steps to physically place the A-line

A
  1. Set up the system and zero the transducer
  2. Position and prep the wrist with chloraprep
  3. Numb with lidocaine if pt is awake
  4. Puncture artery and advance catheter
  5. Remove needle and hook up catheter to the flushed non-compliant tubing
  6. Secure catheter with tegaderm and tape
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22
Q

Calculating MAP with the A-line

A

Integrating the area under the pressure curve

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23
Q

Correlates with cardiac contractility

A

Upstroke

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24
Q

A sharp, vertical upstroke indicates (good/bad) cardiac contractility

A

Good

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25
Q

A sloped, sluggish upstroke indicates (good/bad) cardiac contractility

A

Bad

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26
Q

Correlates with SVR

A

Downstroke

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27
Q

A slow fall on the ABP waveform indicates

A

Vasoconstriction

High SVR

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28
Q

A sharp fall on the ABP waveform indicates

A

Vasodilation

Low SVR

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29
Q

What does the dicrotic notch on the ABP waveform represent?

A
  • During diastole, some of the blood in the aorta comes back towards the heart
  • The blood slams into the aortic valve and then is projected forward again
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30
Q

What is the significance of a dampened waveform?

A
  • Underestimates the systolic, overestimates diastolic

- MAP remains unchanged

31
Q

Causes of a dampened waveform

A
  1. Partially clotted off catheter
  2. A kinked catheter from a flexed wrist
  3. Compliance in tubing
  4. Low pressure in the system
  5. Air bubbles
32
Q

Ways to fix a dampened waveform

A
  1. Try to aspirate the blood/flush the tubing
  2. Try extending the wrist
  3. Make sure the system is pressurized to 300mmHg
  4. Look for air and aspirate bubbles
33
Q

What do you need to look for before treating hypotension?

A
  1. Make sure the waveform is not dampened

2. Be sure the transducer is appropriately leveled

34
Q

Significance of under-dampened waveform

A
  • Overestimation of systolic, underestimation of diastolic

- MAP is unchanged

35
Q

Causes of an under-dampened waveform

A
  1. A defective transducer
  2. Tachycardia
  3. Long tubing
  4. Movement of the catheter
  5. Too large of a catheter
  6. Increased vascular resistance
36
Q

Returns to baseline after one oscillation after flushing of the system

A

Optimally dampened

37
Q

Wave oscillates multiple times before returning to baseline after flushing the system

A

Underdampened

38
Q

Wave returns to baseline without any oscillations after flushing the system

A

Overdampened

39
Q

When the arterial line system is pressurized, it oscillates at a certain frequency

A

Natural (resonant) frequency

40
Q

Estimate of the natural frequency of arterial line systems

A

20 Hz

41
Q

Arterial waveform itself, equal to pulse rate

A

Fundamental frequency

42
Q

If HR is 60 bpm, the fundamental frequency is

A

1 Hz

43
Q

If HR is 120 bpm, the fundamental frequency is

A

2 Hz

44
Q

Fundamental frequency should be between _ Hz

A

1-2 Hz

45
Q

When two or more waves of similar frequency coincide to produce a single wave with a higher peak amplitude

A

Constructive interference

46
Q

Occurs when a wave gets bigger due to an external force of similar frequency being applied

A

Resonance

47
Q

How does resonance occur with arterial lines?

A

The pressurized A-line tubing applies force to the arterial line waveform

48
Q

True/false: The natural resonance frequency should be 5x higher than the fundamental frequency to prevent resonance

A

False; the natural resonance frequency should be approximately 10x higher than fundamental

49
Q

What makes resonance more likely?

A
  • If the fundamental frequency increases (HR increases)

- If the natural (resonant) frequency decreases

50
Q

Is resonance considered underdampening or overdampening?

A

Underdampening

51
Q

Are the largest errors most likely to occur with systolic or diastolic pressure?

A

Systolic pressure

52
Q

Dampened waveform = high/low damping coefficient

A

High

53
Q

Underdamping = high/low damping coefficient

A

Low

54
Q

Why is the radial arterial line the most common place?

A

It is superficial and has low complication rates

55
Q

Significance of ulnar arterial lines

A
  1. Deeper/more difficult than radial
  2. Increased risk of nerve damage
  3. Should not be placed if radial line attempt failed
56
Q

Time for positive Allen’s test

A

<7 seconds

57
Q

Time for negative Allen’s test

A

> 15 seconds

58
Q

Side of axillary art line that makes is more likely to for an embolus to enter the cerebral circulation

A

Right side

59
Q

Complications of femoral arterial lines

A
  1. A possible hole in the back of the femoral artery
  2. Possible nerve damage
  3. Potentially higher infection rates
60
Q

Why would you want to avoid a brachial art line?

A

Due to lack of collateral blood flow

61
Q

Significance of NAVEL

A 
Femoral art line placement. Lateral to medial
Nerve
Artery
Vein
Empty
Lymphatics
62
Q

Most distal A-line cannulation sites

A
  1. Dorsal pedalis

2. Posterior tibial

63
Q

What happens to the waveform as sites become more distal?

A
  1. It becomes more dampened
  2. Higher systolic, lower diastolic, unchanged or slightly lower MAP
  3. Higher BP reading
64
Q

A-line complications

A
  1. Limb ischemia
  2. Neurologic injury
  3. Infection (less likely than central lines)
  4. Hemorrhage
  5. Misinterpretation of data
65
Q

Higher measuring site = (higher/lower) BP readings

A

Lower

66
Q

Lower measuring site = (higher/lower) BP readings

A

Higher

67
Q

Where is the phlebostatic axis located and what does it represent?

A
  • 4th intercostal space along midaxillary line
  • Represents external location of R atrium
  • Point where blood pressure is not affected by gravity of hydrostatic pressure
  • Reference mark for CVP and pulmonary artery catheter transducers
68
Q

In a supine patient, if the transducer is lower than the level of the heart, it will (under/over)estimate the BP and why?

A

Overestimate
When the transducer is lower, the fluid in the tubing is now falling towards the transducer, weighing on it and creating additional hydrostatic pressure

69
Q

For every inch the transducer is below the tip of the catheter, the fluid pressure in the system increases the measurement by:

A

1.87 mmHg

70
Q

Where should the transducer be placed in sitting patients to measure the BP of the brain?
What will it do to CVP, PAP and ABP?

A
  • At the external auditory meatus

- Underestimates CVP, PAP, ABP

71
Q

Where should the transducer be placed in sitting patients to measure CVP, pulmonary arterial pressure and ABP?
What will it do to the pressure at the head?

A
  • Phlebostatic axis

- Overestimates pressure at the head

72
Q

Does arm height change BP readings?

A

Not if the transducer is at the level of the heart

73
Q

Does the transducer have to be zeroed at the level of the heart?

A

Not if you’re using the stopcock closest to the transducer

Patient Monitoring/Instrumentation & SIM (12 decks)

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