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Flashcards in Arterial Lines Deck (15)
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What generates the waveform seen in arterial line monitoring? (Hint: It's basically a Fourier analysis of two separate sine waveforms from two sources)

-Ejection of blood from LV into aorta during systole
-Peripheral arterial runoff of this same SV during systole

(The second is a sine wave displaced on the x-axis to the right with smaller amplitude)


In a normal A-line reading, what does the peak and trough represent?

Peak = peak systolic pressure

Trough = end diastolic pressure


What are the indications for A-line palcement?

-The need for real-time BP control (for example, pt has ruptured aneurysm(s))

-Anticipated or known hemodynamic instability

-The need to monitor response to vasoactive drugs in a continuous fashion

-Procedures that involve significant blood loss or fluid shifts

-Monitoring the safety of anesthetic techniques in significant procedures (cardiopulmonary bypass, deliberate hypotension, etc..)

-Inability to use NIBP

-The need for frequent ABG readings


What are the absolute contraindications for A-line placement?

-Localized infection at site of insertion

-Preexisting ischemia or nerve damage at insertion site

-Raynoud's phenomenon

-Trauma to area proximal of insertion site


What are some relative contraindications for A-line placement?

-Failure to demonstrate collateral flow

-AV fistula in limb of placement site

-Evidence of disrupted lymphatics in limb of placement site


What fluid should you use in the set up of an A-line?

Saline or heparin (risk of HIT though)


How does the site and distance of A-line placement effect its waveform?

-Amplitudes of wave increases (sys increases, dias, decreases)

-MAP decreases

-Waveform narrows

-Delay in pressure pulse


Describe the effects of distal waveform amplification in A-line readings and why it occurs.

-Wider waveform

-Slurred dichrotic notch (slower)

-Delayed upstroke

-More prominent diastolic wave

>>Occurs at more distal A-line placement. Delayed upstroke and slurred dichrotic notch makes sense in the context of increased distance from aortic arch. Wider waveform and more prominent diastolic wave = due to harmonic resonance. (Correct this if I'm wrong, this is just my guess)


What is the effect of decreased arterial distensability (less compliant) on A-line readings?

Note: esp seen in elderly patients

-Delayed systolic peak

-Wider diastolic trough

-Early return of pulse waves, which causes increased pulse pressures


What should you do after you place the A-line catheter and connect it to the T-connector (which is connected to the transducer)?

-Aspirate 2 mL of blood to confirm placement and suck out any air.

-Flush the line with LESS than 3 mL of fluid. (More than that has demonstrated retrograde flow back to cerebral circulation)


What are some identifiable characteristics of overdamped pressure waveforms?

-Diminished pulse pressure

-Slurred upstroke

-Absent dichrotic notch and other sharp characteristics of a normal a-line waveform


What are some causes of an overdamped A-line pressure waveform?

-Arterial obstruction

-Catheter obstruction or clot (assess patency with flushing and aspiration)

-Pressure tubing kinks

-Air in tubing

-Transducer failure

-Loss of flush pressure (pressurize bag again)


What are some identifiable features of an underdamped A-line reading?

-Overshoot, ringing, or resonance (Everything becomes much more amplified)

-Systolic peak overestimates intra-arterial blood pressure (compare to NIBP reading if possible)

-Multiple sharp peak waves (so you can't really tell which one is the dichrotic notch, although you can estimate)


Complications of A-lines? (There are many..)

-Distal ischemia (interruption of arterial flow)


-Arterial-venous fistula (inadvertently creating a connection between artery and vein)



-Peripheral neuropathy

-Misuse of equipment

-Misinterpretation of data


How does height affect A-line readings (BP #s)? (Numbers) --> How can you estimate effect of height on bp readings?

Every 15 cm of height difference = 10 mm Hg

(too low = increase in BP, gravity)