Flashcards in Arterial Lines Deck (15)
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
-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)
-Delay in pressure pulse
Describe the effects of distal waveform amplification in A-line readings and why it occurs.
-Slurred dichrotic notch (slower)
-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
-Absent dichrotic notch and other sharp characteristics of a normal a-line waveform
What are some causes of an overdamped A-line pressure waveform?
-Catheter obstruction or clot (assess patency with flushing and aspiration)
-Pressure tubing kinks
-Air in tubing
-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)
-Misuse of equipment
-Misinterpretation of data