When caring for your critically ill patient, this question often arises. You should definitely know the answer to this question. But, how do you know?
An ICU patient will often have an arterial line placed for continuous invasive blood pressure monitoring, especially if they are receiving vasoactive infusions, unstable & being resuscitated. It is your job as the nurse to make sure this line is set-up correctly, so you can treat your patient appropriately. You are actively making moment by moment decisions to titrate pressors or vasoactive drips up or down, give fluid, blood, you name it based on these numbers. So, it is imperative that you know if you can trust your arterial line.

Make sure your arterial line is set up appropriately:
- Must be transduced & pressurized with 300 mm Hg pressure
- Patient should be supine with HOB 0 – 60 degrees
- Zeroed & leveled to phlebostatic axis (4th intercostal space mid AP – see image below)
- Re-level with every position change
- Zero pre-insertion, post-insertion, disconnecting, reconnecting, or if your numbers are not matching the clinical picture
- Make sure your saline bag has enough volume
- Make sure your connections are tight & remove as much excess tubing as possible
- When priming your tubing, prime with gravity, this reduces air bubbles that can lead to overdamped or underdamped lines


Perform the Dynamic Response Test AKA the “Fast Flush Test” or the “Square Wave Test”
- It helps you decide if you can trust the number
What to look for:
- Perform a 1 second flush
- Assess the square wave form on the monitor
- Count the number of oscillations after the square wave, before it returns to baseline (should see 1 – 2 oscillations in 0.12 seconds)
When to perform:
- Every shift
- When the system is open to air
- When the waveform changes

One pro-tip is that if your arterial line is zeroed & leveled, but overdamped or underdamped, you can always trust the MAP.
Also, don’t be afraid to tell your provider that your arterial line is failing. They don’t last forever, so sometimes you either need a new one or it’s just time to take it out.
If you can embed one thing into your critical care practice, it is to make sure you can answer assuredly whether or not you can trust your arterial line!
Even when focusing on arterial lines, I always find it worthwhile to revisit hemodynamics, resources like Nicole Kupchik’s Hemodynamic Monitoring Bootcamp Online Course are a great reminder that there’s always something new to learn each time you dive back in.
References:
Pulmonary Artery/Central Venous Pressure Monitoring in Adults | Critical Care Nurse |




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