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Operational Readiness- Pressure Lines

In the heat of a stressful moment, we seldom rise to the occasion but rather sink to the level of our training. I was reminded of this last week when my partner and I were setting up for the intubation of a hypotensive septic patient the other day. The two of us are often conducting clinical simulation scenarios in our free time, but usually they are focused on the management of trauma patients. In my local service area, the vast majority of our flight requests are for trauma evacuations. While our intubation followed all standards and we achieved the DASH1-A, or definitive airway sans hypoxia/hypotension on 1st attempt (credit to Dr. Weingart @EMcrit), we felt ourselves shaking off a little rust as we prepared for the management this particularly sick medical patient. In our debrief later in the evening we both concluded that the outcomes would have been the same, but our on-scene time could have been improved significantly. Thankfully at my service, on-scene times are not the metric we are judged upon rather the overall quality of care.

As a preceptor of new nurses in the ED, I always loved recruiting nurses of differing years of experience to participate in training exercises. It offered everyone a chance to "shake off the rust" and identify areas for improvement. This strategy also highlighted the importance of maintaining operational readiness for newly graduated nurses transitioning to practice. Precepting also afforded me the opportunity to sit back and observe nurses performance at times, as opposed to always being in the trenches. This gave me some good insight to the skills that were most lacking within our department. I quickly realized that ED nurses in my hospital hadn’t the slightest clue how to properly set up an arterial line transducer. I doubt I will forget the moment when that reality was apparent. Our team was resuscitating a hypotensive patient receiving a massive transfusion. It was impossible to get digital blood pressures so the physician opted to insert a central line. He inserted the line and reached for the transducer, only to find 3 skilled and seasoned ED nurses fumbling over the tubing. He then asked for something that gives me chills to this day… “Call up to the ICU and get me one of their nurses down here”. For all my ED clinicians out there, you know what a slap in the face that is as ED and ICU are still fighting the greatest healthcare civil war, the likes of which has no end in sight.

It’s vital as emergency and critical care clinicians to be at our best when it comes to the use of our own equipment as there is nothing more embarrassing or frustrating than fumbling with your gear when the crucial moment comes. The above interaction is what sparked my interest in creating a way for nurses to prepare for the insertion of pressure monitoring lines in a simulated environment, where mistakes can be made and lessons can be learned without affecting patient care.

Simulation has gained a deserving foothold in the healthcare setting but remains expensive unless some creativity is applied. Here is my method for creating a pressure line simulator applicable for monitoring CVP, PAP, PAWP and peripheral/central arterial lines.

Equipment for the simulator: Equipment for the pressure line:

IV pump with primary set tubing Transducer tubing

20g IV catheter x 2 Pressure bag

NS bag of any size NS 1 Liter

Betadine or food coloring Monitor and cable

Overall this is a pretty simple setup that can be done with 15 minutes of downtime on your next shift. Come on into our mock ED trauma room and I'll show you around!

This is an example of the completed simulator when it is all set and done.

There are two independent circuits that are set up. The first on the left represents the arterial circulation driven by our simulated heart, the IV pump. Using the IV pump offers pulsatile forward flow, much like the arterial system. This system will be referred to as "circuit 1".

The second half, or "circuit 2" represents the actual pressure line setup. This element may change depending on the manufacturer tubing chosen within your organization.

It is best to set up circuit 1 ahead of time so you can practice priming your pressure tubing (circuit 2) all in one motion.

Here is a close up of circuit 1.

I think it is more realistic to add betadine or red dye to the NS bag to make it easier to discern which circuit is which, but it isn't necessary if supplies are short. The key here is to make a closed loop system. Take the end of the primary tubing and spike it back into the medication port of the NS bag. This can be done with a 20g angiocath or a hypodermic needle. The catheter option offers an extra degree of safety. Determining the flow rate on the pump takes some trial and error depending on the manufacture. The general range is around 200mLs/hr. The goal is to hear the peristaltic pump click approximately at 80-100 beats/min.

When priming circuit 2, it is important to use your organizations policy and procedure to insure you meet the manufacturer specifications. The overall goal is to carefully prime the pressure transducer with saline so that no air enters the system. Then inflate the pressure bag to approximately 300 mmhg.

Level off the pressure line transducer with the actuator pump on the peristaltic IV pump. This will act as your phlebostatic axis. I used to think that utmost precision was required when aligning the transducer. This is a good opportunity to play around with the height of the transducer to see how much it alters the reading.

In order to complete circuit 2, you'll have to cannulate the tubing of circuit 1 with a 20ga IV catheter. This is labeled here as "Arterial catheter" and it represents the actual arterial line placed by the provider. Just a note if you use betadine or dye, once cannulating the "artery" there will be quite a bit of back flow from the blood bag. Make sure to clamp distal to insertion of have some towels handy or else it turns this into a tie-dye uniform arts and crafts project.

Now that the lines are all in place, all that is left to do is connect to your monitor and zero out the transducer. When zeroing your transducer, be sure that the stopcock is OFF to the PATIENT as we want the monitor to read atmospheric air. When the monitor indicates zeroing is complete, turn the stopcock OFF to AIR. It is always embarrassing when the monitor persists with NO WAVEFORM due to a simple stopcock alignment error.

Troubleshooting Tips:

If your waveform seems overly dampened, first play with the scale on your monitor to see if it can be optimized. Next be sure your pressure bag is properly inflated. If neither of those do the trick, change the catheter spiking re-entry to the blood bag to a smaller size. Some IV pumps generate lower forward flow pressures. Dropping the gauge on the outflow catheter creates a little added resistance within the circuit 1 tubing distal to the pump.

Lastly, higher IV flow rates will simulate tachycardia and increase the pressure within the tubing. Play around with the IV flow rates to find one that works best for whatever scenario you are achieving.

Thanks for reading and good luck with your simulations!


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