Ask the Clinical Instructor

“Does your institution use 1 or 2 transducers for cardiac caths? We currently have one for femoral arterial and one for aortic pressures. A single transducer would be more cost effective. How do you flush the sheath with one transducer and do you use a 3- or 4-port manifold?”

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As with many issues that we discuss in this column, there are several different ways to accomplish the same thing, as well as operator (physician) preferences playing a role. Let’s talk for a moment about some of the more common manifold set ups.

The more traditional manifold is a 3-port manifold (Figure 1). In all manifold kits, the first “port” coming off of the catheter should be the arterial line. Having this port first can reduce the occurance of blood, contrast or bubbles being in the line to adversely affect any waveform quality. You will also notice that this arterial line running to the transducer is very stiff. This takes away any pressure absorption as you could likely see if the line was equivalent to IV tubing. The line would “give” a little with each pulsation, which would decrease the true pressure of that waveform. The second port is often the flush solution line. There may or may not be a waste bag system attached within this line. I have also seen the waste bag system being a separate port by itself. The third port is traditionally the contrast line. You will notice that the ports are controlled by a stopcock handle, much like regular stopcocks that you may use (Figure 2).

There is some variation with these stopcocks, as well as the stopcocks on the manifold kit. They can be controlled by a “handles on” or ‘handles off” position. In other words, the longer tab of the stopcock can control flow by where the handle is. “Handles off” means that wherever the longer tab is pointing to, that line is stopped. Conversely, on the “handles on” stopcock, wherever the longer tab is pointing to, that line will allow flow.

Figure 3 shows what some call a “panic stop.” If you ever closely look at a stopcock, you will see that the holes that allow fluid flow are rather small. If you have fluid leak and don’t know where it is coming from, you can turn the stopcock in any direction to an “in-between’ position and all fluid flow will stop.

In some labs, when performing only a right heart catheterization, or if in a procedure where “dual” pressures are needed, you may see a manifold that is 2-port (Figure 4). In this manifold, the only ports are the arterial line and the fluid line.

The question at the beginning of the article mentions that the lab the person works at utilizes a manifold for femoral pressures, and a manifold for aortic pressures. I am not entirely sure of the purpose for using two manifolds for those pressures.

With “dual” pressures, requiring two manifolds, I think of valve analysis. When analyzing the aortic valve, you need to know the pressures on each side of the valve (left ventricle [LV] and ascending aorta [AO]). It’s possible to obtain the dual pressures either through two catheters or a dual lumen catheter (i.e., the Langston dual lumen pigtail catheter [Vascular Solutions]). Either case requires two manifolds and transducers to obtain the simultaneous pressures.

We can also see the simultaneous pressures when evaluating the mitral valve. In that case, we are looking for pressures from the LV and the left atrium (LA)/wedge. Additional resources on valve assessments utilizing dual pressures can be obtained from previous articles:

• Ask the Clinical Instructor: “Why does the physician sometimes use 2 catheters to evaluate a valve, and why sometimes only 1?” September 2010, https://tinyurl.com/CLDSept2010
• Ask the Clinical Instructor: valve assessments
• Part I: Assessing the aortic valve, April 2008, https://tinyurl.com/CLDApril08.
• Part II: Assessing the mitral valve, May 2008, https://tinyurl.com/CLDMay08.
• Part III: Valve interventions that can be done in the cath lab, June 2008, https://tinyurl.com/CLDJune08.

Sheath flushing generally occurs at the sheath itself. Perhaps the question was meant to address how you flush the catheter in the event you are only using a 2-port. This can certainly be a change if you happen to use a 3-port manifold with a waste bag, and you are used to flushing with a ‘closed’ system. With the 2-port system, there are extra steps: making sure to draw back and discard waste, as well as ensuring a “meniscus-to-meniscus” contact when connecting the syringe back to the manifold.

Please visit us at www.facebook.com\RCISREVIEW for weekly questions and answers on topics to prepare you for the registered cardiovascular invasive specialist (RCIS) exam or to just expand your knowledge of the cath lab. Questions are always welcome and each one will be addressed!

Response to June 2012: Exchanging sheaths and maintaining sterility

At the end of our June article on maintaining sterility when exchanging sheaths, I asked others to write in if they have a different methodology. Douglas Clemson, Director of Cardiac Services at Health Management Associates, Inc., in Tampa/St. Petersburg, Florida, was kind enough to share his method on Cath Lab Digest’s LinkedIn page. He notes:

“I drape the patient in the usual fashion after prepping with ChloraPrep (clorahexidine). Then I lay down a 3/4 sheet over the fenestration. Using a disposable scalpel, I cut the suture. Inserting the new wire, I remove the existing sheath, place it on the 3/4 drape and insert the new sheath. I remove the drape with the old sheath and the sharp from the field, and exchange gloves.”