Manometry, or measuring the pressures of a vessel or track, is the gold standard for confirming the venous placement of central venous catheters. Multiple studies have shown it to have a 100% success rate at preventing arterial cannulation when performed correctly.
The question is, how can you perform manometry using the kits and equipment available at your institution?
#1 The T-Piece Approach
I have personally used this technique, and when your system is designed for it, In my mind, it is the gold standard.
This article in Anesthesia and Analgesia details the technique, but I’ll review it here.
Pro: you get an accurate pressure waveform at your needle’s tip before inserting your wire. It also minimizes the disconnections and reconnections that can be troublesome on challenging central lines.
Con: you need a system designed to use it. The three main components are the T connector from Smiths Medical, 50-60cm of pressure tubing, and a transducer attached to a monitor. This is great in the OR, where you can have a consistent environment. For a central line on the floor, not so much.
#2 Transduce Your Needle with the Raulerson’s Syringe
This technique is only available for kits that contain a Raulerson’s Syringe. The equipment needed includes a steel needle, a Raulerson’s syringe, a transduction probe, and transduction tubing. You access the vein in the usual manner, then to confirm the venous placement of your needle tip, you insert the transduction probe in the back of the Raulerson’s syringe and allow a column of blood to fill the tubing before you raise the end of the tubing to watch the column of blood fall.
Pro: you minimized the disconnections needed to transduce the needle.
Con: Although this technique minimizes disconnections, the length of the needle, plus Raulerson’s syringe, plus transduction probe and tubing, makes it very difficult to keep this needle in the vein without moving it.
#3 Transducing the Angiocatheter
I saved this technique for last, but it is my preferred technique for IJ central lines. The difference with this technique is that you access the vein with the angiocatheter and not the steel needle.
To learn more about using an angiocatheter, check out our post comparing a steel needle to an angiocatheter to obtain venous access for your central line.
Pros: quick, you don’t have to hold the needle hub perfectly still while transducing.
Cons: hard to thread angiocatheters in hypovolemic patients and patients with a lot of adipose tissue between the skin and the vein.
In summary, there are many different ways to perform manometry. The variety of techniques and the proven track record of reducing arterial cannulation to zero should make this a standard part of your central venous catheterization routine.
- Bowdle, Andrew MD, PhD; Kharasch, Evan MD, PhD; Schwid, Howard MD, PhD. Pressure Waveform Monitoring During Central Venous Catheterization. Anesthesia & Analgesia 109(6):p 2030-2031, December 2009. | DOI: 10.1213/ANE.0b013e3181bea01d