Can you tell me in what way you find it unfeasible? I'm not saying it isn't impractical, or that it isn't less than ideal, only that it's not physically impossible to accomplish it adequately with the proper tools, time, and training.
Thanks.
No, it is not physically impossible to accomplish. But that is not the same thing as being practical (feasible = practical).
Picture the process of donning sterile gloves, gown, and mask, opening a sterile CVC line kit, cleansing the site, prepping the line, placing the line, flushing all 3 ports of the line, and placing a sterile dressing, all without breaking sterility. Remember, if at any point, anything that should be sterile touches something that is not-sterile, you start over. That means no touching anything at any point during the process, including the patient. And this is all done at the scene, because there is definitely no doing this while moving towards the hospital.
Now think about the time involved here. Even if everything goes well, you are looking at a minimum of 5-10 minutes of prep time alone. In the hospital, the process of placing one of these can easily take 30 minutes or more. And that is by people who do them all the time and have a lot more room and help than you have in the ambulance.
The places where I've done these (and I would guess, most other places that do these prehospital), we simply didn't bother with all that. You open the kit and prep your equipment, put on some sterile gloves, clean the site, and make the stick. You can justify this occasionally with the fact that in some patients in some situations, the need for central access outweighs the risk of infection. But I think you are talking about a really, really small population here, and in most cases we are just exposing the patients unnecessarily to the risk of a difficult procedure in the field and introducing pathogens directly into the central circulation. Not good.
The other thing is indication. Why do you need a central line, anyway? The most common indication for them in the hospital is in patients who are getting multiple infusions (pressors, abx, etc) or caustic meds (chemo, etc) that irritate peripheral veins.
Lastly, CVC's are quite often not easy, even in the best circumstances. US definitely makes them easier and safer, but now you are talking about adding another significant expense and training burden just to do an occasional CVC?
For a program that does a lot of transports of really sick patients, AND has more experienced than average clinicians, AND has a good way to train on them regularly, I think it may make sense to have CVC's in their skills repertoire. But you are mostly just talking about helicopter and some ground CCT programs.
Bu generally speaking, CVC's are just impractical to do in EMS, and very rarely necessary. Especially with the advent of the IO devices we have now.