I would imagine it stands for Licensed Nursing Assistant.
Funny, I started looking into the medical field when my field dried up, too. I'm a contractor in the computer field, and the BOTTOM fell out here in NC. I went 10 months between contracts, and had started taking continuing ed courses at a local community college.
I'm still taking continuing ed classes, and will continue getting actual prerequisites out of the way next semester. My girlfriend is an ex-OR nurse who is now a head nurse, and is a good resource for all my questions and concerns. It sounds like a good field, as long as you know what you're getting into.