You’ll want to use one of the above libraries to manage node. I use nvm.
THEN you can update and install versions of node with nvm, such as $ nvm install 6 and then $ nvm use 6 every time you’re in that project. In older projects, where you might use older versions, you’d do $ nvm use {version}
Without one of these version managers, you might have to re-build or something like that. Usually the only thing that breaks is node sass, which I usually can fix by doing npm rebuild node-sass.
Let us know how it goes.