Interesting question. I think I'd actually use the infinitive instead for that – if I wrote a list of things I needed to do, for instance, I'd say hålla mig vaken. Somehow håll mig vaken sounds like a command to someone else.

For me, I would say "Håll dig vaken" and just talk to myself in 2nd person.

You specified yourself why "somna inte" is not an accepted answer. While it might mean the same thing pragmatically, it does not semantically.