Further to the earlier answers, I'd be interested to know why you feel MISRA would not be suitable?
Yes, I accept fully that MISRA-C:1998 was titled and targeted at Vehicle Based Software but the second edition in 2004 has already changed to Guidelines for the Use of the C Language in Critical Systems, and as such MISRA is applicable to all industries - and (for example) is a reference document for the Joint Strike Fighter coding standards.
MISRA-C has most definitely been adopted by the nuclear and medical industries.
And (putting my MISRA Working Group member hat on for one moment, although I'm posting in a personal capacity only) if there are any specific issues relating to MISRA-C's application to medical devices, then I'm happy to discuss here and/or raise with the team.