If you don't have a PR card, you'll need a Permanent Resident Travel Document (PRTD) to travel back to Canada. I am not sure what the process for this is, or if they are even processing it. I know that this document is supposed to be issued by the local visa office of what ever country you visit.
You might have seen an email address in your CoPR asking you to email them if you're not in Canada. If I were you, I'll email them and say that you have to leave Canada because of a medical emergency, and ask if they can process the card faster, or what they advise you do.
Good luck, and I hope everything works out for you.