I'm guessing there's a high chance he is going to be paralized for the rest of his life. I'm very sorry.
There's only one thing you can do - rest, relax, and reassure him. as >>3 said I would be very frustrated that I would have to rely on my fiance for everything if I was in that situation, as my career and whole life would be upside down instantly. (Men need independence) Emotional shock is nearly impossible to overcome, but at least you can try your best.

If it physically and emotionally tires you out, then maybe you can "relax" a bit so that it's easier on him and you too? If you work up too hard and something happens to you, who's gonna take care of him then?

I normally don't say this but good luck, I hope everything works out for you and your fiance.