So, a really early email?
I'd probably see the sent time, think "he's been on the lash all night" and mentally decide you were finished when you next bothered to show up.
Whilst sympathetic to your position, I'm afraid that for me...
"I’m fine myself, but spent all night supporting her and don’t feel I’d be much use today, as I am exhausted. I’m going to catch up on sleep, so will not call to talk on this occasion."
...sounds a little bit "the dog ate my...