Sorry to hear, I'm going through the same with my 16 yr old cat. We have pushed it back twice now.
Spent last night at the animal emergency center.
We got home yesterday to find she tore her bed apart,and later she starts panting hard and shaking and yelping when she moved. Fear that she ate some of the foam we took her in,after X-rays we find she is compacted from mouth to ass. They kept overnight and did two enimas. Comes to find out she was full of chewed up acorns. Full to the point it hurt to get up/ to lay down. I thought we might lose her,but thank God she's strong and she passed it all. Now we are in the wore out stage.
Sorry for ranting,and sorry for the decision you have to make.
STR8