One of mine ended up in the Dick vet with an impaction colic that ocurred in the freezing cold weather when she wouldnt drink and was kept in.
She was given all the routine stuff at the yard by injection, but the vet didnt tube her.
She went to the vet college and was kept in, they starved her and put an iv in gave pain killers and several large bags of fluid were put in over a 4 day period to help her system cope and flush the impaction through, by flooding her with fluids .she was very sore for a good few days, lost a lot of weight but did recover
Im sending healing vibes and hope your horse recovers