Thank you everyone who posted ! This is a long post post for those who are interested in how our situation all panned out. This all started about 4 yesterday afternoon when Digger become obviously unwell and collapsed and finished when we were able to led him home about 1:30 this morning. It was like a miracle - about 10:30 the vet advised us that there was nothing more she could do and we should consider putting him down. We didn't feel that it was at that point ourselves so we persisted.
We live in a fairly remote area of south east Queensland and she had been conferring with the top horse vet in Queensland via phone. The best help we got was from an old horse dealer from whom we purchase our horses. Whoever said it was shock is right on the money.
Don't know if anyone else has clydesdales and have attempted to tube them but the vet had to use her smallest tube and he was still not impressed especially after having been wormed in this manner earlier in the day. I'd be interested to know if clydesdales are know to have this issue as all three of our's needed the "foal tube".
Anyway she eventually was able to insert the tube and drench him.
We also have previously had wonderful success with homeopathic remedies when a homeopath lived next door(unfortunately that is years ago now). I still had some drops for shock which we gave him just a little while before she was able to drench him. Don't know if that was coincidence but I tend to think not since she had been trying for 5 hours prior to this.
Unfortunately, last night was a bit of a blur and I can't tell you which worming mix she used but I will post the brand when I find out from her later today - we definitely need to know so we don't ever let him have it again!
This morning Digger appears to be fine and everything seems to be moving through him fine- his droppings are full of worms - he must have had a large worm burden.
So thanks again for all your feedback, sorry we were not around on line long enough to respond but we couldn't wait any longer and had to get back to the horse beside the road.