How can a cat resist sedation via shot during constipation treatment

Hello, my cat, male, neutered age 7, is currently at the vet being treated for constipation. He's been there a little over 24 hours now. The vet called last night to tell me they are having trouble getting an exam done because he has resisted all attempts at sedation when they have given him the shot. He is actively fighting off the effects of it. They have tried multiple times and different sedatives. He has Feline Hyperesthesia Syndrome and has a history of resisting sedation. Usually they use a bit extra and can see him. He is a big cat, 20 lbs and a Maine Coon mix. Not overweight. Just very large.   But the vet said they were able to do an X-ray that showed no stool in his colon and his bladder is medium sized. They don't think he has a urinary tract blockage. I told the vet he did pee once since Thursday but has not pooped. He is vomiting. He was laying on his side in my bed growling and trying to poop. He pushed out a small hard rabbit poo sized piece. He has never tried to go outside the litter box before. The vet said it's possible he has a blockage closer to the rectum but unless they can do a rectal exam they can't tell.   What can I do? Can I ask them to keep him a few days so they can see he isn't pooping. They did give him a shot for nausea.

Hello, I just wanted to provide an update. The vet called me around 1 today to come get my cat. He was way too aggressive and they were unable to do anything more with him. They couldn't even get him back in his carrier. I ultimately just ended up updating his vaccines and the vet asked if I wanted them to send his blood work in since there wasn't anything else they could do for him. Since being home he peed once. He ate some wet food. I normally feed him dry, but decided to try wet because it does cause diarrhea sometimes so I'm hoping that at least triggers him to poop. He still hasn't gone. He's been sleeping since coming home.   I just don't understand how he is able to be so resistant to sedation. They tried multiple times with different sedatives and nothing worked. I'm so incredibly interested in cat behavior, beyond my concern about him so I really would love to learn more about if it's something that is common. Google searches have not been helpful at all in that regard. I also want to know how I can help him and make sure he isn't in pain and encourage him to poop.   I should add he drinks lots of water. He has a fountain and also likes to drink from the sink. And once or twice a week he does get a can of salt free tuna with 2 cans of water added to it. He doesn't get any human food at all and rarely gets treats. He is just extremely picky and won't eat them anyway.

Hello and first, I'm sorry that you're all having such a hard time.  Your cat is having a hard time - they sound ill, and also cross and sad and stressed, in the vets.  Many cats will withold pooh and urine in these circumstances, because they don't want to broadcast their presence with urine / poo marks when they feel threatened!  I imagine that you and the vet are anxious about this situation, too.   Sedation is always less reliable in pets whose blood is teaming with adrenaline.   However, if the vet keeps giving more and more sedative in a cat with an unknown illness, there is quite a high chance that when it does hit, it causes side effects or too deep sedation! - so there are limits to how much this can be attempted.   Norwegian forest cats are also big, with a high per centage muscle, and the required doses can be difficult to predict.   Personally, I have always found general anaesthetic to be much more reliable and also safer in the stressed cat, because the drug can be 'stopped' mid procedure and it gives better control of the airway.   More to follow

Furthermore, some veterinary practises are more 'cat specific' than others.   If cats use a separate waiting room to dogs (or even better, only cats are treated there), are kennelled in a quiet, calm place behind scenes, perhaps with pheromones.... if  litter-trays are hidden from the general gaze, and if they don't associate the building with stress, then cats often cope much better.  Many vets ask owners to leave, because cats pick up on their stress also.  I wonder whether there might be a local cat friendly clinic or specialist that you could be referred to? - as this could make the experience rather different.  More to follow

Hello, thank you so much for your response. It's actually a cat only vet that I take him too. He has been red flagged at many of the other area vets because of his aggression and they are one of the few left willing to see him. With me he's perfectly fine. But he just hates people so it's already hard for him to deal with a vet even when he isn't feeling bad. They had me just drop him off as an emergency because they were full and everything was done without me there. Since being home he is still just sleeping. But I know the vaccines can also make him tired too. He had peed a few times now but still no poo. But in the litter box it did sound like he had gas so maybe he will go soon. The vet wants me to call back today and let him know how he is doing. They did send him home with cerenia and gabapentin to give before his next appointment, but he already takes Gabapentin for his FHS so I doubt it will help much. Also he has been grooming himself so I think that's a good sign at least. I mean I know it's something they can do when stressed but I don't know how to explain it, but I know his body language and he seems ok. The way he is grooming himself. He isn't doing it aggressively like with FHS but more like he does when he's relaxed and laying on the pillow with me. I just hope whatever it was will pass soon and he is ok. I would hate to stress him out even more by him returning to the vet.bi guess I just need to wait and see what the blood work says and hope he goes poop soon.

Thank you for the update.  You sound to be in the uneviable position of trying to balance your cats' directly conflicting physical and mental needs.   Im pleased to hear that he seems more at ease in himself now, although obviously i am in no position to assess that.  I wonder whether phone consulting with your vet might be useful as a first point of assessment, so that as little as possible is missed and most of the conulting happens before your cat gets stressed.... either way, we would always reccommend keeping in close contact with them if you have any concerns.   I hope that you manage to get to the bottom of things.