I am a veterinary anesthesiologist so I can answer any questions you have about your kitty's anesthesia.
There are no medical contraindications to any anesthetic technique in CH. However, I think there are "experiential" (if that's a word;-)) considerations, particularly with respect to recovery from general anesthesia. My preference would be to use short-acting or reversible techniques. Inhalant anesthetics such as isoflurane have the advantage of being very short-acting and recovery is rapid once the inhalant is discontinued. In my own CH kitties, I have induced anesthesia either with propofol (a short-acting injectable anesthetic) or isoflurane or sevoflurane by mask. For anesthetic maintenance gas anesthesia is best, maintaining anesthesia with injectable anesthetics for a spay would require doses that would prolong the recovery period. The gas should be delivered by an endotracheal tube rather than a facemask. Anesthetized animals, with or without CH, cannot protect their airways and are at risk for aspiration and/or airway obstruction. I would also recommend the use of an analgesic (pain control medication) and it is best used as a premedication, ie., given prior to the surgical procedure. Usually, this is a narcotic. The doses used for pain control are safe. Occasionally some cats have some behavioral changes when they are given narcotics which can be sedation, euphoria, or dysphoria. These are temporary, they go away as the drug wears off. If the drug effects are unacceptable the narcotic can be reversed.
To dispel any myths...gas anesthesia is not safer than injectable anesthesia but it does offer a number of advantages in many circumstances. In CH kitties rapid recovery is the primary advantage. It is not dangerous to use ketamine in CH kitties but I expect recovery from ketamine to be a very unpleasant experience for a kitty that has difficulty with balance and coordinated movement. Ketamine has a fairly long duration which gets very long if it is used intramuscularly as an anesthetic.
I saw one mention of the use of Dormitor/Antisedan. Dormitor (medetomidine) is a sedative/analgesic that can provide profound sedation and short-term analgesia. It is reversible with Antisedan (atipamezole) which makes it very useful for short procedures. It is not really an anesthetic so I would not recommend it for a spay which is abdominal surgery. I think it is suitable for castrations in young, healthy animals.
If you have any other questions feel free to ask.