Thank you for your email. That doesn't sound like normal behavior, and animals, like people, can have clotting issues after a major surgery like that. Whether it is pain, or whether it is something else, he should probably be reassessed today by your veterinarian. They'll be able to check his pulses, and his breathing, and prescribe him more pain medications if he is in that much pain. I hope that he is okay.
Without an examination and possibly a blood test, it is difficult to say what the cause for Buddy’s symptoms are; however eclampsia is a possible cause and would require immediate attention from a Veterinarian if this is the case. I am not sure about veterinary care in Jordan but I know that there is a veterinary school in Al Ramtha, Irbid, Jordan if that is close to you if you require veterinary care. https://wagwalking.com/cat/condition/eclampsia- www.just.edu.jo/FacultiesandDepartments/FacultyOfVeterinaryMedicine/Pages/Default.aspx
The Chausie was developed from hybrids of the Jungle Cat (Felis chaus), the largest species of the genus Felis, found in Asia. They can grow up to three feet long and weigh 35 pounds, but are generally around 18 pounds. Like the hybrids that developed into the Savannah and Bengal breeds, the males of the first few generations are usually infertile, and the F4 and F5 are considered truly domestic and suitable for cat shows. TICA classifies the Chausie as a championship breed.
Russian Blues have a tolerant nature toward children who treat them kindly and respectfully. They will even put up with the clumsy pats given by toddlers, as if they recognize that no harm is meant, and if necessary they will walk away or climb out of reach to escape being bonked on the head. That said, the patient and gentle Russian Blue should always be protected from rough treatment, so always supervise very young children when they want to pet the cat.
Lethargy and increased respiratory rate are not specific symptoms as they are shared with many conditions; however I’m concerned that they are a common sign that an animal is in pain, but without examining Marilyn I cannot say whether she is in pain or there is another cause for the symptoms. You should visit your Veterinarian for an examination to be on the safe side especially if this has been going on for a day or more. Regards Dr Callum Turner DVM