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      Date:   11 December, 2010  
Focus: Small animals - dogs, cats, hamsters, guinea pigs & rabbits.

Toa Payoh Vets Clinical Research
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Injectable anaesthesia in cat spays
Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS
11 December, 2010 
Be Kind To Pets
Veterinary Education
Project 2010-0129
2 stray cats along streets picked up by a young couple who has hamsters too.
Cat 1 - Black & White, Female, around 8 months, 2.6 kg. Vaccinated her as a kitten and so she would be at the correct age.
Cat 2 - Grey striped, Female, around 9 months, 2.9 kg. Signs of one birth based on changes in mammary gland area were seen.

"Both make a lot of noise (caterwaul) for 5 the past 5 days straight before I bring them to you. Want to go out of the apartment!" the young man said to me. "Neighbours do not complain as they have cats too." Bought into surgery on Thursday Dec 2, 2010 at night.

Friday Dec 3, 2010

Spayed by me from around 10 am. Cat 1 done first followed by Cat 2.

ANAESTHESIA by injection
Both given xylazine 2% at 0.15 ml mixed with ketamine 100 at 0.6 ml totalling 0.75 ml in one syringe IM. I noted that Cat 2 received around 0.70 ml IM due to some movement as my assistant did not gripe the scruff of the neck well. Cat 2 was more active.

5-10 minutes after anaesthetic injection.
Cat 1 - excellent surgical anaesthesia.
Cat 2 - was moving even at 10th minute. "She is heavier," my assistant said. Isoflurane gas for one minute by mask at 5% was sufficient to bring her down to surgical anaesthesia. I was able to spay.

Cat 1 - peed before surgery onto surgical drape. Hooked out the left ovary at 2nd trial.
Cat 2 - bladder full but could not be expressed manually. I did not persist. Just hooked out the ovary. Took several trials as the bladder was obstructing. Uterine body 5 x larger and wider than that of Cat 1. Yellow corpus luteum seen prominently and larger. Why? Took pictures. Both cats not let out of apartment and so would not be pregnant.

Owner wanted to take the cats home one hour after surgery. I advised him to let the cat rest in the surgery as they may get choked and die during transport on the way home.

Went home at 8 pm Friday Dec 3, 2010. Both cats at home vomited when they tried to eat. Cat 1 was more groggy. Both were not so active.

Saturday Dec 4, 2010. 11 am. Owner phoned me.
1. Cat 2 was back to normal, but Cat 1 was not so active. Running here and there.
Cat 2 had licked off her plaster. I advised putting on another one or wrap a bandage round her.

2. 2/0 absorbable suture will dissolve. No need to return for stitch removal. Only one skin horizontal mattress suture. Cat 2 may lick it off but owner says she does not bother with the stitch. She started to eat at 11 a.m, but not Cat 1.

FOOD - Dry food from Royal Canin
Wet food from Whiskas
WATER - freely available.

3. Post op antibiotics. Baytril PO x 1 tablet each at 1/4 tab per day for 4 days. I don't advise e-collars in cat spays. Plaster usually sufficient. I use only one suture pack of 2/0 per cat. The muscle cut was closed with just 2 interrupted sutures at 5 mm apart. The skin incision was approx 1.2 cm from umbilical scar. The incision of skin was around 1 cm. I asked the assistant to untie the front legs and lift up front lower half of Cat 1 if I could not hook out the right uterine horn after ligating left ovary. In Cat 2, there was no problem.

I had my assistant record the start and end of surgery. For Cat 1, it was 7 minutes. Smooth and easy. For Cat 2, it took much longer due to full bladder, abdominal fat which I cut off a piece and extra large uterine bodies.

There is no need to insert another layer of subcutaneous stitching in my over 20 years of spaying cats. However, some vets deem that necessary as the university professors teach this method to close the dead space and prevent haematoma. However, they also stitch the skin incision.

Some cats and dogs do get irritated by this extra S/C layer of stitching and lick the wound vigorously. You will see a red inflamed area in some cases. Simple method is best. Less is best.

It saves time, money (some vets use 2 packets of sutures to spay a cat or a small breed dog) and less painful irritation to the pet. Each vet has his own style. It is hard to change mindsets esp. if University lecturers teach S/C layer to close a spay wound or "concealed" stitching.

As for injectable anaesthesia, xylazine 0.2 ml + ketamine 0.8 ml in one syringe IM is safe for cat spay at 3-5 kg bodyweight. At 2-3 kg, I use xylazine 0.15 ml + ketamine 0.6 ml as in the above two cats. The duration of surgical anaesthesia is sufficient if you start surgery 5-10 minutes after the IM injection and can complete your surgery in 10 minutes as in Cat 1.

Topping up can be done using isoflurane gas at 5%  by mask for <60 seconds to effect or by injection of the combination. I don't use the latter method although I have seen it done using small doses e.g. 0.1 ml of the combination. The above applies to Singapore cats. Each country has its own cat sizes and climate and the dosage may vary.  


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tel: +65 9668-6469, 6254-3326 
Be Kind To Pets
Veterinary Education
Project 2010-0129
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