tpvets_logo.jpg (2726 bytes)TOA PAYOH VETS   Blk 1002, Toa Payoh Lor 8, 01-1477, Singapore 319074   Tel: 6254-3326, 9668-6469, 9668-6468.  
20 May, 2015
  Focus: Small animals - dogs, cats, guinea pigs, hamsters, turtles & rabbits

Injectable Anaesthetic Procedures in
an animal shelter and in Toa Payoh Vets

Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS
First written: 8 May 2008
Updated:  20 May, 2015

PART I. Sharing Knowledge with Veterinarians
Anaesthetic Procedures in NANAS

Sunday, Apr 27, 2008
I visited NANAS (Noah's Ark and Natural Animal Sanctuary), an animal sanctuary in  Johor on a fine cloudy humid Saturday afternoon of April 26, 2008 to know more about animal shelter medicine.  I had the opportunity to study the effects of Zoletil combination being used.

To share knowledge with others working in dog and cat shelter medicine in other countries via the world wide vet, I have recorded below the following effective anaesthetic regime in NANAS. It is an alternative to gas anaesthesia and is less expensive. The dosage is as follows:

1. Zoletil 50 (Virbac) white powder is present in a bottle.
Tiletamine 125mg, Zolazepam 125 mg. I refer to this as the Zoletil bottle.

2. Xylazine 100mg/ml in a bottle.  Put 2 ml of this into the Zoletil bottle.

3. Ketamine 100mg/ml in a bottle. Put 8 ml of this into the Zoletil bottle.

4.  The bottle now contains a clear solution of 10 ml.  This combination is used as shown below:

1-2 kg.  0.15 - 0.18 ml IM
Bigger cats  0.2 ml IM.

I noted that the duration of surgical anaesthesia was more than 30 minutes in cats 1-2 kg being spayed. The tongue is pulled out as a routine to prevent food being vomited during surgery. Such food  gets into the lungs and cause death by inhalation pneumonia.  Surgical incision is midway between umbilical scar and pelvic brim in the young cats being spayed.  

In a dog of around 15kg , a 0.8 ml IM permitted surgical anaesthesia of around 30 minutes in one case of conjunctival growths being removed. As the dog showed signs of waking up (eye reflex and mouth clamping), a 0.6 ml IM was injected. The dog was under surgical anaesthesia within 1 minute.  Topping up may be required at Animal Shelters.

In NANAS, the following were given for cats and dogs.
1. Tolfedine 4% (tolfenamique 4g) at 0.5 ml IM or SC for cats after spay and neuter. A pain-killer.
2. Amoxicillin (Longamox) at 0.5 ml SC for cats after spay. An antibiotic.  

PART II. Sharing Knowledge with Veterinarians
Anaesthetic Procedures in TOA PAYOH VETS, SINGAPORE.

Recently, some owners asked me why there were no antibiotics given after sterilisation of their male cats. Generally, no pain-killers or antibiotics are given to your male and female cats post-operation from Toa Payoh Vets for cases operated by Dr Sing as experience indicates that they are not necessary. Many owners find it hard to give oral medication to cats. 

In big dogs, non-steroidal anti-inflammatory pain-killer and antibiotics may be prescribed after spay.   Typical anaesthetic regimes for cats living and born in Singapore are shared with fellow veterinarians by Dr Sing Kong Yuen.  Some vets may seek such internet information.  They are as follows as at Feb 1, 2009:

For Dr Sing's cases at Toa Payoh Vets, the anaesthetic regime is usually:

Xylazine & Ketamine injectable anaesthesia are used for cats. Dosage is xylazine 20 mg/100 ml at 0.2 ml mixed with ketamine 100 mg/ml 0.8 ml in 1 syringe, IM injection. This dosage is most effective for a cat around 2-4 kg. Onset of anaesthesia is 2 minutes after IM injection in most cases. Duration of surgical anaesthesia is at least 30 minutes.

For fat cats or young ones less than 2 kg, half the above dose is sufficient but surgical anaesthesia is less than 10 minutes compared to 30 minutes in above full dose. If necessary, isoflurane anaesthetic gas at 5% is given by mask for one minute to effect to complete the surgery.
Xylazine & isoflurane gas anaesthesia or gas anaesthesia alone are usually used for dogs by me as I find them to be most effective. I want the patient to wake up within 1 minute at the end of surgery. For injectable anaesthetics, the patient sleeps a long time and this has advantages and disadvantages. Many owners are happy that their pets are already awake after surgery. 

Please note that the xylazine solution I used is 5X less potent than that used for the Zoletil combination at NANAS. It is 20 mg/100 ml xylazine, not 100 mg/ml which is the bottle usually used for horses

Toa Payoh Vets do use Domitor, Antisedan, Zoletil anaesthetic protocols as well.  Experiences are recorded in other webpages.

UPDATE ON MAY 20, 2015. I found that the following formula is effective and safe:
For a healthy and young dog, 10 kg. Domitor 0.4 ml + Ketamine 0.5 ml
IV in one syringe.
Duration of anaesthesia is around 20 -30 minutes
Onset is 5 minutes.
No need for isoflurane and O2 gas top up if the spay can be completed within 20 minutes

For old dogs, 50% of dosage with isoflurane gas top up if necessary
For a 16-year-od sick dog, 10% of dosage for short sedation is safe generally.

In NANAS, I observed that the incision begins at the middle 1/3 area between the umbilical scar and the pelvic brim. Cats I observed were around 6 months of age. The cat's tongue was pulled out to one side of the mouth to prevent vomitus from being swallowed. Bladder was expressed so that the bladder would not be nicked. 

At Toa Payoh Vets, I incise at the cranial 1/3 area, at 1 cm from the umbilical scar in dogs and cats. This position enables me to easily access and ligate the swollen "on-heat" ovaries easily, especially in dogs. Palpate for the full bladder and express it free from urine before spaying. Be careful not to nick the full bladder. Seldom do I encounter a full bladder at this location but there needs to be care in incising the linear alba in case the bladder is just below. Palpate the abdomen first to check for the bladder and express the urine.

Singaporean stray cat

PART III. Sharing Knowledge with Veterinarians
Anaesthetic Procedures in one Singapore veterinary practice

I have insufficient experience with the following anaesthetic regimes but am recording the procedures based on information provided to me by one vet with considerable experience in the following anaesthetic protocol without the need to use gaseous anaesthesia as at Feb 2009.

1. Xylazine 20 & Ketamine 100.
1.1  For example in a Jack Russell, 5 kg dog.  1-5 years old.
Xylazine 20 at 0.4 ml IV, Ketamine 100 at 0.1 ml IV.
Separate syringes. Then top up with Zoletil IM injection if necessary

1.2  For example in a Jack Russell, 6 kg dog.  1-5 years old.
Xylazine 20 at 0.4 ml IV, Ketamine 100 at 0.2 ml IV.
Separate syringes. Then top up with Zoletil IM injection if necessary

1.3  For example in a Jack Russell, 10 kg dog.  1-5 years old.
Xylazine 20 at 0.8 ml IV, Ketamine 100 at 0.2 ml IV.
Separate syringes. Then top up with Zoletil IM injection if necessary

1.4  For example in a Jack Russell, 15 kg dog.  1-5 years old.
Xylazine 20 at 1.3 ml IV, Ketamine 100 at 0.2 ml IV.
Separate syringes. Then top up with Zoletil IM injection if necessary

1.5  For example in a Jack Russell, 20 kg dog.  1-5 years old.
Xylazine 20 at 1.6 ml IV, Ketamine 100 at 0.4 ml IV.
Separate syringes. Then top up with Zoletil IM injection if necessary

1.6  For example in a Jack Russell, 2.5 kg dog.  10 years old.
Xylazine 20 at 0.2 ml IV, Ketamine 100 at 0.05 ml IV.
Separate syringes. Then top up with Zoletil IM or IV injection if necessary

2.  TOPPING UP WITH ZOLETIL when the animal shows signs of movement and recovering from surgical anaesthesia from the xylazine/ketamine combination.
Zoletil 100 powder. Add 10 ml diluent. The solution is equivalent to Zoletil 50 now.
Use 0.1ml Zoletil 50 IM for small breeds
Use 0.2 ml Zoletil 50 IM for big breeds (20 kg) 

Topping up with Zoletil IM in the above protocols is effective. The above is useful for vet surgeries without gas anaesthesia or in field work. It is much more expensive to install gas anaesthesia in certain situations and I hope the above information will be of use for practitioners. Obviously, the older dogs and cats will need half the dose and there is a need to be very careful with injectable anaesthetics. It may be best to refer to other vets with gas anaesthesia facilities, in the best interest of the animal.


1.3 kg. Around  4-5 months old. Neuter.
0.1ml Zoletil 50 IM. Wait 5 minutes. Give 0.05ml Domitor IV ear vein, 27G needle.  Effective general anaesthesia. Rabbit takes >1 hour to wake up. No problem. No need for Antisedan. 

2 kg. Around 8 months
0.1ml Ketamine 100 and 0.05ml Xylazine 20 IV in one syringe gave general anaesthesia >60 minutes for spay.

2.5 kg. Around 1 year
0.1ml Ketamine 100 and 0.1ml Xylazine 20 IV in one syringe gave general anaesthesia >60 minutes for spay. Femoral vein used. 

Cat house in animal sanctuary, NANAS. Toa Payoh Vets
A beautifully designed cat house in NANAS. Waterfront views and wooden floor boards.
Part of NANAS cattery has an open balcony concept. Toa Payoh Vets
An open area permitted cats to get out and enjoy the views and sun.
NANAS - no-kill animal shelter for homeless cats. Toa Payoh Vets.
I introduced a 2nd-year Murdoch University vet student who loves cats to visit NANAS with me so as to expose her to animal shelter medicine. Would she set up a cats only practice in Singapore? Would such a practice be feasible?

PART IV. Sharing Knowledge with Veterinarians - a Singapore PDSA?

A stray male cat after neuter by Dr Sing in 2003 using xylazine 0.2 ml IM and gas anaesthesia at that time. Clipped left ear tip in stray cats indicate they have had been sterilised. But stray dogs do not get such treatment and it is difficult to know the status of whether the female stray has been spayed or not. 

Despite a first-world country status, Singapore unfortunately does not have a charitable foundation like the People's Dispensary for Small Animals (PDSA) in the UK to cater to the treatment of sick street cats and dogs for owners who can't afford veterinary treatment.

I saw practice with a private vet in in England in the 1973 during my 4th year at Glasgow University. He spent 1 day a week at the PDSA to offer his veterinary services. What stuck in my mind was the arrival of a driver/owner of a Jaguar car. He brought in a dog for free treatment. One presumes that the Jaguar car owner does not need the help of the PDSA.    

It is hoped that one day, one of our successful entrepreneurs will set up a Singapore PDSA to help owners who can't afford veterinary attention for their pets. 

2 well loved fat cats of Singapore neutered by Dr Sing. Toa Payoh Vets
Xylazine: ketamine injectable combination for the 2 fat cats of around 5 kg neutered by Dr Sing. Dosage was halved for cats 2-3 kg. Surgical anaesthesia was around 5 minutes as the dosage should be higher. Neutered around 5 minutes after injection. No topping up was needed in this case. If necessary, I would use gas anaesthesia for 1 minute. That would be sufficient to provide surgical anaesthesia.
Many Singapore stray cats are sent to the vet for sterilisation by volunteers. Toa Payoh Vets
For this pregnant 4-kg cat, the xylazine: ketamine at 0.2 ml:0.8 ml IM (usually given to cats 2-3 kg) permitted excellent surgical anaesthesia of around 30 minutes for spaying.
Many Singapore stray cats are sent to the vet for sterilisation by volunteers. Toa Payoh Vets
Dr Sing's incision for spaying of cats is normally 1 cm caudal to the umbilical scar. The incision length is 1 cm if the cat is not pregnant. In this case, it is longer as the womb is much larger due to the presence of foetal lumps. Ligate the uterine body in this pregnant cat two areas although there should be no slippage of sutures with one ligation. 
Spay at 5 months before the cat gets pregnant. Toa Payoh Vets
A street cat weighing less than 2 kg. The xylazine: ketamine dosage was less than half of that used for cats 2-3 kg. The skin incision is around 1 cm. Two horizontal mattress sutures are usually given. 
5-month-cat spayed. Remove plaster in 10 days if the cat has not done so. Toa Payoh Vets
How young should your cat be spayed? If it is a street cat, animal activists get them spayed as young as 4 months.

For your pet cat in Singapore, I would advise 6 months so that her private parts can develop into adult size. If she caterwauls (meowing loudly non-stop), wait till she stops caterwauling to get her spayed as it will be bloody doing it during this stage.

The above cat in Singapore  was spayed around 5 months of age by Dr Sing Kong Yuen.

Dwarf Hamster, Male, 2 months. Neuter to keep female company, without breeding. Toa Payoh Vets
1962-67. Neutering a 2-month-old hamster at Toa Payoh Vets

Cats or Dogs


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All rights reserved. Revised: May 20, 2015
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