Friday, August 5, 2011

531. A 14-year-old Chihuahua has a big breast tumour - IV anaesthesia

It is a difficult decision for the mother and daughter when the beloved 14-year-old Chihuahua had a big breast tumour. To operate and risk her dying on the operating table from anaesthesia or not to operate?

Or just wait and see. But the tumour on the left side of the mammary area had grown bigger. The other tumour on the right side had been excised by me just 2 months ago. The Chihuahua had survived the anaesthesia. Now, another tumour had popped up.

They came on a Saturday morning. Dr Jason Teo was on duty as I don't work on Saturdays. I happened to pop into the Surgery to check on a dwarf hamster with a very itchy face and they saw me. As the dog had eaten, Dr Teo could not operate on the same day and so I scheduled to operate on Sunday after the owners were well advised. "Must sign the form," Dr Teo reminded me quietly. This is the informed consent for surgery. I didn't ask them to sign a form although my associate vets do. I usually speak at length on the dangers of anaesthesia to make sure the owners are aware of what they are doing. Their pet may die under anaesthesia and will not be alive once they go to the operating room. Many times they understand. Some don't want to proceed with the surgery and go home.

Much depends on trust built up over the years but getting the owners to sign an informed consent for surgery and anaesthesia is wise and is practised by surgeons in the Singapore hospitals. To avoid nasty allegations of not being informed of the risks and alternative options by unhappy owners.

So, on a fine Sunday morning of July 31, 2011, I operated with much fear of anaesthetic death for this old companion who would be having her 3rd anaesthesia in 3 months. The second one was for the swollen right breast. The same one. Brown liquid dripped out from the nipple of this breast and the whole length of 5 cm was swollen. Antibiotics were taken and now the breast tumour had consolidated.

This time I used IV anaesthesia. Just sufficient to last for the surgery of less than 30 minutes and no more dosage. Just what is an adequate dosage of domitor and ketamine for IV anaesthesia for a very old dog? This is based on intuition and experience.

I have a domitor and ketamine IV dosage chart on my operating room cabinet which I refer to. This chart is shown in this webpage for the benefit of vets who need an alternative to isoflurane and oxygen anaesthesia.

MY CHART HAS THIS GUIDELINE
DOSAGE OF DOMITOR AND KETAMINE FOR A NORMAL HEALTHY YOUNG DOG 10 KG
FOR 30 MINUTES OF SURGERY

DOSAGE GUIDELINE
CALCULATED DOSAGE
10 kg, healthy young dog
Domitor 0.4 ml. Ketamine 0.5 ml = 0.9 ml in one syringe IV. No need isoflurane gas top up.
This Chihuahua is 4 kg. If she is young and healthy, the formula should be: Domitor around 0.15 ml + Ketamine 0.20 ml IV = 0.35 ml

DOSAGE GIVEN

Very old dog. Dosage should be much reduced. I gave the following much lower dosage:
Domitor 0.05 ml + Ketamine 0.15 ml = 0.20 ml in one syringe to be given via IV drip. I gave atropine 0.3 ml IM.

This formula worked effectively as it gave me around 30 minutes of surgical anaesthesia. The dog lifted her head just as I completed the last stitch. But she was drowsy. So, I gave her the antidote, Antisedan IM. She woke up within 2 minutes as fresh as a daisy. She went home 2 hours later. As the daughter now is an adult, she paid the bill. "No need to do histopathology if you don't want to," I said so as to reduce her cost. I had not asked for blood test. She did not want histopathology this time. The first time, the right breast grape-like tumours were benign adenomas and the blood test were normal for this old dog.



IV drip is advised for long surgeries. Domitor + Ketamine IV at the correct dosage and in healthy dogs give excellent analgesia without the need of isoflurane gas top up. Some countries may have difficulties getting isoflurane vaporisers and isoflurane and IV anaesthesia is an alternative option






Drowsy but is awake at the last stitch
Antisedan injection wakes the dog up fast
Surgery record for knowledge management
Although spayed dogs are said not to get breast tumours, there are a few that will get breast tumours after spay. There are some reports saying that female dogs spayed at less than one year of age will have lower chances of getting breast tumours but I don't find any scientific research to substantiate this. When was this dog spayed as I did not think it was done by me.

"When was this dog spayed?" I asked the daughter who has blossomed into a handsome looking tall lady.

"When I was in JC (junior college)," she put a finger on her chin to think. "It would be in 1998. She was 5 years old. Now, she is 14 years old. 8 years sure had breezed by and gone with the wind. The daughter now becomes the paymaster and the mother must listen to her. Still both bore the responsibility of giving the informed consent. The mum wanted me to operate although Dr Teo would be able to do it. So, that was how I landed with a surgery on a bright Sunday morning. It was a happy ending. But the more I do such risky surgeries, the more the minefields of deaths on the operating table will be stepped on.

So, I will prefer my younger associate vets to shoulder the heavy responsibilities of difficult surgeries and high-risk ones. That is the advantage of team work. There is just no escaping from the jaws of deaths for high-risk surgeries. It is a matter of statistics and probability when more of such cases are done.


updates and more images at:
http://www.sinpets.com/F5/20110806domitor-ketamine-dosage-Singapore-ToaPayohVets.htm





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