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Date:   10 May, 2011  
Focus: Small animals - dogs, cats, hamsters, guinea pigs & rabbits
 
Injectable Anaesthesia & Surgery -
Dermoid In The Shih Tzu
Dr Sing Kong Yuen, BVMS (Glasgow), MRCVS
Date:   10 May, 2011  
toapayohvets.com 
Be Kind To Pets
Veterinary Education
Project 2010-0129
2009 Case: Dermoid Surgery in a Shih Tzu
Case was first recorded: Oct 1,2009
Education of Vet Technicians from Myanmar and one intern from Temasek Polytechnic in this case by using injectable anaesthestics.


Dermoid cyst, eye, Shih Tzu, 8 months. Toa Payoh Vets, SingaporeNormally, I give xylazine 20 at 0.2 ml IM, and after 10-15 minutes give gas mask isoflurane. Then I intubate and it will be a smooth operation.

However, injectable anaesthetics have a place in vet surgery (e.g. devocalisation). Isoflurane and the anaesthestic machine are expensive. Maintenance of the vaporiser is not possible due to the lack of expertise in some developing countries and injectable anaesthesia is the alternative. However, in Caesarean sections, injectable anaesthesia is not advised as the puppies may be delivered dead.

I seldom use injectable anaesthetics. In this case, I did and am sharing my experiences of using injectable anaesthesia below for the benefit of dogs.
 

Shih Tzu, 8 months, 5 kg

1. Xylazine 20 at 0.2 ml + ketamine 100 at 0.2 ml in one syringe = 0.4 ml IV. (The guideline is 0.25 + 0.25 = 0.5 ml for a 5 kg dog)

2. Zoletil 50 at 0.1 ml IM after 5 minutes. Proceed to electro-incision.

3. Excellent surgical anaesthesia for <15 minutes. Time taken to set up electro-surgery equipment delayed surgery. Soon the dog's eyes start to blink under electro-incision.

4. In practices with no isoflurane gas anaesthesia, top up with 0.1 ml Zoletil IM regularly is workable.

5. I gave isoflurane gas by mask, intubate and maintain at 2-2.5% without worries of topping up injections. This surgery needs to be done carefully without the dog waking up or blinking his eye as the cornea is around 2 mm thick and any movement may rupture the cornea via electro-incision.

6. Recovery. The dog woke up smoothly as if he had a good sleep. No painful cries or struggle. 

7. Advantages: No post-xylazine vomiting. No post-Zoletil stiff neck or salivation in this case though no atropine (usually 0.2 ml IM) was used. 

8. Conclusion: In this case, I hope that the mentees can see that the xylazine + ketamine + Zoletil +isoflurane combination takes up more time and is not as efficient as xylazine IM + isoflurane in this surgery.  But it has a place in vet surgery in certain situations like field work, but  the vet must be familiar with this injectable anaesthesia method. 

Not all vets will agree with my philosophy - minimal use of drugs for sedation to avoid reactions and shortest time to achieve surgical anaesthesia. That is why I seldom use the xylazine + Zoletil top up combination or xylazine + ketamine + Zoletil top up combination. It may cause respiratory depression although certain sedatives are synergistic and lead to lower dosages required if used as a combination (e.g. domitor + ketamine). It just takes up too much time to administer top ups when the vet has to focus on a speedy surgery.

Dermoid cyst, eye, Shih Tzu, 8 months. Toa Payoh Vets, Singapore Dermoid cyst, eye, Shih Tzu, 8 months. Superificial keratectomy. Toa Payoh Vets, Singapore Dermoid cyst, eye, Shih Tzu, 8 months. Superificial keratectomy. Toa Payoh Vets, Singapore
Dermoid cyst, eye, Shih Tzu, 8 months. Superificial keratectomy. Toa Payoh Vets, Singapore Dermoid cyst, eye, Shih Tzu, 8 months. Superificial keratectomy. Toa Payoh Vets, Singapore Dermoid cyst, eye, Shih Tzu, 8 months. Superificial keratectomy. Toa Payoh Vets, Singapore
Dermoid Cornea Shih Tzu 8 months keratectomy Toa Payoh Vets Dermoid in right eye excised 
Cornea protected by 3rd eyelid flap for 4 days. Toa Payoh Vets. Shih Tzu, 8 months. Right eye. Dermoid in cornea excised 9 days ago. Toa Payoh Vets Shih Tzu, 8 months. Normal left eye. No dermoid in cornea. Toa Payoh Vets
3rd eyelid flap for 4 days. Day 9 after excision. Cornea heals well. Healing of the cornea should be completed in another 21 days. The normal left eye has a clear cornea.
In the 2009 case, a 3rd eyelid flap and tarsorrhaphy has been done.Cornea protected by 3rd eyelid flap for 4 days. Toa Payoh Vets. The sutures were removed on Day 4 to open the eyelids so as to examine the cornea for infection although antibiotic eye drops were given. The sclera was acutely inflamed. By Day 9, the owner wanted the dog home. 7 more days of nursing would be better for the dog. The domestic worker was taught how to apply the eye drops. E-collar must be worn at all times for 1 month, no exposure of the eye to sunlight and breeze for the next 3-4 weeks. The dog would now enjoy a better quality of life with no irritating Dermoid in his right eye cornea.        

UPDATE: May 10, 2011. No complaints from the owner since the surgery. I presume all are OK with the dog. As many Singapore pet owners go to the nearest veterinary practice, it is not possible for me to follow up some of my interesting surgical cases like this dermoid.

2011 Case: Dermoid Surgery in a Shih Tzu
dermoid, teratoma, shih tzu puppy, toa payoh vets, singaporeIn May 2011, a Pasir Ris breeder brought in a 6-week-old Shih Tzu with a dermoid. He had been a dog breeder for more than 10 years.

I the advised that surgery not be done at this young age. I asked him to postpone surgery till the
cornea becomes thicker with age or sell the puppy at a "loss" and let the new puppy owner get the dermoid cut off when the puppy grows older. He wanted to sell the Shih Tzu at 8 weeks of age. The selling price of the Shih Tzu is around S$500. It is unlikely that any puppy buyer will pay $500 for the puppy. "Even if the cyst is removed, there is still a white patch," I said to him. 

As he consults my associate vet, Dr Vanessa Lin, I did not advise him further. Much depends on the veterinary surgeon on the spot as to whether surgery can be performed at 4 weeks of age or later.       

See also: 2003 Case: Dermoid in a Shih Tzu

P.S
Recording dermoid cases with images online enables the practising vet to refer to how such rare cases are managed when another presents itself. Memories will fade with time and the internet now inexpensively permits knowledge sharing and storage. I hope fellow veterinarians in cyberspace will benefit from this case study. Be sure to have a steady hand when you operate on dermoid! 

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