The opportunity to learn from top flight speakers in feline dentistry and pain relief and to party in Amsterdam proved a popular combination for the newly formed International Society of Feline Medicine (ISFM, formerly the European Society) Congress (June 18 – 20).  Twenty-six countries were represented by the 452 delegates attending from as far afield as the US, China and Korea. UK delegates accounted for a third of those attending.

The ISFM Congress, ‘Feline pain management and dentistry’, sponsors were Boehringer Ingelheim, Hill’s, Merial, Bayer and Intervet-Schering Plough and Pfizer Animal Health.

The keynote speakers on dentistry were Philippe Hennet and Margherita Gracis. Sheilah Robertson, Polly Taylor and Duncan Lascelles spoke on feline pain management.  

In one of her sessions, Sheilah A Robertson, BVMS (Hons), PhD, DACVA, DECVAA, MRCVS, College of Veterinary Medicine, University of Florida, USA, provided ‘Top 10 tips for dental anaesthesia’. In reverse order these were:

10. Measure fluid administration carefully
For dental procedures 5 ml/kg/hour (or less) is sufficient and should be delivered using a syringe pump or a buretrol and micro-drip set. 

9. Use pre-emptive analgesics.

8. Use local anaesthetic blocks whenever possible.

7. Always be prepared when anaesthetising cats that have dental bonding. Cats with dental bonding may require anaesthesia but NOT removal of their bonding. In these cases any emetic drugs (especially the alpha2-adrenergic agonists) should be avoided. They should be pre-oxygenated by mask which prolongs the time to haemoglobin desaturation. While the mouth is being worked on oxygen can be administered using a “tom cat” catheter and anaesthesia can be achieved with slow administration of propofol to prevent apnoea.

6. Prevent accidental extubation
Gauze and tape ties tend to slip especially when they get wet and the movement of a dental patient without a secure endotracheal tube will often result in extubation and may lead to trachaeal damage. This author prefers plastic tubing placed around the cuff which can be tightly secured. Plastic tubing secures the endotracheal tube better than gauze or tape especially when wet.

5. Never use a cuff without a “Murphy” eye. This small opening on the side of the distal tip of
the tube is a safety “valve” that prevents complete airway occlusion in the event that the tip of the tube becomes occluded with blood or mucus.

4. Prevent aspiration of blood, mucus and oral debris. Prevention of aspiration can be achieved by using cuffed endotracheal tubes. Lubricant can help prevent aspiration. Gauze or sponges of an appropriate size can be placed in the oropharynx. A string (eg, dental floss) should be tightly tied to this and then secured outside the mouth (for example, to the anaesthesia circuit) to ensure they are removed before the cat wakes up!

3. Lubricate cuffs
Applying gel or lubricant to an endotracheal tube prior to insertion not only helps it slide more easily into the trachea and prevent tissue damage, but also enhances the seal produced by the cuff. A cuff is not always fully inflated inside the trachea and channels can form allowing fluid or debris to pass.

2. Prevent tracheal rupture
Tracheal rupture is an uncommon sequel to intubation but is reported in cats. In a report of 16
clinical cases, 75% were associated with a variety of dental procedures and in another series of 20 cases,70% occurred after dental prophylaxis.
Possible mechanisms for these injuries include:

• Damage from a stylet during intubation
• Wrong size of endotracheal tube
• Failure to deflate the cuff when repositioning the endotracheal tube or before extubation
• Rotating the patient around a fixed endotracheal tube
• Over-inflation of the endotracheal tube cuff

Cuffs must not be over-inflated; in cats ranging from 3.0 to 7.5 kg and using both HVLP and LVHP endotracheal tubes sized from 3.0 to 5.0 mm (ID) the volume of air required to create a seal ranges from 0 to 3 ml. To test for a leak, the pop off valve should be closed and the reservoir bag gently squeezed to create maximum pressure of 15 cm H2O, if a leak is audible add air in 0.5 ml increments until no air escapes. Using backpressure on the syringe and the size of the balloon as indicators of cuff size are unsafe techniques. It would be wise to only use 3 ml syringes for inflation or to mark all 6 ml and larger syringes with a warning line.
Alternatively non-cuffed tubes could be used and careful placement of pharyngeal packing used to prevent aspiration of fluid.

And the number 1 tip - Avoid hypothermia
Hypothermia is the most common and perhaps most serious but preventable complication of anaesthesia in cats.
The negative effects of hypothermia in cats are greatly underestimated; these include:

• Myocardial irritability and changes in cardiac rhythm
• Slowing of the sino-atrial node and a drop in cardiac output, blood pressure
• Increase in circulating catecholamines
• Fluid shifts resulting in haemoconcentration and increased blood viscosity
• Impaired tissue perfusion
• Increased bleeding secondary to prolonged coagulation times and altered platelet function
• Slowed metabolic rate leading to delayed recovery
• Decreased requirements for inhalant agents - if anaesthetic depth is not closely monitored, animals will receive a relative overdose
• Increased postoperative wound infection
• Impaired immune function
• Postoperative shivering and increased oxygen requirements
• Pain is likely to be worse when an animal shivers

The greatest rate of heat loss is in the first 20 minutes after induction of anaesthesia, but heat loss can begin soon after premedication.

Tips for keeping them warm:

• Prevent the cat from becoming soaked with water from the use of dental cleaning equipment – keep the cat covered.
• Anaesthesia time should be kept to a minimum.
• Ambient temperature – normal operating room temperatures are often 24-26oC. Warmer temperatures would benefit the patients but may increase surgeon’s discomfort. The induction and recovery areas and cages should be kept very warm.
• Warm mattresses – Circulating warm water blankets are effective in small patients. These blankets are more effective when placed on the limbs than on or under the trunk. Socks can be used to cover the limbs.
• Forced warm air devices are effective in veterinary patients.
• Blankets – fleece blankets and thermal insulating blankets can minimise radiation and convective losses.

A full version of this talk is available in the Congress proceedings. The Congress proceedings cost  £40 for members, £48 for non-members and can be ordered online or from ISFM headquarters on 01747 871 872. MP3 recordings of most of the ISFM Amsterdam Congress talks are available to download from www.isfm.net/shop at £2.99 each or £60 for all 22 sessions.

Don’t miss out next year when the ISFM Congress will be held in Vienna (June 23-26) with the combined themes of feline ophthalmology and respiratory disease. Click here for full details.