Anaesthetics block pain sensation. Local anaesthetics are applied to the eye or injected into surface tissue (or around regional nerves) to permit us to carry out a simple procedure such as removing something or putting a few stitches in a minor wound in a conscious cat or dog. Xylocaine is the most common local anaesthetic. General anaesthetics produce unconsciousness and are either injected or inhaled. Although some anaesthetics have mild pain-killing properties, most don’t.
In most circumstances we induce general anaesthesia by giving a short-acting anaesthetic intravenously. The dose is calculated according to your pet’s weight, but also according to its health and what other drugs it has had. Some dog breeds such as Whippets and Greyhounds need less anaesthetic than other breeds of similar weight. Your pet falls asleep as the drug is injected and remains asleep for a variable length of time depending upon what drug is used. As soon as it is unconscious a tube is placed over the tongue into the windpipe (endotracheal tube) and inflated. This keeps the airway clear and is attached to a source of oxygen.
Fast procedures such as x-rays or removing grass seeds from ears often require only the intravenous anaesthetic. For longer procedures such as routine operations, oxygen is mixed in a vaporiser with an anaesthetic gas. During the operation the injected anaesthetic wears off while the vaporised gas continues to maintain unconscious. At the end of the procedure the anaesthetic is withdrawn and only fresh oxygen given. Recovery is immediate or slow depending not only on the injected and inhalation anaesthetics used but also on the pain killers and tranquillisers given before and during surgery.
At the London Veterinary Clinic we usually use intravenous propofol and inhaled isoflurane. An anaesthetised pet awakens minutes after the anaesthetic is stopped. These are very safe drugs but expensive, especially when used on medium to giant dog breeds.
We also use "reversible" anaesthetics for short diagnostic procedures such as x-rays. After a procedure has been completed a drug is given to counteract the effect of the drug that renders unconsciousness.
Tranquillisers, sedatives and narcotic pain killers (but not NSAID pain killers) prolong recovery time from anaesthetics.
If your pet is scheduled for a general anaesthetic please withhold food for 12 hours before the anaesthetic.
This reduces the risk of vomiting food (and choking on it) during or immediately after the anaesthetic. Withhold water for the morning of the procedure unless we tell you to leave down water for a few hours more.