Introduction
Anaesthesia is defined as: The loss of sensation in a part or whole of the body by controlled reversible suppression of the central nervous system.

An anaesthetic drug is: A drug that causes anaesthesia.

Analgesia is defined as: Insensibility to pain.

An analgesic drug is: A drug that reduces the perception of pain without causing loss of consciousness.

Anaesthesia and analgesia are often employed to work hand-in-hand in order primarily to ensure that an animal undergoing a surgical procedure does not suffer trauma during and after an operation. The Protection of Animals Act 1964 legally obligates veterinary surgeons to adopt effective techniques to prevent the suffering of a patient during a painful procedure. In addition to humane reasons, anaesthesia is performed to provide immobility or restraint of a patient.

To recap; anaesthesia is necessary:

1. On humane grounds.
2. To meet legal requirements.
3. To provide immobility or restraint.

Times have changed since the days of chloroform, ether and open circuits. The veterinary nurse now plays an essential role in assisting the veterinary surgeon during anaesthesia in the following ways:

1. Care and maintenance of anaesthetic equipment.
2. Close and accurate monitoring of a patient prior to, during and following an anaesthetic.
3. Performance of specific tasks under the direction and supervision of the veterinary surgeon such as intubation, adjustment of vaporiser control, intermittent positive pressure ventilation and administration of drugs.

IMPORTANT NOTE - INDUCTION OF ANAESTHESIA MUST BE PERFORMED BY A VETERINARY SURGEON.

In order to be able to perform the above tasks safely and accurately, thorough training is necessary in all aspects of anaesthesia. Reading alone is never enough to fully understand the techniques involved; practical lectures and demonstrations are essential. An animal's life may be in your hands, therefore the most vital piece of information is: ALWAYS ASK IF YOU ARE UNSURE REGARDING ANY ASPECT OF ANAESTHESIA.

Learning Objectives

1. To understand the effect of anaesthesia and analgesia on the central nervous system, respiratory system and cardiovascular system.
2. To perform risk assessment of a patient prior to anaesthesia.
3. To understand why premedicant drugs are used.
4. To understand why analgesic drugs are used.
5. To comprehend the different types of anaesthesia available and know when their uses would be suitable.
6. To safely use anaesthetic equipment; including circuits, accessories and the general anaesthetic machine.
7. To accurately monitor the periods and planes of general anaesthesia.
8. To recognise an anaesthetic crisis and be able to act in an emergency.
9. To gain knowledge regarding the anaesthesia of exotic species.
10. To perform risk assessment of personnel involved in anaesthesia.

Remember, this book is intended as a revision guide, and further reading is recommended. Helpful references are included at the end of this chapter.