I
ANAESTHESIA, LOCAL
TECHNIQUES FOR GENERAL ANAESTHESIA
The main phases in the administration
of a general anaesthetic are induction
(bringing about unconsciousness),
maintenance (of unconsciousness),
and emergence (returning the patient
to consciousness). Some of the main
stages are shown below. Often, to
allow surgical manipulation, a muscle
relaxant must be given in addition to
anaesthetic gases or injections.
Because the relaxant temporarily
paralyses the breathing muscles, the
patient’s lungs must be ventilated
artificially. Modern general
anaesthetics have few side effects,
and recovery is usually prompt.
1
Before the
operation, the
anaesthetist talks
to and examines
the patientto
assess his or
her fitness for
anaesthesia and
surgery. He or she
also answers any
questions the
patient may have.
2
The induction agent is usually given
via a cannula inserted into a vein. The
cannula is left in position so that other
drugs can be given rapidly if needed.
3
Sometimes, anaesthesia is induced or
maintained with gases delivered by mask.
If no muscle relaxant is used, the patient may
be able to continue breathing naturally.
DRUGS USED IN GENERAL ANAESTHESIA
Type
Action
Examples
Drugs given as
premedication
Relax patient, relieve
anxiety; some reduce saliva
and mucus formation
Atropine, diazepam, hyoscine,
lorazepam, temazepam
Induction agents
Induce unconsciousness
Etomidate, ketamine, propofol,
thiopental sodium
Anaesthetic gases
and volatile agents
Induce and/or maintain
unconsciousness
Enflurane, halothane,
isoflurane, nitrous oxide
Analgesics
Abolish pain
Fentanyl, ketoprofen, morphine
Muscle relaxants
Relax (paralyse) muscles
Pancuronium, vecuronium
Reversal agents
Reverse muscle relaxation
Neostigmine
unaware ofthe operation. The composition of the
gas mixture, and the patient’s heart rate,
monitored. After surgery, anaesthesia is stopped,
and reversal agents are given if necessary.
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