Local anaesthesia is a reversible loss of sensation in some part of the body induced by a local anaesthetic agent.
The advantages of local anaesthesia involve the following:
• prolonged preoperative preparation is unnecessary;
• it can be used when general anaesthesia (narcosis) is unavailable;
• there is no need for postoperative observation of the patient, as distinct from narcosis.
Outpatient surgeries are often done under local anaesthetics. Similarly, when intubation narcosis is risky, the patient can be operated on under local anaesthetics.
Elderly patients, particularly debilitated ones, as well as those with cardiovascular disease are at increased risk, as far as postoperative mortality rate is concerned. In such cases anaesthesia may outweigh the risk of the operation itself.
Contraindications for local anaesthetics are as follows:
1. The patient's intolerance of local anaesthetics drug (e.g. due to allergies).
2. The patient's age below 10 years.
3. Concurrent psychiatric disease.
4. Scarring or pronounced inflammation of the tissues within the operative field, which may interfere with the infiltration of the anaesthetic.
5. Intractable internal bleeding which requires urgent operation.
6. Thoracic surgery.
Potentiated local anaesthesia can be achieved by combining anaesthetics with neuroleptic drugs (e.g.
Table 1. Local anaesthetic agents
droperidol) and general analgesics (e.g. phentanyl). In combined anaesthesia, which includes local anaesthesia and neuroleptic analgesia, local anaesthetic effect is enhanced by the positive action of the neuroleptic and the patient's psychic status.
Neuroleptic analgesia and general anaesthesia are used to potentiate different kinds of local anaesthesia (infiltration, trunk block, spinal, epidural). With the aid of neuroleptic analgesia and general anaesthesia the dosage and therefore the toxic effect of local as well as narcotic agents can be reduced.