Local and regional anaesthesia
Definitions:
Local anaesthesia:
- The use of a drug to produce anaesthesia by topical application, infiltration or ring block
Regional anaesthesia:
- Is a term reserved to describe major nerve blocks or spinal/epidural techniques
However, the terms are often used interchangeably
Regional versus general anaesthesia:
| Advantages | Disadvantages |
| Avoids adverse effects of general anaesthetic agents: - Respiratory depression
- CVS depression
- Nausea/vomiting
- ‘Hangover’
| Toxicity of local anaesthetic drugs |
| Avoids potential hazards of unconsciousness: - Loss of airway
- Aspiration
- Damage to joints through malpositioning
| Often difficult techniques: - More risk of failure or partial success
- More discomfort while performing block
- May take longer to establish
|
| Minimises endocrine stress response to surgery | Greater co-operation needed from patient |
| Decreased postoperative pain | Sets time limit for surgery |
| Earlier discharge from hospital | Restricts flexibility of surgeon if operation needs to be more extensive |
Hazards of local anaesthetic agents:
Local administration:
- Inadvertent IV injection - rapid onset of toxic effects
- Inadvertent intraneuronal injection - nerve damage
- Incorrect use of adrenaline –containing solution - tissue necrosis
- Vasodilatation - increased bleeding
- Tachyphylaxis - reduced effectiveness of repeated doses
- Spread of infection - if injected into infected area
Regional anaesthesia:
- Marked vasodilatation – fall in BP
- Major nerve compression – haematoma or abscess formation
- Large doses may be needed – risk of overdosage
Effects of overdose:
- CVS:
- Bradycardia
- Fall in cardiac contractility – hypotension
- Cardiac arrest
NB: Cocaine and adrenaline-containing solutions cause tachycardia and hypertension
- CNS:
- Paraesthesiae (especially around the mouth)
- Anxiety
- Tremors
- Fitting
- Coma
Types of local anaesthesia:
- Topical anaesthesia:
- Throat lozenges
- ENT procedures
- Infiltration:
- Ring block:
- Is a quick and effective method of anaesthetising an extremity (typically a finger or toe)
- Nerve blocks
- IV regional anaesthesia (IVRA or Bier’s block):
- Used to anaesthetise the arm (or occasionally the leg), classically before reduction of a fractured wrist
- Also used for minor surgery (e.g. relief of carpal tunnel syndrome)
- Spinal and epidural anaesthesia
