Local Anaesthesia
Mechanism
- agents block sodium channels from inside nerves
- cannot penetrate if low pH (i.e. inflammation)
Complications
Local anaesthesia
- Injection site
- pain
- haematoma
- delayed recovery of sensation
- infection
- Vasoconstrictors
- Systemic effects
- idiosyncratic, allergic - very rare
- inadvertent IV injection or excess dosage
- dizziness
- tinnitus
- nausea & vomiting
- fits
- CNS depression
- slurred speech
- bradycardia
- ventricular fibrillation → asystole
Spinal, epidural or caudal
- Failure
- Headache
- loss of CSF
- minor intrathecal haemorrhae
- Intrathecal bleeding
- esp. if on anticoagulannts
- Unintentionally wide field
- epidural may be infected into wrong tissue plane leading to spinal
aneasthetic
- spinal may flow too far proximally leading to respiratory
depression
- Permanent nerve or spinal cord damage
- Paraspinal infection
- Systemic
- severe hypotension
- postural hypotension
Types
Local Anaesthesia
Calm, cooperative, rational patients - no autonomic discomfort expected
- minor ops
- minor but painful procedures
- unavailability of GA expertise
- patient unfit for GA
- 'day case' surgery
- patient unwilling GA
- use of combine LA + vasoconstrictor (e.g. adrenaline) provides bloodless
operating field
Regional Nerve Block
- minor surgery - wide area of anaesthesia required
- inadvisable to inject LA into operation site
- avoids tissue distortion
- short-lived, wide field for reduction of forearm fracture or hand surgery
Epidural and spinal anaesthesia
- lower limb surgery
- lower abdominal, groin, pelvic & perineal surgery
IV sedation or IV analgesia alone
- short-lived, uncomfortable procedures, LA impractial
IV sedation + local anaesthetic
- Unpleasant procedures, no autonomic side effects
- Lignocaine
- Max 4mg/kg body weight
- Increased to 7mg/kg with adrenaline
- Bupivacaine
- Max 2mg/kg body weight
- Does not increase with adrenaline
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