local anaesthetic- general

• what is LA?

  Are substances which are applied locally around nerve fibres and reversibly blocks conduction along the fibre (local analgesic)
• How does LA work?

  Block sodium channels at nerve endings leading to interruption of conduction of nervous impulses.
• If LA is not absorbed well across intact skin and must be infiltrated locally to have desired site of action.
• LA is absorbed across mucous membranes, reach systemic circulation they penetrate well into the tissue including CNS.
• LA is redistributed to the liver where it is inactivated.
• Order of sensations:

  Pain, cold, warmth, touch, pressure
• What are the benefits of LA:

  • Provides pain relief
  • Reduces amount of GA
  • Minimises cardiopulmonary depression from GA.
  • Quicker recovery
  • Few effects on CVS and Resp system.
  • little sedative effects.
• Negatives to LA:

  • May cause nerve damage or permanent loss of function when injected into nerve fibres.
  • LA can cause tissue irritation, mepivacaine is least irritant.
  • Animals can chew at area
  • Allergic reaction.
  • hypotension after epidural anaesthesia
  • Systemic toxicity risk
• systemic toxicity of LA depends on?

  Rate of uptake/ metabolism of frugs may occur if LA is accidently given I/V.
• Systemic toxicity- affect on CNS?

  Stimulation may lead to seizures, higher doses leads to respiratory depression then respiratory failure.
• Systemic toxicity- affect on heart?

  Decreases contraction force leading to myocardial depression.
• Examples of LA drugs?

  • Lignocaine
  • Bupivacaine
  • Amethocaine
  • Lidocaine