local anaesthesia Flashcards
What is paraesthesia?
Altered sensation.
What is analgesia?
Loss of pain sensation only.
What is anaesthesia?
Loss of all modalities of sensation (pain, touch etc.)
Which 4 factors does the action of LA depend on?
- Time of the exposure.
- Concentration.
- Volume in the vicinity of the nerve.
- Size of the nerve fibres.
8 contraindications to LA
- Lack of cooperation.
- Acute infection
- Hypersensitivity.
- Haemophilia.
- Radiotherapy.
- Antidepressants.
- Age.
- Pregnancy.
Explain how acute infection impacts local anaesthetic.
(think more biologically)
- Infection causes pH to be lowered.
- Less anaesthetic molecules are in an uncharged state SO less can cross the phospholipid bilayer.
- Means less can bind to sodium channels.
- Leads to a reduction in LA potency.
Why is the use of local anaesthetic contraindicated in patients with hepatic or renal impairment?
Because reduced kidney and liver function can affect the metabolism of anaesthetic agents.
LOWER ANAESTHETIC DOSES to be considered.
Why should lower doses be considered in the elderly?
Due to the reduced kidney and liver function.
Cardiovascular disease is also more common so limiting adrenaline use should also be considered.
How should LA use be adapted for patients with bleeding disorders?
Local infiltration techniques are preferred over blocks due to the risk of intramuscular haematoma formation with potential airway compromise.
Why is local anaesthetic use contraindicated during pregnancy?
There is a lack of evidence to say LA has an adverse effect on pregnancy but there is a risk that it may cross the placenta and enter the foetus.
Max dose and duration for BUPIVICAINE.
2 mg/kg
Duration of 120-140 mins.
Max dose and duration of LIDOCAINE.
4.4 mg/kg
Duration of 15-60 mins.
Max dose and duration for MEPIVOCAINE.
7 mg/kg
Duration of 45-90 mins
Max dose and duration for PRILOCAINE.
7 mg/kg
Duration of 30-90 mins.
6 things to check for in an LA cartridge.
- Date
- Any cloudiness?
- Has the cartridge been partially used?
- Air bubbles
- Unbroken seal
- Glass or plastic
Which needle is used for blocks?
LONG NEEDLE - 27G, 35mm
Which needle is used for infils?
SHORT NEEDLE - 30G, 21mm