What you need to know about the safe use of

Local Anaesthesia

Richard Seigne

Anaesthetist

CDHB

Disclosures

None

What you need to know about the safe use of Local Anaesthesia

They’re safe

…..when left in the ampoule in a cupboard

History & Background

Cocaine 1884 – eye drops, toxicity, deaths

Procaine 1904 - anaphylaxis

Lignocaine – 1943 amide

Coca leaves - Peru

History & Background

Bupivacaine – 1963, late ‘70s early 80’s reports of deaths

Ropivacaine – 1996, less cardiotoxic

Procaine – late 1950s, low toxicity, low potency

“Problems with Local Anaesthesia”

Toxicity

Intra-neural injection

Oral use - loss of airway reflexes

Accidental injury

Methaemoglobinaemia

Adrenaline

Anaphylaxis

Faint

Pain on injection

Errors

Acidic

Weak base

More acidic environment

Mechanism of action and pharmacokinetics

“Problems with Local Anaesthesia”

Toxicity -

Intra-neural injectionOral use - loss of airway reflexes

Accidental injury

Methaemoglobinaemia

AdrenalineAnaphylaxis – very rare

Faint

Pain on injection

very rare especially with local infiltration

Errors

Faint

Adrenaline effect

LA toxicity

Toxicity - differentials

Recognition – not following best practice

symptoms - communication

Toxicity

Behavioural change, feeling odd, light headed, tinnitus, visual changes - communication

CNS – excitation then depression (fitting then coma)

CVS – excitation then depression, VF (acidosis)

Toxicity

Tingling lips, tongue (paraesthesia) - communication

Toxicity – too much drug in blood

Plasma concentration –

Accidental direct IV or IA injection

Absorption from tissue

drug dose

proximity of vessels

number of vessels

vasoconstrictors

mass of tissue – patient weight

AspirationSpeed of injectionFractionation

concentrationvolume

Blood factors - (protein binding)

acidosis, hypoxia

Plasma clearance – liver

Drug pharmacokinetics and pharmacodynamics

Toxicity – too much drug in blood

Stop injecting, get help

ABC & CPR - prolonged

Toxicity management

Intra-lipid

Lie patient down, legs up

70kg adult - 500ml Intralipid 20% + 50ml syringe

– Draw up 50ml IV - X2 stat

– Rest of Intralipid IV with giving set over 15 minutes

– Repeat initial bolus up to twice more – if spontaneous circulation has not returned

+ CPR

Toxicity management

Drug dosing

Drug “Max” Dose (with adrenaline) Potency

Lignocaine (Lidocaine) 3mg/kg (7mg/kg) 0.25

Bupivacaine (Marcaine) 2mg/kg (2.5mg/kg) 1

Ropivacaine (Naropin) 3-4mg/kg 0.6

Prilocaine (Citanest) 6mg/kg (9mg/kg) 0.25

NB Doses of different drugs are additive

1% = 10mg/ml – move decimal point to right

“Problems with Local Anaesthesia”

Toxicity

Intra-neural injectionOral use - loss of airway reflexes

Accidental injury

Methaemoglobinaemia

AdrenalineAnaphylaxis

Faint

Pain on injectionErrors

“Problems with Local Anaesthesia”

Toxicity

Intra-neural injectionOral use - loss of airway reflexes

Accidental injury

Methaemoglobinaemia

AdrenalineAnaphylaxis

Faint

Pain on injectionErrors

“Problems with Local Anaesthesia”

Toxicity

Intra-neural injection

Oral use - loss of airway reflexes

Accidental injury

Methaemoglobinaemia

Adrenaline

Anaphylaxis

Faint

Pain on injection

Errors

Methaemoglobinaemia

Prilocaine

> 600mg – 0.5% - 120ml1% - 60ml2% - 30ml

Cyanosis, O2 sats falsely high initially

Usually resolves in 2 hours, methylene blue 1mg/kg over 5 min

“Problems with Local Anaesthesia”

Toxicity

Intra-neural injection

Oral use - loss of airway reflexes

Accidental injury

Methaemoglobinaemia

Adrenaline

Anaphylaxis

Faint

Pain on injection

Errors

Intra-neural injection

Anatomy

Pain on injecting

Difficulty in injecting

“Problems with Local Anaesthesia”

Toxicity

Intra-neural injection

Oral use - loss of airway reflexes

Accidental injury

MethaemoglobinaemiaAnaphylaxis

Faint

Pain on injection

Errors

Adrenaline

Acidic solution

+ AlkaliNaHCO3

More acidic environment

Mechanism of action and pharmacokinetics

“Problems with Local Anaesthesia”

Toxicity -

Intra-neural injection

Oral use - loss of airway reflexes

Accidental injury

Methaemoglobinaemia

Adrenaline

Anaphylaxis – very rare

Faint

Pain on injection

Errors

Additives

Drawing up

Labelling

Errors

Gloves and sharps

Aspiration

Incremental injection

Communication

Distractions

Drawing up

Routine

Errors

Additives

Drawing up

Labelling

Errors

Gloves and sharps

Aspiration

Incremental injection

Communication

Additives

Drawing up

Labelling

Errors

Gloves and sharps

Aspiration

Incremental injection

Communication

Additives

Drawing up

Labelling

Errors

Gloves and sharps

Aspiration

Incremental injection

Communication

Local Anaesthetics reborn

Wound catheters

Local Infiltration Analgesia (LIA)

IV lignocaine infusions

Catheter (wound)

Reservoir – elastomeric ball

Liposomal delivery

(EMLA/AMITOP)

Ultrasound

Summary

Infiltrative local anaesthesia generally very safe

Follow common sense rules – drug preparation and administration

Regional anaesthesia requires more expertise, CPR equipment

Bigger dose – bigger risk