safe use of local anaesthetics - gp cme south/sat_room3_1100_seigne...what you need to know about...
TRANSCRIPT
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
