Local Anaesthetic Toxicity CCC
OVERVIEW
- sodium channel blockade -> arrhythmias and neurotoxicity
CAUSES
- drug overdose
- IV injection
- rapid absorption from highly vascular areas
- accumulation of multiple injections or infusion
PREVENTION
- know your maximum doses
- aspiration before injecting
- small, divided doses
- inject slowly & ask about symptoms
- increased LA effect in – acidosis, hypoxia, hypercarbia
CLINICAL FEATURES
CNS
Excitation phase
- numbness of tongue and circumoral tissue
- restlessness
- tinnitus
- vertigo
- shivering
- muscular twitching & tremors (initially involving muscles of face & distal parts of extremities)
- generalised convulsions
Depression phase
- generalised depression
- decreased LOC
- apnoea
- precise site for LA-induced seizures is not known.
CVS
Initial
- hypertension & tachycardia
Then
- peripheral vasodialatation, profound hypotension -> decreased Q
- sinus bradycardia, intracardiac conduction defects (prolonged PR & QRS complex), ventricular arrhythmias, cardiac arrest.
MANAGEMENT
Goals
(1) limit LA exposure
(2) prolonged normal resuscitation
(3) consider lipid emulsion administration
(4) prevention of acidosis
Mild symptoms – midazolam boluses IV (raises seizure threshold)
Stop injecting or infusion!
Call for help
- A – ETT
- B – FiO2 1.0, hypertentilate (avoid acidosis -> HCO3- 1mmol/kg)
- C – defibrillation, CPR, fluid, inotropes, amiodarone 5mg/kg, bretylium 5-10mg/kg LD -> 1-2mg/min
- D – midazolam, propofol, thiopentone
Lipid emulsion (20% intralipid)
- 1 mL\kg (over 1min) q3min x 3 then
- Infusion 0.25mL\kg\min
Important points
- continue CPR to distribute
- repeat bolus every 3 min up to 3mL\kg total dose until circulation restored
- continue infusion until haemodynamic stability restored
- increase rate to 0.5mL\kg\min if BP declines
- maximum total dose = 8mL\kg
70kg Adult
- 500mL bag of Intralipid 20%
- 70mL bolus stat x3
- infuse rest of bag over 15 minutes
Lipid Emulsion Mechanism
- ?
- lipid sink model – draws LA out of plasma
- may actually facilitate redistribution of LA from target organs to fat stores
- it may overwhelm the inhibition of the translocase by mass action -> increases myocardial energy supply
References and Links
- Flashcard – Local anesthetic toxicity
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC
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Great summary.
I was interested to know the source/reference of your intra-lipid doses as it varies (lower) than most other suggested doses of 1.5ml/kg see:
Management of severe local anaesthetic toxicity