Tox - Viva - LA Toxicity Flashcards
Maximum doses of LA
Lignocaine - 3mg/kg
Lig with Adren 7mg/kg
Bupiv - 2mg/kg
L-bupiv 2mg/kg
Prilocaine - 6mg/kg
List in order with most vascular and therefore most lethal routes of LA admin
Intravenous
Intercostal
Caudal
Lumbar epidural
Brachial
Subcut
Risk factors for LA toxicity
Choice and dose of LA
Site and vascular Itu
Continuous infusion
Block factors - speed of injection, no use of ultrasound, no test dose
(Adrenaline, controversy).
Problems not detected in sedated patients
Patient - Age, weight, liver/renal/cardiac failure, pregnancy
Mechanism of LA (normal)
LA crosses cell membrane unionised
Binds to fast Na channel when ionised, inactive, prevent depolarisation
Reversible prevention of transmission of neuronal AP
Consider also the membrane expansion theory
Signs of LA toxicity
Cardio - collapse, hypotension, arrhythmia, asystole
ECG - sinus Brady, prolonged QRS, AV block,
Neuro - two stage
Excitable - peri oral tingling, tinnitus, tremor, seizures
Depressive - low GCS, coma apnoea
Pathophysiology of LAST
LA antagonises oxidative phos at mitochondria
Heart and brain need aerobic metabolism so vulnerable
OR non-neuronal sodium inhibition - cerebral cortex inhibiting inhibitory pathways, therefore more excitable then depressions
Management LA Toxicity
STOP GIVING IT
This is an emergency call for help
If arrested, CPR as per ALS
ABCDE, secure airway, 100% O2, iv access
Give Intralipid - AAGBI
Bolus 1.5ml/kg over 1 minute
Infuse 15ml/kg/hr
2 further boluses every 5 minutes, and increase to 30mls/kg]
Seizure - benzo, thio, propofol
Crit care
Report to National patient safety agency
Max dose of intra lipid
12ml/kg in first hour
What is intralipid
Lipid emulsion, soya oil, egg phosphatic and glycerol
Mechanism of intralipid
Not really known
Lipid sink - new lipid compartment in iv space, during off LA
Enhanced fatty acid metabolism - heart uses fatty acids as substrate, bupiv inhibits fatty acid oxidation, therefore intralipid is source of fatty acid
Competitive binding - fatty acid in intralipid directly inhibit LA binding
PK - intralipid reduces the CSHT of bupiv
Cytoprotection, activates Akt (Protein kinase B)
