Expansion
Perioral tingling and tinnitus first, then seizures and cardiac arrest
Expansion
Maximum doses
- Lidocaine: 3 mg/kg plain, 7 mg/kg with adrenaline
- Bupivacaine: 2 mg/kg, and adrenaline does not increase the maximum
“1 per cent means 10 mg per ml” is the conversion needed to check a dose.
Features, in order of appearance
- Perioral tingling and numbness, metallic taste
- Tinnitus, visual disturbance, light headedness
- Agitation, confusion, drowsiness
- Seizures
- Cardiovascular: hypotension, bradycardia, broad complex arrhythmia, asystole
“The tongue tingles before the heart stops.” The early symptoms are the warning, which is why patients are asked to report them during infiltration and why aspiration before injection matters.
Bupivacaine is the most cardiotoxic, binding avidly to cardiac sodium channels, and it can cause cardiac arrest with little neurological warning. It must never be used for intravenous regional anaesthesia.
Treatment
- Stop injecting, call for help, secure the airway with 100 per cent oxygen
- Benzodiazepines for seizures
- 20 per cent lipid emulsion: a bolus of 1.5 ml/kg then an infusion, repeated per protocol
- Prolonged CPR may be needed, since recovery can occur after an hour or more