Anaesthetists Handbook - MEDICAL EDUCATION at University ...

Epidural anaesthesia and analgesiaSystemic toxicity to local anaesthetics leads to central nervousexcitability and convulsions. Cardiotoxicity also occurs and usuallyinvolves torsade de pointes – a form of ventricular tachycardiacharacterised by a polymorphous electrocardiographic appearance,delayed repolarisation and a prolonged QT interval – or refractoryventricular fibrillation. Hypokalaemia and hypomagnesaemia arepredisposing factors. Hypomagnesaemia is an occasional finding inlate pregnancy.For life-threatening cardiotoxicity administer life support asnecessary followed promptly by the specific treatment for localanaesthetic toxicity, magnesium sulphate.Rapid administration of magnesium can cause asystole.Torsade de pointes• Activate the emergency call and get someone to call acardiologist.• Apply basic and advanced life support as necessary.• Use the standard labour ward magnesium mix, making up a50 mL syringe containing 10 g MgSO 4.• Give intravenous magnesium sulphate 2 g over 15 minutes(10 mL from 50 mL syringe).• Follow with 1 g h -1 (5 mL h -1 ).Refractory ventricular fibrillation• This is in the context of ongoing ‘cardiac arrest’.• Apply basic and advanced life support as necessary.• Do not delay electrical defibrillation and intravenous adrenaline.• Give magnesium as above.• Intravenous amiodarone has been used successfully.The adult dose of amiodarone is 300 mg made up to 20 mL with 5%glucose. A further dose of 150 mg may be given for recurrent orresistant VT/VF, followed by an infusion of 1 mg mL -1 for six hours.Anaesthetists Handbook January 2010 127