Bretylium Epinephrine

The cornerstone of therapy for ventricular fibrillation is electrical deflbrillation. In the acute setting, defibrination is first-line therapy. Intravenous bretylium can occasionally contribute to conversion, but this is infrequent. In the management of out-of-hospital cardiac arrest, high-dose epinephrine (5 mg intravenously) improves the rate of successful resuscitation in patients with asystole, but not in those with ventricular fibrillation, when compared with the standard dose of 1 mg. Vasopressin (40 U intravenously) may more effective than 1 mg intravenous epinephrine in out-of-hospital patients with ventricular fibrillation that is resistant to electrical defibrillation. The OPTIC smdy (see Connolly et al., 2006) showed that amiodarone plus jS-blocker is superior than sotalol or jS-blocker alone for reducing ICD shocks in patients with reduced left ventricular function and history of sustained VT, VF, or cardiac arrest. 

Resuscitation from bupivacaine cardiovascular toxicity is extremely difficult. However, prompt resuscitation has been successful with standard cardiopulmonary support, including the prompt correction of acidosis by hyperventilation and administration of bicarbonate as well as epinephrine, atropine, and bretylium. Local anesthetics, especially bupivacaine, also inhibit basal and epinephrine-stimulated cAMP production. This finding places greater emphasis on aggressive epinephrine therapy during bupivacaine-induced cardiotoxicity. The (SJ-isomer, levobupivacaine, appears to have a lower propensity for cardiovascular toxicity than the racemic mixture or the (R)-isomer and has recently been approved for clinical use. Ropivacaine, another newer local anesthetic, has clinical effects similar to those of bupivacaine but may be associated with a lower potential for cardiovascular toxicity. Ropivacaine is available only as the (S)-stereoisomer, which has inherently less affinity for the cardiac sodium channel. 

Life threatening. If cardioversion fails. Epinephrine is given prior to defibrillation. If this fails combine IV lidocaine and defibrillation. Either additional doses of lidocaine or Bretylium can then be used with defibrillation. 

The pressor effects of adrenaline (epinephrine) and noradrenaline (norepinephrine) are increased in the presence of bretylium. Amfetamine and protriptyline antagonise the blood pressure lowering effect of bretylium. 

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