What is the antidysrhythmic therapy of choice in VF/pulseless VT?
After CPR has been initiated and the underlying rhythm recognized, immediate defibrillation is the mainstay therapy in the treatment of VF/pulseless VT. The choice of antidys-rhythmic therapy has not been shown to influence outcome if repeated countershocks, epinephrine/vasopressin, and appropriately administered CPR are ineffective in a patient with refractory VF or VT. No drug has clearly proven supe-riority in most cases of intractable VT or VF. Despite this, the 2000 ACLS protocol contains many changes in drug administration in VF/pulseless VT compared with older recommendations. Lidocaine is no longer recommended as the antidysrhythmic drug of choice for the treatment of malignant ventricular ectopy, VT, or VF. Lidocaine and procainamide hydrochloride are now classified as drugs with intermediate evidence for this indication. Bretylium is no longer recommended and has been removed from the ACLS algorithm. Instead, amiodarone is now a Class IIb indication for cardiac arrest from VF/pulseless VT that persists after multiple shocks. Amiodarone has been shown to increase the intermediate outcome of admission-to-hospital following out-of-hospital refractory VF arrest in one prospective double-blinded randomized controlled study.
Nonetheless, amiodarone administration is not associated with improvement of long-term outcome. After attempts to defibrillate and epinephrine and/or vasopressin adminis-tration fail to establish a perfusing rhythm, the new ACLS guidelines indicate consideration of antidysrhythmics as follows (Table 1.1):
· amiodarone 300 mg i.v. push for persistent or recurrent VF/pulseless VT
· magnesium sulfate 1–2 mg i.v. when an underlying hypo-magnesemic state is suspected or in torsades de pointes
· procainamide 50 mg/min in refractory VF (maximum 17 mg/kg)