Anti-Arrhythmics: 

• Amiodarone and Lidocaine have minimal effect over placebo in VT/VF (NEJM article from 2016)
• Amiodarone remains in the ACLS guidelines and you can consider it after a couple of defibrillations since there remains some uncertainty.

Refractory VTach/ VFib:

• For refractory VF/VT, consider Esmolol. A single center retrospective trial suggested that there was benefit in treating refractory VF/VT with it. 
• Double sequence defibrillation is a nice idea but be cautious as there is minimal data for the same and there is some concern for damage to defibrillators. 

References:

Kudenchuk, et al, Amiodarone, Lidocaine, or Placebo in Out-of-Hospital Cardiac Arrest, NEJM, 2016.

Lee et al, Refractory ventricular fibrillation treated with esmolol, Resuscitation, 2016.