I'm writing a paper and need to know what voltage is used to restart a heart both in controlled (surgery) and uncontrolled (emergency) circumstances?

Once an easy ?: You don't say how detailed this needs to be & what once used to be an easy ? no longer is. There are now mult types of defibrillators (Impedance, non-impedance, monophasic & biphasic), why nec. and meds used effect this as well. However, a traditional answer would be during surgery 10 to 20 joules & emergent 200 to 360 joules: www.circ.ahajournals.org/content/122/16_suppl_2/s325, accessed 12/9/16.