You are part of a team attempting to resuscitate a child with ventricular fibrillation cardiac arrest. you delivered 2 unsynchronized shocks. a team member established io access, so you give a dose of epinephrine 0.01 mg/kg io. at the next rhythm check, persistent ventricular fibrillation is present. you administer a 4-j/kg shock and resume cpr. which drug and dose should be administered next?