Dexmedetomidine and Magnesium Sulfate in Preventing Junctional Ectopic Tachycardia After Pediatric Cardiac Surgery

dexmedetomidine 0.5 µg/kg diluted in 50 mL of normal saline intravenously over 20 minutes, After induction followed by 0.5 µg/kg per hour infusion for 72 hours postoperatively or ready for extubation prior to 72 hour time period

Magnesium Sulfate (50 mg/kg) bolus administered at the time of Aortic Cross Clamp Release. with continued administration for 72 hours postoperatively at a dose of 30 mg/kg/day.