 This is a randomized, double-blind, placebo-controlled, two-arm parallel study.. Patients 50kg or more will receive either 1000mg IV acetaminophen or placebo with the first dose given preoperatively in the holding area followed by re-dosing every four hours from that point up to a maximum of 4 doses or 4000mg in 24 hours. Patients 50 kg will receive 12.5mgkg to a maximum of 75 mg per kgper day as per the label dose with repeat dosing Q4 hours. 