Methods of Post Operative Analgesia in Patients Undergoing Thyroidectomy

group L : will receive 1.5 mg/kg bolus of iv lidocaine 10 minutes before anaesthesia induction then continuous iv infusion rate 1.5 mg / kg / h

patients will receive .25 mg / kg bolus of iv ketamine 10 minutes before anaesthesia induction then continuous iv infusion of ketamine at .25 mg /kg /h

group c will be injected with equivalent volumes and rates of .9% saline using the same application scheme as the lidocaine and ketamine as a control group