After intravenous induction and tracheal intubation , the patients in the interventional group received intravenous infusion of 0.5 mg/kg lidocaine and 0.5 mg/kg ketamine , followed by continuous infusion of lidocaine at the rate of 0.5 mgkg ( -1 ) h ( -1 ) till the end of the operation ; the patients in the control group received saline infusion only .