Spinal anesthesia - All study patients will receive spinal anaesthesia prior to induction of GA. Patient will be placed in lateral position, parts painted and draped under strict aseptic precautions. Heavy bupivacaine 40 mg will be administered in all patients at the level of L2-3 or L3-4 intervertebral space in the Spinal group. Heavy bupivacaine (Anawin heavy 0.5%, Neon laboratories LTD, Thane, India) 40 mg mixed with preservative free morphine sulphate 250 mcg (VERMOR 15,Verve health care limited, Delhi, India) will be given in L2-3 or L3-4 space to all patients in the Opioid group. The patient will be then turned to supine position and a 30 degree Trendelenburg position will be maintained till sensory loss to a level of T1 is achieved. The sensory level will be assessed by loss of sensation to cold stimulation (Spirit swab), all the while administering 100% oxygen through a breathing system. Patient will receive 100% oxygen by mask for 10 minutes and in case of respiratory depression will be gently assisted in respiration. Once desired level is achieved, GA in both groups will be induced with midazolam 1-2 mg, ketamine 20-30 mg plus lignocaine 2mg/kg and propofol 20-40 mg titrated to maintain hemodynamics and to loss of eyelash reflex. Inj. Vecuronium bromide 0.1mg/kg will be used as muscle relaxant to facilitate tracheal intubation and lignocaine spray (LOX 10% spray, Neon laboratories LTD, Thane, India) will be used over vocal cords prior to intubation to blunt the sympathetic stimulation.