Ketamine vs Magnesium Sulphate in addition to Ropivacaine for pain relief after surgery

INTERVENTION: Intervention1: ketamine: Comparative Evaluation of intraperitoneal ketamine 0.5 mg per kg versus magnesium sulphate 40 mg per kg as adjuvants to 0.2 percent ropivacaine for postoperative analgesia. To be used once at the time of surgery after removing gall bladder Control Intervention1: magnesium sulphate: Comparative Evaluation of intraperitoneal ketamine 0.5 mg per kg versus magnesium sulphate 40 mg per kg as adjuvants to 0.2 percent ropivacaine for postoperative analgesia. To be used once at the time of surgery after removing gall bladder CONDITION: Health Condition 1: K80‐ Cholelithiasis Health Condition 2: K81‐ Cholecystitis PRIMARY OUTCOME: Total amount of tramadol consumed by the patient in first 24 hours postoperatively.Timepoint: Measurement to be taken at 24h SECONDARY OUTCOME: 1. NRS pain scores at rest and on movement. ; 2. Time of first rescue opioid analgesic. The time interval between the completion of surgery and the first administration of rescue opioid analgesia given for postoperative pain relief. ; 3. Adverse effect if any ; Timepoint: Measurement to be taken at 0h, 30 min, 1h , 2h, 4h, 8h, 12h and 24 h INCLUSION CRITERIA: 1. Patients belonging to any gender, aged 18 to 70 yrs 2. ASA I ,II and III patients 3. Patient scheduled for laparoscopic cholecystectomy under general anaesthesia