Group K:  Patients will receive ketamine 1 mg/kg in saline, total volume 20 ml as subcutaneous infiltration, in and around the incision line as a rectangle, 5 min before skin incision.

Group L:  Patients will receive levobupivacaine 0.25%, total volume 20 ml as subcutaneous infiltration, in and around the incision line as a rectangle, 5 min before skin incision.

Group KL: Patients will receive ketamine 1 mg/kg in levobupivacaine 0.25%, total volume 20 ml as subcutaneous infiltration, in and around the incision line as a rectangle, 5 min before skin incision.

Group assignments will be concealed within opaque envelopes.

PROCEDURE

In the operating room, monitors (electrocardiogram, noninvasive blood pressure, pulse oximeter) will be applied and baseline readings noted. Anaesthesia will be induced with midazolam (1mg), fentanyl (2 µg/kg), propofol 10% (2 mg/kg) followed by vecuronium bromide (0.1 mg/kg) for facilitating insertion of Pro Seal laryngeal mask airway (PLMA).  Anaesthesia will be maintained on oxygen and nitrous oxide (33:66) in isoflurane. Fentanyl (1µg/kg) bolus dose will be given at completion of one hour of anaesthesia induction, for meeting intraoperative analgesic requirement.

Under strict aseptic precautions, after cleaning and draping the patient, the study drug will be infiltrated subcutaneously, in and around the incision line as a rectangle by the operating surgeon. The surgical incision will be given after 5 min have elapsed from the time of study drug administration. Approximately 30 min before the end of surgical procedure, 1 g paracetamol will be given intravenously over 15 min and 4mg ondansetron will be given intravenously over 5 min. At the end of surgery, volatile anaesthetics will be discontinued, residual neuromuscular block will be antagonized with neostigmine 0.05 mg/kg and glycopyrrolate 0.01 mg/kg and the PLMA will be removed when the patient is fully conscious.

Postoperatively, all patients will receive 1 g paracetamol intravenously 8 hourly for pain relief. If VAS score is ≥ 4, pethidine 0.4 mg/kg will be given intravenously, if the VAS score did not decrease within 10 more min, pethidine 0.2 mg/kg will be given to the patient with maximum dose of 1 mg/kg in any 4 h. The total pethidine consumption and time to the first additional pethidine need will be recorded. Finally, occurrence of adverse effects such as nausea, vomiting, sedation and hallucinations will be noted and treated accordingly.

Following parameters will be noted on arrival of patient in the PACU at 0, 15 and 30 min, and at 1, 2, 6, 12, and 24 h postoperatively:

Haemodynamic parameters and respiratory rate (RR)

Severity of pain at rest and on movement using Visual Analogue Scale score (VAS) where 0 indicates no pain, and 10 is worst pain possible. 

Time to first pethidine requirement and cumulative pethidine requirement in 1, 2, 6, 12 and 24 h time frame.

Occurrence of side effects such as nausea, vomiting, sedation, hallucinations.

Occurrence and severity of nausea will be noted. Nausea severity will be graded as none/mild /moderate/severe. Retching will be considered as vomiting for statistical purpose.

Level of sedation will be assessed using a 4-point scale (0 = awake and alert, 1 = minimally sedated, responds to speech, 2 = moderately sedated, arousable by tactile stimulation, and 3 = deeply sedated, arousable only by painful stimulation). 

Patient satisfaction from postoperative analgesia will be assessed at 24 h postoperatively using a 5-point scale (1 = very unsatisfied, 2 = unsatisfied, 3 = fair, 4 = satisfied, and 5 = very satisfied).