Efficacy of Continuous Intravenous Infusion vs. Scheduled Dosing of Lornoxicam on Patient Controlled Morphine Consumption After Orthopaedic Surgery: A Comparative Placebo Study

An independent investigator who was not involved in the study instructed the patients preoperatively about the use of visual analogue scale to assess the severity of postoperative pain (0 mm for no pain and100 mm for worst imaginable pain) and about the use of PCA for their postoperative pain management.

Anaesthetic management was standardized. Oral lorazepam 2 mg was given the night before surgery. Subjects were allocated randomly into three groups (n = 32 for each) by drawing sequentially numbered sealed opaque envelopes containing a software-generated randomization code (Random Allocation Software, version 1.0.0, Isfahan University of Medical Sciences, Isfahan, Iran)into the placebo, scheduled, and continuous infusion groups. The syringes containing placebo and lornoxicam solutions were masked by identical opaque identical cover sheets. The test solution was prepared by one anaesthesiologist before induction of anaesthesia. Another anaesthesiologist, who was blinded to the study solution, gave the anaesthetic and was instructed to avoid using local anaesthetics, and a third anaesthesiologist collected perioperative data. All staff in the operating room were unaware of patient allocation group.

Patient monitoring included electrocardiography, non-invasive blood pressure, pulse oximetry, end-tidal sevoflurane and carbon dioxide (ETCO2) concentrations, response entropy (RE) and state entropy (SE.

After preoxygenation for 3 min, anesthesia was induced with fentanyl 1 - 3 µg/kg, propofol 1.5-2.5 mg/kg (to achieve an SE <50 and a difference<10 between RE and SE; RE-SE) and rocuronium 0.6 mg/kg. Tracheal intubation or slipping of laryngeal mask appropriate for body weight were used according to the discretion of the attending anaesthetist. Anaesthesia was maintained with a 0.6-1 minimum alveolar concentration of sevoflurane (MAC-Sevo) with air in 40% oxygen and fentanyl 1 µg/kg boluses to maintain SE <50 and RE-SE <10 and heart rate and mean arterial blood pressure within 20% of their baseline values. Rocuronium 0.1 mg/kg was given to maintain suppression of the second twitch using a train-of-four stimulation. The patients' lungs were ventilated to maintain an ETCO2 of 30-35 mmHg. Sevoflurane were discontinued at the start of skin closure, residual neuromuscular block was antagonized and the trachea extubated.

Postoperative analgesia was achieved according to the hospital protocol with patient controlled morphine analgesia (1 mg/ml), 1 mg, with a lockout interval of 8 minutes and a maximum 24-hourly limit of 180 mg. respiratory depression defined as the decrease in respiratory rate below 8/min was treated with i.v naloxone 0.2 mg. Nausea and vomiting were treated with i.v granisetron 1 mg and pruritus was treated with i.m promethazine 25 mg.