Efficacy of Perioperative Pregabalin as an Adjunct in Adolescent Scoliosis Surgery

This study aims to determine the efficacy of perioperative pergabalin as an adjunct in adolescent idiopathic scoliosis surgery. A total of 68 patients are assigned into 2 groups - treatment (PRE) group vs placebo (PLA) group. The patient will then receive either single dose oral pregabalin 50mg (in the PRE group) or placebo capsule (in the PLA group) preoperatively. In the ward, further 4 more doses of oral pregabalin 50mg or placebo will be served 12 hourly at post-operation 12 hours, 24 hours, 36 hours and 48 hours post-operatively. The following assessments will be carried out at various time intervals : On the day of admission, pre-operation (one hour after drug administration); post operation 0 hour at PACU, post-operation 4 hours; 8 hours; 12 hours; 24 hours; 48 hours; and 72 hours in the ward. 1. Pain assessment VAS/NRS* 2. Total consumption of patient controlled analgesic (PCA) morphine 3. Frequency of breakthrough pain requiring rescue analgesia in PACU 4. Validated Visual Analog Scale for anxiety (VAS-A)* 5. The anxiety component of the Hospital Anxiety Depression Score (HADS)* 6. Richmond Agitation and Sedation Scale (RASS)* 7. Incidence of nausea, vomiting, sedation, headache, dizziness, visual disturbances and dry mouth. To assess incidence of neuropathic pain post-operation, patient will be assessed using painDETECT questionnaire at 2 weeks, 1 month and 6 months post-operation via phone call. Anaesthetic Protocol The standardized anaesthetic protocol will be applied to both groups of patients. All patients are adequately fasted prior to surgery. Induction of anaesthesia is carried out with intravenous Propofol 2-4mg/kg, target-controlled-infusion (TCI) of intravenous Remifentanil with target effect-site concentration (Cet) of 1 to 5 ng/ml (Minto model), and Intravenous rocuronium 0.9mg/kg followed by endotracheal intubation. Anaesthesia is maintained with inhalational Desflurane at Minimum Alveolar Concentration (MAC) of 0.6 to 0.8 and ventilate with 50% oxygen/air mixture. Standard patient’s monitoring includes continuous invasive arterial blood pressure monitoring, heart rate, pulse oximetry, 3-leads electrocardiogram and Bispectral index (BIS) of 40-60. Intraoperative cell salvage technique is use as blood conservation strategy and Ringer’s lactate solution as maintenance fluid therapy. Intraoperative analgesia is provided by TCI Remifentanil at set target of 2-5 ng/ml. Before the surgery is ended, patient will receive the following analgesics: 1. Intravenous Morphine 0.2mg/kg – 45 minutes before skin closure 2. Intravenous Paracetamol 15mg/kg – 30 minutes before skin closure 3. Intravenous Fentanyl 1mcg/kg – 10 minutes before skin closure At the end of operation, patients will be reversed with IV neostigmine 0.05mg/kg and IV atropine 0.02mg/kg, TCI remifentanil tapered off, and patient will be extubated after meeting criteria for extubation. All patients will receive post-operative nausea and vomiting prophylaxis in the form of is IV dexamethasone 0.10 mg/kg at induction and IV ondansetron 0.10 mg/kg at the end of surgery. In post-operative care unit (PACU), patient is connected immediately to PCA morphine with the following protocol is used: bolus 1mg, lock-out 5 minutes, no basal infusion, and 4 hours limit is set at 20 mg. Rescue analgesia is provided by intravenous Fentanyl 0.5mcg/kg each bolus if required in PACU. Post-operation, patient will continue to receive PCA Morphine (for the next 48 hours) in the ward and regular intravenous Paracetamol 15mg/kg 6 hourly (for the first 24 hours; subsequently change to oral Paracetamol) up to hospital discharge.