Effects of Pregabalin on Post-cesarean Pain

• cumulative patient controlled morphine consumptions [ Time Frame: 24 hours after delivery ] [ Designated as safety issue: No ]
  cumulative patient controlled morphine consumptions 24 hours after delivery
  
  

• postoperative pain scores [ Time Frame: 1, 4, 6, 12, 24 and 48 hours after delivery ] [ Designated as safety issue: No ]
  visual analogue scale to assess the severity of postoperative pain (0 mm for no pain and100 mm for worst imaginable pain) at rest and on movement
  
  
• neonatal Apgar scores [ Time Frame: 1 and 5 min aftr delivery ] [ Designated as safety issue: Yes ]
  
• Neurologic and adaptive capacity scores [ Time Frame: at 15 min, 2h, 24 and 48 h after delivery ] [ Designated as safety issue: Yes ]
  NACS gives a maximum of 40 with a score >35 denoting vigor.The percentage of infants scoring <35 will be determined.
  
  
• Maternal sedation [ Time Frame: every two hours after delivery, for 48 hours after delivery ] [ Designated as safety issue: Yes ]
  sedation (four-point verbal rating scores (VRS): awake, drowsy, rousable or deep sleep),
  
  
• Maternal nausea and vomiting [ Time Frame: at 24 hours after delivery ] [ Designated as safety issue: Yes ]
  nausea and vomiting (0: no nausea; 1: nausea no vomiting; 2: nausea and vomiting),
  
  

• Adverse effects [ Time Frame: 24 hours after delivery ] [ Designated as safety issue: Yes ]
  difficulties in lactation, pruritus, dry mouth, flatulence, hypoglycaemia, dizziness, somnolence, ataxia, vertigo, confusion, incoordination, tremor, dyspnoea, blurred or abnormal vision
  
  

An independent investigator who will not be involved in the study will instruct the patients preoperatively about the use of patient controlled analgesia and visual analogue scale to assess the severity of postoperative pain (0 mm for no pain and100 mm for worst imaginable pain).

Anaesthetic management will be standardized. Oral ranitidine 150 mg and metoclopramide 10 mg will be given the night before and on the morning of surgery, with 0.3 mol/L sodium citrate 30 mL given 15 min before induction.

Ninety minutes before surgery, subjects will be allocated randomly into three groups by drawing sequentially numbered sealed opaque envelopes containing a software-generated randomization code to the placebo (n = 43), pregabalin 150 mg (n = 43) and the pregabalin 300 mg (n = 43) groups. The placebo and pregabalin capsules look identical and will be prepared by a local pharmacy. An anaesthesiologist not otherwise involved in the study and who will be blinded to treatment regimen will provide perioperative care. An independent investigator will collect perioperative data. All staff in the operating room will be unaware of patient allocation group.

Maternal monitoring will include electrocardiography, non-invasive blood pressure, and pulse oximetry. Left uterine displacement will be maintained.

Spinal anesthesia will be performed in all cases in sitting position at L3-L4 or L4-L5 spaces with hyperbaric bupivacaine 0.5% (10-12.5 mg) and fentanyl 20 µg. After the umbilical cord is clamped, a 5-10 IU infusion of oxytocin in 500 mL of lactated Ringer's solution will be infused.

A paediatrician blinded to study group allocation will recordApgar scores at 1 and 5 min, umbilical cord blood gas analysis and NACS at 15 min, 2h, 24 and 48 h after delivery. NACS gives a maximum of 40 with a score >35 denoting vigor.6 The percentage of infants scoring <35 will be determined.

Postoperative analgesic regime will be standardized in all patients with 12-hourly intramuscular diclofenac 75 mg started immediately at the end of surgery and morphine via patient-controlled analgesia (PCA): 1 mg bolus with an 8 minutes lockout. Postoperative nausea or vomiting will be treated with intravenous ondansetron 4 mg as required.