Morbidly obese patients (BMI \> 50 kg/m2) planned to undergo open variant of biliopancreatic diversion with Roux-en-Y gastric bypass (BPD-RYGBP) received standardized general anesthesia (intravenous propofol combined with remifentanyl and muscle relaxation). Preoperatively, in all patients an epidural catheter in the thoracic spine level will be placed between T5 and T8 interspace. All patients will be randomly allocated to six groups:
Group A patients will receive intra-operatively (45 min before the estimated end of the surgery) a bolus dose 2 ml of normal saline, epidurally. Postoperatively, immediately after extubation patient controlled epidural anesthesia (PCEA)with 0.1% levobupivacaine (5ml, lockout interval 10min) , combined with a continuous epidural infusion of morphine 0.2 mg/h will be administered, Group B patients will receive an epidural bolus dose of 1mg of morphine intra-operatively (45 min before the estimated end of the surgery) and postoperatively the same levobupivacaine and morphine regimen as Group A, Group C patients will receive an epidural bolus dose 2 mg of morphine intra-operatively and thereafter the same levobupivacaine and morphine regimen as Group A.
Group D patients will receive intra-operatively an epidural bolus dose of 2 ml of normal saline. Postoperatively, the patients will receive PCEA in a dose of 0.2% levobupivacaine (5ml, lockout interval 10min) combined with a continuous epidural infusion of morphine 0.2 mg/h, Group E patients will receive intra-operatively an epidural bolus dose of 1mg of morphine intra-operatively and postoperatively the same regimen as Group D.
Group F patients will receive intra-operatively an epidural bolus dose of 2 mg of morphine intra-operatively and thereafter the same regimen as Group D.
Pain assessment will be performed using visual analogue scale (VAS, 10cm scale) at rest, at mobilization and at cough. Furthermore, total local anesthetic and morphine consumption, side effects on cardiovascular, respiratory and gastrointestinal systems, including blood pressure,blood gases, spirometric values Forced Expiratory Volume at 1 sec (FEV1), Forced Vital Capacity (FVC), Peak Expiratory Flow Rate (PEFR), incidents of postoperative nausea and vomiting (PONV), pruritus, time to first flatus, postoperative ambulation will be recorded for up to 6 days.
