Perioperative Systemic Lidocaine for Enhanced Bowel Recovery After Bariatric Surgery

Hypothesis

Recognizing the need for enhanced bowel recovery for patients undergoing laparoscopic bariatric surgery, the investigators hypothesize that perioperative administration of low rather than high intravenous infusion rates of lidocaine can achieve early postoperative restoration of bowel motility at lower plasma levels.

Up to the best of the investigators' knowledge there is no study addressed the effects of perioperative administration of systemic lidocaine on postoperative recovery of bowel function in morbidly obese patients undergoing laparoscopic bariatric procedures.

Aim of the study

This trial aims to compare the effects of perioperative administration of escalating doses of intravenous lidocaine (1.0, 1.5 and 2.0 mg/kg/h) on the perioperative changes in hemodynamic, pain scores, and plasma lidocaine concentrations, postoperative recovery of bowel function, cumulative morphine use, hospital length of stay, and lidocaine related adverse effects in obese patients undergoing laparoscopic bariatric surgeries under general anesthesia.

Randomization

Five minutes before induction of general anesthesia, participants will be allocated randomly into four groups by drawing sequentially numbered sealed opaque envelopes containing a software-generated randomization code to receive an intravenous bolus of 0.1 mL/kg of either saline 0.9% or lidocaine 1.5% solution followed by a continuous infusion 0.1 mL/kg/h of Saline 0.9% or lidocaine 1%, 1.5% or 2% solution which will be continued for 24 hours after surgery. All medications in the study protocol will be based on the dosing body weight [ideal body weight (IBW) + 0.4 × (actual body weight-IBW)]. All study solutions looked identical and will be prepared by a local pharmacy. All staff in the operating room will be unaware of patient allocation group.

Perioperative management

An independent anesthesiologist who will not be involved in the study will instruct the participants 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).

Anesthetic management will be standardized. Oral ranitidine 150 mg and metoclopramide 10 mg will be administered the night before and 60 min before arrival in the operating room and subcutaneous enoxaparin 60 mg will be administered 12 h before the scheduled operation for prophylaxis against deep venous thrombosis.

Participant's monitoring includes electrocardiography, non-invasive blood pressure, pulse oximetry, plethysmography variability index (PVI) and capnography.

Following pre-oxygenation, in all participants, anesthesia will be induced with fentanyl 2-3 ug/kg and propofol 1.5-2.5 mg/kg. Rocuronium 0.6 mg/kg will be administered to facilitate tracheal intubation. Anesthesia will be initially maintained with 0.7-1.2 minimum alveolar concentrations (MAC) of sevoflurane in combination with air (1 L/min) and oxygen (1 L/min) mixture to maintain the mean arterial blood pressure (MAP) and heart rate (HR) are ≤20% of the baseline values. Fentanyl 0.5 ug/kg increments will be administered when the MAP and HR are ≥20% of the baseline values despite a MAC of sevoflurane ≥1.0. Rocuronium 0.1 mg/kg, will be used to maintain surgical relaxation.

Lungs will be initially ventilated in pressure-controlled mode to deliver a tidal volume of 8 ml/kg of predicted body weight (0.919 × (height in cm - 152.4) + 45.5 for women or 50 for men) at an I/E ratio of 1:2 and a positive end-expiratory pressure (PEEP) of 5 cmH2O. Respiratory rate will be adjusted to maintain end-tidal carbon dioxide tension (ETCO2) between 35 and 40 mm Hg.

All operations will be performed by the same surgeons. During CO2 pneumoperitoneum, the intra-abdominal pressure will be maintained at 12-14 mm Hg.

Participants position will be changed from supine to a 40° reverse Trendelenburg position.

During the operation, intraoperative fluid management was guided by a goal directed therapy algorithm using the PVI to guide fluid responsiveness. Hemodynamic control is standardized according to the investigators' protocol. Hypotension (defined as MAP value <25% of the baseline value on two consecutive readings within 3 min), not responding to decrease the sevoflurane MAC to 0.7 and a 5 ml/kg mL Ringer lactate or Acetate bolus over 5 min, will be treated with intravenous boluses of ephedrine, 3 mg or norepinephrine, 5 ug IV. Hypertension (defined as >20% increase in mean baseline MAP) will be treated by deepening anesthesia and administering doses of fentanyl, or labetalol, 20 mg. Tachycardia (defined as >20% increase in mean baseline HR) will be treated with esmolol, 20 mg. Bradycardia (HR <45) persisting for >2 min will be treated with glycopyrrolate, 0.2 mg IV, boluses.

Intravenous ondansetron, 4 mg IV, will be given for all participants for prevention of postoperative nausea and vomiting. Before wound closure, bupivacaine 0.25% will be infiltrated at all portals, and residual neuromuscular block will be antagonized with neostigmine, 50 µg/kg IV, and glycopyrrolate, 10 µg/kg IV. After completing surgery, sevoflurane will be discontinued and infusion of study medication will be continued for 24 h after the wound closure. Times from discontinuation of sevoflurane to eye opening, obeying simple commands (e.g., open mouth, squeeze hand) and tracheal extubation will be recorded.

Postoperative analgesic regime will be standardized in all participants including 30 mg of intravenous ketorolac every 6 h and paracetamol 1 g IV every 6 h and rescue doses of intravenous meperidine 25 mg. Participants will be discharged from the post-anesthesia care unit when they have a modified Aldrete score levels.

Intravenous fluids will run at 40 mL/h on the night of surgery and will be discontinued 24 h after surgery. Little attention is paid to urine output or oliguria in the absence of abnormal vital signs. Strict parameters for fluid boluses the night of surgery are in place based on hypotension and tachycardia. Active bedside mobilisation will be enforced for the first time the evening after surgery and assisted ambulation the morning after surgery at least twice a day.

Criteria for hospital discharge are as follows: absence of nausea and vomiting in the last 24 h, return of bowel function (daily defecation) and toleration of full diet, no to minimal pain (VAS less than 4), afebrile and no surgically associated morbidity (fever, wound dehiscence, wound infection, anastomotic leak, abscess). These variables will be recorded by a blind assessor to the allocation, every day at 10:00, 14:00 and 18:00 h. Patients ready for discharge after 14:00 h will be discharged on the following morning. All drains have to be removed before discharge.

Blindness

All staff in the operating room will be unaware of patient allocation group. Patients will be unaware about their allocation group. All study solutions looked identical and will be prepared by a local pharmacy.

Caregivers: An independent anesthesiologist 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) and will give the anesthetics and will be instructed to avoid using local anesthetics. An independent investigator involved in the assessment of the data and participants will be blind to the group assignment.

Statistical analysis:

Data will be tested for normality using the KolmogorovSmirnov test. Repeated-measures analysis of variance will be used for serial changes in the continuous data at different times after administration of study solution and the differences will be then corrected by post-hoc Bonferroni correction test. Fisher's exact test will be used for categorical data. Kruskal-Wallis one-way ANOVA and post-hoc Wilcoxon rank sum t-tests will be used for comparisons of the non-continuous data. Categorical data will be expressed as number (%), ordinal data will be expressed as median [range] and continuous data will be expressed as mean ± SD. A value of P<0.05 is considered to represent statistical significance.

Power analysis and sample size calculation:

Based on a previous study, the time to the return of bowel movements after laparoscopic bariatric surgery was normally distributed with a mean of 70 hours and a standard deviation of 22 hours. An a priori analysis indicated that 45 patients in each group would be sufficient to detect a 20% reduction in mean time to return of bowel movements, with a type I error of 0.005 (0.05/10 possible comparisons) and a power of 80%. The investigators added 15% more patients to account for drop-outs during the study.