Automated Closed Loop Propofol Anaesthesia Versus Desflurane Inhalation Anaesthesia In Bariatric Surgery

After Institutional Ethics Committee approval and written informed consent, forty-participants (20 per group) aged 18-65 years, ASA physical status I/III, BMI >35-kg/m2, of either sex, and undergoing laparoscopic/robotic bariatric surgery (sleeve gastrectomy or gastric bypass) will be included in this single center (Sir Ganga Ram Hospital, New Delhi-110060, India) prospective, double-blinded, two-arm, randomised controlled study.

The patients who qualify inclusion criteria and consent for recruitment will be randomly divided into one of the two groups:

Group-1 [CLADS Group, n=20]: Anaesthesia will be induced and maintained with Propofol administered using the automated CLADS.

Group-2 [Desflurane Group, n=20]: Anaesthesia will be induced with Propofol administered using the automated CLADS and will be maintained with Desflurane.

Sample-size Estimation

In a previous study, the time-to-eye opening with Desflurane and Propofol was 4.2 minutes and 10.7 minutes, respectively. Based on above, a samples size of 15-patients will be required per group to provide 90% power with a bilateral α-risk value of 0.05 to posit a significant difference in time-to-eye opening. We plan to recruit a total of 40-patients to cover up for unanticipated losses after the recruitment.

Randomization, Allocation Concealment

The patients will be randomly allocated to one of the two groups based on a computer-generated random number table (url:stattrek.com/statistics/random-number-generator.aspx). Randomization sequence concealment will include opaque-sealed envelopes with alphabetic codes whose distribution will be in control of an independent analyst. The envelopes will be opened; patient's data-slip will be pasted on them, and will be sent back to the control analyst.

Blinding Strategy

The attending anaesthesiologist will not be blinded to the technique utilized to administer GA and recovery immediately after extubation inside the OR. However, the postoperative patient recovery profile will be evaluated by an independent assessor blinded to the technique of GA.

Management of Anesthesia

Two peripheral venous lines (18G/20G catheter) will be secured. Standard monitoring (EKG, NIBP, pulse oximeter, EtCO2) will be applied. A BIS sensor (Covidien IIc, Mansfield, USA) will be applied over the patient's forehead according to manufacturer's instruction prior to induction of anaesthesia for monitoring depth of anaesthesia. The BIS monitoring module (Model DSC-XP, Aspect medical system, USA) will facilitate monitoring of anaesthesia depth.

Anaesthesia Technique

All the patients will be administered pre-induction fentanyl-citrate analgesia as per a predefined strategy (total 2-µg/kg IV: 1-µg/kg at 0 minute and 3-minute time point). Pre-oxygenation will be initiated at 3-minute time point or prior to that if there is a fall in oxygen saturation (< 94 percent). In both the groups, at 6-minute time point, anesthesia will be induced with Propofol administered by CLADS. In both the groups CLADS will be set to deliver Propofol according to lean body weight (LBW). A BIS-value of 50 will be used as the target for induction of anesthesia. After induction of anesthesia, atracurium besylate 0.05-mg/kg will be administered for skeletal muscle relaxation to facilitate tracheal intubation. Ventilator settings of CMV, tracheal tube size [7.5-mm I.D (male), 6.5-mm I.D (female)], and breathing circuit (circle-CO2 absorber system) will be the standardized in all the patients. Thereafter, the patients in the CLADS group will receive anaesthesia maintenance with Propofol, with the dosing based on adjusted body weight (ABW), and administration controlled with CLADS tuned to consistent anaesthetic depth (BIS-50) feedback from the patients. The patients in Desflurane group will receive anaesthesia maintenance with Desflurane dial concentration titrated to maintain a BIS of 50-55 in all the patients. Oxygen-air mixture (FiO2 0.50) will be used for ventilation in both the groups.

In addition, starting post-intubation, all the patients will receive 1.0-µg/kg/hr fentanyl infusion for intraoperative analgesia. Intraoperative muscle relaxation will be maintained using atracurium boluses controlled by train-of-four response on peripheral neuromuscular monitor (Infinity TridentNMT Smartpod, Draeger Medical Systems, Inc Telford, USA).

Thirty minutes before the end of surgery, non-opioid analgesics, such as paracetamol 1-gm, and tramadol 100-mg will be administered to the patient. The Propofol or Desflurane delivery will be stopped at the point of completion of skin closure. Residual neuromuscular blockade (assessed with train-of-four response) will be reversed with neostigmine (50-µg/kg) and glycopyrrolate (20-µg/kg).

Thirty minutes before the end of surgery, non-opioid analgesics, such as paracetamol 1-gm, and tramadol 100-mg will be administered to the patient. The Propofol or Desflurane delivery will be stopped at the point of completion of skin closure. Residual neuromuscular blockade (assessed with train-of-four response) will be reversed with neostigmine (50-µg/kg) and glycopyrrolate (20-µg/kg).

Inclusion criteria

• Patients of age 18-65 years
• BMI > 35 kg/m2
• Either sex
• ASA physical status II & III
• Undergoing laparoscopic/ robotic bariatric surgery

Exclusion criteria

• Uncompensated cardiovascular disease (e.g. uncontrolled hypertension, atrio-ventricular block, sinus bradycardia, congenital heart disease, reduced LV compliance, diastolic dysfunction)
• Hepato-renal insufficiency
• Uncontrolled endocrinology disease (e.g. diabetes mellitus, hypothyroidism)
• Known allergy/hypersensitivity to the study drug
• Pulmonary dysfunction (obstructive/restrictive lung disease)
• Acute/chronic drug dependence/substance abuse
• Requirement of postoperative ventilation
• Refusal to informed consent