Opioid Consumption Following TAP Block Versus Intraperitoneal/Incisional Bupivicaine in Patients Undergoing Major Gynecologic Surgeries: A Randomized Controlled Trial

All patients will receive standardized general anesthetic with standard monitoring. Anesthesia will be induced with intravenous (IV) tramadol (1milligram/kg), propofol (2 mg/kg) and atracurium 0.5mg/kg. Anaesthesia will be maintained with oxygen/air (40:60) with one MAC(Minimum Alveolar Concentration) of isoflurane.

TAP block will be performed for Group T patients before surgical incision with the help of an ultrasound and will be performed by two of the anesthesiologists who are part of this study. The study drug for the TAP block will be two syringes of 20 ml containing bupivacaine 0.25% with no other additives. For the infiltration group I, a 50ml syringe will contain 25ml of 0.5% Bupivacaine and 25ml of 5mics/ml epinephrine. These solutions will be made there and then by the anesthesiologist and the drugs for these solutions will be provided by the clinical trial unit. Allocation to group T, I and C will be according to the randomization block explained earlier. For group T, the US-guided TAP block technique will be similar to the method described by Hebbard and colleagues; (21) an ultrasound linear probe will be positioned in the mid-axillary line in the axial plane half-way between the iliac crest and the costal margin. Transversus abdominal plain will be located under ultrasound guidance. One ml test injection of the study solution will be permitted to confirm needle location. A total of 20ml of study solution will be injected on each side after aspiration to avoid intravascular placement. Surgical incision will be given after 20 minutes of TAP. Additional doses of Tramadol 10mg IV stat will be given on need basis (Rise of heart rate and blood pressure more than 20 % of baseline).

Towards the end of surgery, 50 ml of solution prepared by the anesthesiologist will be used for Group I. 50ml of 0.25% Bupivicaine with epinephrine will be poured into a sterile galley pot, from which the surgeon will draw up the solution. The surgeon will be asked to spray 10ml of this solution on to the pouch of Douglas, 10ml in the peritoneum, 10ml in the rectus sheath and 20ml in the skin.

The amount of Bupivicaine used for group I and T is less than the maximum safe dose which is 2.5mg per kg. Minimal side effects are reported using an ultrasound guided TAP block technique(22). If an immediate side effect is noted while performing the technique, treatment will be administered and the patient will be withdrawn from the study.

The control group (C) will receive the standard anesthesia and analgesia as mentioned above without any nerve block technique.