The analgesic efficacy of ultrasound guided transversus abdominis plane (TAP) block after laparascopic appendicectomy in children: a prospective randomised trial

All patients will receive a standardised general anaesthetic. This will involve a rapid sequence induction with propofol (3 mg/kg) by an intravenous injection and suxamethonium (1.5-2 mg/kg) by an intravenous injection and continued paralysis with atracurium (initially 0.5 mg/kg intravenous followed by 0.2 mg/kg intravenous at approximately 30 minute intervals). Anaesthesia will be further maintained with nitrous oxide 70 % in O2 and sevoflurane (titrated to effect). All patients will receive intravenous (IV) fentanyl (1 mcg/kg) at the commencement of surgery and ondansetron (200 mcg/kg) to a maximum of 4 mg IV towards the end of the procedure. Standard monitoring including electrocardiogram, non-invasive arterial blood pressure, arterial oxygen saturation and end tidal carbon dioxide monitoring will be used throughout. The surgical technique will also be standardised. All patients will have laparoscopy port sites infiltrated by the surgeons as per routine practice with 0.5 ml/kg of 0.2% Ropivacaine (1 mg/kg total ropivacaine). Technique for Ultrasound guided TAP block. Laparascopic appendicectomy requires that the TAP block be placed bilaterally. A 38 mm linear array Ultrasound probe transducer (Sonosite Micromaxx (Registered) SonoSite, Inc. 21919 30th Drive SE Bothell, WA) is placed in either flank with the probe orientated on a line joining the umbilicus and the 3rd / 4th lumbar vertebrae. A needle is advanced under aseptic conditions from an injection point on the antero-lateral abdominal wall, at about the level of the umbilicus, in the plane of the ultrasound. The needle is advanced until the tip lies between the transversus abdominus and the internal oblique muscles. A total of 1 ml/kg of 0.2% ropivacaine (2 mg/kg total ropivacaine) is drawn up. Half of this volume is injected on the left hand side and the other half on the Right hand side. A remaining 0.5 ml/kg or 0.2 % ropivacaine (1 mg/kg total ropivacaine) will be available to the surgeons for infiltration of port sites. Total dose of ropivacaine will be restricted to 3 mg / kg in according with published dose recommendations. Post-operatively each patient will be prescribed intravenous Patient Controlled analgesia with morphine as per the Sydney Children’s Hospital protocol and regular paracetamol 15 mg/kg Per Orum every 4 hours. The Sydney Children's Hospital protocol is to draw up 750 microg / kg of morphine into a 50 ml syringe and dilute to 50 ml with normal saline. The patient will be prescribed 1 ml intravenous boluses as required with a machine lockout period of 5 minutes. This will mean that each bolus of intravenous morphine will be 15 microg/kg. There must be no background infusion on the Patient controlled analgesia (PCA). No other analgesics are to be prescribed during the first 16 hours post-operatively unless commenced by the Acute Pain Service. Patients must also be prescribed post-operatively ondansetron 200 microg/kg intravenous (to a maximum of 4 mg) every 8 hours when necessary.