Comparison of ultrasound guided placement of local anaesthetic in the abdominal muscle and local anaesthetic under the skin for pain relief during and following surgical repair of belly button hernias in children

Anaesthesia and intraoperative management General anaesthesia will be induced with 1-8% sevoflurane via a facemask. Anaesthesia will be maintained with 1 minimum alveolar concentration (MAC) sevoflurane. Intraoperative monitoring will include pulse oximetry, non-invasive blood pressure, electrocardiogram (ECG), end tidal carbon dioxide concentration and heart rate. An intraoperative increase in respiratory rate, heart rate or mean arterial pressure of >20% following skin incision or during surgery will be defined as insufficient analgesia and treated with 0.25 ug/kg fentanyl intravenously. Local wound infiltration Once general anaesthesia has been established the surgeon will perform all subcutaneous periumbilical local anaesthetic infiltrations. Following aseptic preparation of the site a total of 0.3ml/kg (to a maximum of 5ml) of combined 1% lignocaine and 1% ropivacaine will be infiltrated 5 minutes prior to skin incision. Ultrasound guided Rectus sheath blocks Once general anaesthesia has been established the primary investigator, or consultant anaesthetist experienced in ultrasound-guided regional anaesthesia in children, will perform the bilateral rectus sheath block. A Micromaxx ultrasound machine with either a hockey stick or high frequency linear (HFL) probe will be used to identify the relevant structures within the rectus sheath. Following aseptic preparation of the puncture site and the ultrasound probe, the rectus sheath block will be performed under cross-sectional continuous ultrasound imaging. A 22g spinal needle will be used to facilitate placement on both sides of the umbilicus. The injection site will be defined where the optimal ultrasonic visualisation of the posterior sheath is achieved. Once the needle is correctly positioned within the rectus sheath a predetermined volume of 1% lignocaine and 1% Ropivacaine will be injected following a negative aspiration test. A total of 0.3ml/kg (to a maximum of 5ml) of combined 1% lignocaine and 1% ropivacaine will infiltrated bilaterally 5 minutes prior to skin incision.