A Randomised Controlled Trial To Compare Postoperative Analgesia Between Ultrasound Guided Transversus Abdominis Plane Block And Erector Spinae Plane Block In Children Undergoing Abdominal Surgery

The study will be conducted only after approval from the institutional ethical committee and will be registered with Clinical Trials Registry India (CTRI). Patients fulfilling the inclusion criteria will be recruited for the study. A detailed pre-anaesthetic check-up and investigations will be done for all patients. Informed consent will be taken from parents before the participation of their children in the study. Randomisation and concealment of allocation will be done. An anaesthesiologist with an experience of at least 25 successful blocks in children will carry out the procedure. Observation and data collection will be done by an independent anaesthesiologist, who will be blinded to the block given. Patients will be randomised to one of the two groups in the operating room prior to giving anaesthesia:

Group T - 0.5mL/Kg of 0.25% levobupivacaine with clonidine 1μg/Kg in transversus abdominis plane block on each side.

Group E - 0.5mL/Kg of 0.25% levobupivacaine with clonidine 1μg/Kg in erector spinae plane block on each side.

Patients will be kept nil per oral (NPO) for at least 6 hours for solid foods prior to surgery as per standard guidelines. The children will be premedicated with oral midazolam (0.5 mg/Kg) 30 min before the surgical procedure. After arrival in the operating room, an 22G/24G peripheral intravenous catheter will be inserted. Standard monitoring will be applied, including non-invasive blood pressure (NIBP), electrocardiograph (ECG) with heart rate (HR), pulse oximetry (SpO2) and temperature.

Patients will be pre-oxygenated with 100% oxygen for 3 minutes and anaesthesia will be induced intravenously with injection fentanyl 2 μg/Kg and injection propofol 2 mg/Kg. After confirming adequate mask ventilation, injection rocuronium 0.6 mg/Kg will be administered intravenously for neuromuscular blockade. Trachea will be intubated under direct vision with an appropriately sized Microcuff® endotracheal tube. Anaesthesia will be maintained with oxygen in nitrous oxide (N2O) and sevoflurane, maintaining a minimum alveolar concentration (MAC) of 1.0-1.2, with the patient on controlled mechanical ventilation. Electrocardiography with HR, NIBP, SpO2, end tidal carbon dioxide concentration (EtCO2), end tidal anaesthetic gas concentration, MAC and temperature will be monitored for all patients throughout.

TAP technique (Group T):

Under all aseptic precautions patients will be administered USG guided TAP block. The USG probe (M-turbo broadband linear array, 6-13 MHz paediatric probe Sonosite®, Bothell, Washington, USA) will be sheathed. The ultrasonic probe will be positioned between the lower costal border and iliac crest in the midaxillary line, in a transverse plane to the lateral abdominal wall, to obtain a transverse view of the abdominal layers. A 22G, 50 mm Pajunk® needle for USG guided blocks will be introduced at the appropriate dermatomal level, 1 cm medial to the probe and advanced utilising the in-plane approach with real-time USG assessment. The injection site will be in the neurovascular plane between internal oblique and transversus abdominis muscles. Following a negative aspiration, the correct tip position will be verified by hydro-dissecting the plane with sterile saline, which will be followed by the administration of the medication in smaller increment doses and gentle intermittent aspiration. Patients of Group T will be given 0.25% levobupivacaine with clonidine 1μg/Kg in a volume 0.5 mL/Kg on each side. The same will be repeated on the other side. A hypoechoic enlargement on USG will show the dispersion of the local anaesthetic (LA) solution during the injection. Blocks will not be administered if the needle slides into the muscle during LA injection (to avoid intramuscular spread and haematoma formation). The patient would subsequently be handed over to the surgeon for the procedure. At the end of the surgery, anaesthesia will be terminated, neuromuscular blockade will be reversed and the patient’s trachea will be extubated. The patient will then be transferred to the post-anesthesia care unit (PACU).

ESP technique (Group E):

Under all aseptic precautions patients will be administered USG guided ESP block. The USG probe (M-turbo broadband linear array, 6-13 MHz paediatric probe Sonosite®, Bothell, Washington, USA) will be sheathed. Patients will be turned laterally to one side and the appropriate spinous process will be marked for block performance. The transducer probe will then be moved 3 cm laterally from the midline to see the erector spinae muscle and the transverse process.  A 22G, 50 mm Pajunk® needle for USG guided blocks will be introduced at the appropriate dermatomal level, 1 cm medial to the probe and advanced utilising the in-plane approach with real-time USG assessment. The needle will be placed into the interfascial plane between the transverse process and erector spinae muscle, reaching into the plane from cranial to caudal. Following a negative aspiration, the correct tip position will be verified by hydro-dissecting the plane with sterile saline, which will be followed by the administration of the medication in smaller increment doses and gentle intermittent aspiration. Patients of Group E will be given 0.25% levobupivacaine with clonidine 1μg/Kg in a volume 0.5mL/Kg on each side. The same will be repeated on the other side. A hypoechoic enlargement on USG will show the dispersion of the local anaesthetic (LA) solution during the injection. The patient would subsequently be handed over to the surgeon for the procedure. At the end of the surgery, anaesthesia will be terminated, neuromuscular blockade will be reversed and the patient’s trachea will be extubated. The patient will then be transferred to the post-anesthesia care unit (PACU).

All patients will be administered IV paracetamol 15 mg/Kg every 8 hours postoperatively. The duration of postoperative analgesia, defined as time (in hours) from giving of the TAP/ESP block to the time of first analgesic request in the postoperative period will be recorded. Pain will be assessed by an independent anaesthesiologist using Children’s Hospital Eastern Ontario Pain Scale (CHEOPS) postoperatively at 30 minutes, 1 hour, 3 hours, 6 hours, 12 hours and 24 hours. If the pain score is > 6, injection fentanyl will be given as the rescue analgesic at a dose of 1μg/Kg intravenously and noted. Fentanyl at a dose of 1μg/Kg IV will be repeated if there is no reduction in pain score after 30 minutes. If the patient still complains of pain, diclofenac sodium suppository in a dose 0.5 mg/Kg will be administered per rectally and noted. Sedation will be assessed as per University of Michigan Sedation Scale (UMSS) at 30 minutes, 1 hour, 3 hours, 6 hours, 12 hours and 24 hours postoperatively and noted. Any drug side effects (sedation, hypotension, bradycardia and dry mouth) will also be recorded. Episodes of hypotension, defined as fall in systolic blood pressure of greater than 20% from the baseline, will be treated with IV bolus of normal saline (10- 20mL/Kg in divided doses). Bradycardia, defined as a fall in heart rate of greater than 20% from the baseline, will be treated with injection atropine 0.01 mg/kg administered intravenously. Patients will be monitored for local anaesthetic systemic toxicity (LAST) and any such event will be managed as per American Society of Regional Anesthesia (ASRA) checklist. Total requirement of analgesics in the first 24 hours postoperatively will be noted. Parent satisfaction will be assessed using five-point satisfaction scale (Likert scale) 24 hours postoperatively and noted. All the observations will be made by an independent observer blinded to the group allocation.