1. What data in particular will be shared?
   Response - Individual participant data that underlie the results reported in this article, after de-identification (text, tables, figures, and appendices).
   


2. What additional supporting information will be shared?
   Response -  Study Protocol
   Response -  Statistical Analysis Plan
   Response - Informed Consent Form
   
   
3. Who will be able to view these files?
   Response - Researchers whose proposed use of the data has been approved by an independent review committee identified for this purpose.
   


4. For what types of analyses will this data be available?
   Response - For individual participant data meta-analysis.
   


5. By what mechanism will data be made available?
   Response - Proposals should be directed to [doc.aanchalb@gmail.com].
   


6. For how long will this data be available start date provided 01-10-2025 and end date provided 01-10-2030?
   Response - Beginning 3 months and ending 5 years following article publication.
   


7. Any URL or additional information regarding plan/policy for sharing IPD? 
   Additional Information - NIL

INTRODUCTION

There is an increasing incidence of cancer and breast cancer is the most common cancer in women accounting to 25.8 per 100,000 women, in India¹.  Surgery remains the prime modality of treatment for these patients. About 10-20% of surgical patients experience acute post-operative pain, which may progress to post mastectomy pain syndrome in 25-60% patients if adequate pain relief is not provided^2.

Regional anesthesia techniques provide excellent perioperative analgesia ³and also reduce post-operative nausea, vomiting.  Several regional anaesthesia techniques have been described for perioperative analgesia, however no single technique is proven better than the other. Erector spinae plane block and costo-transverse plane block are recent additions under US guided posterior thoracic blocks. Seelam et al used US guided ESPB for female patients undergoing modified radical mastectomy and evaluated its analgesic efficacy in reducing perioperative pain⁴. Nielsen et al in his cadaveric study, described US guided costo- transverse block as relatively new peri-paravertebral block. They checked for spread of injected dye in this block and erector spinae plane block⁵. The spread of local anaesthetic in costotransverse block involved better spread to ventral ramus than erector spinae plane block which possibly will give better analgesia.

Methodology :After obtaining written informed consent computer generated randomization will be done. Patients will be  randomized to receive either a single‐shot US‐guided ESPB (ESP group) or single-shot US- guided costo transverse block After confirming nil by mouth status , patients will be wheeled in operation room and ASA standard monitors will be connected. General anaesthesia using iv Xylocard 1.5 mg/kg ,iv Fentanyl 2mcg/kg (ideal body weight ), iv Propofol 1.5 -2mg/kg.and  neuromuscular block will be achieved with  atracurium 0.5mg/kg. Airway will be secured with an appropriately sized Supraglottic airway/ ETT General anesthesia will be maintained with oxygen- medical air and Sevoflurane using volume controlled ventilation and dial concentration adjusted to target end tidal concentration of  isoflurane of 1.2 .Dexamethasone 0.1mg/kg,  iv Magnesium 40mgs/kg, iv Paracetamol 20mg/kg (maximum 1 gm) will be given after induction.as a part of multimodal analgesia. Post induction patients will be placed in lateral decubitus position and as per group allocated either US guided  ESPB or US guided costo transverse block will be performed . Fentanyl 0.5 mcg/kg (maximum 50 mcg) will be administered to all the patients who have a sympathetic response to pain on incision i.e. if the heart rate and blood pressure is raised by at least 20% of baseline. Post extubation patient will be shifted to a high‐dependency unit. The Numerical rating scale will be used to assess pain postoperatively. Intravenous paracetamol 1 g every 8 h will be continued in the postoperative period. Intravenous morphine will be used as rescue analgesic in both groups, if the NRS score was more than 4, 3mg iv morphine will be administered, and patient will be reassessed after 15 mins. If NRS is more than 4 a repeat dose of 3mg of morphine will be given.

US‐guided ESPB technique :A linear array high‐frequency US probe (GE VENUE GO ^TM) will be used for performing the block, which will be placed in craniocaudal orientation in the midline. The probe will then be moved laterally to identify T4 transverse process (TP), which is usually at 2.5–3 cm from spinous process laterally. ESM, rhomboidus major, and trapezius muscle will be identified. Under aseptic precautions 10 cm block needle (StimuplexUltra 36022 G, B‐Braun) will be introduced in‐plane craniocaudally under vision and navigated till the TP is encountered. Hydro dissection with 2 ml normal saline will be done to confirm separation of ESM from TP. Under US guidance, 25ml 0.5% bupivacaine will be injected and drug spread will be seen in the ESP plane craniocaudally in real time.

USG guided CTB block :A high frequency linear USG transducer will be placed 2-2.5cm lateral to the spinous process of the 4th thoracic vertebra. CTB block will be performed unilaterally on the ipsilateral side of surgery. The skin and subcutaneous layers, trapezius and erector spinae muscles, third and fourth transverse processes, intertransverse and superior costotransverse ligaments (SCTL) as well as the pleura will be placed in the field of view. A needle will be advanced parallel to the SCTL, will be stopped immediately before reaching the cranial part of the fourth rib. In-plane technique will be used  and the needle will be advanced  cephalo-caudally. Here, 25ml 0.5% bupivacaine will be injected.