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After getting clearance from the institutional ethics committee (IEC) and the academic committee, the proposed study will be conducted at Chittaranjan National Cancer Institute, on 93 female patients diagnosed with breast cancer posted for MRM, randomized into 3 groups of 31 patients each, by using AI generated randomization software. Appropriate informed consent will be taken from all the patients. After proper preoperative evaluation, the patients will be shifted to the OT, on the day of surgery. The standard monitors including ECG, pulse oximeter, NIBP and temperature will be attached. Injection Paracetamol 15 mg/kg will be given to all patients 1 hour before the start of surgery, as pre-emptive analgesic. A conventional balanced general anaesthesia will be administered to all patients. Premedication consisting of injection fentanyl (2mcg/kg b.w) and loxicard 2% 2 ml, will be given. Induction will consist of injection Propofol (2 mg/kg b.w). After ensuring adequacy of bag mask ventilation, muscle relaxant (injection Atracurium 0.5 mg/kg) will be given. Second generation supraglottic airway will be placed, and will be confirmed by capnography. IPPV will be initiated and will be maintained with gas mixture of oxygen, air and sevoflurane, along with supplements of atracurium (0.1 mg/kg b.w). After completion of surgery, two surgical drains will be placed, in the pectoral and the axillary regions by the surgeon, as per institutional protocol. The Group D patients, will receive Drain Block with 2% lignocaine (4 mg/kg b.w), 0.5%

isobaric bupivacaine (2 mg/kg bw) and 2 ml (500mg/ml) of MgSO4, divided equally in either surgical drains (total volume 40 ml). After completion of wound instillation, the drains will be clamped for twenty minutes, following which they will be de-clamped. The patients belonging to Group S will receive ultrasound guided SIFB with of 2% lignocaine (4 mg/kg), 0.5% isobaric bupivacaine (2 mg/kg) and 2 ml (500 mg/ml) of MgSO4 (total volume 40 ml). The patients belonging to Group C will be the control group and will only receive paracetamol (15 mg/kg b.w) 8 hourly. The time required for the administration of group specific analgesic intervention will be duly recorded using a digital stopwatch.

After completion of the procedure, injection ondansetron 4 mg will be given. Reversal of neuromuscular blockade will be done using injection neostigmine (0.05mg/kg b.w) and glycopyrrolate (0.01mg/kg b.w). After extubation, the range of motion and the pain score (both static and dynamic) will be assessed using goniometer and VAS respectively. Thereafter, the patients will be shifted to postoperative care unit (PACU) for observation.

Subsequent range of motion and the pain scores will be documented at 4, 8, 12, 18 and 24 hours post extubation. Intravenous injection tramadol (2 mg/kg b.w) will be reserved as rescue analgesic and will be administered if and when VAS exceeds 4. The timing of the first requirement and the total cumulative requirement of the rescue analgesic for the first 24 hours will be documented.