Ultrasound-guided subtransverse interligamentary (STIL) block versus erector spinae plane (ESP) block for postoperative analgesia in patients undergoing modified radical mastectomy (MRM) - A randomised comparative study.

Background and aims: Ultrasound-guided regional anaesthesia has led to the development of various paraspinal block techniques, with the most notable being the erector spinae plane (ESP) block and the subtransverse interligamentary (STIL) block. The objective of this study was to assess and compare the analgesic efficacy of STIL block with ESP block in patients undergoing modified radical mastectomy (MRM) surgery, in terms of postoperative pain scores, 24-h opioid consumption, rescue analgesia requirements and adverse effects.

Methods: One hundred twenty female patients, aged 18-65 years, scheduled to undergo MRM, were randomised to receive either ESP (Group I) or STIL (Group II) blocks with 20 mL of 0.25% levobupivacaine and dexamethasone 4 mg. The primary outcome was pain scores at 12 h. The secondary outcomes were 24-h opioid requirement, total duration of analgesia and number of rescue analgesia doses required. Paired Student's t-test was used to compare normally distributed quantitative data, while Mann-Whitney U test was conducted to analyse non-normally distributed quantitative variables. The Chi-square test was employed to assess the association between categorical variables. A P value of less than 0.05 was considered statistically significant.

Results: The median Numerical Rating Scale (NRS) scores were significantly lower in Group II compared to Group I at 2, 6, 12 h (P < 0.001) and 24 h (P < 0.008). The total opioid requirement (P < 0.0001) and the number of rescue analgesia doses (P < 0.001) were significantly lower in Group II. The duration of analgesia was significantly longer in Group II (P < 0.001). The time taken to perform the procedure was significantly less in Group I (P < 0.001).

Conclusion: The STIL block is associated with a lower NRS score and decreased postoperative opioid consumption compared to the ESP block in patients undergoing MRM.