Comparison of Analgesic Efficacy of Ultrasound Guided PEC II Block Using Dexamethasone as an Adjuvant to Ropivacaine Versus Plain Ropivacaine in Patients Undergoing Modified Radical Mastectomy: A Double-Blind, Randomized Controlled Trial.

Introduction:  Pain after breast cancer surgery is one of the main reasons for postoperative morbidity and pulmonary complications leading to increased hospital stay. Therefore, effective management of postoperative pain becomes necessary to alleviate patients' suffering and allow early mobilization and hospital discharge. Traditionally, opioids have been used to manage perioperative pain but they are associated with side effects. So, an opioid-sparing multimodal analgesia approach is used nowadays. Ultrasound-guided pectoral type-II (PEC II) block is increasingly being used to address acute postoperative pain after breast cancer surgery. However, to date, not many studies have been done regarding prolonging the duration of analgesia of PEC II blocks for postoperative pain relief in patients undergoing modified radical mastectomy (MRM). So, we undertook this study to compare the analgesic efficacy of PEC II block using dexamethasone as an adjuvant to ropivacaine versus plain ropivacaine in patients undergoing MRM.

Methods:  After obtaining approval from the institute ethics committee and written informed consent from the patients, this prospective, double-blind, parallel group, randomized controlled study was carried out at All India Institute of Medical Sciences (AIIMS) Raipur, from March 2021 to March 2022. Sixty-four female patients, aged 18 years and above, belonging to the American Society of Anesthesiologists, physical status I, II, and III, undergoing unilateral, elective MRM under general anesthesia, were randomly allocated to two groups A and B, with 32 patients in each to receive 30 mL of 0.25% ropivacaine plus 2 mL (8 mg) of dexamethasone and 30 mL of 0.25% ropivacaine plus 2 mL of normal saline, respectively. The primary outcome measure was total opioid consumption till 12 hours postoperatively. Secondary outcome measures were the difference in pain scores based on the numeric rating scale till 12 hours postoperatively, post-operative sedation scores, the incidence of postoperative nausea vomiting (PONV), and other adverse events (if any).

Results: The mean (SD) of morphine (mg) consumed intraoperatively was 5.50 (1.05) and 5.95 (0.86) with P = 0.033 and that consumed postoperatively was 1.00 (0.00) and 1.69 (0.93) with P <0.001 in group A and B respectively, with morphine consumption being higher in the group. The difference in the NRS score for pain at rest was statistically significant at 2 h (=0.030), 4 h (=0.004), 6 h (=0.002), and, 12 h (=0.039) time points with the score being higher in group B. The groups were comparable in terms of postoperative sedation score (P > 0.05) and incidence of postoperative nausea and vomiting. None of the patients in group A and 6.2% of the patients in group B had nausea (P = 0.492). None of the patients in either of the groups had vomiting. No other complication occurred during the entire study in either of the groups.

Conclusion: In comparison to plain ropivacaine, the addition of dexamethasone as an adjuvant to ropivacaine for PEC II block in patients undergoing MRM significantly reduced perioperative opioid consumption and postoperative NRS scores. No significant change was noted in terms of postoperative sedation score, incidence of PONV, and other side effects between the groups. Therefore, we conclude that the analgesic efficacy of US-guided PEC II block using dexamethasone, as an adjuvant to ropivacaine is superior to that of plain ropivacaine in patients undergoing MRM.