Comparison of the Efficacy of Ultrasound-guided Pectoral versus Erector Spinae Plane Blocks for Postoperative Analgesia in Patients undergoing Modified Radical Mastectomy: A Randomised Controlled Trial

Introduction: Postmastectomy pain is more common following carcinoma breast surgery. Preventive analgesia for breast carcinoma includes administration of local infiltration or regional anaesthesia in the form of a paravertebral block, epidural, pectoral nerve block or intercostal block. Interfascial blocks, such as ultrasound guided pectoral nerve (PECS II) and Erector Spinae Plane (ESP) block have been shown to provide effective analgesia for mastectomy surgeries. Aim: To compare the postoperative analgesic efficacy of PECSII block and ESP block following mastectomy surgeries. Materials and Methods: The present study was a doubleblinded randomised controlled study. Patients scheduled for an elective unilateral modified radical mastectomy surgery of age 18-70 years, American Society of Anaesthesiologists (ASA) physical status I- II, were endrolled in the study. Sixty patients (ASA I- II) were divided into two groups. (30 in the PECS II group and 30 in the ESP group). The patients received respective blocks under ultrasound guidance after general anaesthesia. The primary outcome measured was the time of first request analgesia between groups. The secondary outcomes were postoperative Numeric Rating Scale (NRS) at eight different time-points (0.5, 1st, 2nd, 4th, 6th, 8th 12th and 24th hour) and intraoperative fentanyl requirement and haemodynamics (heart rate and mean arterial pressure). Total postoperative intravenous paracetamol consumption and rescue analgesic requirement in the first 24 hours postoperatively were noted. Statistical analysis was conducted by using Statistical Package for the Social Sciences (SPSS) version 20.0. Pearson's Chi-square test was performed to compare ratios, and categorical variables were compared using Fisher's exact test. A p-value value <0.05 was taken as statistically significant. Results: The time of first request analgesia was prolonged and significant in ESP block (255.5 +/- 48.76 minutes) than PEC II (197.5 +/- 31.35 minutes) (p=0.000347). In the postoperative ward, NRS scores at the 30th min, first and second hour were significantly lower in ESP block than PECS II group (2.3 +/- 0.4 vs. 5.2 +/- 0.8; 3.2 +/- 0.4 vs. 4.4 +/- 0.3, 3.7 +/- 0.4 vs. 5.2 +/- 0.4); p=0.041 p=0.047, p=0.037 respectively. From the second postoperative hour to the end of the observation period, there were no significant changes in NRS scores among groups. Postoperative paracetamol consumption was significantly higher in PECS II than ESPB (1.25 +/- 0.5 grams vs 2.33 +/- 1.2 grams, p<0.043824). There was no change in intraoperative fentanyl consumption and haemodynamics between groups. Conclusion: ESP block had better pain control, reduced postoperative pain scores and rescue analgesia than PECS II when given as preventive analgesia in mastectomy surgeries.