Pectoral nerve block1 versus modified pectoral nerve block2 for postoperative pain relief in patients undergoing modified radical mastectomy: a randomized clinical trial.

Background: Pectoral nerve block1 (PEC1) given between pectoralis major and minor, and modified pectoral nerve block2 (mPEC2) performed between pectoralis minor and serratus anterior, can provide continuous analgesia after modified radical mastectomy (MRM) when catheters are placed before skin closure. This study was designed to compare PEC1 and mPEC2 block for providing postoperative pain relief after MRM.

Methods: Sixty-two physically fit patients undergoing MRM were assigned into two groups (Group PEC1, n=31 and Group mPEC2, n=31). Before wound closure, epidural catheter was placed in the group designated muscle plane and 30ml of 0.25% bupivacaine was injected through the catheter after wound closure. Bupivacaine 15ml of 0.25% top up was given on patient's demand or whenever visual analogue scale (VAS) score was>4. Time for first analgesia (TFA), number of top ups and VAS was recorded at 0.5, 6, 12, 18, 24 h after surgery. Sensory blockade was assessed 30 min after extubation.

Results: Analgesia was significantly prolonged in group mPEC2 [mean(SD)] 313.45(43.05) vs 258.87(34.71) min in group PEC1, P<0.001. Total pain experienced over 24 h was significantly less in group mPEC2 [mean(SD)] 9.77(6.93) than in group PEC1 24.19(10.81), P<0.0001. Consequently, top up requirements were significantly reduced in group mPEC2 than in group PEC1 [median(range)] 3(2-4) vs 4(3-5) respectively, P<0.001. Lateral pectoral (77.42% and 35.48%) and thoracodorsal nerves (93.55% and 48.39%) had higher incidence of sensory block in group mPEC2 than group PEC1, P<0.001.

Conclusions: mPEC2 provides better postoperative analgesia than PEC1 when catheters are placed under direct vision after MRM.

Clinical trial registration: CTRI/2017/02/007811 (REF/2015/11/010185).