Background and aims Erector spinae plane (ESP) block is a myo-fascial plane block employed as an analgesic technique to provide sensory block at multi-dermatomal levels across the chest wall. It was first used by Forero et al, who had described the two techniques (superficial and deep) with different levels of sensory blockade.

The aim of this study was to compare the analgesic requirement and sensory blockade after injecting drug superficial or deep to erector spinae muscle in patients undergoing modified radical mastectomies (MRM).

Methods 40 ASA I/II female patients scheduled for unilateral MRM were enrolled in this prospective randomized double blind study. Group 1 received 25 ml 0.2% ropivacaine deep to ES at the T4 level. Group 2 received 25 ml 0.2% ropivacaine superficial to ES at the T4 level. The various parameters studied included: level of sensory blockade assessed preoperatively, duration of analgesia and requirement of opioids postoperatively in 24 hours.

Results The mean duration of analgesia was significantly higher in group 1 (6.75 + 0.79 hours vs 5.54 +1.03 hours) (p value = 0.00). The requirement of opioids was significantly less in-group 1 (4.30 +0.87 hours vs 6.10 +1.15 hours) (p value=0.00). There was no statistically significant difference in the dermatomal blockade in either group.

Conclusions ESP block (deep to the muscle technique) is a better technique in terms of duration of analgesia and requirement of opioids in the postoperative period for patients undergoing MRM. Further randomized controlled trials are required to substantiate these results.