Analgesic efficacy of superficial versus deep serratus plane block for modified radical mastectomy under general anaesthesia: A randomised comparative study

Background and Aims: Serratus anterior plane (SAP) blocks can be given either superficial or deep to the serratus anterior muscle to block the branches of intercostal nerves providing analgesia to the anterolateral chest wall. This prospective randomised comparative study aimed to compare the analgesic efficacy of superficial and deep SAP block in breast surgeries. Methods: Forty female patients scheduled to undergo elective modified radical mastectomy under general anaesthesia (GA) were randomly assigned to receive ultrasound guided SAP block with 30 ml 0.375% ropivacaine either superficial (group S, n = 20) or deep (group D, n = 20) to the serratus anterior muscle, before the induction of GA. The primary outcome was post operative fentanyl requirement over 24 hours and secondary outcomes were comparison of numerical rating scale (NRS) scores for pain, sensory block mapping, time to perform the block, number of needle attempts, etc. Results: The post operative 24-hour fentanyl requirement was comparable between group S and D (318.75 +/- 80.65 versus 272.5 +/- 80.25 mu g, P = 0.07). NRS pain scores were comparable between the groups. Sensory block mapping done at various levels showed T3-T7 block in most of the patients with no difference between the groups. Block performance time (6.05 +/- 3.27 versus 8.35 +/- 3.26 minutes, P = 0.034) and number of needle attempts was significantly lesser in group D. Conclusion: There was no difference in analgesic efficacy when SAP block was given superficial or deep to serratus anterior muscle for modified radical mastectomies. However, deep SAP block required less time and number of attempts to perform than superficial technique.