Analgesia and spread of erector spinae plane block in breast cancer surgeries: a randomized controlled trial

BACKGROUND: To evaluate the analgesic efficacy and spread of variable volumes of local anesthetics (LA) in Erector spinae plane block (ESPB). METHODS: Sixty patients aged between 18 and 50 years with an ASA I-II and scheduled for breast cancer surgery were randomized to receive either ESPB with 20 ml 0.25% bupivacaine (Standard volume ESPB), or with 40 ml 0.125% bupivacaine (High volume ESPB), or no ESPB (GA only group). The primary outcome was pain intensity evaluated by the visual analogue scale (VAS), 12 hours after surgery. P-values < 0.05 were considered the cutoff point for statistical significance. The secondary outcomes were pain at rest and pain on movement evaluated by the VAS, craniocaudal injectate spread, to paravertebral (PV) and epidural spaces assessed by CT, clinical dermatomal spread, level of sedation or agitation, and patient satisfaction with anesthesia and analgesia. RESULTS: VAS at rest 12 h after surgery was less in both intervention groups compared to the control (1.75 ± 0.79 vs. 1.6 ± 0.88 vs. 3.4 ± 1.96, p = 0.001). The LA had extended further in the high volume group than the standard volume group (11.20 ± 3.07 vs. 9.15 ± 2.54 vertebral levels, p = 0.027). No difference of the spread to PV or epidural spaces between the 2 intervention groups. More dermatomes were covered in the high volume group (7.20 ± 2.12 vs. 5.75 ± 1.37 dermatomes, p = 0.014). Agitation was higher in the GA only group than both ESPB groups in the first 8 postoperative hours. Patients were more satisfied in both ESPB groups than the GA only group. CONCLUSIONS: Preoperative ESPB is an excellent analgesic modality and it can also attenuate both postoperative agitation and sedation. Doubling the injectate volume enhances the craniocaudal spreading and may be useful for surgeries requiring multiple dermatomes. However, larger volume has no effect on analgesic efficacy or patient satisfaction as there is no further spread to the PV, epidural spaces or spinal nerve rami. TRIAL REGISTRATION: NCT04796363 (12/3/2021).