Results
bradycardia, intraoperative bleeding, ESPB, SD, pain, NRS pain, hypotension
SECONDARY, INTRAOPERATIVE BLEEDING
Fifteen ESPB and 15 control procedures were performed between February 2021 and June 2022. The estimated sample size indicated on ClinicalTrial.gov was double (60) the enrolled sample size (30), but we had to conclude the study early, because of the delays with respect to the schedule mostly due to the COVID-19 pandemic period (the study was expected to end in December 2021).The study adheres to the CONSORT guidelines for randomised controlled clinical trials, the CONSORT flowchart is reported in Fig. 
CONSORT flowchart of the study
Descriptive analysis of the ESPB group vs. control group (morphine-only postoperative analgesia)Age(years)BMI(kg·mASA, American Society of Anesthesiology score; BMI, body mass index; N, absolute number; SD, standard deviation;. p-value refers to the mean ± SD and is considered significant when < 0.05.
Statistical analysis of the primary and secondary outcomes of the studyNRSat 2 hNRSat 6 hNRSat 12 hNRSat 24 hNRSat 36 hNRSat 48 hPCA0–2 h (mg)PCA2–6 h (mg)PCA6–12 h (mg)PCA12–24 h (mg)PCA24–36 h (mg)PCA36–48 h (mg)LOS(days)LOS, length of hospital stay; mcg, micrograms; N, absolute number; NRS, pain numeric rating scale; PCA, patient controlled analgesia (mg of morphine used at any time-interval); SD, standard deviation; IQR, interquartile range. Patients’ satisfaction is expressed with a vote from 1 (extremely bad) to 10 (extremely good) by the patient on the day of PCA pump removal. p-value refers to Mann-Whitney analysis and is considered significant when < 0.05.The primary outcome was postoperative PCA morphine consumption: it was significantly lower at any time point during the first 48 h than in the control group. Fig. Intraoperative fentanyl use was significantly lower in the ESPB group than in the control group (203.3 ± 121.7 mcg vs. 322.0 ± 148.2 mcg, p-value = 0.021). No differences in terms of intraoperative bleeding were detected, and no cases of hypotension or bradycardia were associated with the ESPB, testifying to the safety of the procedure. No significant side effects of ESPB were observed.
PCA morphine consumptionx-axis, time; y-axis, milligrams of morphine; black line with dots, ESPB group; gray line with triangles, morphine-only groupNRS values were significantly lower in the ESPB group than in the control group up to 36 h after surgery. Fig. 
NRS pain scorex-axis, time; y-axis, NRS; black line with dots, ESPB group; gray line with triangles, morphine-only groupDespite not reaching statistical significance, LOS resulted 2 days longer in the control group, likely impacting the economic burden of the perioperative management of these patients. (7.67 ± 6.62 days vs. 9.67 ± 7.41 days, p-value = 0.192).The final satisfaction expressed by the patients with a vote from 1 (awfully bad) to 10 (exceptionally positive) was significantly higher in the ESPB group than in patients managed with the standard analgesic protocol (8.4 ± 1.2 vs. 6.0 ± 1.2, p-value < 0.001).