Potential limitations and biases
PONV, NRS, ESPB
SECONDARY
The major limitations of our study are mostly due to the loss of clinical information. It was not possible to collect data about the exact duration of ESPB performance, the duration of GA, and surgical intervention from the operation theatre;. From the ward it was not possible to collect or retrieve data about PONV, rescue ketoprofen doses, required PCA doses (not just dispensed) and NRS on movement; considerable data were missing at 48 h, limiting their relevance. This was probably due to the non-academic nature of our institution, lacking dedicated research facilities and personnel, but this did not affect the measurement and reliability of primary and secondary outcomes. Anyway, this could also be interpreted as a strength of this study: the positive outcomes recorded were measurable and significant already during the everyday clinical practice, with no extra-fundings required, and presumably impact the real postoperative process of the patients.The limited sample size was a consequence of the COVID-19 pandemic and the slowing down of daily clinical practice:. despite a 6-month extension of the study insurance, it was not possible to respect the expected enrolment pace.Another possible source of bias was regarding the intraoperative use of fentanyl: the unblinding of the anesthesiologists to the ESPB procedure, might affect their propensity to administer the drug. All the other steps have been standardised and are reproducible by other authors. Finally, due to the monocentric nature of the study, the reproducibility might be reduced and the results affected by local practices.