Ethical approval for this study (ethics committee n° 1957_OPBG_2019) was provided by the Ethics Committee of Ospedale Pediatrico Bambino Gesù IRCCS, Rome, Italy (Chairperson Prof. G. Andria), on 18 September 2019. The requirement for written informed consent was waived by the Ethics Committee of Ospedale Pediatrico Bambino Gesù IRCCS. All methods were performed in accordance with the ethical standards as laid down in the Declaration of Helsinki and its later amendments or comparable ethical standards.

This is a retrospective analysis of a single institution’s experience, and patients’ confidentiality was protected.

All children who underwent day-case surgery procedures in anesthesia between 12 September 2012 and 18 April 2018 were included in the study. Inclusion criteria for day-case surgery were as follows: ASA physical status classification system grades I or II, length of surgery lower than 90, and procedures which do not require urinary catheter at the end of surgery. Exclusion criteria were as follows: newborns, obesity, ASA physical status classification system grade III or upper, potential difficult airway management, familiarity for sudden infant death syndrome, QT syndrome, asthma episode in the last month, procedures which cause bleeding up than 10% of blood volume, sleep apneas, and procedure with relevant pain at the end.

This manuscript adheres to the applicable Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines (www.strobe-statement.org).

We made a retrospective analysis of the hospital database and focused on children requiring unplanned admission to the hospital for the night. Admission in hospital we implied as any admission from day-case surgery unit to the historical headquarters. Investigators identified unplanned admissions by the software packages “OBG Clinico®” and “GSED®,” which provides all database about patients of Ospedale Pediatrico Bambino Gesù. We also investigated distribution of patients about kind of surgery and experience in pediatrics of anesthesiologists. The experience of anesthesiologists was divided in three classes: less than 5 years of experience in pediatrics, between 5 and 15 years of experience in pediatrics, and more than 15 years of experience in pediatrics.

Anesthesiologists and surgeons selected patients the day before surgery investigating clinical history and objective examination (excluding patients with respiratory infections) and gave informational materials in addition to the information material that the families received at the time of the first surgical visit which indicated the procedure.

To evaluate families and patient’s education, anesthesiologists used a checklist (Table 1) to assess 10 parameters. During the preoperative examination on the day before the procedure, the anesthesiologist used the checklist at the end of the visit to complete the training of parents or caregivers and test their level of understanding. For example, it was explained to parents or caregivers that before discharge from the day surgery unit, the risk of patients falling was high, and the instructions of the health personnel had to be followed.

If one or more parameters resulted “inadequate,” the procedure was performed in the main venue of the hospital. The anesthesiologist was responsible for assessing the suitability of parents or caregivers’ level of education, understanding, and compliance with rules, through the use of the checklist (Table 1).

Parents or caregivers signed the informed anesthetic and surgical consent at the end of the visit. After the procedure and at the discharge from the surgical unit, a prescription for analgesia was filled. Potential postoperative complications were explained to the family, and the phone number of an advice and support line was provided. For this reason, the first night after surgery, patients and their families must stay overnight in the proximity of the hospital (100 km) providing, for example, to stay in a hotel for those patients who live far away. The parents, or legal guardians of the patients, are informed about the need to stay overnight for the first postoperative night within 100 km of the hospital and undertake to respect this rule.

The day after the surgery, patients returned to the “San Paolo” venue for a surgical control and medications to evaluate pain and minor surgical complications. The surgeon has the responsibility to discharge the patient after his evaluation and to contact any missing patients.

All children who underwent day-case surgery procedures under anesthesia between 12 September 2012 and 18 April 2018 were included in the study.

Anesthesia technique consisted in a general anesthesia with sevoflurane and O2/N2O (without neuromuscular blocking drugs), associated with topic and local anesthesia, or peripheric nerve blocks by ropivacaine 0.2% (with maximum dose 2 mg/kg), for avoiding opioids. For postoperative analgesia, paracetamol iv or paracetamol/tramadol was administered. Standard intraoperative monitoring required the use of heart rate (HR), oxygen peripheral saturation (SpO2), electrocardiogram (EKG), noninvasive blood pressure, temperature, and CO2 capnography and then continued in recovery rooms.

All patients were in spontaneous breathing with facial mask or laryngeal mask, and, in case of dentistry, oral intubation was performed.

Discharge criteria from the recovery room were as follows: Aldrete score 9 or equal to the preoperative evaluation. The discharge criteria from the day-case surgery unit were as follows: Aldrete score 10 or equal to the preoperative evaluation, hemodynamic stability, the presence of protecting reflexes, good mobilization, pain score less than 4 of face legs, activity, cry, consolability (FLACC) scale or visual analogic scale (VAS), no PONV, and no requirement of urinary catheter.

The unplanned admission rate, the anesthetic reasons, and the correlation with the experience of the anesthesiologist were evaluated.

Anesthetic reasons for ward admission after surgery were perioperative complications: bronchospasm, laryngospasm, hemodynamic instability, anaphylaxis, PONV, and pain (with a FLACC or VAS score upper than 4). We implied perioperative complications as events that required immediate intervention, as they were potentially dangerous for the patient, and that after the procedure provoked an Aldrete score < 10 or less than the preoperative evaluation, or which did not allow the discharge criteria from the day-case surgical unit.

The primary endpoint was the rate of unplanned admission following day-case surgery, to evaluate the system level of patient safety. The secondary goal was to evaluate the influence of the anesthesiologist’s expertise in pediatrics on safety (in terms of rate of unplanned admissions).

Categorical data are presented as number and percentage and continuous data as median range. The chi-square test for association was used to determine if there is any association between procedures performed over the years and the different levels of experience in pediatrics. The null hypothesis is that the study variables are not associated (i.e., independent).