his prospective, observational, exploratory, and multicenter study aims to describe the evolution of propofol effect-site concentration administered via target-controlled infusion (TCI) based on the Eleveld model-with adjustments for opioid co-administration-guided by the bispectral index (BIS) during the transition from inhalational anesthesia with sevoflurane to total intravenous anesthesia (TIVA) in pediatric patients.The study population will include 50 pediatric patients, aged 2 to 12 years, scheduled for elective low- or medium-complexity surgeries. Induction will be performed with sevoflurane, followed by intravenous access placement and transition to TIVA using propofol and remifentanil via TCI. As part of the neuromonitoring, the bispectral index, spectral edge frequency (SEF), and median frequency (MF) will be recorded. Additionally, hemodynamic parameters will be recorded on a minute-by-minute basis.The primary objective is to describe BIS-guided adjustments of propofol during the anesthetic transition. Secondary objectives include describing interindividual variability in propofol titration, time to reach a BIS of 40-60, burst suppression patterns, SEF, MF, drug consumption, hemodynamic stability, and clinical adverse events. Statistical analysis will be primarily descriptive, examining correlations between BIS, propofol, and the minimum alveolar concentration (MAC) of sevoflurane.

Inclusion Criteria:

• Age 2 to 12 years
• Scheduled for elective low- or intermediate-risk surgery according to the National Institute for Health and Care Excellence (NICE) surgical risk stratification (e.g., tonsillectomy, adenoidectomy, postioplasty, orchidectomy, orchidopexy, inguinal herniorrhaphy)
• American Society of Anesthesiologists (ASA) Physical Status Classification I or II

Exclusion Criteria:

• Refusal of parents/legal guardians to sign informed consent, or refusal of the child to provide assent when applicable
• Cardiovascular or neurological disease that may interfere with anesthesia or with the pharmacokinetic model
• History of allergy or adverse reaction to inhalational or intravenous anesthetic agents used in the protocol
• Airway malformations or conditions that complicate standard intubation or airway management
• Psychological or neurological conditions requiring sedative or hypnotic premedication prior to the anesthetic procedure
• Treatment with drugs that may alter the pharmacokinetics or pharmacodynamics of the anesthetic agents
• Difficult peripheral venous access

Pediatric patients aged 2 to 12 years scheduled for elective low- or intermediate-risk surgery at Hospital de Clínicas José de San Martín and Hospital General de Niños Pedro de Elizalde, Buenos Aires, Argentina. Recruitment will aim for balanced representation across three age strata (2 to <4 years, 4 to <8 years, and 8 to 12 years), although age stratification is not an inclusion criterion. Patients will be enrolled by consecutive non-probability sampling over an estimated 4-month period, with a target sample size of 50 participants.

A formal individual participant data (IPD) sharing plan has not yet been established. The current informed consent and assent forms approved by the Ethics Committees do not specifically authorize sharing of individual-level data with third parties; only aggregated, anonymized results are planned for dissemination through scientific publications and conference presentations. A decision regarding IPD sharing may be reconsidered after study completion, subject to ethics committee approval, additional consent provisions if required, and a formal data sharing agreement.