Deep sedation or general anesthesia is frequently required for infant that need radiotherapy to treat malignancies. As radiation therapy usually consist of several sessions, these patients are exposure to several consecutive anesthetic exposures (e.g. for some central nervous system tumors 30 sessions of radiotherapy are required). In our center, this 30-min anesthetic exposure are with sevoflurane. Considering that repeated daily exposure to such potent drugs, as general anesthetics, may induce tolerance, it is reasonable to explore whether this phenomenon is occurring in this population.

The aim of this observational study was to determine if a repeated exposure to sevoflurane is associated with the development of clinical and electroencephalographic tolerance.

We will enroll 16 pediatric patients, and we will measure the time needed to appropriately place the laryngeal mask (clinical effect) and we also will compare the electroencephalographic signal under anesthesia across the different sessions (electroencephalographic effect).

The purpose of this study is to evaluate the development of tolerance to sevoflurane in children undergoing repeated drug exposure.

We will evaluate the development of tolerance in two ways:

Clinical: as the time needed to perform the inhalation induction, with a standardized protocol.

Electroencephalographic: we will record every 3 sessions the electroencephalographic activity of the patients. We will perform classical spectral analysis, and coherence analysis as well.

This observational study will be mainly exploratory since there are no other previous report in this topic

Inclusion Criteria:

• Patients undergoing radiotherapy
• Requiring general anesthesia

Exclusion Criteria:

• Previous Radiotherapy
• Malignant Hyperthermia history

All consecutive pediatric patients schedule for radiotherapy treatment under general anesthesia.