The purpose of this study is to determine the incidence of pain, emergence delirium and the combination of those postoperative negative behaviours during the first 15 minutes after awakening from sevoflurane anesthesia in pre-school children. Additionally this study will evaluate the relationship between emergence delirium and postoperative pain behaviour after adenotonsil surgery.

Tonsillectomy and/or adenoidectomy is the most common surgery performed in paediatric population. Sevoflurane is the most frequently volatile anaesthetic used in paediatric population. It is well tolerated, allows rapid anaesthesia induction, faster emergence, orientation. A child who emerges from sevoflurane anaesthesia may experience a variety of behavioural disturbances described as "emergence delirium" (ED).

ED has been described as "a mental disturbance during the recovery from general anaesthesia consisting of hallucinations, delusions and confusion manifested by moaning, restlessness, involuntary physical activity, and thrashing about in bed" in the immediate post anaesthesia period. Additionally paranoid ideation has been observed in combination with these emergence behaviours.

Restless recovery from anaesthesia is an important problem. It may lead, along with injury to the child, bleeding from surgical site, to accidental removal of IV catheters and drains. Once ED occur, extra nursing care may be necessary, as well as supplemental sedative and/or analgesic medications, which may be associated to respiratory depression or airway obstruction and may delay patient discharge. Although long-term psychological implications of ED remain unknown, children with restless recovery from anaesthesia are seven times more likely to have new-onset separation anxiety, apathy, eating and sleep problems.

ED after sevoflurane anaesthesia has been suggested both to be and not to be associated with postoperative pain behaviour. Accordingly, adequate pain relief has been found to reduce or have no effect on ED after sevoflurane anaesthesia. Because a self-evaluation is difficult In preschool boy observational scales based on behaviour like CHIPPS, FLACC or CHEOPS are used for the measurement of pain.

Given that the child's behaviour evaluation at emergence is made with observational scales, a superimposition between ED and pain measurement is possible. Nurses and doctors using behavioural scales for the evaluation of ED and pain may not be able to differentiate pain from ED during awakening. This may led to the treatment of an autolimitated disturb (ED) or to the under treatment of pain after surgery.

Inclusion Criteria:

• Male and Female children from 2 to 6 years of age
• American Society of Anaesthesiologists Classification (ASA) I: without systemic disease
• American Society of Anaesthesiologists Classification (ASA) II: moderate systemic disease
• Scheduled for elective tonsillectomy and/or adenoidectomy.
• Children whose parents (or legal tutors) have given their informed written consent

Exclusion Criteria:

• Emergency surgery.
• Children whose parents (or legal tutors) denied their own consensus
• Children with known cognitive impairment
• A story of kidney, liver, pulmonary or cardiac disease.
• A history of chronic pain or use of analgesic drugs.
• Familiar or personal history of malignant hyperthermia
• Need premedication or total intravenous anaesthesia.