Introduction: remifentanil's optimal dose for children intubation without neuromuscular blockade is unknown. Method: phase IV adaptative trial using Dixon's up-and-down method for modeling remifentanil's dose-response curve for adequate intubation conditions as defined by previous studies.

Introduction: remifentanil's optimal dose for children intubation without neuromuscular blockade is unknown.

Method: phase IV adaptative trial using Dixon's up-and-down method for modeling remifentanil's dose-response curve for adequate intubation conditions as defined by previous studies. Remifentanil doses starting from 2mg/kg will be infused before intubation. When a success occurs next patient's dose will be decreased by 0.25mg/kg/h. When a success does not occur the next patient's dose will be increased by 0.25mg/kg/h. Intubation will be considered adequate if patient does not cough, does not move, if vocal cords are open, if larigocsocpic Cormack grade I or II.

Inclusion Criteria:

• ASA I or II
• Scheduled for surgery under general anesthesia.

Exclusion Criteria:

• Predicted difficult airway
• Severe neurologic or cardiologic conditions
• Recent upper airway infectious diseases