Wisdom teeth removal under general anaesthesia is usually suitable for ambulatory surgery.

The choice of opioid in dental day surgery is based on the need for a rapid and full recovery, as well as less morphine administration. Whether remifentanil can achieve these goals remains to be proved, especially regarding remifentanil-induced hyperalgesia, the potential prolonged Post Anesthesia Care Unit (PACU) stay, or remifentanil-induced workload for nurses.

Patients will be enrolled during the preoperative anaesthetic assessment. Premedication will be achieved with oral administration of hydroxyzine 1 mg/kg the morning before surgery.

The induction of general anaesthesia will be achieved using TARGET CONTROLLED INFUSION (TCI) of propofol associated to TCI of remifentanil or sufentanil, depending on randomization.

The conditions of endotracheal intubation will be evaluated by the Percentage Of Glottic Opening Score (POGO) and the Cormack and Lehane Score.

Mechanical volume-controled ventilation will aim to maintain normocapnia. The baseline inspiratory gas will be a mixture of 45% oxygen and 55% nitrous oxide.

Bispectral Index recording and vital signs monitoring (heart rate and arterial blood pressure) will be used to monitor the depth of anaesthesia.

Dexamethasone 0.3 mg/kg will be administered after induction of general anaesthesia as part of our routine practice.

Patients will be extubated as soon as possible after the end of the surgery and transferred to the PACU.

Nurses in charge patients included in the study will be blinded to the opiod agent administered peroperatively.

Postoperative pain will be assessed using the simple numeric scale. A pain score above 3/10 will prompt the intravenous administration of titrated morphine chlorhydrate, as guided by a written protocol.

Patient will be transferred from the PACU to the ambulatory surgery unit when the Aldrete score is greater or equal to 9. Every patient included will received 1 gr of intravenous paracetamol two hours after the arrival hour in the PACU.

Pain monitoring will be continued in the ambulatory surgery unit, and morphine chlorhydrate will be orally administered (10 mg) if pain score is above 3/10.

Post anaesthetic discharge for home readiness will be given when the Post Anesthetic Discharge Scoring System (PADSS) is greater or equal to 9.

48 hours after the surgery, one of us, blinded to the opiod agent received by the patient, will contact every included patient by phone, in order to evaluate postoperative pain, potential side effects including nausea and vomiting, and patient satisfaction.

Inclusion Criteria:

• -age between 15 and 35 years old
• American Society of Anaesthesiologists (ASA) physical status I or II
• Surgical removal of three to four wisdom teeth
• general anaesthesia
• Ambulatory surgery

Exclusion Criteria:

• Obesity (Body mass index > 30 kg.m-²)
• Pregnancy
• Contraindication for nitrous oxide inhalation
• Patient refusal