Inclusion Criteria:  Age ≥ 18 years old; Naive patient of BOM; Support at the day hospital; Affiliated with a social security scheme; Having signed a free, informed and written consent.  Exclusion Criteria:  Pregnant or breastfeeding woman; Emergency surgery; Patients consuming long-term opiates preoperatively; Substance addiction ; Patient unable to understand the rating scales; Palliative care patients; Deaf and / or dumb patients; Patients with psychiatric pathologies (schizophrenia, bipolarity); Patients for whom there is a contraindication to MEOPA; Adult persons subject to legal protection (safeguard of justice, curatorship, guardianship), persons deprived of their liberty.