Clinical Research Directory

Inclusion Criteria: * Age 18 to 75 years old; * Sickle-cell patient. * Signs of a vaso-occlusive crisis (migratory bone pain, which may occur in the limbs, spine, thorax, pelvis, skull) or crisis known as such by the patient; * Severe pain (NRS ≥ 6/10) on admission to the ED; * Registered with the social security scheme or his beneficiaries (except AME) * Signature of free and informed consen. Exclusion Criteria: * Strong opioids received in the previous 6 hours; * Pregnancy or breastfeeding; * Woman not menopausal nor sterile without effective contraception (HAS criteria) * Oxygen saturation below 93%; * Patients who cannot cooperate because of a State of agitation or a Cognitive impairment * Unable to communicate; * Unable to do self-assessment; * Allergy or intolerance to opiates or nitrous oxide. * Abuse or addiction to opioids * Liver insufficiency * Renal insufficiency * Severe asthma or chronic obstructive bronchopulmonary disease * Pulmonary disease necessitating oxygen * Presence of seriousness signs: * All respiratory seriousness signs * all neurologic signs or consciousness impairment (coma Glasgow scale under 15) * hyperthermia over than 39°C * Signs of intolerance of acute anemia * Signs of hemodynamic failure * Known organ failure (renal insufficiency, pulmonary high blood pressure) * A description by the patient of a non usual crisis. * Current treatment with nasal vasoconstrictors is ongoing * Head injury with suspicion of high intracranial pressure * Severe thoracic trauma or decompensated respiratory insufficiency * Contraindications of intranasal administration: * Facial trauma * Nose or sinusal surgery in the previous 6 months before inclusion * Chronic nose and upper airway alteration (ex. facial malformation) * Acute nose and upper airway alteration (ex. Epistaxis, acute respiratory infection, sinusitis). * Contraindication to nitrous oxide * Contraindication to morphine * Patient's refusal to participate in the study. * Previous inclusion in the study of less than 14 days.