Objective: To investigate the use of ketamine combined with dexmedetomidine for sedation in children with autism spectrum disorder, Methods:aged 2-6 years,, ASA grade I or II. The children were randomly divided into three groups using a random number table method: a low-dose dexmedetomidine group (DEXL group,n=100）The high-dose group of dexmedetomidine (DEXH group,n=100) and the group of esketamine combined with dexmedetomidine (DEXE group,n=100). The DEXL group received 2.5 μ g/kg of dexmedetomidine nasal drops, the DEXH group received 3 μ g/kg of dexmedetomidine nasal drops, and the DEXE group received 2 μ g/kg of dexmedetomidine nasal drops plus 0.5 mg/kg of ketamine nasal drops. Record the success rate of the first dose of nasal sedation, the onset time of sedation, the time of sedation recovery, the quality of recovery, and the satisfaction of the examining physician. Record the vital signs of three groups of patients during the examination process, including before sedation (T0), after successful sedation (T1), after the end of the examination (T2), and upon awakening (T3).

Autism Spectrum Disorder (ASD), also known as Autism Spectrum Disorder (ASD), is a condition in which approximately 60% to 70% of autistic children have intellectual disabilities that significantly affect their ability to take care of themselves and bring immense pressure to society and families. Autistic children often have neurological disorders, and therefore require head magnetic resonance imaging (MRI) examinations. MRI examinations can detect abnormal changes in brain structure and function, providing more objective evidence for early diagnosis and valuable treatment time for autistic patients. However, MRI examinations require children to maintain a calm and quiet state, minimizing physical activity as much as possible. Due to the specific interests and behaviors of autistic children, as well as their refusal to accept environmental changes, completing MRI examinations often requires sedation or anesthesia. The main drugs currently used for sedation in pediatric outpatient examinations include dexmedetomidine, midazolam, ketamine, etc. This study aims to select children with ASD who are scheduled to undergo head MRI in outpatient settings, and explore the safety and efficacy of intranasal administration of ketamine combined with dexmedetomidine for sedation, providing reference methods and evidence for sedation in children with autism spectrum disorder.

Inclusion Criteria:

Clinical diagnosis of autism spectrum disorder Aged 2-6 years, ASA grade I or II

Exclusion Criteria:

Upper respiratory tract infections, Severe respiratory system related diseases Congenital heart disease Liver and kidney dysfunction. Contraindications for ketamine and dexmedetomidine, Expected difficult airways. Anesthetic or sedative drugs used in the last week.