For pediatric patients undergoing general anesthesia, poor anesthesia induction compliance often has adverse effects on individual behavior in the early postoperative period. Dexmedetomidine can reduce the cardiovascular responses and postoperative mental adverse reactions caused by esketamine anesthesia induction [6]. This study aims to explore the ED50 and ED95 and clinical effects of the combination of dexmedetomidine and esketamine nasal drops for preoperative sedation in children of different ages undergoing general anesthesia, providing a theoretical basis for the combined use of dexmedetomidine and esketamine for preoperative sedation in children undergoing general anesthesia.

Children scheduled for general anesthesia were randomly divided into two groups based on age: Group T consisted of toddlers aged 1 - 3 years old, and Group P consisted of preschool children aged 3 - 6 years old. The initial dose for both groups was dexmedetomidine 1μg/kg and esketamine 0.5mg/kg.

The sedation depth of the children was assessed using the Ramsay Sedation Scale. An unbiased coin - flipping design was adopted: after esketamine 0.5mg/kg was administered intranasally via a nasal dropper, dexmedetomidine 1μg/kg was given intranasally. The adjusted dose of dexmedetomidine was 0.25μg/kg. If the sedation of the previous child failed, the intranasal dose of dexmedetomidine for the next child would be increased by 0.25μg/kg. If the sedation of the previous child was successful, a card would be drawn to decide the induction dose for the next patient. A total of 20 cards, which were identical in appearance, were prepared. The probability of administering the same dose was 19/20 (95%), and the probability of reducing the dose for the next patient by 0.25μg/kg was 1/20 (5%).

After drug administration, an anesthesiologist who was unaware of the medication usage would rate the sedation level using the Ramsay Sedation Scale every 5 minutes. The non - invasive blood pressure (NIBP), heart rate (HR), respiratory rate (RR), and blood oxygen saturation (SpO2) were recorded before drug administration (0 minutes, baseline) and at 5, 10, 15, 20, 25, and 30 minutes after drug administration.The onset time was defined as the time from intranasal administration to an RSS score of ≥ 4. Thirty minutes after intranasal administration, an experienced nurse who was unaware of the intranasal drug dose performed intravenous cannulation. The emotional state was assessed using the Emotional State Scale (ESS - 4) during intravenous cannulation. Successful intravenous cannulation was defined as an ESS - 4 score of ≤ 2 during cannulation, regardless of whether the intravenous infusion catheter was successfully inserted.The Pediatric Anesthesia Emergence Delirium (PAED) scale was used to assess the degree of emergence delirium in children. The onset time of sedation (the time to reach an RSS score of ≥4 after intranasal drug administration), surgical time (from the start to the end of the surgery), and awakening time (from the closure of the sevoflurane vaporizer to an Aldrete score of 9 or above) were recorded.

Inclusion Criteria:

1. ASA physical status classification Grade I or II;
2. Age 1-6 years old;
3. Children who need to undergo general anesthesia for elective surgery;
4. Weight within the normal range;
5. Signed informed consent form. -

Exclusion Criteria:

1. The child's guardian or the child themselves refuses to participate in the study;
2. Patients with contraindications for sedation/anesthesia or a history of abnormal recovery from sedation/anesthesia;
3. Individuals known to be allergic to the study drugs, opioid drugs, or rescue medications;
4. Individuals with a history of heart, brain, liver, kidney, or metabolic diseases;
5. Individuals with an upper respiratory tract infection within the past two weeks;
6. Individuals with other diseases that may cause harm to the subject. -