This study was approved by the Ethics Committee of the Affiliated Hospital of Binzhou Medical University, No. (2021KT-014). This project was registered in the Chinese Clinical Trial Registry on November 6, 2021, with the registration number ChiCTR2100052830.
This project was a sequential enrollment study. All pediatric patients were anesthetized and awakened in the Pediatric Endoscopy Center of our hospital. After the evaluation in the anesthesia clinic, the legal guardians of the children voluntarily signed the informed consent. Pediatric patients enrolled in this study aged 1-14 years, with a BMI of 18-25kg/m2, American Society of Anesthesiologists (ASA) physical status I -Ⅱ, and normal development. Exclusion criteria included: (1) allergy to esketamine or propofol; (2) definite difficult airway; (3) ongoing sedative therapy (e.g., propofol, morphine, fentanyl, sufentanil, midazolam, dexmedetomidine, ketamine) or recent use of sedatives (withdrawal time < 24 h); (4) cardiac or respiratory system diseases; (5) hepatic or renal malfunction; (6) developmental malformations.
Anesthesia methods and gastroscopic procedure
All children were fasted for at least 6 hours, and peripheral intravenous access was established. A total of 50 ml of Pronase solution (400 U/ml ) was drunk 5 min before endoscopy to eliminate foam and improve endoscopic graphic clarity, which was a proteolytic enzymes that can dissolve mucus in stomach. Oxygen was inhaled continuously at 3 L/min through a nasal catheter throughout the process. Children’s heart rate (HR), noninvasive blood pressure (right upper arm), pulse oximetry (SPO2), and electrocardiogram (ECG) were monitored during the gastroscopy and recovery. The patients were placed in the left lateral decubitus position with neck extension. Rescue medication and emergency airway equipment were prepared in advance. All clinical operations were performed by experienced endoscopists and anesthesiologists.
Esketamine (50 mg/2 ml, Jiangsu Hengrui Pharmaceutical Co., Ltd., China) was diluted to 50 ml by another researcher unaware of the research content. The diluted drug concentration was 1 mg/ml, which was easy to calculate and use. The first child was administered with 0.1 mg/kg esketamine; 30 seconds after injection, 3 mg/kg propofol (200 mg/20 ml, Beijing Fresenius Kabi Co., Ltd., China ) was injected slowly by an experienced anesthesiologist. After the child was sedated successfully, the pediatrician attempted to insert the gastroscope. The study was carried out with a sequential method. If the induction of anesthesia failed (significant body movement or choking) in the first child, the dosage of esketamine would increase to 0.15 mg/kg (0.05 mg/kg interval difference) for the next patient. Otherwise, the dosage of esketamine would decrease to 0.05 mg/kg. The study was not terminated until nine crossover inflection points were reached. According to the Modified Observer’s Assessment of Alertness/Sedation scale (MOAA/S)[6], all the children were sedated at the level of MOAA/S score = 1 (response only after trapezius squeeze stimulus). If sedation was unsatisfactory, 10-50 mg of propofol was intravenous injected until the endoscopy was completed. During the period of anesthesia maintenance, 0.5 mg/kg propofol was added according to the examination time and the patient's response.
Once the child encountered bradycardia during the examination, 0.15 mg/kg atropine was immediately administered intravenously. If SPO2≤ 90%, mask-assisted ventilation was operated. If the child had hypotension (systolic blood pressure below 30% of baseline), 3-6 mg of ephedrine was administered. After the examination, the modified Aldrete scale was used to assess the departure of patients from the recovery room only if they reached a score of nine points or more[3].
Observational indicators
The primary outcome was the median effective dose (ED50) of esketamine adjunct to 3 mg/kg propofol for pediatric patients to suppress the upper gastroscopy insertion response.
Secondary outcomes were as follows: total dosage of propofol; HR, SpO2, and blood pressure at time points before anesthesia induction (T0), immediately after esketamine injection (T1), immediately after propofol injection (T2), immediately after removal of gastroscope (T3), and 1 min after recovery (T4); endoscopy time; wake-up time; adverse reactions, e.g., nausea, delirium, delayed awakening, and respiratory depression.
The arousal time was defined as the period between gastroscopy extraction and the time when the children could open their eyes and cooperate. Arousal time exceeding 30 minutes implied delayed awakening. The Paediatric Anaesthesia Emergence Delirium(PAED) scale was used to evaluate the emergence delirium in children. SpO2 ≤ 90% indicated the presence of respiratory depression. Other unexpected complications were also recorded.
Statistical analysis
The primary outcome ED50 and 95% confidence interval of esketamine were calculated using probit regression according to the data collected in this up-and-down sequential research. Due to the characteristics of this sequential study, the esketamine dose in the next patient depended on the success or failure of anesthesia induction in the previous patient. If the child showed significant choking, involuntary body movement, or airway obstruction preventing endoscope insertion, the anesthesia induction was recognized as “failure,” and the esketamine dose in the next child would be improved by 0.05 mg/kg. Conversely, the dosage was lessened by 0.05 mg/kg when it was “success.” Enrollment was stopped until the ninth crossover inflection point appeared.
Software SPSS version 26.0 (IBM Inc., Armonk, NY, USA) was used for statistical analyses. Normally distributed continuous data were expressed as the mean ± standard deviation. The Shapiro-Wilk test was used to determine whether the collected parameters were normally distributed. Non-normally distributed data were expressed as median (interquartile range, IQR). P < 0.05 was considered statistical significance.