BACKGROUND Emergence agitation is a common paediatric complication after inhalational anaesthesia. Intranasal dexmedetomidine can prevent emergence agitation effectively, but the optimal dose is uncertain.OBJECTIVE The aim of our study was to investigate the 95% effective dose (ED 95 ) of intranasal dexmedetomidine for the prevention of emergence agitation after inhalational anaesthesia for paediatric ambulatory surgery.DESIGN A prospective, randomised, placebo-controlled, double-blind, clinical trial. SETTINGThe study was conducted in Guangzhou Women and Children's Medical Center in China from August 2017 to December 2018.PATIENTS Three hundred and eighteen children scheduled for ambulatory surgery were enrolled into two age groups of less than 3 years and at least 3 years. INTERVENTIONSThe children in each age group were randomised into five equal subgroups to receive either intranasal dexmedetomidine 0.5, 1.0, 1.5 or 2.0 mg kg À1 (Groups D 0.5 , D 1.0 , D 1.5 and D 2.0 ), or intranasal isotonic saline (group C) after induction.MAIN OUTCOME MEASURES The primary outcome was the ED 95 dose of intranasal dexmedetomidine for preventing emergence agitation after inhalational anaesthesia for paediatric ambulatory surgery. RESULTSThe incidences of emergence agitation for Groups C, D 0.5 , D 1.0 , D 1.5 and D 2.0 were 63, 40, 23, 13 and 3% in children less than 3 years, and 43, 27, 17, 7 and 3% in children at least 3 years. The ED 95 of intranasal dexmedetomidine for preventing emergence agitation was 1.99 mg kg À1 [95% confidence interval (CI), 1.83 to 3.80 mg kg À1 ] in children less than 3 years, and 1.78 mg kg À1 (95% CI, 0.93 to 4.29 mg kg À1 ) in children at least 3 years. LMA removal time for groups D 1.5 and D 2.0 was 9.6 AE 2.2 and 9.7 AE 2.5 min, respectively, for children less than 3 years, and 9.4 AE 2.0 and 9.9 AE 2.7 min in children at least 3 years, respectively. Length of stay in the postanaesthesia care unit for Groups D 1.5 and D 2.0 was 34.3 AE 9.6 and 37.1 AE 11.2 min, respectively, in children less than 3 years, and 34.7 AE 10.2 and 37.3 AE 8.3 min in children at least 3 years, respectively. These times were longer in the D 1.5 and D 2.0 subgroups than in the control subgroup in the two age groups of less than 3 years and at least 3 years, respectively: 7.2 AE 1.9 min in children less than 3 years and 7.3 AE 2.5 min in children at least 3 years for LMA removal time, 22.2 AE 7.9 min in children less than 3 years and 22.0 AE 7.7 min in children at least 3 years for PACU stay time in control subgroup, respectively (P < 0.05).CONCLUSION Intranasal dexmedetomidine prevented emergence agitation after paediatric surgery in a dose-dependent manner. The optimal dose of intranasal dexmedetomidine for preventing emergence agitation was higher in younger children.

Background The spread of spinal anesthesia was influenced by many factors, and the effect of body height on spinal anesthesia is still arguable. This study aimed to explore the impact of height on the spread of spinal anesthesia and the stress response in parturients. Methods A total of ninety-seven parturients were allocated into two groups according to their height: the shorter group (body height was shorter than 158 cm) and taller group (body height was taller than 165 cm). Spinal anesthesia was performed with the same amount of 12 mg plain ropivacaine in mothers of different heights. The primary outcome of the study was the success or failure of the spinal anesthesia. The secondary outcomes of the study were stress response, time to T6 sensory level, the incidence of hypotension, the satisfaction of abdominal muscle relaxation and patient VAS scores. Results The rate of successful spinal anesthesia in the shorter group was significantly higher than that in the taller group (p = 0.02). The increase of maternal cortisol level in the shorter group was lower than that in the taller group at skin closure (p = 0.001). The incidence of hypotension (p = 0.013), time to T6 sensory block (p = 0.005), the quality of abdominal muscle relaxation (p <  0.001), and VAS values in stretching abdominal muscles and uterine exteriorization (p <  0.001) in the shorter group were significantly different from those in the taller group. Multivariate analysis showed that vertebral column length (p <  0.001), abdominal girth (p = 0.022), amniotic fluid index (p = 0.022) were significantly associated with successful spinal anesthesia. Conclusions It’s difficult to use a single factor to predict the spread of spinal anesthesia. Patient’s vertebral column length, amniotic fluid index and abdominal girth were the high determinant factors for predicting the spread of spinal anesthesia. Trials registration ChiCTR-ROC-17012030 (Chictr.org.cn), registered on 18/07/2017.

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