Objective: To evaluate the influence of preoperative fasting duration on blood volume status of pediatric patients during induction based on ultrasonic technique. Methods: One hundred and ten pediatric patients, scheduled for elective operation in the Second Affiliated Hospital & Yuying Children's Hospital, were recruited during January and October in 2018. After sedation by inhalation of sevoflurane, the maximum (expiratory) and minimum (inspiratory) diameter of inferior vena cava (IVC(max), IVC(min)) and aorta velocity-time integral (VTI) in apical five-chamber cardiac view were measured with an ultrasound machine. Respiratory variabilities of these parameters were further calculated. Furthermore, passive leg raising (PLR) test was performed and above measurements/calculations were repeated. The correlation between the duration of fasting and IVC respiratory variations index (IVC(RVI)) or aortic VTI variability (ΔVTI) was then analyzed. Results: Before PLR, IVC(max), IVC(min) and IVC(RVI) were (0.78±0.19), (0.43±0.15) cm and 0.45±0.12, respectively. After PLR, IVC(max) and IVC(min) increased to (0.94±0.20), (0.55±0.18) cm, while IVC(RVI) decreased to 0.42±0.13, the differences were statistically significant (t=15.66, 10.85, 3.14, all P<0.05). However, IVC(max), IVC(min) and IVC(RVI) were not significantly correlated with the duration of fasting analyzed by linear regression (before PLR: r=0.052, 0.163, 0.171; after PLR, r=0.062, 0.169, 0.165, all P>0.05). Before PLR, expiratory aortic VTI (VTI(max)), inspiratory aortic VTI (VTI(min)) and ΔVTI were 21±5, 17±4 and 17±8, respectively. After PLR, the VTI(max) and VTI(min) significantly increased to 23±5 and 19±4 (t=13.60, 10.43, all P<0.05), but ΔVTI was not changed significantly, which was 17±8(t=0.34, P>0.05). Linear regression analysis showed that VTI(max), VTI(min) and ΔVTI were not significantly correlated with the duration of fasting (before PLR: r=0.111, 0.100, 0.047; after PLR: r=0.003, 0.033, 0.073, all P>0.05). Further multiple linear regression analysis indicated that, age and body weight were independent factors influencing IVC(RVI) and ΔVTI before and after PLR (IVC(RVI): β=-0.441, 0.515, -0.451, 0.507; ΔVTI: β=-0.442, 0.545, -2.422, 2.850; all P<0.05). However, the duration of fasting was not correlated with IVC(RVI) and ΔVTI after adjusting the age and weight (IVC(RVI): β=0.177, 0.160; ΔVTI: β=0.037, 0.054; all P>0.05). Conclusion: Age and weight, but not preoperative fasting duration, are correlated with respiratory variabilities of inferior vena cava diameter and aortic VTI in pediatric patients.

Objective To evaluate the effect of dexmedetomidine on postoperative outcomes in ped?iatric patients undergoing open reduction and internal fixation following upper limb fracture performed under sevoflurane anesthesia combined with brachial plexus block. Methods Sixty American Society of Anesthe?siologists physical status Ⅰ pediatric patients of both sexes, aged 6-12 yr, with body mass index <24 kg∕m2, scheduled for elective open reduction and internal fixation following upper limb fracture, were ran?domly divided into ropivacaine group(group R)and dexmedetomidine mixed with ropivacaine group (group DR), with 30 cases in each group. Interscalene brachial plexus block was performed under ultra?sound guidance after sevoflurane anesthesia, 0.25% ropivacaine plus 1 μg∕kg dexmedetomidine(0.3 ml∕kg)was given in group DR, and 0.25% ropivacaine 0.3 ml∕kg was given in group R. The emergence time was recorded, and the development of agitation was observed immediately after emergence from anes?thesia. Sensory block duration, motor block duration, consumption of sedatives and analgesics during post?anesthesia care unit(PACU), consumption of rescue analgesics within 24 h after operation, length of stay in PACU and adverse reactions in the perioperative period were observed and recorded. Results Compared with group R, the incidence of agitation immediately after emergence from anesthesia was significantly de?creased, sensory block duration was prolonged, the consumption of sedatives and analgesics during PACU and rescue analgesics within 24 h after operation was reduced, and the emergence time and length of stay in PACU were prolonged in group DR(P<0.05). There was no significant difference in the incidence of bradycardia between the two groups(P>0.05). No adverse reactions were found in the perioperative period in the two groups. Conclusion Dexmedetomidine can promote postoperative outcomes in pediatric patients undergoing open reduction and internal fixation following upper limb fracture performed under sevoflurane anesthesia combined with brachial plexus block.