Objective To determine the gastric emptying time for liquids in the healthy volunteers by magnetic resonance imaging (MRI) and to provide a reference for reasonable preoperative fasting time.Methods Nineteen healthy volunteers of both sexes,of ASA physical status Ⅰ or Ⅱ,aged 20-60 yr,were enrolled in the study.The volunteers were fasted from the intake of liquids or solids starting from 22:00 the night before the trial,and 12.5％ carbohydrate solution 400 ml containing 40 g maltodextrin and 10 g sucrose was given orally.MRI was performed to measure the baseline gastric fluid volume at 8:00 on the day of the trial (T0).The gastric fluid volume was measured immediately after administration of the oral solution,and then measured every 25 min until the gastric fluid volume was returned to the baseline before administration of the oral solution or to ＜25 ml,and was recorded as T25,T50,T75,T100,et al.The gastric fluid volume was drawn using a computer to obtain the curve for gastric emptying.The gastric half and total emptying time was calculated using the curves.Results The gastric half emptying time was (32± 12) min,and the gastric total emptying time was (99±22) min in the volunteers.Compared with those at Tb,the gastric fluid volume was significantly increased at T25,T50,T75,T100,and no significant change was found in gastric fluid volume at T125,T150and T175.Conclusion After oral intake of liquids,the gastric emptying time is about 2 h,indicating that the preoperative fasting time for liquids can be shortened to 2 h before anesthesia in the healthy volunteers.

Objective:To explore the investigation level of individual monitoring for medical radiation workers.Methods:Monitoring and analysis of individual doses to the medical radiation workers in Guangdong province were performed, from 2016 to 2019, by the Individual Dose Monitoring Department of Guangdong Provincial Hospital for Occupational Disease Prevention and Control.Results:The numbers of monitored workers were diagnostic radiology 53 674, dental radiology 2 563, nuclear medicine 5 001, radiotherapy 16 687, interventional radiology 22 272 and others 2 087 from 2016 to 2019, of which the number of individuals with doses in excess of investigation level 1.25 mSv, were 76, 6, 18, 28, 133 and 2 respectively. The non-real doses made up 67.1 %, 100 %, 55.6 %, 82.1 %, 76.7 % and 100 % of their respective totals. Their 99th percentile doses P99 were 0.37, 0.39, 0.67, 0.35, 0.54 and 0.30 mSv, and the average periodic dose equivalent were 0.07, 0.06, 0.11, 0.06, 0.07 and 0.05 mSv respectively, indicating a statistically significant difference existing in the average annual effective dose between groups ( Z=-26.139--2.681, P<0.001). Conclusions:Due to non-reality of doses in excess of investigation levels and high labor cost, it is suggested to currently use 0.40 mSv per 3 months as investigation level for diagnostic radiology, dental radiology, radiotherapy and others, and 0.70 mSv per 3 months as for nuclear medicine and interventional radiology.

Objective To discuss the feasibility of preoperative diet by measuring gastric emptying time of carbohydrate and protein nutrient solutions in healthy volunteers.Methods A total of 20 healthy volunteers were collected from August 2013 to May 2014.On the morning of the trial,baseline gastric residual volume of each volunteer was measured with magnetic resonance imaging at 8 a.m.,then each of the 20 healthy volunteers took 12.5％ carbohydrate solution 400 ml (containing 40 g of maltodextrin and 10 g of sucrose) or 12.5％ whey protein solution (containing 50 g whey protein) in 5 minutes.Magnetic resonance imaging was conducted to measure the gastric residual volume every 25 minutes.The volunteers were shifted to the other nutrient solution after a 1-week interval.The gastric emptying time of both nutrient solutions was calculated to generate the curves illustrating the process of gastric emptying.Results The baseline gastric residual volume of the volunteers was (14.90 ± 9.39) ml.The total gastric emptying time of carbohydrate solution was (104.90 ± 27.98) min (95 ％ CI 98.64-111.16 min),while that of whey protein solution was (199.6 ± 34.17) min (95％ CI 184.47-214.73 min).There was a significant difference between these two types of nutrient solution in terms of gastric emptying time (P ＜ 0.000 1).Conclusions The induction of anesthesia could be performed 2 hours after carbohydrate administration,and at least 4 hours after whey protein administration.

Objective:To evaluate the accuracy of target-controlled infusion (TCI) of sufentanil at low concentration during combined intravenous and inhalational general anesthesia.Methods:Thirty American Society of Anesthesiologists physical status Ⅰ or Ⅱ patients, aged 18-68 yr, with body mass index <35 kg/m 2, scheduled for elective laparoscopic surgery under combined intravenous and inhalational general anesthesia, were selected in the study.Anesthesia was induced with sufentanil TCI, propofol and rocuronium and maintained with sufentanil TCI combined with inhalation of sevoflurane.The patients were divided into 2 groups ( n=15 each) using the computer-generated sequence of random numbers method: 0.10 ng/ml group (groupⅠ) and 0.15 ng/ml group (groupⅡ). Arterial blood samples were collected from the radial artery for determination of plasma sufentanil concentrations by liquid chromatography-mass spectrometry/mass spectrometry.The bias, precision and wobble were calculated. Results:In Ⅰ and Ⅱ groups, the bias of sufentanil TCI was 17.0% and -3.0%, respectively, the precision was 22.4% and 20.3%, respectively, and the wobble was 23.0% and 21.7%, respectively.The pooled bias, precision and wobble were 6.0%, 22.0% and 22.0%, respectively.Conclusion:The accuracy of TCI of sufentanil at low concentration during combined intravenous and inhalational general anesthesia is within the clinically acceptable range, and the measured blood concentration of sufentanil is about 6% higher than the target concentration.