In-depth study of the components of polymyxins is the key to controlling the quality of this class of antibiotics. Similarities and variations of components present significant analytical challenges. A two-dimensional (2D) liquid chromatography-mass spectrometr (LC-MS) method was established for screening and comprehensive profiling of compositions of the antibiotic colistimethate sodium (CMS). A high concentration of phosphate buffer mobile phase was used in the first-dimensional LC system to get the components well separated. For efficient and high-accuracy screening of CMS, a targeted method based on a self-constructed high resolution (HR) mass spectrum database of CMS components was established. The database was built based on the commercial MassHunter Personal Compound Database and Library (PCDL) software and its accuracy of the compound matching result was verified with six known components before being applied to genuine sample screening. On this basis, the unknown peaks in the CMS chromatograms were deduced and assigned. The molecular formula, group composition, and origins of a total of 99 compounds, of which the combined area percentage accounted for more than 95% of CMS components, were deduced by this 2D-LC-MS method combined with the MassHunter PCDL. This profiling method was highly efficient and could distinguish hundreds of components within 3 h, providing reliable results for quality control of this kind of complex drugs.

Objective     To identify the heart sounds of aortic stenosis by deep learning model based on DenseNet121 architecture, and to explore its application potential in clinical screening aortic stenosis. Methods      We prospectively collected heart sounds and clinical data of  patients with aortic stenosis in Tianjin Chest Hospital, from June 2021 to February 2022. The collected heart sound data were used to train, verify and test a deep learning model. We evaluated the performance of the model by drawing receiver operating characteristic curve and precision-recall curve.  Results     A total of 100 patients including 11 asymptomatic patients were included. There were 50 aortic stenosis patients with 30 males and 20 females at an average age of 68.18±10.63 years in an aortic stenosis group (stenosis group). And 50 patients without aortic valve disease were in a negative group, including 26 males and 24 females at an average age of 45.98±12.51 years. The model had an excellent ability to distinguish heart sound data collected from patients with aortic stenosis in clinical settings: accuracy at 91.67%, sensitivity at 90.00%, specificity at 92.50%, and area under receiver operating characteristic curve was 0.917.   Conclusion     The model of heart sound diagnosis of aortic stenosis based on deep learning has excellent application prospects in clinical screening, which can provide a new idea for the early identification of patients with aortic stenosis.

Objective: To evaluate the composite external fixation in the treatment of children with fracture of lower extremity metaphysis. Methods: A retrospective analysis was conducted of the 42 children with fracture of lower extremity metaphysis who had been admitted to Zhengda Shaoyang Orthopaedic Hospital between September 2016 and September 2018. They were 24 boys and 18 girls, aged from 3 to 14 years (mean, 8.3 years). Open injury occurred in 10 cases, with type Ⅰ in 2, type Ⅱ in 7 and type Ⅲ in one according to the Gustilo-Anderson classification, and closed injury in the other 32 ones. The fracture happened at distal femur in 12, at proximal tibia in 9 and at distal tibia in 21 cases. All the patients were fixated with composite external brackets. Fracture healing, functional recovery of the knee and ankle joints, and complications were recorded. Results: All the 42 patients were followed up for 12 to 18 months (mean, 15.8 months). All fractures healed well by the first intention with no malunion or no alignment change on the full length X-ray films of both lower limbs. Irritant growth within 1.5 cm was observed in 2 cases. No loosening occurred in the external fixation which was removed 3 to 5 months after surgery (mean, 3.8 months). Functional recovery of the knee and ankle joints was good at the last follow-up. For the patients with distal femoral metaphysis fracture, the knee function by the Merchan scoring was excellent in 3 cases, good in 7 cases, fair in one and poor in one; for the patients with proximal tibial metaphysis fracture, the knee function by the Merchan scoring was excellent in 3, good in 4 and fair in 2 cases; for the patients with distal tibial metaphysis fracture, the ankle function by the Kofoed scoring was excellent in 11, good in 7 and fair in 3 cases, giving an excellent and good rate of 83.3%. Of a total of 228 needle channels in the 42 patients, 58 were infected mildly or moderately, giving an infection rate of 25.4%. All the infections responded to active dressing change. Conclusion The composite external fixation brackets are a good choice for the treatment of children with fracture of lower extremity metaphysis, because they are easy in manipulation and stable in configuration, and can reduce the iatrogenic injury to the epiphyseal plate, spare cross-articular fixation and allow early functional exercise.