Effect of mechanical ventilation under intubation on respiratory tract change of bacterial count and alteration of bacterial flora.

Background: The most common 'second strike' in mechanically ventilated patients is a pulmonary infection caused by the ease with which bacteria can invade and colonize the lungs due to mechanical ventilation. At the same time, metastasis of lower airway microbiota may have significant implications in developing intubation mechanical ventilation lung inflammation. Thus, we establish a rat model of tracheal intubation with mechanical ventilation and explore the effects of mechanical ventilation on lung injury and microbiological changes in rats. To provide a reference for preventing and treating bacterial flora imbalance and pulmonary infection injury caused by mechanical ventilation of tracheal intubation. Methods: Sprague-Dawley rats were randomly divided into Control, Mechanical ventilation under intubation (1, 3, 6 h) groups, and Spontaneously breathing under intubation (1, 3, 6 h). Lung histopathological injury scores were evaluated. 16SrDNA sequencing was performed to explore respiratory microbiota changes, especially, changes of bacterial count and alteration of bacterial flora. Results: Compared to groups C and SV, critical pathological changes in pulmonary lesions occurred in the MV group after 6 h (p < 0.05). The Alpha diversity and Beta diversity of lower respiratory tract microbiota in MV6, SV6, and C groups were statistically significant (p < 0.05). The main dominant bacterial phyla in the respiratory tract of rats were Proteobacteria, Firmicutes, Bacteroidetes, and Cyanobacteria. Acinetobacter radioresistens in group C was significant, Megaonas in group MV6 was significantly increased, and Parvibacter in group SV6 was significantly increased. Anaerobic, biofilm formation, and Gram-negative bacteria-related functional genes were altered during mechanical ventilation with endotracheal intubation. Conclusion: Mechanical ventilation under intubation may cause dysregulation of lower respiratory microbiota in rats.

Effects of parecoxib on morphine dosage in postoperative patient-controlled analgesia following thoracoscope-assisted thoracotomy / 南方医科大学学报

<p><b>OBJECTIVE</b>To observe the effect of parecoxib on morphine dosage in patient-controlled analgesia (PCA) following thoracoscope-assisted thoracotomy.</p><p><b>METHODS</b>A consecutive series of 100 patients undergoing thoracoscope-assisted thoracotomy were randomized into 5 groups and received PCA with morphine doses at 0, 5, 10, 15, and 20 mg given in 200 ml saline (groups P(1), P(2), P(3), P(4), and P(5), respectively). Parecoxib (40 mg) was given in all the patients immediately before the operation, and the mixture (4-5 ml) of lidocaine and ropivacaine was administered into the 3 intercostal spaces upper and lower to the incision before chest closure. PCA was administered for each patient. The visual analogue scale (VAS) at rest and coughing and the respiratory functional parameters were recorded at 1, 2, 4, 8, 12, 24, 36, and 48 h after the start of PCA, and the actual and effective button-pressing times (D(1)/D(2)) in PCA were also recorded.</p><p><b>RESULTS</b>No patients showed signs of respiratory inhibition within 24 h after the operation, and the resting VAS was comparable between the groups within the initial 6 postoperative hours. At 8 to 24 h postoperatively, the VAS scores at rest and coughing were significantly higher in P(1) group than in the other groups (P<0.05), and no significant differences were found between the groups at 36 to 48 h. D(1)/D(2) in groups P(1) and P(2) were significantly different from those in the other 3 groups at 4-24 h, but no such difference was found between groups P(3), P(4), and P(5).</p><p><b>CONCLUSION</b>The application of parecoxib may reduce the dosage of morphine in PCA following thoracoscope-assisted thoracotomy and results in good analgesic effect without affecting the patients respiratory function and sputum elimination.</p>

Experimental study of cerebral protection by retrograde vs selective antegrade cerebral perfusion during deep hypothermic circulatory arrest / 南方医科大学学报

<p><b>OBJECTIVE</b>To compare the effect of cerebral protection between retrograde cerebral perfusion (RCP) and selective antegrade cerebral perfusion (SACP) during deep hypothermic circulatory arrest (DHCA) in canine models.</p><p><b>METHODS</b>Fifteen healthy adult dogs were randomly divided into 3 groups (n=5), namely the simple DHCA group (group I), DHCA+RCP group (group II) and DHCA+SACP group (group III). Extrocorporeal circulatory was established routinely in the dogs, and DHCA commenced when the nasopharyngeal temperature was reduced to 18 degrees C. During DHCA, RCP and SACP were applied in groups II and III, respectively. All the models were rewarmed after 90 min of DHCA and the cerebral reperfusion continued for 90 min. Cerebral oxygenous metabolic function, cerebral temperature and ultrastructural changes of the neurons were observed in the 3 groups at different time points during the operation.</p><p><b>RESULTS</b>The jugular venous oxygen saturation (SjvO(2)) increased with the temperature reduction, and then decreased after DHCA commencement, showing significant changes at different time points in groups I and II. SjvO(2) in group III were significantly higher than that in the other two groups after 90 min of DHCA (P=0.000). Brain temperature significantly increased in group I during DHCA as compared with that in groups II and III (P=0.000), but showed no significant difference between the latter two groups (P=0.195). The ultrastructure of the neurons underwent obvious changes after reperfusion for 30 min in group I. In group II the neuronal ultrastructure was basically normal at 60 min during DHCA and changed slightly at 90 min, but in group III no obvious changes were seen at 90 min during DHCA and only slight changes occurred at 30 min of reperfusion.</p><p><b>CONCLUSIONS</b>RCP can not supply enough oxygen but can maintain low cerebral temperature, and provide short-term brain protection. DHCA+SACP provides better brain protection than simple DHCA and DHCA+RCP, and has a promising prospect in cardiac surgery.</p>