[Efficacy of extended-infusion of carbapenem plus sulbactam for ventilator-associated pneumonia caused by extensive drug-resistant Acinetobacter baumannii]

Objective: To evaluate the efficacy of extended-infusion of carbapenem plus sulbactam for ventilator-associated pneumonia caused by extensive drug-resistant Acinetobacter baumannii (XDRAB). Methods: Clinical data of patients with ventilator-associated pneumonia caused by XDRAB who were treated with extended-infusion carbapenem plus sulbactam or tigecycline-based therapy in Peking University First Hospital from January 2015 to December 2016 were collected and reviewed in this retrospective study. Twenty-one patients were treated with extended-infusion carbapenem plus sulbactam, and 20 other patients received tigecycline combined with other antibiotics. The general status of the patient, microbiological eradication rate, superinfection rate, new microorganism colonization rate, clinical resolution rate on the third day, clinical cure rate and mortality during treatment were compared between the two groups. Results: The two groups shared similar characteristics except that patients in the carbapenem group were younger. Microbiological eradication was not observed. Superinfections occurred in 1 patients (4.8%) in the carbapenem group and 0 patients in the tigecycline group (P=1.000), the occurrences of new microorganisms colonization were 14.3% and 25.0% respectively (P=0.638). Clinical cure were achieved in 57.1% of the patients in the carbapenem group and 50.0% of the patients in the tigecycline group (P=0.647), the clinical resolution rates on the third day were 52.4% and 45.0% respectively (P=0.636). The mortality during treatment was 9.5% in carbapenem group, and 20.0% in tigecycline group (P=0.612). No serious adverse drug reactions occurred. Conclusions: Ventilator-associated pneumonia caused by XDRAB treated with either extended-infusion carbapenem plus sulbactam or tigecycline-based therapy has a similar clinical outcome.

Underlying heart disease and microbiological spectrum of adult infective endocarditis in one Chinese university hospital: a 10-year retrospective study

BACKGROUND AND AIM

To identify the underlying heart disease and microbiological pathogen associated with infective endocarditis (IE) in Chinese patients in one university hospital over a 10-year period.

METHODS

We recruited 115 adult patients admitted to Peking University First Hospital from 2002 to 2011 who were diagnosed with definite IE. Statistical analysis was performed to analyse data on demographics, clinical and laboratory findings, as well as microbiological pathogens.

RESULTS

The most common underlying heart diseases for IE were congenital heart disease (24.3%) followed by degenerative valvular disease (17.4%). Aortic (44.3%) and mitral (43.5%) valves were most frequently affected. The right-sided IE cases were all found in patients with congenital heart disease. The age of patients was younger in right-sided cases than that in left-sided ones (P = 0.001). There was no difference in the mortality among groups with different underlying heart disease (P = 0.841). Forty-four (38.3%) patients were infected with viridans group streptococci. The isolation rate of staphylococci in right-sided IE was higher than that in the left-sided IE group (P = 0.021). More than 85% of streptococci were susceptible to β-lactams.

CONCLUSIONS

Congenital heart disease and degenerative valvular disease have overtaken rheumatic heart disease as the major underlying heart diseases associated with IE. Viridans group streptococci are the most common microbial cause of IE.

Homeokinesis and short-term variability of human airway caliber

We hypothesized that short-term variation in airway caliber could be quantified by frequency distributions of respiratory impedance (Zrs) measured at high frequency. We measured Zrs at 6 Hz by forced oscillations during quiet breathing for 15 min in 10 seated asthmatic patients and 6 normal subjects in upright and supine positions before and after methacholine (MCh). We plotted frequency distributions of Zrs and calculated means, skewness, kurtosis, and significance of differences between normal and log-normal frequency distributions. The data were close to, but usually significantly different from, a log-normal frequency distribution. Mean lnZrs in upright and supine positions was significantly less in normal subjects than in asthmatic patients, but not after MCh and MCh in the supine position. The lnZrs SD (a measure of variation), in the upright position and after MCh was significantly less in normal subjects than in asthmatic patients, but not in normal subjects in the supine position and after MCh in the supine position. We conclude that 1) the configuration of the normal tracheobronchial tree is continuously changing and that this change is exaggerated in asthma, 2) in normal lungs, control of airway caliber is homeokinetic, maintaining variation within acceptable limits, 3) normal airway smooth muscle (ASM) when activated and unloaded closely mimics asthmatic ASM, 4) in asthma, generalized airway narrowing results primarily from ASM activation, whereas ASM unloading by increasing shortening velocity allows faster caliber fluctuations, 5) activation moves ASM farther from thermodynamic equilibrium, and 6) asthma may be a low-entropy disease exhibiting not only generalized airway narrowing but also an increased appearance of statistically unlikely airway configurations.

Introduction to a new inspiratory threshold loading device

Inspiratory threshold loading is an important tool in assessing inspiratory muscle function and has been widely used in studies of respiratory mechanics. A simple system was designed to provide a pure and precise inspiratory threshold load. The inspiratory threshold loading system comprises a flow generator attached via a pressure chamber, to the inspiratory port of a Hans-Rudolph valve. By limiting the circulation of air generated by the flow generator between the room and the pressure chamber, different levels of negative pressure are produced in the pressure chamber and applied to the inspiratory valve. An inspiratory pressure equal to the negative pressure in the chamber has to be generated to open the inspiratory valve for flow. The system was tested in four subjects by measuring mouth pressure (Pm), threshold pressure (Pth) and valve resistance (R). The Pm at the beginning of inspiratory flow was defined as the opening pressure (Pop). The Pth was constant throughout inspiration. Pop was linearly related to Pth (p<0.0001), with slopes within 2% of identity and intercepts within +/-0.2 cmH2O. R was between 0.7-1.1 cmH2O x L(-1) x s(-1) under all conditions and was independent of both Pth (p=0.76) and inspiratory flow (p=0.24). The results demonstrate that this system can provide a constant inspiratory threshold load throughout inspiration with little flow resistance, and is therefore ideal for respiratory studies.