Ventilator-Associated Pneumonia (VAP) is defined as pneumonia that develops 48-72 hours
or more following the initiation of mechanical ventilation. It is a critical infection
acquired in the Intensive Care Unit (ICU), significantly contributing to increased
mortality rates, extended ICU stays, and elevated healthcare costs for patients on
ventilators[1]. VAP is reported to affect 5-40% of patients receiving mechanical
ventilation, with an average incidence of 20-25%. This proportion has been exacerbated in
recent years by the COVID-19 pandemic[2-4]. A meta-analysis encompassing 195 studies
found that the overall cumulative incidence of VAP in mainland China is 23.8% (95% CI
20.6-27.2%)[5].
Numerous risk factors, such as prolonged mechanical ventilation, advanced age, supine
body position, prior antibiotic use, and various comorbidities, in addition to the
endotracheal intubation itself, have been associated with the development of VAP[6, 7].
VAP results from the invasion of pulmonary parenchyma by pathogenic bacteria, which
overwhelm the host's weakened defense capability. The primary sources of these bacteria
include oropharyngeal colonization, secretions around the endotracheal tube cuff, and
biofilm formation on the tracheal tube. The infectious process initiates at the time of
intubation and progresses over several days. Reports indicate that the daily risk of VAP
peaks between days 5 and 9 of incubation, underscoring the need for early preventive
measures[8]. Despite decades of research highlighting interventions such as patient
positioning adjustments, daily awakening and weaning protocols, oral decontamination, and
systemic antibiotics to reduce VAP incidence, the burden remains unacceptably high.
Systemic antibiotics are commonly used for both treatment and prevention of VAP. However,
the risk of resistant bacteria selection is a significant concern. A meta-analysis of six
trials indicated that prophylactic antibiotics administered via nebulization effectively
reduced VAP occurrence without increasing the risk of multidrug resistant (MDR)
pathogen-related VAP[9]. Another Meta-Analysis consisting seven RCTs also confirmed that
pro- phylactic antibiotics delivered via the respiratory tract reduced the risk of VAP,
particularly for those treated with nebulized aminoglycosides[10]. Additionally, a short
course of aerosolized ceftazidime significantly decreased VAP frequency in critically ill
trauma patients without adversely affecting bacterial pathogen profiles and sensitivity
patterns[11]. Recently, a study of 3-day course of inhaled amikacin was shown to
effectively reduce the incidence of VAP[12, 13]. Stephan Ehrmann's team confirmed the
possibility of inhaled amikacin to lessen the VAP burden during a 28-day follow-up
period. This study provides us with excellent inspiration and suggests promising
prospects for the use of nebulized antibiotics in preventing VAP. However, there are
still more than 10% of patients who have amikacin resistance that can not be covered
among all participants and the burden of MDR-VAP has becoming increasingly heavy with
variations across different regions. Data from China Antimicrobial Surveillance Network
(CHINET 2024) shows the resistance rates of Acinetobacter baumannii (AB), Klebsiella
pneumoniae (KP), and Pseudomonas aeruginosa (PA) to amikacin are 49.5%, 15.5%, and 3.4%,
respectively. In contrast, the resistance rates of carbapenem-resistant Acinetobacter
baumannii (CRAB), carbapenem-resistant Klebsiella pneumoniae (CRKP), and
carbapenem-resistant Pseudomonas aeruginosa (CRPA) to amikacin are as high as 77.4%,
67.1%, and 11.4%, respectively.
Given the effectiveness of CMS against gram-negative bacteria including
carbapenem-resistant organisms (CRO), we are optimistic about the potential of nebulized
CMS inhalation to prevent VAP. So we designed the study to evaluate the efficacy and
safety of prophylactic CMS nebulization in preventing VAP among incubated patients at
high risk of MDR-VAP. We hypothesize that administering a 3-day course of pre-emptive
inhaled CMS after 2 days of ventilation will reduce the subsequent incidence of VAP.