Study population
This retrospective observational, single-center cohort study was conducted at Xuanwu Hospital Capital Medical University, China. Neurosurgery is a key specialty, with a total of 38 NICU beds in this hospital. From January to December 2019, we retrospectively analyzed clinical data of all NICU patients who fulfilled the following:
Inclusion criteria:
(1) Age≥18 years and intubation within 48 hours of onset; (2) no clinical symptoms or signs of infection at the time of intubation; and (3) mechanical ventilation time greater than 7 days, to minimize the effect of mechanical ventilation time and ICU stay time on EOVAP.
Exclusion criteria:
(1) Pre-existing chronic pulmonary diseases, such as chronic obstructive pulmonary disease, asthma, bronchiectasis, active tuberculosis, empyema and other diseases. (2) chest radiograph or CT examination before admission showing atelectasis or pneumonia. (3) patients with acute and chronic liver failure, kidney failure, cancer or severe immunodeficiency[10].
EOVAP Definitions
To maintain consistency with the literature, EOVAP was defined as pneumonia that occurred during the first 7 days after the onset of mechanical ventilation[8, 11].
VAP criteria were as follows: [12, 13] presence of new and/or progressive pulmonary infiltrates on a chest radiograph in a patient ventilated for more than 48 hours plus 2 or more of the following:
(1) Temperature > 38 °C; (2) leukocytosis (white blood cell count ≥ 12,000 cells/ mm3) or leukopenia (white blood cell count < 4,000 cells/mm3); (3) presence of purulent tracheal aspirate.
Microbiological Evaluation
EOVAP was diagnosed by noninvasive sampling and semiquantitative culture as recommended in the guidelines [14]. All patients admitted to the NICU and intubated will have received tracheobronchial aspiration (TBAS) through a closed-suction system. The TBAS was sent to the hospital's microbiology laboratories for the detection of bacteria and fungi. In the microbiology laboratory, the TBAS was plated on agar medium (3 days of culture for aerobic bacteria and 2 weeks for fungi) using a semi-quantitative culture method. Bacterial identification and antibiotic susceptibility tests using standard methods were performed for samples that showed positive growth, as recommended in CDC guidelines[15].
Data collection
The following data were obtained: age (categorized as ≥65 and <65 years), sex, smoking, body mass index (BMI), pre-existing comorbidities (coronary artery disease, hypertension, diabetes), intubation time (hospital admission or prehospital intubation), Acute Physiology and Chronic Health Evaluation II (APACHE II), The Glasgow Coma Scale/Score(GCS). Laboratory data and medications administered were also obtained, which included: albumin, C-reactive protein (CRP), procalcitonin (PCT), full blood count, alanine aminotransferase (ALT), serum creatinine (Scr), chest X-ray, norepinephrine, glucocorticoid, barbiturates, mannitol, therapeutic hypothermia, antibiotics administered after the intubation and 28-day mortality.
Statistical Analysis
All statistical analyses were performed using SPSS statistical software version 19.0. Continuous data were presented as mean ± standard deviation or median and interquartile range (IQR; 25th–75th percentile) for those that were not normally distributed. Independent-Samples T-Test or Mann-Whitney non-parametric test was used to compare differences in continuous variables. Chi-square test was used to compare categorical data. Binary multivariable logistic regression analysis was performed for parameters with p<0.10 on univariate analysis and the odds ratio (OR) with 95% confidence interval (95% CI) were calculated. All tests were two-tailed, with the significance level set at p<0.05.