Major Articles
Surveillance of ventilator-associated pneumonia in very–low-birth-weight infants*,**

https://doi.org/10.1067/mic.2002.119995Get rights and content

Abstract

Background: Surveillance of ventilator-associated pneumonia (VAP) is an essential part of quality patient care. Very-low-birth-weight (VLBW) infants, many with tracheal microbial colonization and bronchopulmonary dysplasia (BPD), comprise a difficult group in whom to make a diagnosis of pneumonia with the Centers for Disease Control and Prevention (CDC) criteria for infants younger than 1 year. Objective: Our objective was to retrospectively compare VAP surveillance diagnoses made by the hospital infection control practitioner (ICP) with those made by a panel of experts with the same clinical and laboratory evidence and supportive radiologic data. A secondary objective was to compare radiologic diagnosis of pneumonia made by the general hospital radiologists, by the panel of experts, and by a pediatric radiologist from another hospital. Study Population: Thirty-seven VLBW infants identified as at risk for VAP by the ICP on the basis of a positive bacterial tracheal culture and the application of CDC criteria for the definition of pneumonia were studied. Methods: Clinical and laboratory evidence and routine radiologic reports made by the general radiologist were reviewed independently by a panel of experts composed of 3 experienced neonatologists. Chest x-rays from the day before, day of, and day after the surveillance date were reviewed separately by the 3 neonatologists and also by a pediatric radiologist. Results: After inter-reader reliability was found satisfactory (kappa's coefficient, 0.47-0.75; P <.05), the panel of neonatologists determined that the 37 VLBW infants represented 4 distinct clinical categories. Group 1 comprised 12 airway-colonized infants, aged 14 to 30 days, who on the surveillance date, albeit intubated, were asymptomatic, not treated with antibiotics, and survived. Group 2 comprised 11 airway-colonized infants, aged 7 to 42 days, who presented with equivocal clinical, laboratory, or radiologic signs of VAP and survived. Group 3 comprised 7 airway-colonized infants, aged 14 to 21 days, who were acutely ill (3 died) and had clinical and laboratory evidence of nosocomial bloodstream infection (BSI) but no radiologic signs of pneumonia. Group 4 comprised 7 infants, aged 14 to 28 days, who were acutely ill (4 died) and had clinical and laboratory evidence of infection and radiologic changes consistent with VAP. Radiologic Findings: General radiologists, neonatologists, and the pediatric radiologist agreed that none of the asymptomatic airway-colonized infants (Group 1) had VAP. General radiologists reported signs suggestive of pneumonia in 8 of 11 infants (Group 2), a finding not corroborated by the others. Everybody agreed on the absence of radiologic pneumonia in 6 of 7 patients with nosocomial BSI (Group 3) and on the presence of signs consistent with pneumonia in the remaining 7 infants (Group 4). Conclusion: Surveillance diagnosis of VAP in VLBW infants is difficult because current CDC definitions are not specific for this population. Isolated positive tracheal culture alone does not distinguish between bacterial colonization and respiratory infection. Clinical and laboratory signs of VAP, mostly nonspecific, can be found in other conditions such as bronchopulmonary dysplasia and nosocomial BSI. Routine radiologic reports suggestive of pneumonia in airway-colonized infants without definitive clinical and laboratory evidence of infection could be misleading. To improve accuracy, surveillance diagnosis of VAP in special populations such as VLBW infants should be reformulated; meanwhile, ICPs should seek consultation with experienced clinicians for interpretation of data. (Am J Infect Control 2002;30:32-9.)

Section snippets

Methods

The patient population comprised 37 VLBW infants born in 1998 and 1999 who were identified as at risk for VAP by the ICP on the basis of a bacteriologically positive tracheal culture (TC) and the interpretation of CDC guidelines. Of the 37 VLBW infants, 17 (40%) were boys and 33 (85%) were white, with a mean birth weight of 795 ± 224 g and a mean gestational age of 26 ± 2 weeks. All infants were intubated in the delivery room and received mechanical ventilation for 36 ± 20 days. Twenty-one

Data collection and statistical analysis

Our NICU was managed under a plan of patient care that did not change during the study period. Patient demographic, clinical, and laboratory information was obtained from hospital records. Subgroups were formed for specific analyses. The results are reported as mean (SD). Inter-reader reliability of the panel of experts for interpretation of evidence was 69% to 83% for clinical reports, 70% to 75% for laboratory reports, 83% to 97% for microbiologic reports, 89% to 98% for routine radiologic

Results

After completion of the review, the panel of experts determined that the 37 VLBW infants with surveillance diagnosis of VAP represented 4 distinct clinical categories: 3 groups of airway-colonized infants and 1 group of 7 infants with pneumonia.

Discussion

A TC positive for pathogens taken shortly after birth with clinical and radiologic signs can identify the cause of perinatal pneumonia.2 TAs from mechanically ventilated VLBW infants are frequently obtained in the evaluation of suspected sepsis, tracheitis, or VAP. Criteria for clinical interpretation of isolated TC, however, are not available, and few papers relate to the use or interpretation of TA in this special patient population. General microbial monitoring of patients in intensive care

Surveillance diagnosis of pneumonia

An ICP surveying VLBW infants for a diagnosis of VAP faces the problem of inadequate criteria for definition of pneumonia in this special population. Current CDC definitions of pneumonia for infants younger than 1 year do not address the uniqueness of mechanically ventilated VLBW infants who seldom develop fever, wheezing, rhonchi, or cough8, 9, 10 (see Table 5). Furthermore, radiographic changes and the presence of a respiratory pathogen in blood alone as criteria have low specificity, low

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    *

    Statistical consultant: Larry M. Sachs, PhD, Associate Professor Emeritus, The Ohio State University, College of Medicine.

    **

    Reprint requests: Leandro Cordero, MD, The Ohio State University Medical Center, N118 Doan Hall, 410 W 10th Ave, Columbus, OH 43210-1228.

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    Copyright © 2002 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.