|Year : 2014 | Volume
| Issue : 1 | Page : 73-77
Ventilator-associated pneumonia in the neonatal intensive care unit
Ahmed A. Khattab, Dalia M. El-Lahony, Wessam F. Soliman
Department of Pediatrics, Faculty of Medicine, Menoufiya University, Menoufiya, Egypt
|Date of Submission||08-Jun-2013|
|Date of Acceptance||20-Nov-2013|
|Date of Web Publication||20-May-2014|
Wessam F. Soliman
MBBCh, Neonatal Intensive Care Unit, Benha Children's Hospital, Banha, 13511
Source of Support: None, Conflict of Interest: None
Ventilator-associated pneumonia (VAP) is defined as nosocomial pneumonia in mechanically ventilated patients. It is considered to be most important cause of infection-related death in the ICU. We studied the characteristics and risk factors of VAP in critically ill neonates.
VAP, which was not present at the time of intubation, accounted for up to 30% of nosocomial infections in neonatal intensive care unit (NICU) patients.
Patients and methods
This study was carried out in the NICU in Benha Children's Hospital on 85 neonates with different diagnoses admitted from April to October 2012 who needed mechanical ventilation. All studied neonates were subjected to history taking, clinical examination, routine investigations (assessment of complete blood count, C-reactive protein levels, and arterial blood gas volumes, blood culture, and liver, serum albumin, and kidney function tests), and chest radiography daily, as well as to nonbronchoscopic alveolar lavage culture.
Of 85 neonates who needed mechanical ventilation, 55.2% developed VAP. Prematurity, low birth weight, and prolonged duration of mechanical ventilation were risk factors for developing VAP. Increased total leukocyte count, C-reactive protein, and hypoalbuminemia were significantly present in the VAP group. There were significant differences between VAP and non-VAP groups regarding hypothermia, mucopurulent endotracheal tube secretion, PaCO 2 , and PaO 2 . The microorganisms associated with bloodstream infection in the VAP-diagnosed group were Staphylococcus aureus (15%), Klebsiella spp.(8.5%), Candida spp.(6.5%), Pseudomonas spp. (4.2%), and Escherichia coli (4.2%); 61.7% of obtained blood cultures in VAP patients were sterile. The results of nonbronchoscopic bronchoalveolar lavage cultures revealed the presence of Klebsiella spp. (34%), Pseudomonas spp. (25.5%), S. aureus (17%), E. coli (17%), and Candida spp. (6.4%). K. pneumoniae was the most commonly isolated pathogen in nonbronchoscopic bronchoalveolar lavage.
The most important risk factors of VAP are prematurity, low birth weight, prolonged duration of mechanical ventilation, enteral nutrition, and umbilical catheterization.
Keywords: Mechanical ventilation, neonatal pneumonia, nonbronchoscopic bronchoalveolar lavage
|How to cite this article:|
Khattab AA, El-Lahony DM, Soliman WF. Ventilator-associated pneumonia in the neonatal intensive care unit. Menoufia Med J 2014;27:73-7
|How to cite this URL:|
Khattab AA, El-Lahony DM, Soliman WF. Ventilator-associated pneumonia in the neonatal intensive care unit. Menoufia Med J [serial online] 2014 [cited 2017 Oct 24];27:73-7. Available from: http://www.mmj.eg.net/text.asp?2014/27/1/73/132753
| Introduction|| |
Ventilator-associated pneumonia (VAP) is defined as hospital-acquired pneumonia occurring in patients receiving mechanical ventilation through an endotracheal or tracheostomy tube . The VAP that occurs within 48-72 h after tracheal intubation is usually termed early-onset pneumonia, which often results from aspiration complicating the intubation process, whereas the VAP that occurs after 72 h is considered late-onset pneumonia .
VAP accounts for up to 30% of nosocomial infections in neonatal intensive care unit (NICU) patients and complicates the course of 8-28% of patients receiving mechanical ventilation . The pathogenesis of VAP involves two processes: bacterial colonization of the aerodigestive tract; and aspiration of contaminated oral secretions into the lower airways because endotracheal tubes used to ventilate neonates are not cuffed .
The etiologic agent of VAP may differ according to length of hospital stay, comorbid conditions, and exposition of antimicrobials . Aerobic Gram-negative bacilli account for more than 60% of VAP cases. However, some investigators have reported that Gram-positive bacteria have become increasingly more common, with Staphylococcus aureus being the predominant isolate .
The criteria used to diagnose VAP in neonates include the following: mechanical ventilation within 48 h of onset of suspected VAP; worsening gas exchange with an increase in oxygen or ventilatory requirements; two or more chest radiographs that show new infiltrates, consolidation, cavitation, or pneumatoceles; and at least three signs and symptoms, which include temperature instability, wheezing, tachypnea, cough, abnormal heart rate, change in secretions, or an abnormal leukocyte count. The criteria have not been validated in neonates, and they are often open to subjective interpretation because they overlap with other diseases .
Clinical criteria for the diagnosis of VAP have been established by the National Nosocomial Infection Surveillance System and CDC (2004) as follows: in patients who are mechanically ventilated for 48 h or more, three or more of the following criteria have been established: rectal temperature more than 38°C or less than 35.5°C, blood leukocytosis more than 10 × 10 3 /mm 3 and/or shift to the left or blood leukopenia (<3 × 10 3 /mm 3 ), more than 10 leukocytes in the Gram stain of the tracheal aspirate (in high-power field), positive culture from the endotracheal aspirate, and new, persistent, or progressive radiological infiltrate .
However, in patients without underlying pulmonary or cardiac disease (respiratory distress syndrome, bronchopulmonary dysplasia, pulmonary edema, or chronic obstructive pulmonary disease), one definitive chest radiograph is acceptable. In addition to abnormal chest radiographs, a patient must have at least one of the following symptoms - fever (>38°C) with no other recognized cause, leukopenia (<4000/mm 3 ), or leukocytosis (>12 000/mm 3 ) - and at least two of the following criteria - new onset of purulent sputum, change in the character of sputum, increased respiratory secretions, increased suctioning requirements, new onset of cough, dyspnea, or tachypnea, rales or bronchial breath sounds, worsening gas exchange, increased oxygen requirements, or increased ventilation demand .
The detection of the causative organism in VAP is imperative for guiding appropriate therapy, as there is strong evidence of the adverse effect of inadequate empirical treatment on outcome . Microbial diagnosis of VAP is based on the culture of samples obtained from the lower respiratory tract by tracheal aspirate, which is considered a less invasive method that may have an acceptable diagnostic accuracy .
The aim of this work was to determine the characteristics and risk factors of VAP in critically ill newborn infants admitted to the NICU in Benha Children's Hospital.
| Patients and methods|| |
This study was carried out in the NICU in Benha Children's Hospital on 85 neonates who received mechanical ventilation (>48 h) and were admitted to the NICU because of various illnesses.
- Neonates of either sex under mechanical ventilation for more than 48 h.
- Suffering from any medical cause or surgical nonpulmonary cause leading to mechanical ventilation.
- Age greater than 1 month.
- Surgical problem related to the respiratory system.
- Presence of congenital pneumonia.
- Presence of pneumonia.
- Incidence of meconium aspiration.
All neonates of both groups were subjected to clinical assessment by:
- Full history taking, including:
- Patient data.
- Parents' data.
- Perinatal history.
- Present history.
- Family history.
- Full clinical examination.
- Laboratory investigations including
- Complete blood count using a coulter apparatus.
- C-reactive protein (CRP) by turbidimetry (normal value <6).
- Liver function tests.
- Kidney function tests (urea, creatinine).
- Blood culture on sulfonated broth media.
- Chest radiography on admission and repeated as required.
- Arterial blood gases (PaCO 2 , PaO 2 ).
- Monitoring of the ventilator settings, including peak inspiratory pressure, peak end expiratory pressure, respiratory rate, inspiratory time (Ti), and fraction of inspired oxygen (FIO 2 ).
- Nonbronchoscopic bronchoalveolar lavage (NB-BAL).
| Results|| |
The VAP and non-VAP groups differed significantly with respect to gestational age and weight. Duration on mechanical ventilation was highly significantly longer in VAP patients than in non-VAP patients. Meanwhile, there were no significant differences with regard to sex, mode of delivery, and indication for NICU admission. Analysis of clinical and radiological characteristics revealed that hypothermia, mucopurulent secretions from the endotracheal tube, and presence of infiltration in chest radiographs were significantly more prevalent in VAP patients. Inotropic drugs were used significantly more in VAP patients who also needed more invasive procedures compared with non-VAP patients. A significant increase in TLC, CRP, and PaCO 2 level in blood gases with significant decrease in albumin and PaO 2 was observed. The microorganisms associated with bloodstream infection in the VAP-diagnosed group were S. aureus (15%), Klebsiella spp. (8.5%), Candida spp. (6.5%), Pseudomonas spp. (4.2%), and Escherichia More Details coli (4.2%); 61.7% of obtained blood cultures in VAP patients were sterile. The NB-BAL cultures revealed the presence of Klebsiella spp. (34%), Pseudomonas spp. (25.5%), S. aureus (17%), E. coli (17%), and Candida spp. (6.4%). K. pneumoniae was the most commonly isolated pathogen in the NB-BAL cultures (34%), whereas Candida spp. (6.4%) was the least common [Table 1],[Table 2],[Table 3],[Table 4] and [Table 5].
|Table 1: Comparison between studied groups with regard to gestational age, weight, duration in neonatal intensive care unit, duration on mechanical ventilation, sex, mode of delivery, and indication of neonatal intensive care unit admission|
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|Table 2: Comparison between studied groups with regard to clinical findings|
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|Table 3: Comparison between the studied groups with regard to laboratory investigation and blood gas results|
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|Table 4: Comparison between studied groups with regard to blood culture results|
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|Table 5: Comparison between studied groups as regarding nonbronchoscopic bronchoalveolar lavage culture results|
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| Discussion|| |
Mechanical ventilation is an essential feature of modern NICU care. Unfortunately, mechanical ventilation is associated with a substantial risk for VAP . Tracheal intubation is associated with a 3-21-fold risk of developing pneumonia. In addition, poor nutritional state and hypoalbuminemia also contribute to the development of VAP .
In this study, the mean gestational age of infants diagnosed with VAP was significantly lower than that of the non-VAP group. This result was in agreement with other studies that reported that VAP rates significantly increase with decreasing gestational age . Also, the mean birth weight of the VAP group was significantly lower than that of the non-VAP group (P = 0.05). This result was similar to the results obtained by Chastre et al.  who reported in a cross-sectional study that VAP rates were highest for the 1-1.5 kg birth weight categories.
Prolonged duration of NICU admission was a significant risk factor for VAP. Also, prolonged duration of ventilation generally increases the risk of infection due to exposure to other devices such as nebulizers, humidifiers, and ventilator circuits, which have been proven to be important sources and media for microorganisms .
In this study, hypothermia, presence of auscultatory chest findings, and mucopurulent ETT secretions characterized the VAP group. Similar results were reported by other studies . Chest radiographs were diagnostic in all cases clinically diagnosed as VAP, which was in agreement with the results of Erbay et al. .
In this study, there were significant differences between VAP and non-VAP groups regarding total leukocyte count and CRP titer. This is in agreement with the results of Povoa et al. . Hypoalbuminemia, which is considered an indicator of poor nutritional status, was significantly encountered in the VAP group, which may be due to favored hepatic production of acute-phase proteins such as globulins, fibrinogen, and haptoglobin .
In this study, the predominant microorganism associated with bloodstream infection in the VAP-diagnosed group was Staphylococcus spp. (15%); 61.7% of obtained blood cultures were sterile. This is in agreement with the results of Berthelot et al. . The results of NB-BAL cultures reported in our study revealed that Gram-negative bacteria were isolated from the majority of VAP patients (76.5%), with Klebsiella spp. predominating the Gram-negative culture (34%). In contrast, Gram-positive infection comprised 17% of the total cultures, with S. aureus predominating the positive cultures (17%) and Candida spp. being positive in 6.4% of the samples examined. Koksal et al.  mentioned that Acinobacter was the most predominating causative agent, whereas Petdachai  reported that Pseudomonas spp. was the most common organism isolated.
| Conclusion|| |
The most important risk factors for the development of VAP in our unit include prematurity, low birth weight, prolonged duration of mechanical ventilation, enteral feeding, and invasive devices such as umbilical catheters. Gram-negative microorganisms comprise the majority of cultures obtained by NB-BAL. Therefore, we recommended strict training and supervision of infection control protocols, educated and expert nursing care, usage of disposable ventilator circuits, avoidance of unnecessary central venous catheters and other invasive procedures, closed suction, and wide use of NB-BAL cultures for early diagnosis of VAP. Additional studies are necessary for developing interventions that prevent neonatal VAP.
| Acknowledgements|| |
Conflicts of interest
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]