Ventilator-associated pneumonia in extremely preterm neonates in a neonatal intensive care unit: characteristics, risk factors, and outcomes

Risk factors and outcomes for ventilator-associated pneumonia in neonatal intensive care unit patients

In order to determine the risk factors and outcomes of ventilator-associated pneumonia (VAP) in the neonatal intensive care unit (NICU), a retrospective cohort study was conducted on 259 patients who were ventilated >48 h. Clinical characteristics and risk factors were compared and non-conditional logistic regression analysis was performed to determine independent predictors for VAP. There were 52 episodes of VAP (20.1%). The main pathogens were G(-) bacterium (82.1%, 23/28). Hospital stay in the VAP group was 19.9+/-5.9 vs. 16.7+/-7.2 days in controls (P<0.01). The mortality rate of the VAP group was 13.5% (7/52) vs. 12.1% in controls (P>0.05). By logistic regression analysis the following independently predicted VAP: re-intubation (OR 5.3, 95% CI 2.0, 14.0), duration of mechanical ventilation (OR 4.8, 95% CI 2.2, 10.4), treatment with opiates (OR 3.8, 95% CI 1.8, 8.5) and endotracheal suctioning (OR 3.5, 95% CI 1.6, 7.4). VAP occurred at significant rates among mechanically ventilated NICU patients and is associated with care procedures. The risk factors of neonatal VAP were re-intubation, duration of mechanical ventilation, treatment with opiates and endotracheal suctioning. Additional studies are necessary to develop interventions to prevent neonatal VAP.

Ventilator-associated pneumonia in neonatal and pediatric intensive care unit patients

Ventilator-associated pneumonia (VAP) is the second most common hospital-acquired infection among pediatric intensive care unit (ICU) patients. Empiric therapy for VAP accounts for approximately 50% of antibiotic use in pediatric ICUs. VAP is associated with an excess of 3 days of mechanical ventilation among pediatric cardiothoracic surgery patients. The attributable mortality and excess length of ICU stay for patients with VAP have not been defined in matched case control studies. VAP is associated with an estimated $30,000 in attributable cost. Surveillance for VAP is complex and usually performed using clinical definitions established by the CDC. Invasive testing via bronchoalveolar lavage increases the sensitivity and specificity of the diagnosis. The pathogenesis in children is poorly understood, but several prospective cohort studies suggest that aspiration and immunodeficiency are risk factors. Educational interventions and efforts to improve adherence to hand hygiene for children have been associated with decreased VAP rates. Studies of antibiotic cycling in pediatric patients have not consistently shown this measure to prevent colonization with multidrug-resistant gram-negative rods. More consistent and precise approaches to the diagnosis of pediatric VAP are needed to better define the attributable morbidity and mortality, pathophysiology, and appropriate interventions to prevent this disease.

High positive end-expiratory pressure levels promote bacterial translocation in experimental pneumonia

OBJECTIVE

A previous study in piglets with experimental pneumonia showed that reducing atelectasis by means of open lung ventilation attenuated bacterial translocation compared to conventional ventilation settings. This study examined the effect of open lung ventilation with higher than necessary positive end-expiratory pressures (PEEP) on bacterial translocation.

DESIGN AND SETTING

Prospective animal study in a university-affiliated research laboratory.

SUBJECTS

Thirty piglets.

INTERVENTIONS

Animals were surfactant-depleted by whole-lung lavage and infected with group B streptococci. Thereafter the animals were ventilated for 5 h according to either a conventional ventilation strategy, open lung strategy, or open lung/high-PEEP strategy. Blood samples for blood gas analysis and blood bacterial counts were taken every hour. After 5 h of ventilation surviving animals were killed, and lung colony forming units and lung mechanics parameters were determined.

RESULTS

All animals in both open lung groups survived but only 30% of those in the conventional ventilation group. Open lung ventilation resulted in significantly less bacterial translocation than either conventional or high-PEEP ventilation. Lung function in the conventional ventilated group was significantly less than in the two open lung groups.

CONCLUSIONS

The lowest level of bacterial translocation was observed during optimal ventilation (open lung) which was achieved by using individually tailored settings. Deviation to either side can be harmful, as shown by the increased bacterial translocation during conventional and high-PEEP ventilation.

Nosocomial infection in a neonatal intensive care unit: a prospective study in Taiwan

BACKGROUND

We performed a prospective analysis to determine the prevalence of nosocomial infection and associated risk factors in our neonatal intensive care unit (NICU).

METHODS

Data were collected prospectively on underlying diagnoses, therapeutic interventions/treatments, infections, and outcomes at 9 am every day from November 2004 through October 2005. Prevalence of nosocomial infection and infection site definitions were according to the National Nosocomial Infections Surveillance system of the Centers for Disease Control and Prevention.

RESULTS

Among 528 infants enrolled, 60 (11.4%) had 97 nosocomial infections. The survival rate was 92%. The prevalence of nosocomial infections was 17.5%: bloodstream infection, 4.7%, clinical sepsis, 6.3%, pneumonia, 5.1%, urinary tract infections (UTIs), 0.7%, surgical site infection, 0.7%. Intervention-associated infection rate: central intravascular catheter-associated bloodstream infection, 13.7%, TPN-associated bloodstream infection, 15.8%, ventilator-associated pneumonia, 18.6%, surgical site infection 13.7%, urinary catheter-associated UTI, 17.3%. Cut-off values of onset of central intravascular catheter-associated bloodstream infection and ventilator-associated pneumonia were 6 days and 10 days after intervention, respectively. Patients with a birth weight <1000 g (relative risk, 11.8, 95% confidence interval, 7.66-18.18; P < .001) were at the greatest risk for nosocomial infection.

CONCLUSIONS

This study revealed the high prevalence of nosocomial infections in NICU patients, and the urgent need for a national surveillance and more effective prevention interventions.

Perfluorocarbon suppresses lipopolysaccharide- and alpha-toxin-induced interleukin-8 release from alveolar epithelial cells

BACKGROUND/AIMS

Human pulmonary alveolar epithelial (A549) cells release interleukin-8 (IL-8) on stimulation by lipopolysaccharide (LPS) and alpha-toxin. We hypothesised that the perfluorocarbons (PFCs), perflubron and FC-84, would block stimulation of A549 cells by these toxins.

METHODS

The levels of IL-8 production in A549 cells were measured following exposure to toxins for 24 h with or without PFC. The amount of IL-8 released from A549 cells was measured by enzyme-linked immunosorbent assay, and the level of IL-8 mRNA was measured by real-time RT-PCR.

RESULTS

When stimulated with LPS or alpha-toxin, IL-8 release from A549 cells increased. There were no significant differences in level of IL-8 release between cells pre-incubated for 24 h with or without PFC after toxin stimulation for 24 h. When PFC was administered along with LPS stimulation, the level of IL-8 release was decreased (LPS control, 1,398 +/- 110 pg/well; FC-84, 686 +/- 50 pg/well; perflubron, 749 +/- 137 pg/well; p < 0.05). Levels of IL-8 mRNA expression were significantly higher with than without LPS, and those with LPS and perflubron were significantly lower than those with LPS alone.

CONCLUSIONS

The results show that PFCs block stimulation of A549 cells by LPS or alpha-toxin. PFC may be useful clinically in treatment of pulmonary inflammation in the alveolar space.

Infection control, hospital epidemiology, and patient safety

Health care-acquired are a major risk for hospitalized children. Similar to adult patients, children are vulnerable to infections related to medical devices. Children also are at significant risk of nosocomial transmission of common pediatric viral illness, such as respiratory syncytial virus and varicella. In addition, pediatric patients have unique or incompletely developed immune system.

Pulmonary and systemic induction of SAA3 after ventilation and endotoxin in preterm lambs

Serum amyloid A (SAA), an acute phase reactant (APR) protein, is induced in liver during systemic inflammation. Serum amyloid A3 (SAA3), an isoform of SAA, is induced in both liver and extra hepatic sites in response to proinflammatory stimuli such as cytokines. Previously, we showed a modest increase in plasma cytokine levels in a preterm lamb model of lung injury. The study objective was to determine the relative contributions of lung and liver to the acute phase response during postnatal lung injury. Preterm (130d) and near term (141d) newborn lambs (term=150d) were randomized to either no ventilation (controls), ventilation+intratracheal (IT) endotoxin (endo) or ventilation+IT saline. A group of near term lambs were exposed to ventilation+IV endotoxin. In the lungs, ventilation alone increased SAA3 mRNA 3- and 13-fold while ventilation+IT endotoxin increased SAA3 mRNA 64 and 366-fold above controls in preterm and near term lambs, respectively. In the liver, SAA3 mRNA was induced by ventilation alone (three-fold) and ventilation+IT endotoxin (45-fold) above controls in both preterm and near term animals. Ventilation + IV endotoxin caused the highest increase in SAA3 mRNA (212-fold) in the liver of near term animals. A different isoform, identified as SAA-Liver inducible was maximally induced in liver by ventilation alone with minimal further response to endotoxin. Lung SAA3 mRNA expression was detected primarily in airway epithelium, bronchial glands, perichondrium of bronchial cartilage and vascular smooth muscle cells. Our experiments show rapid induction of an APR gene in lung in response to proinflammatory stimuli.

Use of computerized surveillance to detect nosocomial pneumonia in neonatal intensive care unit patients

BACKGROUND

Pneumonia surveillance is difficult and time-consuming. The definition is complicated, and there are many opportunities for subjectivity in determining infection status.

OBJECTIVE

To compare traditional infection control professional (ICP) surveillance for pneumonia among neonatal intensive care unit (NICU) patients with computerized surveillance of chest x-ray reports using an automated detection system based on a natural language processor.

METHODS

This system evaluated chest x-rays from 2 NICUs over a 2-year period. It flagged x-rays indicative of pneumonia according to rules derived from the National Nosocomial Infection Surveillance System definition as applied to radiology reports. Data from the automated system were compared with pneumonia data collected prospectively by an ICP.

RESULTS

Sensitivity of the computerized surveillance in NICU 1 was 71%, and specificity was 99.8%. The positive predictive value was 7.9%, and the negative predictive value (NPV) was >99%. Data from NICU 2 were incomplete.

CONCLUSIONS

Computer-assisted surveillance has the potential to decrease ICP workload and make pneumonia surveillance feasible. The high NPV means the system can safely screen out many chest x-rays of noninfected patients. However, all data must be available to the computer system and must be analyzed the same way for results to be comparable.

Risk factors for pulmonary candidiasis in preterm infants with a birth weight of less than 1250 g

To evaluate the epidemiology of pulmonary candidiasis (PC) and to identify risk factors in premature infants during the 1st month of life, all infants with a birth weight <1250 g admitted to our neonatal intensive care unit with PC between January 1994 and December 2001 were retrospectively reviewed. Infants with PC ( n =20) were compared with a control group ( n =20), matched for gestational age and birth weight, with regard to possible perinatal and postnatal risk factors. Among 325 infants with a birth weight <1250 g, 20 out of 233 ventilated infants (8.6%) developed PC. Candida albicans ( n =12) and C. parapsilosis ( n =4) were the predominant isolates. Neonates with PC were significantly different from controls with regard to male prevalence ( P =0.002), rates of preterm premature rupture of membranes (PPROM) ( P =0.02), longer duration of antibiotic therapy ( P =0.01) and of ventilation ( P =0.02). The difference between groups did not attain significance with regard to postnatal dexamethasone administration, duration of central vein catheterisation and duration of parenteral nutrition. Multivariate logistic regression analysis indicated as significant predictors of PC, among perinatal data, the male gender (OR =26.3; 95%CI 2.44 to 284) and PPROM (OR =12.3; 95%CI 1.16 to 130) and, among postnatal data, the duration of ventilation (OR =1.54; 95%CI 1.01 to 2.34).

CONCLUSION

The presence of preterm premature rupture of membranes and the duration of ventilation are significant risk factors for developing pulmonary candidiasis and should be considered in the preventive efforts to reduce this disease in infants with a birth weight <1250 g.

Clinical microbiology of bacterial and fungal sepsis in very-low-birth-weight infants

Twenty percent of very-low-birth-weight (<1500 g) preterm infants experience a serious systemic infection, and despite advances in neonatal intensive care and antimicrobials, mortality is as much as threefold higher for these infants who develop sepsis than their counterparts without sepsis during their hospitalization. Outcomes may be improved by preventative strategies, earlier and accurate diagnosis, and adjunct therapies to combat infection and protect the vulnerable preterm infant during an infection. Earlier diagnosis on the basis of factors such as abnormal heart rate characteristics may offer the ability to initiate treatment prior to the onset of clinical symptoms. Molecular and adjunctive diagnostics may also aid in diagnosing invasive infection when clinical symptoms indicate infection but no organisms are isolated in culture. Due to the high morbidity and mortality, preventative and adjunctive therapies are needed. Prophylaxis has been effective in preventing early-onset group B streptococcal sepsis and late-onset Candida sepsis. Future research in prophylaxis using active and passive immunization strategies offers prevention without the risk of resistance to antimicrobials. Identification of the differences in neonatal intensive care units with low and high infection rates and implementation of infection control measures remain paramount in each neonatal intensive care unit caring for preterm infants.

Reducing atelectasis attenuates bacterial growth and translocation in experimental pneumonia

Besides being one of the mechanisms responsible for ventilator-induced lung injury, atelectasis also seems to aggravate the course of experimental pneumonia. In this study, we examined the effect of reducing the degree of atelectasis by natural modified surfactant and/or open lung ventilation on bacterial growth and translocation in a piglet model of Group B streptococcal pneumonia. After creating surfactant deficiency by whole lung lavage, intratracheal instillation of bacteria induced severe pneumonia with bacterial translocation into the blood stream, resulting in a mortality rate of almost 80%. Treatment with 300 mg/kg of exogenous surfactant before instillation of streptococci attenuated both bacterial growth and translocation and prevented clinical deterioration. This goal was also achieved by reversing atelectasis in lavaged animals via open lung ventilation. Combining both exogenous surfactant and open lung ventilation prevented bacterial translocation completely, comparable to Group B streptococci instillation into healthy animals. We conclude that exogenous surfactant and open lung ventilation attenuate bacterial growth and translocation in experimental pneumonia and that this attenuation is at least in part mediated by a reduction in atelectasis. These findings suggest that minimizing alveolar collapse by exogenous surfactant and open lung ventilation may reduce the risk of pneumonia and subsequent sepsis in ventilated patients.