| BackgroundVentilator-associated pneumonia(VAP) is pneumonia in mechanically ventilated patients that develops later than or at 48h after the patient has been placed on mechanical ventilation.VAP is one of the most common complications in mechanically ventilated patients.The incidence of VAP reported in China was 20.8%-60%.The most recent American National Nosocomial Infection Surveillance (NNIS) data from 2002 to 2004 showed neonatal intensive care unit(NICU) VAP rates ranging from 1.4 to 3.5 per 1,000 ventilator days.Research showed that VAP is the second most common hospital-acquired infection among neonatal intensive care unit patients,only less than skin and mucous membrane infection.VAP is associated with longer duration of mechanical ventilation,delay of extubation,excessive length of NICU stay.Fisher et al. performed a prospective cohort study to determine the delay of extubation attributable to VAP among 272 neonates and children undergoing repair of congenital heart disease,they found that the median delay of extubation attributable to VAP was 3.7 days.VAP can cause additional utilization of antibiotic administration, also has been showed to increase hospital cost for about $3000. Apisarnthanarak's research showed that VAP occurred at high rates in extremely preterm neonates and was an independent predictor of mortality. As a common and serious intensive care unit complication,VAP has been the focus of research.Many risk factors for the development of VAP in adults have been identified,but scant data exist for neonates. Apisarnthanarak's research showed that previous blood-stream-infection was the independent risk factor for neonatal VAP.Research in China showed that re-intubation,duration of ventilation,utilization of central depressant,basic pulmonary disease, utilization of large dosage gamma globulin,gestational age,birth weight were the risk factor for neonatal VAP. Some research in China only have no more than 80 neonates enrolled in the study,most of the research only performed univariate analysis,neglecting the interact of factors with each other.There is no nursing research performs univariate analysis and multivariate analysis of risk factors of neonatal VAP.ObjectiveExplore the risk factors of neonatal VAP.Subjects and MethodsAll patients ventilated for≥48h were enrolled from admissions to the NICU of Shenzhen People's Hospital between January 2005 and October 2010.The study population was divided into two clinical groups according to diagnosis:VAP and control.The data collected in this study consisted of 182 NICU patients,48 VAP and 134 controls.The diagnosis criteria of VAP:Patients who are mechanically ventilated for≥48h,fever with no other recognized cause,new onset of purulent sputum,change in character of sputum,microbiologic examination of sputum obtained from tracheobronchial can see bacterium,leukocytosis or white blood cells increase 25%,the difference of oxygen pressure between alveoli and arterial increase,X-ray can see new or advanced infection,quantitative culture of sputum obtained from trachea is positive,colony account>103/ml.Sputum culture can see>25 white blood cells/low powered field and< 10 squamous cells/low powered field.The incidence of VAP was studied by multiple regression analysis of relevant factors:gender,gestational age(< 37w,≥37w),birth weight (< 2.5kg,≥2.5kg),delivery pattern(cesarean section,spontaneous labor),re-intubation,closed thoracic drainage,nasogastric feeding,mechanical assistance sputum ejection,endotracheal suction (≥6/d,<6/d),duration of mechanical ventilation((≥5d,<5d),parenteral nutrition.Statistics:SPSS 13.0 software package was used to perform non-conditional logistic regression analysis(univariate analysis and multivariate stepwise logistic regression analysis).Results1.Incidence of VAPThere were 48 episodes of VAP in 182 neonates who were ventilated for≥48 hours. The incidence of VAP was 26.37%(95%CI:20.13%-33.40%),42.17/1000 ventilator days.2.Mortality rateThe mortality rate was 6.25% in VAP neonates Versus 4.48% in control group neonates,χ2value was 0.01,P>0.05.3.PathogensMicrobiologic examination of sputum could find bacteriums in 31 neonates among the 48 VAP neonates.Positive rate was 64.58%. The main pathogens were G-bacteriums(83.87%),7 strains of stenotrophomonas maltophilia,5 strains of pseudomonas aeruginosa,6 strains of baumanii,5 strains of meningitis septico-flavobacterium,l strain of flavobacterium,l strain of klebsiella pneumoniae(ESBLs),1 strain of flavobacterium gleum. Other bacteriums were all G+ bacteriums(16.13%),2 strains of staphylococcus aureus(1 of them was MRSA),2 strains of staphylococcus haemolyticus,l strain of streptococcus.4.Univariate non-conditional logistic regression analysisUnivariate non-conditional logistic regression analysis showed that gestational age,low birth weight,duration of mechanical ventilation≥5d, endotracheal suction≥6/d were associated with the development of neonatal VAP.5.Multivariate stepwise logistic regression analysisMultivariate stepwise logistic regression analysis showed that duration of mechanical ventilation,low birth weight, endotracheal suction were predicted factors for the development of VAP.ConclusionsDuration of mechanical ventilation(≥5d),birth weight(<2.5kg), endotracheal suction(≥6/d) were risk factors for the development of neonatal VAP.The development of neonatal VAP was associated with patient's internal agent and external medical environments.Excessive suctioning is harmful to the mucous membrane of respiratory tract.It can irritate the mucous membrane,cause increase of secretion,even can cause other complications like mucosal edema,mucosal bleeding,mucosal abrasion.On the other hand,bacteriums on the endotracheal tube can reinoculate on the low respiratory tract with each repeated suctioning. All these can increase the opportunity of nosocomial infection. We suggest to minimize endotracheal suction frequency, suction the baby's tracheal as soon as necessary.Intubation can destroy the defensive barrier of respiratory tract, weaken the cough reflex and ciliary movement,make the secretion more difficult to eliminate,affect the function of secretory IgA.Siltation of secretion around the endotracheal tube make the bacteriums more easily to invade into bronchus and alveoli.Pollution of ventilator therapeutic tool,especially pollution of nebulizer and humidifier can lead to infection. Condensed water is a good bacteriums storeroom,if the condensed water flow into lower respiratory tract,it can make the baby in high risk of VAP. Ventilation tubing also is a good bacteriums storeroom,the longer of mechanical ventilation,the more bacteriums will planting on the tubing.Bacteriums on the tubing can invade into lower respiratory tract.The longer duration of mechanical ventilaton,infant are at higer risk of VAP. We suggest to reduce duration of mechanical ventilation as soon as possible.Measures to reduce duration of mechanical ventilation:①Use pulmonary surfactant in premature infant;②Use non-invasive ventilation as soon as possible,for example,we can use nasal continuous positive airway pressure(NCPAP).It was reported that the VAP rate significantly higher than the pneumonia rate during NCPAP treatment. Withdraw the mechanically ventilation earlier as soon as possible,NCPAP can be a transition measure.Low birth weight infants have immature body systems, immature cell immunity and humoral immunity,deficiency of antibody from mother,low IgG in the blood,weak skin and mucosal barrier,all these can make them in high risk of infection.We suggest to use comprehensive measures to prevent neonatal VAP,includes:①Enhance health-care worker education and training;②Hand hygiene. Handwashing is the most important and least expensive measure to prevent transmission of nosocomial infections.Good hand hygiene can reduce neonatal VAP.The neonatal unit should prepare enough facilities of hand hygiene.Doctors and nurses in the unit should wash hands strictly,especially before and after performing sterile operation such as suctioning and tracheal intubation.Alcoholic antiseptic disinfectant is used generally,it is wellknown because of it's rapid activity,superior efficacy,minimal time consumption,allows 100% compliance without interfering with the quality of patient care;③Using sterile technique when performing sterile operation.Use disposable sterile suction tubing and wear sterile gloves when suction the baby's tracheal with open endotracheal suction system. Avoid environmental contamination of the suction tubing.Avoid instillation of isotonic sodium chloride solution during endotracheal tube suctioning,because it can cause VAP;④Isolation and management of infants with multidrug-resistant organism;⑤Keep the environment of NICU clean.⑥Reducing the risk of aspiration.We can elevate the head of bed,feed the baby slowly,suction the baby's tracheal after feeding the baby 30 minutes later or suction the baby's tracheal before feeding;⑦Use humidification system that can provide optimal humidification(temperature of water vapor 37℃, relative humidity 100%, absolute humidity 44mgH2O/L);⑧Management of breathing circuit.Change the breathing circuit(i.e.,ventilator tubing and exhalation valve and the attached humidifier) once a week. Change the circuit immediately when it is visibly soiled or mechanically malfunction. Periodically drain and discard any condensate that collects in the tubing of mechanical ventilator,taking precautions not to allow condensate to drain toward the patient.Use sterile water to fill humidifier.⑨Use gamma globulin to enhance the baby's immunity. |
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