A prospective cohort study design was used. The primary outcome examined was the incidence of VAP in mechanically ventilated patients. All patients who required mechanical ventilation for more than 48 hours from 1 April 2001 to 1 April 2003 were enrolled in the study. The following patient data were recorded: age, gen-der, underlying disease, duration of hospital stay, duration of mechanical ventilation, prior use of antibiotics, and risk factors for VAP.
Definition criteria for VAP in our study were
1) Fever > 38.5 °C or < 36 °C and WBC > 11,000 or < 4,000/mm2, 2) Increase in purulent excretions,
3) Positive tracheal aspirate culture,
4) Presence of new, persistant pulmonary inflitrates in chest radiographs.
VAP was diagnosed if two of the criteria were present.
In each case of definite pneumonia, we performed bronhoscopy to collect bac-teriological samples by bronchoalveolar lavage (BAL). Acquired specimens were transferred to a microbiological laboratory within 45 min. The media and incubation conditions were appropriate for the cultivation of the most probable respiratory pat-hogens. Standart disk effussion method was used for antibiotic sensitivity testing.
Results
A total of 1174 patients was admitted to ICU over the study period. 512 patients required mechanical ventilation for more than 48 hours. VAP developed in 37 ven-tilated patients (7.2%). Incidence of VAP was 13.6 per 1,000 ventilator days. The majority of patients had neurological disorders (Table 1).
Different pathogens isolated over the study period are shown in Table 2. One pathogen was isolated from 17 patients, two pathogens from 14, and three pathogens from 2 patients. Cultures from 4 patients were negative.
0
Figure 1. Antibacterial resistance (%) of Gram-negative microorganisms isolated from patients with VAP.
Izolēto Gram-negatīvo mikroorganismu antibakteriālā rezistence (%) pacientiem ar VAP
Discussion
Incidence of VAP in our study was 7.2%, or 13.6 cases per 1,000 ventilator days, to provide a better comparison. Overall rates reported by other researchers are most commonly 10 to 15 cases per 1,000 ventilator days, depending on the popula-tions studied 3.
There is no accepted “gold standart” for diagnosis of VAP. We had to choose the approach most suitable for our clinical setting. A postmortem study with similar de-finitions established 69% sensitivity and 75% specificity of the method 4. Available evidence at the time of the selection of our methodology indicated that the diagnosis of VAP is associated with about 30−35% false negative and 20−25% false positive results 5. Four patients were BAL culture negative. We could speculate that their radiological infiltrates were not of infectious aetiology.
Crude ICU mortality rates of 24 to 76% have been reported for VAP in different institutions. In our study, mortality in patients with VAP was 29.7%. It is difficult to determine whether such patients would have survived if VAP had not occurred.
The majority of patients with VAP in our study were males. Male sex has been associated with higher incidence of VAP in several studies 6. We cannot make such conclusions because a significant proportion of patients with head injuries are males.
Patients with head injuries contribute to many VAP cases in our study (Table 1)
Kristīne Geldnere, Dace Māliņa, Dace Spilnere, Arta Balode, Pēteris Ošs, Uga Dumpis. 39 Ar plaušu mākslīgo ventilāciju asociētās pneimonijas Intensīvās terapijas nodaļā Latvijā
Table 1 Characteristics of patients with VAP
VAP pacientu raksturojums
Characteristics Patients with VAP
Age, yr Mean 51 (range 18−85)
Gender Time of hospitalization before VAP 12,6 (SD = ±10.3) Time of mechanical ventilation before VAP 10 (SD = ±8) Onset of VAP
Early (<96 h)
Late (>96 h) 7 (19%)
30 (81%)
Mortality rate 29.7 % (11/37)
A higher incidence of VAP was registered in summer months. This most likely could not be atributed only to the outbreak of certain bacteria because an increased number of different pathogens were isolated. We can speculate that infection control measures were not sufficient at that time.
Conceptually, VAP can be divided into an early-onset and late-onset disease, according to the day of the onset. In our study, 19% of patients had an early-onset disease. There was a diference in the etiology of early-onset disease and late-onset disease (data not shown).
The most frequent pathogens isolated from our patients were Gram-negative rods. Pseudomonas aeruginosa was isolated from half of VAP patients. These fin-dings are similar to previously published information7. Most of the isolates were highly resistant to fluoroquinolones, ceftazidime, and gentamycin. Carbapenem re-sistant Acinetobacter baumanii was detected during our study in one patient. These findings could have potential severe implications that could make the choice of em-pirical treatment difficult and expensive.
Table 2 The number of main pathogens isolated over the study period.
Galveno izolēto mikroorganismu skaits pētījuma laikā April
Interestingly, only 4 oxacillin-sensitive Staphylococcus aureus isolates were identified as a possible cause of VAP. MRSA and VRE (Vancomycin-resistant en-terococcus) were not endemic in our hospital at the time of the survey. Once they will occur, we expect rapid spread of these pathogens due to lack of serious infection control measures in our ICU.
Multiple pathogens were isolated by BAL from nearly half of the studied pa-tients. Polymicrobial flora complicates the choice of empirical treatment and can have a serious impact on the outcome of the disease. The number of patients in our study was too small to assess the impact of polimicrobial flora on mortality. For the same reason, we were not able to analyse the impact of different antibiotic treatment regimens on the outcome and microbiological clearance of infection.
This is the first study in Latvia of patients with VAP performed to date. Findings of this study indicate that VAP is an important morbid outcome among critically ill patients in our Multidisciplinary University Hospital ICU. Surveillance of VAP is useful to characterise the epidemiological situation and improve the quality of pre-vention measures and empirical treatment. Further studies evaluating prepre-vention and treatment strategies are needed.
Kristīne Geldnere, Dace Māliņa, Dace Spilnere, Arta Balode, Pēteris Ošs, Uga Dumpis. 41 Ar plaušu mākslīgo ventilāciju asociētās pneimonijas Intensīvās terapijas nodaļā Latvijā
Acknowledgements
We thank the Hospital administration and the ICU staff for supporting the study.
Work on this paper has been supported by the grant No. 1100.1 of Latvian Council of Science.
References
1. Vincent jL, Bihari Dj, Suter PM, et al. The prevalence of nosocomial infection in intensive care units in Europe. Results of the European Prevalence of Infection in Intensive Care (EPIC) Study. EPIC International Advisory Committee. JAMA 1995, 274: 639−44.
2. Fagon jY, Chastre j, Hance Aj, et al. Nosocomial pneumonia in ventilated patients: a cohort study evaluating attributable mortality and hospital stay. Am J Med 1993, 94: 281−8.
3. Craven DE. Epidemiology of ventilator-associated pneumonia. Chest 2000, 117:
186S−7S.
4. Torres A, el Ebiary M, Padro L, et al. Validation of different techniques for the diagnosis of ventilator-associated pneumonia. Comparison with immediate postmortem pulmonary biopsy. Am J Respir Crit Care Med 1994, 149: 324−31.
5. Fabregas N, Ewig S, Torres A et al. Clinical diagnosis of ventilator-associated pneumonia revisited: comparative validation using immediate post-mortem lung biopsies. Thorax 1999, 54: 867−73.
6. Kollef MH. Epidemiology and risk factors for nosocomial pneumonia. Emphasis on prevention. Clin Chest Med 1999, 20: 653−70.
7. Fagon jY, Chastre j, Domart Y et al. Mortality due to ventilator-associated pneumonia or colonization with Pseudomonas or Acinetobacter species: assessment by quantitative culture of samples obtained by a protected specimen brush. Clin Infect Dis 1996, 23:
538−42.
Kopsavilkums
Veikts divus gadus ilgs prospektīvs pētījums, lai noskaidrotu ar ventilāciju asociētas pneimonijas (VAP) incidenci un biežākos tās izraisītājus Paula Stradiņa Klīniskās universitātes slimnīcas (Rīga, Latvija) Intensīvās terapijas nodaļā.
Izpētē izmantots prospektīva kohortas pētījuma dizains. Kā primārais iznākums tika definēta VAP incidence pacientiem ar mākslīgo plaušu ventilāciju. Pētījumā tika iekļauti visi pacienti, kuru ārstēšanā laika posmā no 2001. gada 1. aprīļa līdz 2003. gada 1. aprīlim bija nepieciešama mākslīgā plaušu ventilācija. Tika dokumentēti šādi pacientu dati: vecums, dzimums, pamatslimība, hospitalizācijas ilgums, mākslīgās plaušu ventilācijas ilgums, iepriekšēja antibakteriālās terapijas lietošana, VAP attīstības riska faktori.
VAP attīstījās 37 (7,2%) no 512 pacientiem, kuriem tika izmantota mākslīgā plaušu ventilācija.
Aprēķinātā VAP incidence bija 13,6 uz 1000 ventilācijas dienām. Vasarā VAP incidence bija ievērojami augstāka. 7% no VAP pacientiem bija vīrieši. Pacientu mirstība ar VAP bija 29,7%.
Bronhoalveolārās lavāžas laikā tika iegūti paraugi mikrobioloģiskai izmeklēšanai. Viens mikroorganisms tika izolēts 17 pacientiem, 2 mikroorganismi – 14 pacientiem un 3 mikro- organismi – 2 pacientiem. Četriem pacientiem uzsējumi bija negatīvi. Pseudomonas
aeruginosa tika izolēta 19 (51%) pacientiem, Acinetobacter baumanii – 11 (30%), Klebsiella pneumoniae – 13 (23%) un Staphylococcus aureus – 4 (11%) pacientiem.
Gram-negatīvām baktērijām tika konstatēta izteikta rezistence pret antibiotikām. Pseudomonas aeruginosa rezistence pret imipenēmu/ cilastatīnu, ceftazidīmu, gentamicīnu un ciprofloksacīnu sasniedza 60%, bet Acinetobacter baumanii rezistence pret karbapenēmiem bija 10%.
Meticilīnrezistentais staphylococcus aureus (MRSA) pētījuma laikā netika izolēts.
Šī pētījuma dati atspoguļo VAP klīnisko nozīmību un Gram-negatīvo baktēriju antibakteriālo rezistenci Intensīvās terapijas nodaļā Latvijā. Nepieciešami turpmāki pētījumi, lai novērtētu VAP novēršanas iespējas un iespējamās ārstēšanas stratēģijas.
LATVIjAS UNIVERSITāTES RAKSTI. 2008, 735. sēj.:
MEDICīNA