Ventilator-Associated Events & Ventilator-associated Respiratory Infections (VARI)

1. Introduction.

Ventilator-associated respiratory infections (VAP) remains as an important condition that is associated with increased mortality (VAP), morbidity (VAP & VAT) and health care costs (VAP & VAT). It is the most frequent intensive care unit (ICU) infection and it serves as a measurement of quality and safety in care. Increase in stay is why so many efforts have been directed towards its prevention. Actual definition for VAP is highly unspecific and it is not correlated with hysto-pathologic findings of pneumonia, independently of microbiologic methods use for its diagnosis.  Overall, 50% of episodes remains with unknown pathogen. Yeast should not considered respiratory pathogens.

The U.S Centers for Disease Control and Prevention has replaced the VAP surveillance with the ventilator associated-event (VAE) surveillance in January 2013. VAE definitions were designed to overcome some of the major limitations of VAP surveillance. VAE surveillance shifts the focus not only to pneumonia but towards a syndrome characterized by respiratory worsening while on mechanical ventilation. This approach provides three major advantages: sidesteps the limited accuracy of VAP surveillance definitions, broadens the focus to include additional morbid events, beyond just pneumonia, and allows objective surveillance based on objective and measurable parameters. The major disadvantage is that is not considering pathogens and is useless for antibiotic administration.

2. Surveillance programmes.

The VAE surveillance programme should enclose the following definitions: ventilator-associated conditions (VAC), infection-related ventilator-associated complications (IVAC): ventilator-associated tracheobronchitis and (probable or possible) pneumonia (VAP). There have been, however, insufficient efforts identifying risk factors for VAEs, which might be useful target for preventive interventions. Incidence in Europe until nowadays is limited and there is barely any experience in paediatric ICUs.

2.1 Target population.

Patients who are on an ICU of a participating centre and on mechanical ventilation for at least for 48 consecutive hours.

Inclusion criteria:

  • ICU admission;
  • Mechanical ventilation via Endotracheal or tracheostomy.

Exclusion criteria:

  • Mechanical ventilation for less than 48 hours. However, episodes within 48h developed as a consequence of an invasive procedure should be considered nosocomial.

2.2 Surveillance.

Ventilator-associated event surveillance data:

  • daily minimum PEEP and FiO2;
  • daily minimum and maximum temperature;
  • daily minimum and maximum white blood cell count

Whether endotracheal aspirate or BAL obtained:

  • cram stain neutrophil count (quantitative or semi-quantitative);
  • culture result (organism and quantity using a quantitative or semi-quantitative scale). Thresholds for pathogen identification should be considered similar for VAP or VAT;
  • antibiotics (yes / no for each agent for each day).

2.3 Surveillance Definitions.

VAC: increase in positive end expiratory pressure (PEEP) minimally by ≥3cmH2O or increase in the fraction of inspired oxygen (FiO2) minimally by ≥0, 20 after a period of stability of ≥2 days or improvement period. Improvement defined as a period of ≥2 days in which daily minimum PEEP or FiO2 have decrease.

IVAC: VAC plus leucocytosis (≥12,000 cells/ml) or leucopenia (≤ 4000cells/ml) or fever (≥38ºC) or hypothermia (≤ 36ºC) and the beginning of a new antibiotic during ≥ 4days.

VAT (Ventilator-associated trachea-bronchitis):presence of purulent respiratory secretions, increased inflamation (fever, WBC count or CRP), but absence of new pulmonary opacities at CXR.

Possible pneumonia: IVAC plus purulent secretions or growth of a pathogenic microorganism on an endotracheal aspiration (EA) or a broncheoalveolar lavage (BAL) culture. (Excluding normal oropharyngeal flora, Candida spp, or non specified yeast, coagulase-negative Staphylococcus and Enterococcus spp). Purulent secretions are defined as tracheal, bronchial or lung secretions that contain >25 neutrophils and <10 scamous epithelial cells by field.

Probable pneumonia: IVAC plus purulent secretions and:

A) Moderate or more growth of a pathogenic microorganism in culture defined depending on how sample was collected as follows:

  • ETA ≥ 105 CFU/ml or semiquantitative equivalent;
  • BAL ≥ 104 CFU/ml or semiquantitative equivalent;
  • lung tissue: ≥ 104 CFU/g o semiquantitativeequivalent;
  • protected brush: ≥ 103 CFU/ml o semiquantitative equivalent.

B) Or one of the following without purulent secretions:

  • positive pleural effuse culture (obtains by thoracocenthesis or at the moment of placing a chest tube, not from one already placed);
  • lung positive histopathology;
  • positive test for Legionella spp.;
  • positive test for influenza, respiratory syncytial virus, adenovirus, rhinovirus, human metapneumovirus or coronavirus.

2.4 Risk factors surveillance data (to be measured daily):

  • sedative choices: continuous, intermittent, or no sedatives;
  • muscle relaxants;
  • sedation level (Ramsay score);
  • spontaneous breathing trials or Spontaneous awakening trials;
  • delirium screening;
  • fluid balance (in litres);
  • considerations:
    • PIRO score should be measured to stratify severity is patients diagnosed as VAP;
    • episodes associated with tracheostomy or intubation should be considered different.

2.5 Indicators.

  • VAP / 1,000 ventilator-days (in ET tube)
  • VAP / 1,000 ventilator-days (in tracheostomy)
  • VAT / 1,000 ventilator-days (in ET Tube)
  • VAT / 1,000 ventilator / days (in tracheostomy)
  • VARI: VAP + VAT
  • VAC
  • IVAC

Original contribution from: 

Jordi Rello, Clinical Research& Innovation in Pneumonia and Sepsis (CRIPS) Group Valld' Hebron University

Hospital Barcelona, Spain.