HAP/VAP

Hospital-acquired pneumonia/ventilator-acquired pneumonia (HAP/VAP) are forms of pneumonia contracted whilst in hospital or when a ventilator is being used. A patient with HAP has an acute bacterial pneumonia, and has either been hospitalised for ≥48hrs or developed pneumonia within 7 days of being discharged from hospital. Conversely, a patient with VAP has an acute bacterial pneumonia following mechanical ventilation for ≥48hrs.

The inclusion criteria for HAP/VAP are:

• All patients must have a lung CT or chest radiograph, within 48 hrs, showing the presence of new or progressive infiltrate(s) suggestive of bacterial pneumonia
• Patients must have one of the following signs:

  • Hypothermia (e.g. core body temperature ≤35°C)

  • Leukocytosis – total peripheral white blood cell (WBC) count ≥10,000 cells/mm³

  • Documented fever

  • Leukopenia – total peripheral WBC count ≤4500 cells/mm³

  • Peripheral blood smear showing >15% immature neutrophils (bands)
• Patients must have one of the following clinical features:
  • Hypoxemia (e.g. a partial pressure of oxygen <60mmHg while breathing room air)

  • New onset or worsening of pulmonary symptoms/signs: cough, tachypnoea (breathing too fast), dyspnoea (shortness of breath), sputum production, requiring mechanical ventilation
  • New onset of, or increase in, suctioned respiratory secretions (amount or characteristics) suggesting evidence of inflammation and absence of contamination
  • Acute changes required in the ventilator support system to enhance oxygenation – determined by worsening oxygenation (ABG or PaO2/FiO2)

Once HAP/VAP has been clinically diagnosed, the infectious pathogen needs to be identified to ensure the most effective treatment is given. Pseudomonas species (particularly P. aeruginosa) and Acinetobacter species are the most frequent NFGNB that cause HAP/VAP. However, another NFGNB species, Stenotrophomonas, has also been identified as infrequently causing HAP/VAP.

Similar to other infections, the antibiotic(s) given can depend on the microbial pathogen that has been detected. Other factors that also influence the choice of antibiotics given are: whether it is HAP or VAP, mortality risk of the patient (may require ventilation/septic shock), and MRSA likelihood. Common antibiotics used for HAP/VAP are aminoglycosides, polymyxins, carbapenems, ampicillin/sulbactam. This list is not exhaustive and is dependent on many factors as well as the species of the causative agent.