FRCA Notes

Ventilator Associated Pneumonia

The CRQ questions on VAP from 2018 (pass rate 39%) and 2023 (30%) were poorly answered, it would seem. In the 2018 exam, performance on the VAP question correlated with overall performance while in 2023 it was the lowest scoring question.

Resources

  • Ventilator-associated pnuemonia (VAP) is defined as tracheobronchitis or pneumonia occurring >48hrs after the initiation of mechanical ventilation
    • It can be further sub-classified into early (onset ≤5 days) or late (onset >5 days) VAP
  • Incidence 8 - 25% of mechanically ventilated patients
    • Rate of 13.6 per 1,000 ventilator days
    • The risk of developing VAP is ∽3%/day for the first five days of ventilation

  • Responsible for 50% of all antibiotics given on ICU
  • Associated mortality is highly variable; 24 - 76%
    • Late VAP has a poorer outcome owing to its causation by typically drug-resistant organisms

    Risk factors

    Patient factors Ventilatory factors
    Age >55yrs Supine position
    Existing lung disease Prolonged paralysis
    Malnutrition, anaemia or renal failure Frequent ventilator circuit changes
    Polytrauma Re-intubation following unsuccessful extubation
    Chest or upper abdominal surgery Prolonged duration of I&V
    Previous antibtioics, esp. if broad-spectrum


  • The causative organisms tend to relate to the timing between onset of mechanical ventilation and start of VAP
  • It may be polymicrobial in nature

Early VAP

  • Methicillin-sensitive Staphylococcus aureus (MSSA)
  • Streptococcus pneumoniae
  • H. influenzae

Late VAP

  • Aerobic, gram-negative bacilli
    • Pseudomonas
    • Klebsiella
    • Enterobacter
    • Acinetobacter
      •
  • Drug-resistant organisms
    • MRSA
    • VRE

  • The presence of ETT or tracheostomy interferes with normal anatomy and physiology of the respiratory tract
    • Impaired cough
    • Impaired mucociliary action

  • Additionally, a reduced conscious level e.g. from sedation to facilitate I&V leads to:
    • Impaired secretion clearance
    • Pooling of secretions in the oropharynx, leading to (micro/macro) aspiration

  • There is a proliferation of normal oral flora, which form an antibiotic - resistant biofilm
  • This is exacerbated by the inability to mount an immune response due to critical illness

  • Diagnosis is based upon the triad of:
    1. Clinical suspicion
    2. Radiological evidence of infection
    3. Microbiological results
      • NB No evidence that BAL is superior to simple tracheal aspirate culture
      • Although blood cultures should be taken, an organism isolated in the bloodstream mayn't necessarily be the same one as that causing the VAP

Clinical scoring systems

  • The Clinical Pulmonary Infection Score (CPIS) is a validated clinical scoring system
  • Patients are scored on:
    • Temperature
    • White cell count
    • Tracheal secretions
    • Chest radiography
    • Oxygenation (P/F ratio)

  • A score of >6 is felt to represent VAP
  • CPIS suffers from a poor sensitivity and specificity

Prevention

  • Prevention is the key; use of ventilator care bundle can reduce the incidence of VAP by up to 50%
Minimise time on ventilator Reduce risk of aspiration Optimise microbial ecology
Avoid (re-)intubation Elevate head 30 - 45° Stop SUP in low-risk patients
Early extubation/early weaning protocol Subglottic suction/aspiration Oral hygiene: BD toothbrushing & QDS chlorhex mouthwash
Daily sedation breaks ± sedation level assessment Maintain cuff pressure 20 - 30cmH2O, measuring 4hrly Avoid routine ventilator circuit changes

Treatment once present

  • Antibiotics
    • Tailored according to microbiological advice, local resistances and cultures
    • Patients with early-onset VAP and no previous antibiotic use may 'get away with' single agents (although realistically it'll be tazocin)
    • Patients with late-onset VAP or previous Abx courses need Pseudomonas cover with anti-pseudomonal beta-lactams or carbapenems

  • Ongoing microbiological advice
    • Input from Microbiology regarding antimicrobial selection/organism resistance locally
    • Audit of local VAP rates

  • A care bundle is:

    • A group of evidence-based interventions which, when delivered together, lead to a better clinical outcome than performing interventions individually


  • A recent review suggests the effect of ICU care bundles on patient outcomes may be inconclusive, except for the sepsis bundles (BMJ Open, 2023)

Examples

  • Central line insertion care bundle
    • Implementation of a CVC care bundle reduced catheter-related bloodstream infections to 66% of pre-bundle levels

  • Sepsis six care bundle
    • Implementation associated with a reduction in mortality of ∽6% over 2yrs

  • Delirium prevention care bundle