Ventilator Associated Pneumonia

OVERVIEW

Ventilator Associated Pneumonia (VAP) is pneumonia occurring in people who had mechanical ventilation within 48 hours of the onset of infection

• VAP is a subgroup of hospital-acquired pneumonia
• VAP applies to patients with an endoctracheal tube or a tracheostomy tube – does not include patients receiving non-invasive ventilation (NIV)
• common complication in ICU (15-20% incidence if >48h ventilation)
• a gold standard test for diagnosis does not exist

PATHOGENESIS

Events leading to VAP:

• Colonization of the oral cavity, upper airway, endotracheal tube and circuit with pathogenic organisms
• Passage of pathogenic bacteria from the above sites into the lower airways through aspiration or microaspiration of secretions and suction catheters

Endotracheal cuffs

• effective at preventing macro-aspiration
• small folds on the surface of the cuff act as conduits for microaspiration of secretions pooled above the cuff
• In older patients, who may have tracheomalacia, there may be a leak around the cuff despite high intra-cuff pressure

CAUSATIVE ORGANISMS

< 48 hours in hospital

• often community organism

48 hours – 5 days:

• community + hospital organisms

> 5 days

• often hospital grown multi-resistant organisms (MROs) such as methicilin-resistant Staphylococcus aureus (MRSA) and Gram-negative bacilli (GNB):
  • Pseudomonas aeruginosa
  • Klebsiella
  • Enterobacter
  • Acinetobacter baumannii
  • Stenotrophomonas maltophilia

RISK FACTORS

• See preventative measures below

ASSESSMENT

Clinical suspicion of VAP when:

• new infiltrates are present on chest x-ray, and
• at least one of the following is present:
  • Fever
  • leukocytosis
  • or purulent tracheo-bronchial secretion

INVESTIGATIONS

• see diagnostic criteria below
• microbiological sampling options:

1. Lukens trap (deep suctioning via sterile catheter)
2. bronchscopic protected catheter brush
3. bronchoscopic alveolar lavage (BAL)

• no conclusive evidence in favour of any approach, so a Lukens trap is commonly used because is practical

DIAGNOSTIC CRITERIA

Clinical

• lung findings such as fremitus, dullness, bronchial breathing, crackles
• purulent sputum
• fever

Laboratory

• inflammatory marker elevation
• positive cultures (sputum or blood)
• 4 fold increase in antibody titres
• histopathology consistent with pneumonia

Radiological

• infiltrate or consolidation consistent with pneumonia

MANAGEMENT

Empiric antibiotics initially (use local guidelines)

• cover MDR organisms
• stop antibiotics for VAP at 6-8 days (evidence that longer courses lead to colonisation with MROs)
• treat Pseudomonas aeruginosa, Acinetobacter species or Stenotrophomonas maltophilia for 15 days

-> tazocin or timentin or cefepime
-> AND gentamicin to cover MDR organisms (use ciprofloxacin if age >65y, GFR <50 or recently on gentamicin)
-> if suspected MRSA add in vancomycin (pre-existing long-term lines, prior MRSA, in hospital > 7day or recent admission <3 months)
-> add teicoplanin if VRE colonized

-> if treatment fails:  cover MRSA with vancomycin or linezolid or teicoplanin + gram negatives with amikacin or tobramycin or colistin

Other

• supportive care including a protective lung ventilation strategy
• physiotherapy
• sputum clearance

PROGNOSIS

• VAP event adds 6 days to mean ICU LOS
• overall attributable mortality is 13%, with higher rates for surgical patients (Melsen et al, 2013)

PREVENTION

Not all measures used have been proven to prevent VAP

Implementation

• MDT approach with staff commitment (doctors, nurses, infectious diseases team, physiotherapy, management)
• Recognition of the problem (determine VAP base rate in the unit)
• Identify interventions that improve outcome
• Educate staff (nursing education shown to decrease VAP incidence)
• implement preventative strategy as a ‘bundle of care’ with ongoing education and reminders
• audit and feedback results

Infrastructure and general measures

• infection control: hand hygiene compliance, cross control of infection, surveillance, close communication
• antibiotic cover: adequate cover to reduce risk of MDR organisms
• good staffing levels: decreases cross contamination
• environment: targeted environmental sampling, disinfection during outbreaks

Patient Care

Prevent colonization of the upper respiratory and gastrointestinal tract

• good oral care (use 0.12-0.2% chlorhexidine twice daily with a sponge swab, brushing teeth)
• Oropharyngeal decontamination or selective digestive decontamination (reduces VAP rate but generally not used due to concern over MDR organism selection)
• Stress ulcer prophylaxis only when indicated (i.e. high risk: burns, traumatic brain or spinal cord injury, severe sepsis, coagulopathy and those receiving steroids equivalent of hydrocortisone > 250mg/day; or active peptic ulcer disease)
• silver coated ETT shown to decrease the rate of VAP
• probiotics (decreases VAP)

Prevent aspiration

• Maintain the head of the bed at 30-45° unless contraindicated (decreases VAP)
• Subglottic secretion drainage (SSD) (decreases VAP with NNT=11 if ventilated for more than 24-48h, but when combined with head up nursing no difference observed)
• maintain ETT cuff pressures between 20-30 cmH2O, check q4h
• No benefit from ultrathin or tapered cuff endotracheal tubes (Jaillette et al, 2017)
• Consider early gastrostomy if indicated (may decrease microaspiration)

Minimize the duration of mechanical ventilation

• Assess readiness for extubation daily
• Optimize use of sedation and analgesia (avoid oversedation, decreases time on mechanical ventilation and thus VAP)
• Early mobilization
• Early tracheostomy (data controversial, only applicable to selected patients e.g. neurosurgical patients, high spinal patients)
• Use NIV if appropriate (decreases VAP)

Endotracheal suction, humidification and care of the circuit

• Endotracheal suction when airway secretions are present (closed and open suction with a single use catheter are equivalent)
• Humidification and heating of the inspired gases (HME vs heated humifiers: data conflicting, considered equivalent if heated humidification with heating wire in the inspiratory or both limbs of the circuit is used to prevent condensation)
• Avoid routine ventilator circuit change (frequent changes doesn’t change VAP rate)

Other

• use blood conservation strategies (transfusion independently increases VAP)

References and Links

Journal articles

• Coppadoro A, Bittner E, Berra L. Novel preventive strategies for ventilator-associated pneumonia. Crit Care. 2012 Dec 12;16(2):210. doi: 10.1186/cc11225. [pubmed]  [article]
• Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. American Journal of Respiratory and Critical Care Medicine. 2005; 171(4):388-416. [pubmed] [article]
• Guillamet CV, Kollef MH. Ventilator associated pneumonia in the ICU: where has it gone? Current opinion in pulmonary medicine. 2015; 21(3):226-31. [pubmed]
• Jaillette E, Girault C, Brunin G, et al. Impact of tapered-cuff tracheal tube on microaspiration of gastric contents in intubated critically ill patients: a multicenter cluster-randomized cross-over controlled trial. Intensive care medicine. 2017; epublished [pubmed]
• Melsen WG, Rovers MM, Groenwold RH. Attributable mortality of ventilator-associated pneumonia: a meta-analysis of individual patient data from randomised prevention studies. The Lancet. Infectious Diseases. 2013; 13(8):665-71. [pubmed]
• Nair GB, Niederman MS. Ventilator-associated pneumonia: present understanding and ongoing debates. Intensive care medicine. 2015; 41(1):34-48. [pubmed]

FOAM and web resources

• CDC – Surveillance for Ventilator-Associated Pneumonia (VAP) Events