Ventilator-Associated pneumonia in the ICU

BY Dr. Chamika Huruggamuwa

Registrar In AnaesthesiaTH Kandy

Introduction• pneumonia that occurs 48–72 hours or thereafter following

endotracheal intubation, • characterized by the presence of a • new or progressive infiltrate, • signs of systemic infection (fever, altered white blood cell count), • Changes in sputum characteristics, and • detection of a causative agent

• Early onset VAP is defined as pneumonia that occurs within 4 days and this is usually attributed to antibiotic sensitive pathogens

• Late onset VAP is more likely caused by multidrug resistant (MDR) bacteria and emerges after 4 days of intubation

Epidemiology• VAP contributes to approximately half of all cases of hospital-acquired

pneumonia.• VAP is estimated to occur in 9–27 % of all mechanically ventilated

patients• VAP is associated with increased intensive care unit stay, patient

ventilator days, and mortality.• The incidence of VAP can be reduced by many means including the

use of care bundles and modified TTs.

• Approximately 50 % of all antibiotics administered in ICUs are for treatment of VAP.

• Independent risk factors for development of VAP are • male sex, • admission for trauma• intermediate underlying disease severity

Pathogenesis

complex interplay between the Endotracheal tube,

Presence of risk factors, virulence of the invading bacteria

host immunity

• The main pathogenic factor in the development of VAP is

biofilm formation within the tracheal tube (TT) microaspiration of secretions

endotracheal tube

violation of natural defense mechanisms

(the cough reflex of glottis and larynx) against microaspiration around the cuff of the tube

• Infectious bacteria obtain direct access to the lower respiratory tract via:• (1) microaspiration, which can occur during intubation itself; • (2) development of a biofilm laden with bacteria (typically Gram-

negative bacteria and fungal species) within the endotracheal tube; • (3) pooling and trickling of secretions around the cuff ; • (4) impairment of mucociliary clearance of secretions with gravity

dependence of mucus flow within the airways •

• Pathogenic material can also collect in surrounding anatomic structures, such as the stomach, sinuses, nasopharynx and oropharynx, with replacement of normal flora by more virulent strains• constantly thrust forward by the positive pressure• reintubation following extubation increases VAP rates, • the use of non-invasive positive pressure ventilation has been

associated with significantly lower VAP rates

• critically ill patients may have impaired phagocytosis

Microbiology• Type of organism depends on the duration of mechanical ventilation• Early VAP is caused by • pathogens that are sensitive to antibiotics, • whereas late onset VAP is caused by multi-drug resistant and more difficult to

treat bacteria.

• Early-onset VAP include Streptococcus pneumoniae (as well as other streptococcus species), Hemophilus influenzae, methicillin-sensitive Staphylococcus aureus (MSSA), antibiotic-sensitive enteric Gram-negative bacilli, Escherichia coli, Klebsiella pneumonia, Enterobacter species, Proteus species and Serratia marcescens.• Late VAP are typically MDR bacteria, such as methicillin-resistant S.

aureu (MRSA), Acinetobacter, Pseudomonas aeruginosa, and extended-spectrum beta-lactamase producing bacteria

Diagnosis• Currently, the diagnosis of VAP is based on a combination of clinical,

Radiological, and Microbiological criteria• DD ARDS pulmonary oedema pulmonary contusion Tracheobronchitis Thromboembolic disease.

• no universally accepted, gold standard diagnostic criterion for VAP

• no radiological criteria pathognomonic of VAP and the interpretation of chest radiographs in ventilated patients is very difficult.

• Single air bronchograms and fissure abutment are highly specific, but they lack sensitivity

• Invasive and non-invasive sampling techniques are used to Obtain microbiological specimens to diagnose VAP.

• Broncho Alveolar Lavage (BAL) mini BALs• Protected specimen brushings (PSB)

• Tracheal aspirates• Th e American Th oracic Society (ATS) and the

• Infectious Diseases Society of America (IDSA

BAL gold standard over others,,,,, however• It cannot guarantee sampling from the area of the lung most affected,

the sensitivity of this test is low, although the specificity is quite high (significant false-negative rate).

• CPIS -clinical, physiological, microbiological and radiographic evidence

• Scores can range between zero and 12 with a score of ≥ 6 showing good correlation with the presence of VAP• Despite the clinical popularity of the CPIS, debate continues regarding

its diagnostic validity.

• The Johannson criteria• The HELICS criteria• The United States Centre for Disease Control (CDC) definition

Treatment• antibiotic depends on the duration of mechanical ventilation.

• Late onset VAP (> 4 days) broad spectrum antibiotics

• Early onset (≤ 4 days) limited spectrum antibiotics

• The usual duration of treatment for early onset VAP is 8 days and longer in the case of late-onset VAP or if MDR organisms are suspected or identified

• Despite therapy, if no response is observed, it may be prudent to reconsider the diagnosis, reassess the organism being treated or search for other reasons for signs and symptoms.

Prevention• The role of care bundles

A care bundle refers to a group of evidence-based interventions related to a particular condition which when applied together significantly

improves patient outcome.

TT modification• TT cuff design to prevent microaspiration.

Cuff pressure control

• cuff pressure <20 cm H2O favors increased passage of secretions between the cuff and the wall of the trachea, while >30cmH2O may

cause tracheal mucosal damage.

Subglottic secretion drainage

A meta-analysis of 13 randomized controlled trials showed that subglottic secretion drainage was effective at reducing VAP rates, also

reducing the time to onset of first VAP, reduced duration of mechanical ventilation, and reduced ICU LOS.

TT cuff design

high volume–low pressure cuff Vs A tapered cuff shape

TT coating

Silver-coated TT or a standard TT chlorhexidine and titanium dioxide.

Significant reduction in VAP rates

NO Reduction in ICU LOS or duration of ventilationNASCENT TRIAL

Nebulized gentamicin

• Nebulized gentamicin attained a higher concentration within the TT and there was a lower incidence of biofilm formation

Kinetic therapy

Mucociliary clearance is inhibited by immobility.• Mechanical rotation of patients with 40° turns achieves more

significant clearance of secretions than current standard therapy of 2 hourly turns

Lower the incidence of VAP

No effect on duration of ventilation, LOS, or mortality.

Requires specialist equipment and has been

associated with significant complications such as

intolerance torotation, unplanned

extubations, loss of vascular access, and

arrhythmias.

Care of airway equipment

• Studies have shown that TT colonization and biofilm formation begins within 24 h of intubation.

Reducing biofilm formation can be achieved by,

Strict attention to hand hygiene when handling the TT, closed-circuit suction systems,

use of heat and moisture exchangers, limiting ventilator tube changes to whenever they are soiled,

Feeding

• early establishment of enteral feeding is of benefit to critical care patients.• reflux and aspiration of gastric contents is the main cause of VAP.• post-pyloric feeding may reduce the incidence of VAP.

Intubation-related events

Reducing the duration of intubation with the use of sedationholds and weaning protocols

reducing unplanned extubationsminimizing re-intubation have also been shown to reduce VAP

incidence

The major goals of VAP management

early, appropriate antibiotics in adequate doses followed by de-escalation based on microbiological culture results and the clinical

response of the patient.

Antimicrobial stewardship programs involving pharmacists, physicians and other healthcare providers optimize antibiotic selection, dose, and duration to increase efficacy in targeting causative pathogens and allow

the best clinical outcome