Diagnosing Pulmonary Infections in the ICU

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Diagnosing Pulmonary Infections in the
ICUVentilator Associated Pneumonia (VAP)
Dr. S. K. Jindal www.jindalchest.com
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Hospital Acquired Pneumonias

• Occurrence of pneumonia in a hospitalized
  patient when the infecting organisms are neither
  present nor incubating at the time of admission.
• Pneumonia occuring in a ventilated patient is
  called a ventilator associated pneumonia (VAP).

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When to suspect RTI ?

• Clinical General Respiratory
• Radiological shadows
• Laboratory abnormalities

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Clinical Diagnosis

• New or progressive lung infiltrates (Plus 2 of
  the following criteria) after 48 hours of
  hospital admission
• Fever
• Purulent sputum
• Leucocytosis

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Chest Roentgenography

• New infiltrates / opacities
• Alveolar shadows consolidation
  (Lobar/segemental/ others)
• Pleural effusion / pneumothorax
• Air cysts / cavities
• Interstitial / miliary shadows
• Hilar L.N. infiltrates

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False-negative chest radiographs

• Early course of disease
• PCP pneumonia / miliary TB
• Dehydration
• Neutropenia/rare

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False-positive chest radiographs

• Interstitial lung diseases
• Vasculitis
• Atelectasis
• Congestive heart failure
• Pulmonary infarcts
• Malignancies
• Miscellaneous

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General Laboratory Tests

• Leucocytosis (polymorphonuclear)
• Raised ESR
• Arterial blood gases
• S. electrolytes liver renal function tests
• Blood sugar
• H.I.V. serology
• Blood cultures
• Others

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Pulmonary Samples for Diagnosis

• Sputum / tracheal secretions
• Bronchoscopic
• - Washings
• - Bronchial / bronchoalveolar lavage
• - Biopsy (bronchial / TBLB)
• - Needle aspiration
• Transthoracic needle biopsy
• Transtracheal aspiration
• Pleural aspirate / biopsy
• Thoracoscopic specimens

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Sputum/ trach sec. examination

• Quantity
• Naked eye examination
• Cytological
• Lower airways gt25 PMN / field on low power lt10
  epithelial cells/field
• Malignant cells Parasites, fungi, etc.
• Microbiological
• Gram staining
• Culture and sensitivity

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Good Quality sample

• Before antibiotic treatment
• Prior mouth rinse
• Deep cough
• Purulent, thick part (minimal saliva)
• Early processing

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Approach to Diagnosis

• Clinical
  Microbiological
• Empirical Invasive
• 
  Combined

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Scoring Systems

• Clinical Pulmonary Infection score (CPIS)
• Each criteria worth 0-2 points
• Fever
• Quantity and purulence of tracheal secretions
• Oxygenation
• Type of radiographic abnormalities (Results of
  sputum culture gram stain)
• Bacterial index by Pugin et al.
• Modified CPIS

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CPIS Clinical Criteria
Variables Points 0 1 2 Points 0 1 2 Points 0 1 2
Temperature C gt36.1 to lt38.4 gt38.5 to lt38.9 gt39 to lt 36
WBC count /µ L gt4,000 to lt 11,000 lt 4,000 to gt 11,000
Secretions Absent Present, nonpurulent Present, purulent
PaO2/fraction of inspired oxygen gt240 or ARDS lt240 and no ARDS
Chest radiography No infiltrate Diffuse or patchy infiltrate Localized infiltrate
Microbiology No or light growth Moderate/heavy growth add 1point for same organism on Gram stain
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National Nosocomial Infection Surveillance System

• Radiographic Two or more serial chest
  radiographs with
• new or progressive and persistent
  infiltrate/or cavitation or consolidation
• (one radiograph sufficient in patients
  without underlying cardiopulmonary disease)
• Clinical One of the following
• Fever gt 38o C (gt100.4o F) with no other
  recognized cause
• WBC count lt4,000/ µ L or gt 12,000 µ L
• For adults gt 70 yr old, altered mental status
  with no other recognized cause
• And at least two of the following
• New-onset purulent sputum change in character,
  or increase in respir. secretions
• New-onset or worsening cough, dyspnea, or
  tachypnea
• Rales or bronchial breath sounds
• Worsening gas exchange, increased oxygen
  requirements, and ventilatory support
• Microbiology (optional) Positive culture result
  (one) blood (unrelated to other source),pleural
  fluid/ quantitative culture by BAL or PSB, gt5
  BAL-obtained cells contain intracellular bacteria

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Risk factors for MDR Pathogens

• Antibiotics in the preceding 90 d
• Hospitalization in preceding 90 d
• Current hospitalization gt 5 d
• Duration of mechanical ventilation gt 7 d
• History of regular visits to an infusion or
  dialysis centre
• Residence in a nursing home or extended-care
  facility
• Immunosuppressive disease or therapy
• High frequency of antibiotic resistance in the
  community or the ICU
• From American Thoracic Society and Trouillet et al

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Problems with clinical approach

• Two thirds of all patients with clinical
  diagnosis of VAP may not meet microbiological
  criteria for infection
• Clinical definition not specific
• Many patients with clinical VAP may have
  non-infectious etiologies

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But

• Mortality in VAP is reduced when prompt and
  adequate empiric therapy is initiated.
• Luna et al 1997
• Kollef et al 1999

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Clinical approach to VAP
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Invasive Approach

• Quantitative, Bacterial diagnosis
• Tightly protocolized therapeutic decisions based
  on results of direct examination of distal
  pulmonary samples and of quantitative cultures

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Techniques
Bronchoscopic Nonbronchoscopic
Proper selection of sample site Poor site selection
Complications Occasional Less invasive
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Protected Specimen Brush technique

1. Use of FOB
2. Double lumen catheter brush
3. Use of a brush to calibrate the volume of
   secretion
4. Quantitative cultures

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Quantitative Culture - Diagnostic threshold

• Pathogens 105 106 CFU/mL
• Contaminants lt104 CFU/mL
• PSB (0.001-0.01mL) Presence of 103 CFU
  represents
• 105 106 CFU/mL
• BAL (1mL) 104 CFU/mL represents
• 105 106 CFU/mL

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Invasive strategy for VAP
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Immuno suppressed Host (eg Transplant
patients)Diagnostic clues

1. Underlying disease
2. Known microbiological spectrum
3. Radiological features
4. Respiratory secretions Tracheal, BAL
5. Biopsies
6. Indirect Biochemical, serological
7. Therapeutic trial/Empiric therapies

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Summary

• Diagnosis of VAP is mostly based on clinical
  criteria/scoring system
• Empiric treatment need not wait for the
  microbiological diagnosis made from BAL, PSB etc.
• 3. Diagnosis in the immuno suppressed patients
  requires invasive tests (FOB, aspiration
  cytology, biopsy)

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