Community Acquired Pneumonia

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Community Acquired Pneumonia

• Manav Bhavsar
• ICM Study Day 22nd June 2007

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Introduction

• Inflammation of the lower air passages and air
  sacs of lungs resulting from inf of parenchyma
  of lungs
• Guidelines 2001 2004
  www.brit-thoracic.org.uk
• Level of evidence graded

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Definition CAP

• Diagnosis in hospital benefit chest radiography
• Symptoms signs consistent with an acute LRTI
  associated with new radiographic shadowing for
  which there is no other explanation (e.g. not
  pulm oedema or infarction)
• The illness is the primary reason for hospital
  admission and is managed as pneumonia

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Epidemiology

• 5-11 per 1000 population
• 83000 admission each year
• Fifth leading cause of death, mortality can be as
  high as 50
• Most episodes occur in winter autumn

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Risk Factors

• Age infants, young chidren, over 65
• Smoking, alcoholism
• COPD, malignancy, bronchiectasis, CF
• Pre-existing chest infection, esp bronchitis
• Immunosuppression, AIDS, cytotoxic drug
• Cardiac failure
• Diabetes

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Aetiology

• CAP cause by small no. organism
• Bacterial common Streptococcus pneumoniae Ib
• Viral 13, Influenza A B, autumn winter,
  recent travel or contact - Influenza type disease
• Low freq of legionella, mycoplasm, Chlamydia
  psittaci Coxiella burnetii infection, mainly
  elderly

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Clinical Features and Epidemiological features
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Clinical Radiological Feature

• Likely aetiological agent cant be predicted from
  clinical or radiological feature II
• Term atypical pneumonia be abandoned as it
  incorrectly implies characteristic clinical
  features with inf caused by atypicalpathogens
  II
• Radiological resolution often lags behind
  clinical improvement from CAP, esp folloeing
  legionella bacteraemic pneumococcal inf III

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Clinical Radiological Feature

• Radiographic changes caused by atypical pathogens
  clear more quickly than those caused by
  bacterial infection III
• Radiological resolution is slower to resolve
  elderly and in multilobe involvement Ib

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Investigations

• General
• chest radiograph C
• full blood count B
• urea, electrolytes and liver function tests C
• C reactive protein (CRP) B
• oxygenation assessment C
• Microbiological investigations

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Microbiological Investigation

• Blood culture
• Sputum samples
• Serological Tests
• Urine Antigen test - S pneumoniae (BINAX NOW) and
  Leigonella

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Blood Cultures

• Ideally obtained before antibiotic therapy starts
  D
• Severe CAP result more likely lead change
  antibiotics
• Only about 11 will be positive, highly specific,
  unlikely to be contaminated by respiratory tract
  commensals
• A positive BC in absence of septicaemia or other
  focus of infection is a definitive test
• Positive BC are more often found S. pneumoniae
  and H. influenzae serotype B (the incidence
  of which has now been reduced by vaccination)
• BTS Guidelines Management CAP

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Sputum Samples

• Non-severe CAP, C/S test samples as able to
  expectorate purulent samples have not received
  prior antibiotic treatment A-
• Severe CAP, be performed for patients or those
  who fail to improve A-
• Laboratories should offer a reliable Gram stain
  in pt with severe CAP or complications should
  adhere to strict and locally agreed criteria for
  interpretation and reporting of results B

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Serological Tests

• Paired serological tests be performed D
• patients with severe CAP
• who are unresponsive to ß-lactam antibiotics
• selected patients epidemiological risk factors
• whom a specific microbiological diagnosis is
  important for public health measures
• during outbreaks and when needed for the purposes
  of surveillance

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Antigen Tests

• Pneumococcal antigen tests should be used for
  patients with severe CAP, if available locally
  B
• Investigations for legionella infection are
  recommended for all patients with severe CAP,
  with specific risk factors, and for all with CAP
  during outbreaks B
• Rapid testing reporting legionella urine
  antigen available in at least one lab per region
  B
• Legionella cultures routinely performed on
  invasive respiratory samples (e.g. obtained by
  bronchoscopy) from patients with CAP D

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Atypical Pathogens

• Serological assays with complement fixation tests
  (CFTs), diagnosis for atypical and common
  respiratory viral pathogens C
• Chlamydial antigen detection tests should be
  available for invasive respiratory samples from
  patients with severe CAP or where there is a
  strong suspicionof psittacosis D
• The CFT remains the most suitable and practical
  serological assay for routine diagnosis of
  respiratory mycoplasmal and chlamydial infections
  B

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Severity Assessment

• Recommended as the key to planning, D, where to
  treat, which test to carry out, which antibiotic
  regimen
• Certain adverse prognostic features asso with an
  increased risk of death, should be assessed in
  all pt A
• None of the available predictive models or the
  algorithms allow unequivocal categorisation pt
  into definite risk groups be regarded as an aid
  to clinical judgement D
• Regular reassessment of severity during course of
  illness is mandatory, Mx to be adjusted
  appropriately D

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Management - General

• Oxygen therapy aim to maintain PaO2 gt8 kPa, SaO2
  gt92. High conc oxygen D
• Oxygen therapy, careful COPD complicated
  ventilatory failure guided by repeated ABGs C
• Assessed volume depletion - IV fluids C
• Nutritional support - prolonged illness C
• Temp, RR, HR, BP, mental status, SaO2 FiO2 conc
  monitored initially at least twice daily more
  freq severe CAP or on reg O2 C
• CRP be remeasured B CXR repeated C in
  patients not progressing satisfactorily

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Antibiotics

• Choice, dose and route of adm depends on severity
  of disease, pathogen and local resistance
  patterns
• Agent chosen always cover most likely pathogens
  S pneumoniae H. influenza
• Nursing home acquired pneumonia no changes in
  regimen Ib Eur Respir J 2001 18(2)362-368

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Antibiotics

• An alternative regimen
• intolerant of or hypersensitive to preferred
  regimen
• where there are local concerns over C difficile
  associated diarrhoea related to beta- lactam use
• Clarithromycin may be substituted for those with
  GI intolerance to oral erythromycin
• Levofloxacin moxifloxacin only currently UK
  licensed fluoroquinolones with activity against S
  pneumoniae
• Switch from parenteral drug to equivalent oral
  preparation as soon as feasible

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Non-invasive Ventilation

• Several studies, NIV in severe CAP can lead to
  initial improvement in SaO2 and fall in pulse,
  but over 50 later deteriorated requiring
  intubation
• ABG prior starting NIV not predictive of outcome
• There were a higher failure rate of those with an
  initial RR gt 38/min those aged gt 40 years
• May have a place in the initial management, but
  very close observation needed to detect
  deterioration and need for intubation

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Staphylococcus aureus

• Versatile, dangerous 10 CAP (ATS 2001)
• ? incidence by 200
  CAPO database study (11 countries
  2001-03)
• Nursing home
• MSSA is suspected,
  BTS recommends flucloxacilin with
  or without rifampcin
• ATS recommends a beta-lactum plus macrolide
  or fluroquinolone
• MRSA pneumonia - vancomycin or linezolid
• Cochrane Database of Systematic Reviews 2007
  Issue 1

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Other Therapies

• Vitamin C may be in cases with low plasma value
• Cochrane Database of Systematic Reviews 2007
  Issue 1
• Pneumococcal vaccine efficacy 50 corresponds to
  a NNT of 20,000 vaccinations per infection
  avoided, and perhaps 50,000 per death avoided
• Cochrane Database of Systematic Reviews 2003,
  Issue 4
• Granulocyte colony stimulating factor (G-CSF) no
  current evidence
• Cochrane Database of Systematic Reviews 2007,
  Issue 2

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References

• Guidelines for the Management of Community
  Acquired Pneumonia in Adults 2001 guidelines
  Thorax 2001 56 (suppl 4)
• Guidelines for the Management of Community
  Acquired Pneumonia in Adults 2004 update
• www.brit-thoracic.org.uk