Pneumonia and its types ?
Introduction
Defined as acute respiratory illness associated with recently developed radiological pulmonary shadowing which may be segmental, lobar and or multilobar.
Clinical forms of pneumonia suggests of likely organism(s) involved and hence the immediate choice of antibiotics.
Classified as: community-acquired, hospital-acquired (nowadays called as Health care acquired pneumonia HCAP), or pneumonia in immunocompromised hosts or patients with underlying damaged lung (including suppurative and aspirational pneumonias).
Can be classified anatomically: Lobar pneumonia- referring to homogeneous consolidation of one or more lung lobes, Bronchopneumonia- patchy alveolar consolidation (affecting lower lobes)
Community-Acquired Pneumonia
Usually spread by droplet infection and occurs in previously healthy individual.
Factors that predispose to pneumonia are: cigarette smoking, URTI, alcohol, corticosteroid therapy, old age, recent influenza infection, pre-existing lung disease.
Classical pathological response evolves through the phases of congestion, red and then grey hepatization, and finally resolution with little or no scarring.
Common organisms:
Step pneumonae
Chlamydia pneumoniae
Mycoplasma pneumoniae
Legionella pneumophila
Uncommon organisms:
Hemophilus infuenzae
Staphylococcus aureus
Chlamydia psittaci
Coxiella burnetti
Klebsiella
Actinomyces israelii
Clinical features
Symptoms
Systemic features of acute illness- fever, rigors, shivering and vomiting. Loss of appetite and headache.
Pulmonary symptoms: Pulmonary symptoms include cough, which at first is characteristically short, painful and dry, later expectoration of mucopurulent sputum.
Rust-coloured sputum may be seen in patients with Streptococcus pneumoniae, occasional patient may report haemoptysis.
Pleuritic chest pain
Signs-
Inspection: tachypnoea, central cyanosis (if severe)
Palpation: decreased expansion,
Percussion: dull on percussion,
Auscultation: Bronchial breath sounds and increased vocal resonance over consolidation, pleural rub if pleurisy.
The majority of cases of CAP are due to infection with Strep. pneumoniae
Mycoplasma pneumoniae and Chlamydia pneumoniae are common in young adults but seldom reported in the elderly,
Haemophilus influenzae- in elderly patients,
Post-influenza viral infection may predispose to Staph aureus but most common is Strep penumonae.
Differential diagnosis
Pulmonary infraction
Pulmonary/pleural TB
Pulmonary oedema (can be unilateral)
Pulmonary eosinophilia
Malignancy: bronchoalveolar cell carcinoma
bronchitis,
acute exacerbations of chronic bronchitis,
heart failure,
pulmonary embolism, and
radiation pneumonitis.
Investigations
Radiological examination- chest X-ray
Microbiological investigations-
All patients
Sputum-direct smear by Gram and Ziehl-Neelsen stains. Culture and antimicrobial sensitivity testing
Blood culture-frequently positive in pneumococcal pneumonia
Serology-acute and convalescent titres to diagnose Mycoplasma, Chlamydia, Legionella and viral infections. Pneumococcal antigen detection in serum
Severe community-acquired pneumonia
The above tests plus consider: Tracheal aspirate, Fluorescent antibody stain for Legionella and viruses
Serology-Legionella antigen in urine. Pneumococcal antigen in sputum and blood. Immediate IgM for Mycoplasma
Cold agglutinins-positive in 50% of patients with Mycoplasma
Selected patients
Throat/nasopharyngeal swabs-helpful in children or during influenza epidemic
Pleural fluid-should always be sampled when present in more than trivial amounts, preferably with ultrasound guidance
Blood tests- complete blood count, blood cultures.
Assessment of gas exchange- pulse oximeter.
Assessment of disease severity- any of:
Confusion
Urea >7mmol/l (>20mg/dl)
Respiratory rate 30/min
Blood preassure (systolic <90mmHg or diastolic 60mmHg)
Age 65 years, score 1 point for each feature present.
CURB-65 (0-1)- likely to be suitable for home treatment
2- consider hospital-supervised treatment
3 or more- manage in hospital as severe pneumonia
Assess for ICU admissioin, especially if CURB-65 score = 4 or 5
Management
Advise to rest
Avoid smoking
Oxygenation, fluid balance and antibiotic therapy.
Oxygen- Oxygen should be administered to all patients with tachypnoea, hypoxaemia, hypotension or acidosis with the aim of maintaining the PaO2 ≥ 8 kPa (60 mmHg) or SaO2 ≥ 92%.
High concentrations (> 35%), preferably humidified.
Assisted ventilation should be considered at an early stage in those who remain hypoxaemic despite adequate oxygen therapy.
Fluid balance- oral intake or IV
Antibiotic treatment-
Indication for referral to ITU (intensive treatment unit)
CURB score 4-5 failing to respond rapidly to initial management
Persisting hypoxia (PaO2 < 8kPa (60mmHg)) despite high concentration of oxygen
Progressive hypercapnia
Severe acidosis
Shock
Depressed consiousness
Antibiotic treatment for CAP
Uncomplicated CAP-
Amoxicillin 500mg 8-hourly orally
If patient is allergic to penicillin: clarithromycin 500mg 12-hourly orally or erythromycin 500mg 6 hourly orally
If Staphylococcus is cultured or suspected: Flucloxacillin 1-2g 6 hourly i.v. plus clathromycin 500mg 12 hourly i.v.
If Mycoplasma or Legionella is suspected: clathromycin 500mg 12 hourly orally or i.v. or Erythromycin 500mg 6hourly orally or i.v. plus Rifampicin 600mg 12 hourly i.v. in severe cases
Severe CAP
Clathromycin 500mg 12-hourly i.v. or Erythromycin 500 mg 6-hourly i.v. plus
Co-amoxiclav 1.2 g 8-hourly i.v. or Ceftriaxone 1-2g daily i.v. or Cefuroxime 1.5g 8-hourly i.v. or Amoxicillin 1g 6hourly i.v. plus flucloxacillin 2g 6-hourly i.v.
Complications
Para-pneumonic effusion-common
Empyema
Retention of sputum causing lobar collapse
Development of thromboembolic disease
Pneumothorax-particularly with Staph. aureus
Suppurative pneumonia/lung abscess
ARDS, renal failure, multi-organ failure
Ectopic abscess formation (Staph. aureus)
Hepatitis, pericarditis, myocarditis, meningoencephalitis
Pyrexia due to drug hypersensitivity
Discharge and follow up
Discharge from hospital should only be contemplated with no more than one of the following clinical signs:
Temperature >37.8 C,
Heart rate >100/min,
respiratory rate > 24/min,
systolic BP < 90 mmHg,
SaO2 < 90%, inability to maintain oral intake and abnormal mental status.
Chest X-ray typically lagging behind clinical recovery, it need not be repeated before discharge in those who have made a satisfactory clinical recovery.
Clinical review by GP or hospital should be arranged at around 6 weeks and a chest X-ray obtained if there are persistent symptoms and physical signs.
Prevention
Influenza vaccination
Pneumococcal vaccination
Essentials of Diagnosis
Symptoms and signs of an acute lung infection: fever or hypothermia, cough with or without sputum, dyspnea, chest discomfort, sweats, or rigors.
Bronchial breath sounds or rales are frequent auscultatory findings.
Parenchymal infiltrate on chest radiograph.
Occurs outside of the hospital or less than 48 hours after admission in a patient who is not hospitalized or residing in a long-term care facility for more than 14 days before the onset of symptoms.
Hospital-Acquired Pneumonia
Hospital-acquired or nosocomial pneumonia refers to a new episode of pneumonia occurring at least 2 days after admission to hospital.
The term includes post-operative and certain forms of aspiration pneumonia, and pneumonia or bronchopneumonia developing in patients with chronic lung disease, general debility or those receiving assisted ventilation.
Aetiology
The majority of hospital-acquired infections caused by Gram-negative bacteria.
Include Escherichia, Pseudomonas and Klebsiella species. Infections caused by Staph. aureus (including multidrug-resistant-MRSA-forms)
Clinical features- very similar to CAP
Management
A third generation cephalosporin (eg. Cefotaxim) plus an aminoglycoside (eg. gentamicin) or
Meropenem or
A monocyclic beta-lactam (eg. aztreonam) plus fucloxacillin.
Aspiration pneumonia can be treated with co-amoxiclav 1.2g 8hourly + metronidazole 500mg 8hourly.
Suppurative and aspirational pneumonia
Term used to describe a form of pneumonic consolidation in which there is destruction of the lung parenchyma by the inflammatory process.
May be produced infection or previously healthy tissue with Staph aureus or Klebsiella pneumoniae.
Clinical features
Symptoms
Cough productive of large amounts of sputum which is sometimes fetid and blood-stained
Pleural pain common
Sudden expectoration of copious amounts of foul sputum occurs if abscess ruptures into a bronchus
Clinical signs
High remittent pyrexia
Profound systemic upset
Digital clubbing may develop quickly (10-14 days)
Chest examination usually reveals signs of consolidation; signs of cavitation rarely found
Pleural rub common
Rapid deterioration in general health with marked weight loss can occur if disease not adequately treated
Management
Amoxicillin 500mg 6-hourly
If anaerobic bacteria present then Metronidazole 400mg 8-hourly should be added.
Should be modified according to culture and sensitivity report of the sputum.
Physiotherapy
