Pneumonia

• Stages of lobar pneumonia:

  1. Congestion - Blood vessels and alveoli fill with excess fluid
  2. Red hepatization - exudate made up of RBCs, neutrophils and fibrin fill airspaces creating liver-like appearance and making them more solid
  3. Grey hepatization - still firm but color change due to RBCs broken down
  4. Resolution - exudate is digested ingested or coughed up
• Classification of pneumonia by clinical setting:

  • Community acquired
  • Hospital acquired
  • Aspiration
  • Immunocompromised
• Pneumonia describes any inflammatory condition affecting the alveoli of the lungs, but in the vast majority of patients this is secondary to a bacterial infection.
• Risk factors for pneumonia:

  • Age less than 5 or over 65
  • Smoking
  • Recent viral respiratory tract infection
  • Chronic respiratory diseases e.g. cystic fibrosis and COPD
  • Immunosuppression e.g. cytotoxic drug therapy or HIV
  • Patients at risk of aspiration: e.g. those with neurological diseases such as Parkinson's disease or those with oesophageal obstruction
  • IV drug users
  • Other non-respiratory co-morbidities: e.g. diabetes and cardiovascular disease
• Causative organisms of pneumonia:

  • Streptococcus pneumoniae - most common organism
  • Haemophilius influenzae - Common in COPD patients
  • Staphylococcus aureus - usually follows influenza infection
  • Mycoplasma pneumoniae - atypical, presents with autoimmune hemolytic anemia and erythema multiforme
  • Legionella pneumophilia - atypical, comes from infected water droplets such as ACs or hot tubs
  • Pneumocystis jiroveci - common in HIV patients
• Clinical features of pneumonia:

  • Cough
  • Sputum
  • Dyspnoea
  • Pleuritic chest pain
  • Fever
  • Malaise
  • Anorexia
  • Reduced oxygen saturation
  • Auscultation - reduced breath sounds, bronchial breathing, crackles
• Investigations for pneumonia:

  • Chest X-ray - look for consolidations
  • Blood and sputum cultures
  • CRP
• Management of pneumonia:

  • Assess patients using CURB-65 score
  • Low severity CAP - Amoxicillin
  • High severity CAP - Amoxicillin + macrolide
• • The CURB-65 score is used to assess severity of pneumonia
  • C - Confusion - abbreviated mental test score<10
  • U - Urea >7 mmol/L
  • R - Respiratory rate >30/min
  • B - Blood pressure: systolic <90 mmHg and/or diastolic <60 mmHg
  • 65 - more than 65 years old
  • Score 0-1: low risk, treat at home
  • Score 2: intermediate risk, treat at hospital
  • Score 3+: high risk, treat in ICU
• Complications of pneumonia:

  • Pleural effusion
  • Empyema
  • Lung abscess
  • Acute respiratory distress syndrome
  • Pneumothorax
  • Sepsis
  • Pericarditis
  • Acute kidney injury
• Aspiration pneumonia is a pneumonia that develops as a result of foreign materials gaining entry to the bronchial tree, usually oral or gastric contents such as food and saliva.
• Aspiration pneumonia risk factors:

  • Poor dental hygiene
  • Swallowing difficulties
  • Prolonged hospitalization or surgical procedures
  • Impaired consciousness
  • Impaired mucociliary clearance
• The right middle and lower lung lobes are the most common sites affected by aspiration pneumonia , due to the larger calibre and more vertical orientation of the right main bronchus.
• Aerobic bacteria implicated in aspiration pneumonia:

  • Streptococcus pneumoniae
  • Staphylococcus aureus
  • Haemophilius influenzae
  • Pseudomonas aeruginosa
  • Klebsiella - most often seen in alcoholics
• Anaerobic bacteria implicated in aspiration pneumonia:

  • Bacteroides
  • Prevotella
  • Fusobacterium
  • Peptostreptococcus