Pneumonia

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Introduction

  • An inflammation of the lung parenchyma
  • Various bacterial species, fungi and viruses may cause pneumonia
  • The setting in which infection is acquired could be a predictor of the infecting pathogen

Bacterial Pneumonia:  is defined as bacterial infection of the lung parenchyma associated with recently developed radiological shadowing which may be segmental, lobar or multi lobar.

Types

  • Community Acquired Pneumonia (CAP)
  • Hospital Acquired pneumonia (HAP)
  • Ventilator Associated pneumonia (VAP)
  • Health care associated Pneumonia (HCAP)
  • Pneumonia in the immunocompromised
  • Aspiration pneumonia

Streptococcus pneumoniae is the most common pathogen in community-acquired pneumonia

Common bacteria causing CAP:

  • Streptococcus pneumonia
  • Mycoplasma pneumonia
  • Legionella pneumophilia
  • Chlamydia pneumonia
  • Haemophilus influenza
  • Staphylococcus aureus
  • Chlamydia psittaci
  • Coxiella burnetti
  • Klebsiella pneumonia
  • Actinomyces israelli
  • Haemophilus influenzae
  • Mycoplasma pneumoniae
  • Pseudomonas aeruginosa (usually implicated in nosocomial pneumonia)

Clinical features

Typical pneumonia:

  • Sudden onset fever, chills and rigors
  • Cough with purulent sputum production
  • Pleuritic chest pain
  • Breathlessness with short inspiratory efforts

Signs:

  • Fever
  • Herpes labialis
  • Tachypnoea
  • Signs of lung consolidation
    • Pleural friction rubs
    • Chest signs are very helpful depending on the phase of the inflammatory response
    • Dull percusision
    • Increased Tactile and vocal fremitus
    • Bronchial breath sounds
    • Whispering pectoriloquy
    • Crepitations

Signs of severity

  • Confusion
  • Urea > 7mmol/L
  • Respiratory rate > 30/min
  • Sys tolic BP < 90
  • Age ≤ 65years

Score 1 point for any of the above features  present

0 or 1- home treatment

2 - Hospital-supervised treatment

3 or more- manage in Hospital as severe pneumonia

4 or 5 – ICU Admission

Atypical pneumonia:

  • Gradual onset
  • Dry cough
  • Prominent extra-pulmonary symptoms
  • Headache
  • Sore throat
  • Fatigue
  • Myalgia
  • Chest crackles or rales

Differential diagnosis

  • Acute bronchitis
  • COPD Exacerbation
  • Pulmonary embolism/infarction
  • TB
  • Pulmonary eosinophilia

Complications

  • Empyema Thoracis
  • Pleural effusion
  • Lung abscess
  • Lobar collapse
  • Deep vein thrombosis and pulmonary embolism
  • Pneumothorax
  • ARDS
  • Multi organ failure
  • Hepatitis, pericarditis, myocarditis, meningoencephalitis
  • Pyrexia from drug hypersensitivity

Investigations

  • FBC +ESR+ CRP
  • Serum Electrolyte, Urea and Creatinine
  • LFT
  • Blood Culture
  • Serology
  • Cold agglutinins
  • Arterial blood gases/ SPO2
  • Sputum gram stain ,M/C/S
  • Urine pneumococcal and legionella antigen
  • Chest X-ray
  • Pleural fluid M/C/S

Treatment goals

  • Eliminate the infection
  • Return to normal lung function

Drug treatment

  • Oxygen to maintain Pa02 at or above 8kPa
  • IV fluids especially in severe cases
  • Anti pyretics
  • Antibiotics
  • Uncomplicated CAP + No modifying  factor, no antibiotics   use  in the last 3months:

Co-amoxiclav 

Adult  : 1g 12hourly for 5 – 7 days

Child :

Neonate and premature infants, 25mg/kg  12 hourly;

Infants up to 3 months, 25mg/kg 8 hourly;

3months – 12years, 25mg/kg 8 hourly increased to 6 hourly in more severe infections.

OR

Benzyl penicillin

Adult : initially 2 million units 6 hourly.

Child :

preterm and neonate under 7 days, 25mg/kg by IM injection Or by slow IV injection or infusion every 12 hours; double dose in severe infections.

Neonate 7 – 28 days: 25mg/kg 8 hourly; double dose in severe infections.

1 month – 18years : 25mg/kg 4 – 6hourly. Double dose in severe infections. 

Commence oral therapy as soon as possible.

OR

Macrolide (azithromycin 500mg  stat ,then 250mg daily, or Clarithromycin 500mg twice daily for up to 14 days)

OR

Cefuroxime axetil

Adult : 500mg orally 8 hourly for 5 – 7 days

Child : 

3 months – 2 years 10mg/kg (maximum 125mg) orally 12 hourly

2 – 12 years 15mg/kg orally 12 hourly

12 – 18 years 12 hourly. May double doses in severe infections.

Patients with history of recent use of antibiotics

  • Respiratory quinolone (levofloxacin).
    • Quinolones are generally better avoided in TB endemic areas because of their potential use as part of 2nd line regimen in the treatment of MDR-TB.
  • Advanced macrolide+ amoxycillin
  • Advanced macrolide + amoxycillin + clavulanic acid

Complicated CAP

  • IV β lactam + advanced macrolide
  • Iv respiratory quinolones + advanced macrolide
  • Penicillin G + advanced macrolide
  • Consider Pneumocystis jiroveci in HIV patients: Co-trimoxazole

Notable adverse drug reactions, contraindications, caution

  • Co-amoxiclav: nausea, diarrhoea, skin rashes, contraindicated in penicillin hypersensitive individuals.
  • Cefuroxime: nausea, vomiting, abdominal discomfort, headaches, rarely antibiotic associated colitis.
  • Macrolides: similar to those mentioned above but usually milder. Hepatoxicity and antibiotic associated colitis are quite rare.

Prevention

  • Pneumococcal vaccine
  • Haemophilus influenzae vaccine