PNEUMONIA

Written by Sarah Lee

Last Reviewed: April 2019

Review Due: April 2020

DEFINITION

‘an infection of the lower respiratory tract leading to inflammation and consolidation of the lung, typically categorised by the causative organism and source of infection’

Hospital-Acquired Pneumonia (HAP) is one which develops after 48 hours of hospital admission. A Community-Acquired Pneumonia (CAP) is one acquired outwith a healthcare facility.

AETIOLOGY

Typical causative organisms in CAP include Streptococcus Pneumoniae and Haemophilus Influenzae. Atypical organisms include Mycoplasma Pneumoniae, Staphylococcus Aureus, Legionalla species and Chlamydia.

Common organisms associated with HAP include Gram-Negative Enterobacteria, Staphylococcus Aureus, Pseudomonas and Klebsiella.

Viruses such as Influenza and Parainfluenza account for up to 15% of all cases. In immunocompromised patients, Streptococcus Pneumoniae, Haemophilus Influenzae, Pneumocystis Jirovecii, Cytomegalovirus and Varicella Zoster Virus may be found.

RISK FACTORS

Age >65 years
Living in nursing homes or healthcare settings
Underlying lung disease (e.g. COPD, bronchiectasis, asthma)
Smoking
Immunosuppression

SIGNS AND SYMPTOMS

Classically, patients present with an acute - subacute onset of:

Breathlessness

Productive Cough (green/yellow sputum)

Pleuritic Chest Pain

Fever +/- Rigors

Fatigue and Malaise

Signs include:

Pyrexia

Confusion (especially elderly patients)

Tachypnoea

EXAMINATION

Auscultation: reduced breath sounds, crackles of the chest

Bronchial breathing - rare

Reduced chest expansion

Signs of consolidation:

Dull percussion

Increased vocal resonance

Increased tactile fremitus

PATHOPHYSIOLOGY

Defence mechanisms of the lung and lower airways are compromised, leading to colonisation and inflammation of the lung. Inflammation increases the permeability of capillaries lining the lung, leading to exudative congestion within alveoli. Consolidation of the lung ensues

Lobar Pneumonia: Consolidation of entire lobe(s) within lung in a focal manner.

Bronchopneumonia: Infection and congestion of terminal bronchioles and the surrounding alveoli, usually causes patchy consolidation of the lung.

Interstitial Pneumonia: Pneumonia affecting the lung interstitium.

Investigations

Sputum/Blood Culture: To identify the causative organism and check antibiotic sensitivities

FBC: Leukocytosis

CRP: Raised

U&Es: Assess baseline kidney function and check urea for severity scoring

CXR: Consolidation of the affected lobe(s)

TREATMENT

severity scoring

The CURB65 severity score predicts mortality and guides the management of patients with pneumonia. One point is awarded for each of the following:

Confusion (abbreviated mental test ≤ 8)
Urea >7mmol/L
Respiratory Rate ≥30/min
Blood Pressure <90mmHg Systolic and/or 60mmHg Diastolic

Age ≥ 65

management

COMPLICATIONS

Parapneumonic effusion
Empyema
Septic shock
ARDS
Lung abscess

EPIDEMIOLOGY

Men and women are equally affected (M:F 1:1)
Highest rates of pneumonia are among the young (under 5 years of age) and the old (ages 70 and up)
Within the UK, the mortality rate of pneumonia from 2001-2010 was 214 deaths for every million people.