Pneumonia in adult

Definition

·       Pneumonia is defined as inflammation of the lung parenchyma

·       The microorganisms gain entry into the lungs by:

• Inhalation
• Aspiration
• Haematogenous spread
• Direct spread
• Reactivation of latent infection

Classification and Epidemiology

·       Classification is based on various characteristics of the illness such as

• The setting or mechanism of acquisition
• Pathogen responsible/aetiology
• Anatomic or radiologic distribution

Classification Based on Setting or Mechanism of Acquisition of Infection

Community-acquired Pneumonia (CAP)

·       Defined as pneumonia that develops in the outpatient setting or within 48 hours of admission to a hospital.

·       The incidence varies with age, being much higher in the very young and the elderly.

·       Pneumonia accounts for almost one-fifth of childhood deaths world-wide, with approximately 2 million children under 5 dying each year

·       CAP is usually spread by droplet infection and most cases occur in previously healthy individuals.

·       Several factors can impair the effectiveness of local defences and predispose to pneumonia.

• Cigarette smoking
• Upper respiratory tract infections
• Alcohol
• Corticosteroid therapy
• Old age
• Recent influenza infection
• Pre-existing lung disease

·       Once the organism settles in the alveoli, an inflammatory response ensues. The classical pathological responses evolve through the phases of congestion, red and then grey hepatisation, and finally resolution with little or no scarring.

·       The majority of cases of CAP are due to infection with Strep. pneumoniae

·       Thereafter the most likely alternatives depend on the age of the patient and the clinical circumstances.

·       For example, Mycoplasma  pneumoniae and Chlamydia  pneumoniae are common in young adults but seldom reported in the elderly, whereas Haemophilus influenzae should be considered in elderly patients but is rarely reported in young adults.

Clinical Features

·       CAP typically presents as an acute illness in which systemic features such as fever, rigors, shivering and vomiting often predominate.

·       The appetite is usually lost and headache frequently reported.

·       Pulmonary symptoms include cough, which at first is characteristically short, painful and dry, but later accompanied by the expectoration of mucopurulent sputum.

·       Rust-coloured sputum may be seen in patients with Streptococcus pneumoniae, and the occasional patient may report haemoptysis.

·       Pleuritic chest pain may be a presenting feature and on occasion may be referred to the shoulder or anterior abdominal wall.

·       Upper abdominal tenderness is sometimes apparent in patients with lower lobe pneumonia or if there is associated hepatitis.

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.

·       The factors predisposing to the development of pneumonia in a hospitalised patient are

• Reduced host defences against bacteria
• Reduced immune defences (e.g. corticosteroid treatment, diabetes, malignancy)
• Reduced cough reflex (e.g. post-operative)
• Disordered mucociliary clearance (e.g. anaesthetic agents)
• Bulbar or vocal cord palsy
• Aspiration of nasopharyngeal or gastric secretions

§  Immobility or reduced conscious level

§  Vomiting, dysphagia, achalasia or severe reflux

§  Nasogastric intubation

• Bacteria introduced into lower respiratory tract

§  Endotracheal intubation/tracheostomy

§  Infected ventilators/nebulisers/bronchoscopes

§  Dental or sinus infection

• Bacteraemia

§  Abdominal sepsis

§  Intravenous cannula infection

§  Infected emboli

Aetiology of Hospital Acquired Pneumonia

·       Majority of hospital-acquired infections are caused by Gram-negative bacteria.

·       These include Escherichia, Pseudomonas and Klebsiella species. Infections caused by Staphylococcus aureus (including multidrug-resistant-MRSA-forms) are also common in hospital, and anaerobic organisms are much more likely than in pneumonia acquired in the community.

·       Physiotherapy is of particular importance in the immobile and elderly, and adequate oxygen therapy, fluid support and monitoring are essential. The mortality from hospital-acquired pneumonia is high (approximately 30%).

Suppurative and Aspirational Pneumonia

·       Suppurative pneumonia is the term used to describe a form of pneumonic consolidation in which there is destruction of the lung parenchyma by the inflammatory process.

·       Suppurative pneumonia may be produced by infection of previously healthy lung tissue with Staphylococcus aureus or Klebsiella pneumoniae.

·       These are, in effect, primary bacterial pneumonias associated with pulmonary suppuration.

·        More frequently, suppurative pneumonia and pulmonary abscess develop after the inhalation of septic material during operations on the nose, mouth or throat under general anaesthesia, or of vomitus during anaesthesia or coma.

·        In such circumstances gross oral sepsis may be a predisposing factor.

·        Additional risk factors for aspiration pneumonia include bulbar or vocal cord palsy, achalasia or oesophageal reflux and alcoholism.

·       Aspiration into the lungs of acid gastric contents can give rise to a severe haemorrhagic pneumonia often complicated by the acute respiratory distress syndrome (ARDS).

·       Injection drug-users are at particular risk of developing haematogenous lung abscess.

·       Bacterial infection of a pulmonary infarct or of a collapsed lobe may also produce a suppurative pneumonia or a lung abscess.

·       The organism(s) isolated from the sputum include Strep pneumoniae, Staph. aureus, Strep. pyogenes, H. influenzae and, in some cases, anaerobic bacteria.

Clinical Features of Suppurative Pneumonia

·       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

·       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.

Pneumonia in Immunocompromised Patient

·       Pulmonary infection is common in patients receiving immunosuppressive drugs and in those with diseases causing defects of cellular or humoral immune mechanisms.

·       It is important to appreciate that the majority of infections are caused by the same common pathogens that cause pneumonia in non-immunocompromised individuals

·       Gram-negative bacteria, especially Pseudomonas aeruginosa, are more of a problem than Gram-positive organisms, and unusual organisms or those normally considered to be of low virulence or non-pathogenic may become 'opportunistic' pathogens.  Importantly infection is often due to more than one organism.

Clinical Features

·       The patient usually presents with fever, cough, breathlessness and infiltrates on the chest X-ray.

·       Patients may develop non-specific symptoms.

  Refer to Handout 5.1: Pathophysiology and Classification of Pneumonia

Symptoms and Signs of Pneumonia

Symptoms

·       The presence of cough, particularly cough productive of sputum, is the most consistent presenting symptom.

·The character of the sputum may suggest a particular pathogen, as follows: 

• Rust-colored sputum  - frequently associated with infection by S pneumoniae
• Currant-jelly sputum  - frequently associated with infection by Klebsiella species
• Foul-smelling or bad-tasting sputum  - often produced by anaerobic infections

·       Chest pain

·       Dyspnea

·       Hemoptysis (when clearly delineated from hematemesis)

·       Decreased exercise tolerance

·       Abdominal pain from pleuritis is also highly indicative of a pulmonary process 

·       Nonspecific symptoms such as high grade fever, rigors or shaking chills, and malaise are common.

·       Other nonspecific symptoms that may be seen with pneumonia include myalgias, headache, nausea, vomiting, diarrhoea, and altered sensorium.

Signs

·       Hyperthermia (fever, typically >38°C) or hypothermia (<35°C)

·       Tachypnea (>18 respirations/min)

·       Use of accessory muscles of respiration

·       Tachycardia (>100 breaths per minute) or bradycardia (<60 beat per minute)

·       Central cyanosis

·       Altered mental status

Other Signs

·       Adventitious breath sounds, such as rales/crackles, rhonchi or wheezes and bronchial breathing sounds during consolidation stage decreased intensity of breath sounds

·       Egophony

·       Whispering pectoriloquy

·       Dullness to percussion

·       Lymphadenopathy

Differential Diagnosis, Investigations, Treatment and Complications of Pneumonia

Differential Diagnosis of Pneumonia

·       Pneumocystis jerovecii pneumonia (Formally called Pneumocystis carinii pneumonia)

·       Chronic obstructive pulmonary disease (COPD)

·       Bronchiectasis

·       Chronic bronchitis

·       Foreign body aspiration

·       Influenza

·       Lung abscess

Investigation

·       Sputum

• Gram- or Ziehl-Neelsen staining
• Culture and sensitivity (this can be done at hospital level)

·       Chest x-ray (only at hospital level)

• In Lobar pneumonia the findings are Homogeneous opacity localized to the affected lobe or segment. This is usually appears within 12-18 hours of the onset of illness.
• In bronchopneumonia the findings: Patchy alveolar consolidation

·       Blood (mostly at hospital level)

• Culture and sensitivity- hospital level
• Full blood picture

§  Neutrophilia favours the diagnosis of bacterial pneumonia, particularly pneumococcal pneumonia

Treatment

·       Oxygen therapy or Mechanical ventilation-depending on severity. This requires referral of the patient to hospital because oxygen therapy is not readily available in primary health care facilities

·       Intravenous fluid

• Most patients with moderate to severe pneumonia also require intravenous fluids and occasionally inotropic support.

·       Analgesics

• They are important to allow the patient to breathe normally and cough efficiently e.g.   Paracetamol

·       Antibiotics

A: Uncomplicated Community Acquired Pneumonia

·       Duration of treatment: 7-10 days are adequate, although treatment may require 14 days or more in patients with Legionella, staphylococcal or Klebsiella pneumonia.

·       Amoxicillin 500 mg 8 hourly orally

    If patient is allergic to penicillin

·       Clarithromycin 500 mg 12 hourly orally.  Or Erythromycin or Tetracycline 500 mg 6 hourly orally

B: Severe Community Acquired Pneumonia

·       The patient needs to be admitted in intensive care unit (at hospital level).

·       Ampicillin IV or Benzyl penicillin IM  plus Chloramphenicol or

·       Ceftriaxone 1-2 g daily IV with

·       Supportive care e.g. monitor vital signs, Oxygen therapy, analgesics, bed rest, IV fluids

Suppurative Pneumonia

·       Ampicillin IV 6 hourly or IM Benzyl penicillin then followed by oral Amoxicillin.

·       If an anaerobic bacterial infection is suspected (e.g. from fetor of the sputum), oral Metronidazole 400 mg 8-hourly should be added sputum.

·       Prolonged treatment for 4-6 weeks may be required in some patients with lung abscess.

·       Removal or treatment of any obstructing endobronchial lesion is essential.

Complications

·       Lung abscesses

·       Development of bacteremia with metastatic abscess in other organs to cause (Meningitis, Endocarditis, Arthritis, Pericarditis, Hepatitis)

·       Spread to pleural cavities producing empyema

·       Spread to pericardial cavity leading to suppurative pericarditis

·       Consolidation of the lung parenchyma

·       Para Pneumonic effusion presenting as Pleural effusion

·       Retention of sputum causing lobar collapse

·       Pyrexia due to drug hypersensitivity

Prognosis

Features associated with a high mortality in pneumonia are as outlined below

·       Clinical parameters

• Age: ≥60 years
• Respiratory rate: > 30 cycles/min
• Diastolic blood pressure: <60 mmHg
• Confusion
• More than one lobe involved on chest x-ray
• Presence of underlying disease

·       Therefore, all patients who are thought of having severe form of pneumonia should be referred to hospital for proper diagnosis and treatment.