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MBBS IV - Junior Clerkship WCS > JC14 (Medicine) - Lower respiratory tract infections > Flashcards

JC14 (Medicine) - Lower respiratory tract infections Flashcards

1
Q

Define pneumonia

A

inflammation of lung parenchyma, commonly due to infective agents

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2
Q

Typical clinical picture of acute pneuomia

A

Symptoms:
Systemic: fever, rigors, shivering, malaise, headache, ↓appetite, ± delirium

Pulmonary:
→ Cough: short, painful, dry (initial) → productive with mucopurulent sputum ± haemoptysis (later)
→ Pleuritic chest pain when visceral pleura is involved
→ Dyspnoea

Others:
→ Upper abdominal tenderness if lower lobe pneumonia or associated hepatitis

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3
Q

Explain how pneumonia leads to dyspnea and pleurisy

A

Pathological: form of acute respiratory infection that alveoli are filled with pus and fluid, making breathing painful and limits O2 intake

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4
Q

Classify pneumonia by anatomical regions involved

A

Anatomical:
→ Lobar pneumonia: homogeneous consolidation of ≥1 lobes

→ Bronchopneumonia: more patchy alveolar consolidation a/w bronchial and bronchiolar inflammation

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5
Q

Classify pneumonia by aetiological organisms (3)

A

Aetiological: bacterial, viral, fungal

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6
Q

Types of pneumonia (5)

A

→ Community-acquired pneumonia (CAP)
→ Hospital-acquired pneumonia (HAP)
→ Ventilator-associated pneumonia
→ Aspiration pneumonia
→ Pneumonia in immunocompromised patients

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7
Q

List causative bacteria of Community acquired pneumonia

A

Gram +

  • Streptococus pneumoniae*
  • Haemophilus influenzae non-typeable*

Atypical
- Mycoplasma pneumoniae, Chlaymdophila pneumoniae, Legionelaa pneumophila

(Gram -)
Klebsiella pneumoniae
Pseudomonas aeruginosa

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8
Q

List causative bacteria of hospital acquired pneumonia

A

Gram +

  • Streptococus pneumoniae*
  • Haemophilus influenzae non-typeable*
  • Methicillin-resistance staphylococcus aureus (MRSA)

Gram -

  • Klebsiella pneumoniae ***
  • Pseudomonas aeruginosa ***

Anaerobes
- Bacteroides species

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9
Q

List causative bacteria of aspiration pneumonia

A

Gram -

  • Klebsiella pneumoniae *
  • Pseudomonas aeruginosa *
  • Other nosocomial gram - bacteria

Anaerobes
- Bacteroides species **

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10
Q

Typical PE signs of lobar pneumonia

A

□ Vitals: fever, ↓BP, ↑HR, ↑RR, ± ↓SpO2

□ Chest
→ Decrease air entry
→ Coarse crackles
→ Consolidation signs: percussion dullness, bronchial breath sounds, ↑vocal resonance

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11
Q

Baseline investigations for suspected pneumonia **

A
  1. CXR
    - gold-standard for CAP diagnosis
    - clinical suspicious with negative CXR > CT/MRI
  2. Blood (severity)
    - CBC with WBC differential
    - RFT
    - LFT
    - ESR/CRP
    - Arterial blood gas
  3. Microbiology
    - Sputum: gram stain, C/ST
    - Blood: culture and serology
    - Nasopharyngeal aspirate: RAT for influenze, PCR for virus, M. pneumoniae
    - Urine: RAT for Legionella, S. pneumoniae
    - BAL/ Transbronchial biopsy, thoracoscopic biopsy
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12
Q

Describe atypical pneumonia syndrome

A

□ Cause: usually refers to M. pneumoniae, C. pneumoniae and L. pneumophila

□ Characterized by:
→ Symptomatology: less severe, prominent systemic complaints
→ Ix: relatively normal WBC counts (vs neutrophilia in typical bacterial pneumonia

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13
Q

Clinical approach to pneumonia

A
  • Diagnosis of CAP
  • Assessment of severity
  • Empirical treatment based on:
     Likely causative pathogens
     Clinical severity
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14
Q

Ddx of pneumonia

A
  • Pulmonary oedema
  • Pulmonary/pleural TB
  • Eosinophilic pneumonia
  • Bronchoalveolar carcinoma
  • Cryptogenic organizing pneumonia (rare)
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15
Q

Typical RFT and LFT results for community-acquired pneumonia

A

□ RFT: ↑urea*, hypoNa*, renal dosing of Abx
□ LFT: liver involvement (in basal pneumonia), ↓Alb*

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16
Q

List all samples needed for microbiological diagnosis of pneumonia

A
  • Sputum: gram stain, C/ST
  • Blood: culture and serology
  • Nasopharyngeal aspirate: RAT for influenze, PCR for virus, M. pneumoniae
  • Urine: RAT for Legionella, S. pneumoniae
  • BAL/ Transbronchial biopsy, thoracoscopic biopsy
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17
Q

Most common pathogen causing acute CAP in elderly

A

Strep. pneumoniae (most common)

Haemophilus pneumoniae

Klebsiella pneumoniae (esp. DM, alcoholic)

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18
Q

Most common pathogen causing acute CAP in the young

A

Mycoplasma pneumoniae

Streptococcus pneumoniae

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19
Q

Complications of mycoplasma pneumoniae infection

A

haemolysis (60%), cold agglutinin disease, erythema multiforme, encephalitis

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20
Q

Complications of Klebsiella pneumoniae infection

A

UTI and renal abscess, liver abscess, endophthalmitis

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21
Q

Typical route of spread for Legionella pneumophila

A

from aqueous environment (water tanks, cooling towers, spas…)

Route of infection: breathe in contaminated droplets and mists from artificial water systems (eg. hot water baths) or handle garden soils, compost, potting mixes

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22
Q

Typical presentation of Legionella pneumophila infection

A

S/S: classically prodromal flu-like S/S with CNS (confusion) and GI (diarrhea) involvement

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23
Q

Specific investigations and diagnostic tests for Legionella pneumophila infection

A

→ Bloods: classically lymphopenia w/o marked leukocytosis, T1RF, SIADH, dLFT

→ CXR: lobar or multilobar consolidation

→ Microbiology: G- bacillus not well-visualized on Gram stain (WBC++ no organisms), culture require special selective media and takes 1-3w → usually diagnosed by urine antigen test (for serotype 1)

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24
Q

Typical viruses that cause acute CAP

A

influenza, parainfluenza, RSV, measles*

More common in children than adults

25
Q

Specific pathogen that cause opportunistic infection and pneumonia in HIV patients

A

Pneumocystis jirovecii

patients with HIV or severe immunocompromised state (eg. post-chemo)

26
Q

Criteria for assessment of clinical severity of CAP

A

CURB-65

Confusion
Urea > 7mmol/L
Respiratory rate > 30/min
Blood pressure: SBP < 90 or DBP <60
Age > 65

0 or 1 = home treatment
2 or more factors = immediate hospital admission
3 or more = ICU

27
Q

Outline management of CAP

A
  1. Oxygen therapy
    - all patients with resp. failure
    - Target SaO2 > 92%
    - High concentration oxygen/ CPAP/ Mechanical ventilation
  2. Fluid rehydration
  3. Antibiotics coverage
  4. Analgesia for pleuritic pain
    - simple analgesics
  5. Manage complications
28
Q

Antibiotics coverage for CAP

  • Timing
  • Coverage
  • Choice of antibiotics
A
  • Admin within 6-8 hours, duration 7-10d
  • All CAP needs Strep. pneumoniae coverage; All severe CAP needs Legionella pneumophila coverage

Typical pathogen:
□ Penicillin + β-lactamase inhibitor → Eg. augmentin

Atypical pathogens:
□ ± macrolide or tetracycline
→ Eg. clarithromycin (klacid), azithromycin, doxycycline

29
Q

Risk factors for multi-drug resistant pathogens causing CAP

A

□ Recent or frequent Abx use
□ Recent or frequent hospitalization
□ Nursing home resident
□ Immunocompromised state

30
Q

Choice of antibiotics for:

  • Outpatient CAP
  • Moderate inpatient CAP
  • Severe inpatient CAP
A
  • Outpatient CAP
    PO amoxicillin-clavulanate (Augmentin) ± macrolide or doxycycline
  • Moderate inpatient CAP
    PO/IV amoxicillin-clavulanate (Augmentin) ± macrolide or doxycycline
    Alternatives: IV ceftriaxone or cefotaxime ± macrolide or doxycycline
  • Severe inpatient CAP
    IV piperacillin-tazobactam (Tazocin) or ceftriaxone or cefepime ± macrolide or doxycycline
31
Q

Follow-up for CAP

A

Chest physiotherapy: helps expectoration

clinical review 6 weeks later

CXR if persistent S/S or suspect underlying malignancy

32
Q

Possible ddx for delayed recovery from CAP

A

→ Complications, eg. abscess, parapneumonic effusion
→ Alternative dx, eg. ILD, TB
→ Underlying cause, eg. obstruction, recurrent aspiration

33
Q

Complications of CAP

A

□ Respiratory failure

□ Lung abscess

□ Pathogen Spread:
→ Septicaemia with multi-organ failure
→ Parapneumonic effusion
→ Empyema thoracis

□ Systemic effects:
→ Electrolyte abnormalities, eg. hypoNa due to SIADH
→ Cardiac complications: acute MI, cardiac arrhythmia (esp AF)

34
Q

Causes of recurrent CAP

A

→ Underlying structural disease, eg. bronchial obstruction, bronchiectasis

→ Host factors, eg. recurrent aspiration, immunocompromised state

35
Q

Define Hospital-Acquired Pneumonia (HAP)

Typical route of infection?

A

pneumonia occurring ≥48h after hospitalization + excluding incubating infection at admission

aspiration of oropharyngeal secretions colonized by hospital-acquired organisms

36
Q

Predisposing factors of HAP

A

□ General debility and old age
□ Smoking and COPD
□ ↑risk of aspiration: post-GA, nasogastric tube
□ ↓gastric aciditiy: antacids, H2 blockers (↑GI colonization)
□ Mechanical ventilation (ventilator-associated pneumonia (VAP))

37
Q

Typical bacteria causing HAP

A

□ Early onset (<4-5d of admission): similar to CAP

□ Late-onset:
→ Gram - bacilli, eg. Escherichia, Klebsiella spp
→ Non-fermenters, eg. Pseudomonas, Acinetobacter baumanii
→ Multi-resistant bacteria, eg. MRSA
→ Anaerobes, eg. Bacteroides

38
Q

Empirical treatment for HAP

A

Early onset:
3rd generation cephalosporin
OR
β-lactam/β-lactamase inhibitor (Augmentin, Unasyn)

Late onset:
Anti-pseudomonal β-lactam/β-lactamase inhibitor (Tazocin) OR
Anti-pseudomonal cephalosporin (Cefepime [4G]) OR
Anti-pseudomonal carbapenem (imipenem, meropenem)
± aminoglycoside OR fluoroquinolone
± vancomycin after careful assessment of indications

39
Q

Define aspiration pneumonia

A

pneumonia due to aspiration of a relatively large amount of material

40
Q

Predisposing factors of aspiration pneumonia

A

□ Impaired gag reflex: ↓GCS, alcoholism, bulbar palsy, vocal cord palsy, terminal illness

□ Regurgitation/vomiting: dysphagia and oesophageal diseases, vomiting, drowning

□ Others: severe dental infection or URTI, tracheo-esophageal fistula

41
Q

Causative agents of aspiration pneumonia

A

□ Chemical pneumonitis due to aspiration of acidic materials

□ Infection by oropharyngeal flora
→ Anaerobes, eg. Bacteroides, Porphyromonas, Prevotella, Fusobacterium
→ Others: Streptcoccus, S. aureus, G- bacilli

42
Q

Investigations for aspiration pneumonia

A

□ CXR: consolidations, usually in dependent parts of lungs
→ Lower lobes (classically recurrent RLL pneumonia)
→ Posterior segments of upper lobe (if recumbent)

□ VFSS for swallowing problems
→ Follow-up CXR shows contrast medium in lung fields

43
Q

Management of aspiration pneumonia

A

□ Treatment of underlying conditions

□ Abx to cover oropharyngeal flora: augmentin ± metronidazole

□ Non-oral feeding (eg. PEG tube, NG tube) → prevent further aspiration

44
Q

Diagnostic tests of influenza

A

Rapid antigen test on nasopharyngeal aspirate

RT-PCR

Viral Culture

Serology

45
Q

Influenza

  • Incubation period
  • S/S
A

Incubation period: 1-4 days

□ Systemic: fever (37.8-40oC), myalgia, arthralgia, malaise
□ URTI: running nose, sore throat, cough, sputum

46
Q

List major influenza types in humans, avians and swines

A

Notable influenza types:
Human: H1N1 (Spanish), H2N2 (Asian), H3N2 (Hong Kong)
Avian: H5N1, H7N7, H7N9
Swine: H1N1

47
Q

Extra-respiratory manifestations of influenza infection

A

Pneumonia: primary viral or superimposed bacterial (S. pneumoniae, S. aureus, esp >65y)

GI involvement: vomiting, diarrhea

CNS involvement: encephalitis, transverse myelitis, aseptic meningitis, GBS

Others: myositis, myocarditis, pericarditis, Reye’s syndrome

48
Q

Management of influenza infection

A

□ General: personal hygiene, symptomatic Tx, droplet precaution

□ Neuraminidase inhibitors: effective in both flu A/B
Examples: oseltamivir (Tamiflu, PO 75mg BD x5d), zanamivir (Relenza, 10mg BD inhaler puff x5d)

MoA: inhibit neuraminidase → cannot cleave sialic acid on cell surface → interfere with release of progeny → decrease viral propagation

49
Q

Define bronchiectasis

A

pathological dilatation of bronchi

50
Q

Causes of bronchiectasis

A

□ Congenital:
→ Cystic fibrosis (rare in Chinese)
→ Ciliary dysfunction: eg. ciliary dyskinesia, Kartagener syndrome
→ Predisposition to infections (eg. 1o hypoγglobulinemia)

□ Acquired:
→ Previous infections, eg. TB, suppurative pneumonia, childhood measles or pertussis
→ Obstruction, eg. foreign body, tumours
→ Rhuematic disorders, eg. RA, Sjogren’s syndrome
→ Gastro-esophageal reflux (leading to chronic aspiration)
→ Lung fibrosis (leading to traction bronchiectasis)

51
Q

Typical symptoms of bronchiectasis

A

Chronic course (years) with acute infective exacerbations

  • Cough (98%): chronic, persistent
  • Daily sputum production (78%): copious, tenacious, purulent, foul-smelling
  • Haemoptysis (27%): only streaks of blood
  • Exertional dyspnoea ± wheezes
  • Pleuritic pain
  • Systemic symptoms: weight loss, fatigue, anorexia
52
Q

Signs of bronchiectasis on PE

A

□ General: cachexia, clubbing, halitosis

□ Varies with severity:

  • Coarse crackles that disappear/change in quality after coughing
  • Obstructive pattern → ↓breath sounds, ↓chest wall movement
  • Chronic localized fibrosis → bronchial breath sounds
  • Cor pulmonale (↑JVP, peripheral oedema, hepatic congestion, parasternal heave, loud P2)
  • Respiratory failure (central cyanosis)
53
Q

Ddx bronchiectasis

A

COPD: also with recurrent bouts of dyspnoea, productive cough, wheezes, coarse crackles

Asthma: also with recurrent exacerbation of dyspnoea, productive cough and wheezes

Lung fibrosis: also with dyspnoea, cough, crackles and finger clubbing

54
Q

Typical radiological features of bronchiectasis on CXR

A

CXR: only abnormal in 50%
→ Ring shadows: dilated bronchi seen from front
→ Tramline shadows: dilated bronchi seen from side (usually in lower lobes)
→ Tubular shadows: dilated bronchi filled with secretions
→ Cystic dilatation ± fluid levels in severe cases

55
Q

Typical radiological features of bronchiectasis on HRCT

A

1) Thickened, dilated airways (ring shadows)
- Wider than accompanying arterioles (signet ring sign)
- No peripheral tapering with visible peripheral airway ≤1cm of pleural lining

2) Mucus plugging (darker than airway wall):
- Air-fluid levels visible within cystic dilatation of airway
- Tree-in-bud appearance when peripheral airways are involved

3) Atelactasis, consolidation, abscesses

56
Q

5 specific diagnostic tests for underlying cause of bronchiectasis

A

→ Immunoglobulins and neutrophil function test for immunodeficiency

→ Auto-Ab (eg. RF) for autoimmune diseases

→ Ba studies or 24h oesophageal pH monitoring for aspiration causes

→ Ciliary and sperm analysis for primary ciliary dyskinesia

→ Sweat test for cystic fibrosis

57
Q

Causes of acute exacerbation of bronchiectasis

Treatment

A

Potential organisms: H. influenzae, S. aureus, P. aeruginosa (if long-standing)

□ Choice of Abx:
→ Anti-pseudomonal penicillins (first-line), eg. piperacillin-tazobactam (tazocin)
→ 3rd and 4th generation cephalosporin, eg. ceftazidime
→ Carbapenems, eg. meropenem, imipenem
→ Aminoglycosides, eg. amikacin
→ Fluoroquinolones, eg. levofloxacin

□ Duration: recommend 14 days

58
Q

Long-term management of bronchiectasis

A

□ Treatment of underlying aetiology, eg. GERD, immunodeficiency

□ Long-term (≥3mo) antibiotics for immunomodulatory effect to decrease exacerbations
- Oral Macrolides

□ Airway clearance:

  • Chest physiotherapy
  • Expectorant or mucolytic

□ Adjuncts:

  • Bronchodilators (esp β-agonist): for SOB and obstructive pattern, bronchospasm
  • Inhaled corticosteroids (not routine)

□ Surgery (rare)
→ Excision of bronchiectactic areas (eg. lobectomy)
→ Percutaneous embolization of bronchial vessels

MBBS IV - Junior Clerkship WCS (131 decks)

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