Respirology - Infection

Question 1

List the common pathogens for community acquired pneumonia

Answer 1

Typical
- Strep pneumonia
- haemophilus influenza
- moraxella catarrhalis
- enterobacteria including Kliebsiella, E coli
- staph aureus
Atypical
- Chlamydia pneumonia
- Mycoplasma pneumonia
- Legionella pneumonia
Aspiration
- anaerobes
Ventilator Acquired Pneumonia
- pseudomonas aeruginosa
- klebsiella
- acinebacter
- enterobacter
- proteus

Question 2

Discuss the pathophysiology and complications of pneumonia

Answer 2

Pathophysiology
- pathogen enter respiratory tract through direct inhalation, aspiration, direct spread from upper respiratory tract, or hematogenous spread
- pathogen colonize and proliferate
- immune system cause inflammation and migration of neutrophils into air space
Complications
- pleural effusion which can be transudate or exudate (empyema)
- lung abscess
- pneumatocele
- necrotizing pneumonia
- right heart failure
- dehydration

Question 3

Discuss the presentation and investigations for pneumonia

Answer 3

Presentation
- productive cough with colored sputum
- SOB
- pleuritic chest pain
- fever, chills
- dullness to percussion
- increased tactile fremitus
- crackles and decreased air entry
- increased whispered pectoriloquy
- egophany
Investigations
- CBC, electrolytes, BUN, blood glucose and blood gas
- Chest x-ray
       - bronchopneumonia: diffuse patchy consolidation with multiple foci of isolated consolidation
       - lobar pneumonia: localized continuous consolidation of distinct region
       - intersitial pneumonia: reticular nodular pattern with increased lung markings throughout

Question 4

Discuss the indications for hospitalization for pneumonia

Answer 4

Pneumonia Severity index
- class 1 and 2 as outpatient
- class 3 treated in observation or short hospitalization
- class 4 and 5 as inpatient
CURB65
- Confusion
- Urea >7
- Respiratory Rate >30
- BP <90 or <60
- Age >65
- <=1 can be treated as outpatient, 2 as inpatient, >=3 in ICU

Question 5

Discuss antibiotic choice for inpatient pneumonia

Answer 5

Choice
- Ceftriaxone 1g IV Q24H + Azithromycin 500mg IV Q24 if
- severely ill with HR>125 or hypotension <90, tachypnea >30 or hypoxic <90%
- allergy to quinolone
- received quinolone within last 3 months
- Otherwise Levofloxacin 750mg PO Q24H
Switch from IV to PO
- hemodynamically stable
- clinical improvement
- ability to tolerate PO
- normal functioning GI tract
Stepping Down Ceftriaxone + Azithromycin
- Cefuroxime 500mg PO Q12H +/- Azithromycin 250-500mg PO Q24H
- Levofloxacin 750mg PO Q24H
Duration
- discontinue if patient afebrile for 2-3 days and have <=1 of the CAP associated signs of instability
- temperature >37.8
- HR >100
- Systolic BP <90
- RR >24
- O2 Sat <90% on room air or PaO2 <60
- Altered mental status
- 5 days for patients that are not immune compromised or do not have structural lung disease
- 7 days for patients who are moderately immune compromised or structural lung disease
- 10 days for slow clinical response or significant immune compromised

Question 6

Discuss signs and investigations for pleural effusion

Answer 6

Presentation
- possibly asymptomatic
- SOB
- asymmetric chest expansion
- dullness to percussion, decreased tactile fremitus
- decreased air entry
Investigation
- Chest x-ray
- Thoracocentesis (if >1cm of fluid on lateral decubitus x-ray)
- appearence of pleural fluid
- cell count and differential
- biochemistry: LDH, protein, glucose, pH, albumin
- gram stain, acid fast stain, culture
- cytology

Question 7

Discuss the Light’s criteria for transudative vs exudative pleural effusion

Answer 7

Exudative if any of the following

• pleural fluid protein/serum protein >0.5
• pleural fluid LDH/serum LDH >0.6
• pleural fluid LDH >2/3 upper normal limit of serum LDH

Question 8

Discuss the differential for transudative vs exudative effusion

Answer 8

Transudative
- CHF
- nephrotic syndrome
- hypoalbumin (liver failure)
Exudative
- infection
- malignancy
- pulmonary embol

Question 9

Differentiate between para-pneumonic effusion and empyema

Answer 9

Parapneumonic effusion is pleural effusion related to pneumonia abscess or bronchiectasis

• can progress to empyema
• Pleural fluid >=7.2 in parapneumonic
• glucose >=3.33
• LDH <1000
• Gram stain negative
• No frank pus

Question 10

Discuss the differential for Chronic Cough

Answer 10

Mechanical
- post-nasal drip
- GERD
Infection
- TB
- pneumonia
Inflammation
- COPD
- Asthma
Medication
- ACE inhibitor
Neoplasm
- Bronchogenic carcinoma
- lung cancer
- lung metatasis
Other
- intersitial lung disease

Question 11

Discuss the investigation for chronic cough

Answer 11

PFT with Methcholine Challenge
- if hx suggest asthma
PPI
- for GERD
Abx
- pneumonia: purulent sputum, systemic signs of infection
Smoking Cessation
Stop ACE Inhibitor
Non of the Above
- CXR
- Normal CXR then 3 week empiric anti-histamine for post-nasal drip
      - if partially effective add nasal glucocorticoid
- CT
- Bronchoscopy
- Cardiac Studies