Pneumonia (CAP, HAP & VAP) Flashcards
Define “pneumonia”.
Lower respiratory tract infection of the lung parenchyma
Due to abnormal proliferation of microbial pathogens in alveolar level (normally sterile), commonly via bacteria
Briefly describe the pathogenesis of pneumonia.
Bacteria enter the lower respiratory tract through various MOA:
- Aspiration of oropharyngeal secretions
- Inhalation of infected aerosolised droplets containing bacteria
- Hematogenous spreading (i.e. bacteremia) from extrapulmonary source
What are some signs and symptoms displayed by pt with pneumonia?
Localised: Cough, chest pain, SOB/dyspnea, hypoxia
Systemic:
- Fever > 38 deg C, chills
- Tachypnea, tachycardia, hypotension
- Leukocytosis (i.e. elevated WBC)
- Malaise, anorexia, nausea, changes in mental status (esp. elderly pt.)
What are the clinical tests available that may aid in the diagnosis of pneumonia?
1) Physical examination
- Diminished breath sounds over the affected area of lungs using a stethoscope
- Inspiratory crackles during lung expansion
2) Radiological findings
- Chest x-ray (more commonly used; less expensive) > CT scan (used if Tx failure or immunocompromised)
- Observed for new infiltrates or dense consolidations
3) Laboratory findings (e.g. C-reactive protein, procalcitonin)
- Non-specific & limited discriminatory potential when used alone (e.g. CKD pt. has elevated [procalcitonin])
- Not recommended for routine use to guide Abx initiation or continuation
4) Respiratory cultures
- Sputum is most readily available, but low yields due to frequent contamination by oropharyngeal secretions; quality sample must include > 10 neutrophils & < 25 epithelial cells per low-power field
- Lower respiratory tract samples are preferred due to less contamination risk but require invasive sampling (e.g. bronchoalveolar lavage)
5) Blood culture
- Rule out bacteremia in hospitalized pt.
6) Urinary antigen tests
- Specific to S. pneumonia & Legionella pneumophilia serogroup 1
- Not routinely used; indicate exposure to respective antigens & NOT necessarily infections
How is pneumonia clinically diagnosed?
Look for pulmonary signs & smx during clinical examination & correlate to chest radiological findings to establish presence of pneumonia!
Many cases of pneumonia are empirically Tx; Abx is initiated upon clinical suspicion before pathogen identification (due to difficulties obtaining cultures).
Briefly explain the classification of pneumonia.
Community-acquired pneumonia (CAP):
Onset in community or < 48h after hospital admission
Healthcare-associated pneumonia (HAP):
Onset >= 48h after hospital admission
Ventilatory-acquired pneumonia (VAP):
Onset >= 48h after mechanical ventilation
Nosocomial pneumonia includes both HAP & VAP.
- Healthcare-associated pneumonia (HCAP) is obsolete
List the risk factors associated with pneumonia.
> 65 y/o Previous hospitalisation for CAP Smoking Selected comorbidities such as: - COPD, DM, HF, cancer & immunocompromised
What are some preventive measures that can be taken to minimise the risk of pneumonia?
Smoking cessation
Vaccinations (influenza & pneumococcal)
- Post-influenza bacterial pneumonia can be a serious complication
- PCV is highly effective due to the prevalence of S. pneumoniae as a common causative pathogen
Describe the microbiology of CAP.
Outpatient:
- S. pneumoniae
- H. influenzae
- Atypicals: Mycoplasma pneumoniae, Chlamydophilia pneumoniae
Inpatient (Non-Severe): Aforementioned + Legionella pneumophilia
Inpatient (Severe): Aforementioned + S. aureus + other gram-negative bacilli
- Klebsiella pneumoniae
- Burkholderia pseudomallei
Which microorganism is specifically found as part of the microbiology of severe inpatient CAP in Singapore?
Burkholderia pseudomallei
- unique pathogen that causes melioidosis (severe pneumonia)
- endemic in Asia & thus not mentioned in IDSA guidelines
- important implication in empiric Abx selection in inpatient settings
What are some consideration in the general Tx approach to CAP?
Severity of CAP pt’s clinical presentation determines:
- Location of treatment (outpatient vs general ward vs ICU)
- Coverage against specific pathogens
- Empiric Abx regimen
- ROA (PO vs IV)
Describe the two validated scoring systems that help with the prediction of CAP pt’s mortality & Tx outcomes.
1) Pneumonia Severity Index (PSI)
- Class I & II: outpatients
- Class III: short-term hospitalisation or observation
- Class IV & V: inpatients
- Complexity limits use in clinical settings as 20 variables are used to stratify
2) CURB-65
+1 Confusion
+1 Urea > 7 mmol/L
+1 Respiratory Rate >= 30 breaths per min
+1 Blood pressure (SBP < 90 mmHG or DBP <= 60 mmHg)
+1 Age >= 65 y/o
- 0-1 are outpatients; 2 is inpatient; 3-5 is inpatient w/ ICU consideration
- Easy to use with 5 readily available parameters to stratify into 3 mortality risk classes
Based on IDSA guidelines, what is considered severe CAP?
> = 1 major criteria OR >= 3 minor criteria
Major: - mechanical ventilation - septic shock requiring vasoactive medications (to counteract hypotension) Minor: - Confusion / disorientation - Uremia (urea > 7 mmol/L) - RR >= 30 breaths/min - Hypotension requiring aggressive fluid resuscitation - PaO2/FiO2 <= 250 (marker of hypoxia) - Multilobar infiltrates - Hypothermia (core temp < 36 deg C) - Leukopenia (WBC < 4 x 10^9 /L)
Which patient populations are identified to require atypical coverage when treating pt with CAP in outpatient settings?
Chronic heart, lung, kidney, liver diseases Diabetes mellitus Alcoholism Malignancy Asplenia
WH is a 48-year-old female with a past medical history significant for heartburn, hypothyroidism and migraine. She presented to the emergency department with a 2-day history of cough and shortness of breath. She was diagnosed with pneumonia but her doctor felt that she was well enough to return home. WH has never been admitted to the hospital, has normal renal function and has no known drug allergies. Recommend the most appropriate Abx regimen to treat WH’s infection.
Amoxicillin PO 1g TDS x at least 5 days
YH is a 45-year-old female with a past medical history significant for T2DM. She presented to the emergency department with a 2-day history of cough and shortness of breath. She was diagnosed with pneumonia but her doctor felt that she was well enough to return home. WH has never been admitted to the hospital, has normal renal function and has no known drug allergies. Recommend the most appropriate Abx regimen to treat YH’s infection.
Beta-lactams + macrolides/doxycycline as standard regimen PO for at least 5 days
Beta-lactams:
1) Amoxicillin/clavulanate 625 mg TDS OR 2g BD or
2) Cefuroxime 500 mg BD
- to cover for beta-lactamase strains for H. influenzae
and Macrolides/Doxycycline:
1) Azithromycin 500 mg OD or
2) Clarithromycin 500 mg BD or
3) Doxycycline 100mg BD
- to cover for atypical (Mycoplasma & Chlamydia)
ZH is a 60-year-old male with a past medical history significant for osteoporosis. He presented to the emergency department with a 2-day history of cough and shortness of breath. He was diagnosed with pneumonia but his doctor felt that he was well enough to return home. ZH has never been admitted to the hospital, has normal renal function and has a known drug allergy to penicillins. Recommend the most appropriate Abx regimen to treat ZH’s infection.
Levofloxacin PO 750mg OD x at least 5 days
For a patient diagnosed with outpatient CAP with a known penicillin allergy, PO ciprofloxacin 500mg BD for at least 5 days is an appropriate Tx option. True or false?
False! Ciprofloxacin is NOT a respiratory fluoroquinolone, i.e. does not have activity against gram-positive S. pneumoniae!
Why is erythromycin not recommended as a treatment option in addition to beta-lactams when treating an outpatient CAP patient with CKD?
Older macrolide with greater GI side effects, thus newer macrolides such as clarithromycin or azithromycin are recommended instead.
A 68 y/o male with PMH of T2DM presented to A&E with cough, chest pain, fever, and confusion x 2 days. He was diagnosed with CAP and was admitted to the general medicine ward for treatment.
T 38.4 deg C, BP 126/86, HR 76, RR 22 Oxygen saturation 92% (room air) WBC 11.8 x 10^9/L, urea 5.4 mmol/L Allergies: no known drug allergies Previous hospitalization: none Chest XR: dense consolidation in the right lower lobe
Recommend the most appropriate Abx regimen to treat the patient’s infection.
IV Beta-lactams + PO macrolides/doxycycline as standard regimen for at least 5 days (subjected to step-down Tx)
IV Beta-lactams:
1) Amoxicillin/clavulanate 1.2g q8h or
2) Ceftriaxone 1-2g q24h
and PO Macrolides/Doxycycline:
1) Azithromycin 500 mg OD or
2) Clarithromycin 500 mg BD or
3) Doxycycline 100mg BD
A 68 y/o male with PMH of T2DM presented to A&E with cough, chest pain, fever, nausea & vomiting and confusion x 2 days. He was diagnosed with CAP and would be admitted to the general medicine ward for treatment.
T 38.4 deg C, BP 126/86, HR 76, RR 22 Oxygen saturation 92% (room air) WBC 11.8 x 10^9/L, urea 5.4 mmol/L Allergies: no known drug allergies Previous hospitalization: none Chest XR: dense consolidation in the right lower lobe
Recommend the most appropriate Abx regimen to treat the patient’s infection.
IV Beta-lactams + IV macrolides/doxycycline as standard regimen for at least 5 days (subjected to step-down Tx)
IV Beta-lactams:
1) Amoxicillin/clavulanate 1.2g q8h or
2) Ceftriaxone 1-2g q24h
and IV Macrolides/Doxycycline (due to N/V):
1) Azithromycin 500 mg q24h or
2) Clarithromycin 500 mg q12h or
3) Doxycycline 100mg BD
A 68 y/o male with PMH of T2DM presented to A&E with cough, chest pain, fever, and confusion x 2 days. He was diagnosed with CAP and would be admitted to the general medicine ward for treatment.
T 38.4 deg C, BP 126/86, HR 76, RR 22 Oxygen saturation 92% (room air) WBC 11.8 x 10^9/L, urea 5.4 mmol/L Allergies: penicillin (hives) Previous hospitalization: none Chest XR: dense consolidation in the right lower lobe
Recommend the most appropriate Abx regimen to treat the patient’s infection.
Levofloxacin IV 750mg q24h for at least 5 days (subjected to step-down Tx)
A 63 y/o male with PMH of T2DM presented to A&E with cough, chest pain, fever, nausea & vomiting and confusion x 2 days. He was diagnosed with CAP and would be admitted to the hospital for treatment.
T 38.4 deg C, BP 126/86, HR 76, RR 31
Oxygen saturation 92% (room air)
WBC 11.8 x 10^9/L, urea 7.4 mmol/L
Allergies: no known drug allergies
Previous hospitalization: 1 month ago; received ceftriaxone IV for UTI
Chest XR: dense consolidation in the right lower lobe
Recommend the most appropriate Abx regimen to treat the patient’s infection.
IV Beta-lactams + IV macrolides/doxycycline + IV ceftazidime as standard regimen for at least 5 days (subjected to step-down Tx)
IV Beta-lactams:
1) Amoxicillin/clavulanate 1.2g q8h or
2) Ceftriaxone 1-2g q24h
and IV Macrolides/Doxycycline (due to N/V):
1) Azithromycin 500 mg q24h or
2) Clarithromycin 500 mg q12h or
3) Doxycycline 100mg BD
PLUS IV ceftazidime 2g q8h for specific coverage against Burkholderia pseudomallei
A 62 y/o male with PMH of T2DM presented to A&E with cough, chest pain, fever, and confusion x 2 days. He was diagnosed with CAP and would be admitted to the hospital for treatment.
T 38.4 deg C, BP 126/86, HR 76, RR 31
Oxygen saturation 92% (room air)
WBC 11.8 x 10^9/L, urea 7.4 mmol/L
Allergies: penicillin (rash)
Previous hospitalization: 1 month ago; received ceftriaxone IV for UTI
Chest XR: dense consolidation in the right lower lobe
Recommend the most appropriate Abx regimen to treat the patient’s infection.
Levofloxacin IV 750mg q24h for at least 5 days (subjected to step-down Tx) due to penicillin allergy
- If penicillin allergy is mild & possible to challenge, IV cefepime 2g q8h may be used.
PLUS IV ceftazidime 2g q8h for specific coverage against Burkholderia pseudomallei
- possible to tolerate 3rd gen cephalosporins & incidence of cross-reactivity is low for ceftazidime for mild penicillin allergy
- however, for severe penicillin allergy, can omit ceftazidime as there is no other effective alternative to target B. pseudomallei
- need to monitor closely & follow up with cultures to inform our Abx Tx further
