This document discusses community acquired pneumonia (CAP) and severe CAP. Patients with severe CAP require ICU management and have a higher mortality rate. Empiric antibiotic therapy differs from non-severe CAP. Severity of illness scores like CURB-65 are used to define severe CAP but clinical judgment is also important. The most common causes of severe CAP are Streptococcus pneumoniae, Legionella sp, Haemophilus influenzae, and gram-negative rods. Combination antibiotic therapy including a macrolide is recommended. Factors that increase risk of multidrug resistant pathogens are discussed. Biomarkers and bacterial load quantification may help determine prognosis and guide treatment. Long term mortality is increased due to cardiovascular complications post CAP.

1. COMMUNITY ACQUIRED
PNEUMONIA
2015
SAMIR EL ANSARY

2. Global Critical Care
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3. Patients with severe CAP have a
number of characteristics:
They generally require (ICU) management.
They have a higher mortality rate than do
patients with nonsevere CAP.
Empiric antibiotic therapy in this group differs
from that in patients with nonsevere CAP.
Unfortunately, it is challenging to prospectively identify this
cohort of patients. Of particular concern are patients who are
initially triaged as having nonsevere CAP but subsequently need
ICU admission (up to 50% of ICU admissions fall under this
category in some studies).

4. Such patients tend to have
a higher mortality
than equally sick patients
who have been directly
admitted to an ICU.

5. A number of severity of illness scores have
been developed to help define severe CAP, a
popular one being derived from the joint Infectious Diseases
Society of America-American Thoracic Society guidelines for the
management of CAP in adults, which incorporates
elements of the confusion, urea ,respiratory
rate, and blood pressure (CURB) score.
By this definition, patients with one major
criterion or three minor criteria are designated
as having severe CAP.
Another widely used score is the
Pneumonia Severity Index (PSI).

6. However, none of these scores has
been prospectively validated for
individual patients.
Clinical judgment remains
critical; do not blindly
follow scores!
In recent years other approaches
have been explored to identify
patients with severe CAP .

7. CRITERIA FOR SEVERE CAP
Minor Criteria
Respiratory rate >30 breaths/min
Pa02/Fi02 ratio < 250
Multilobar infiltrates
Confusion or disorientation
Uremia (blood urea nitrogen level >20 mg/dL)
Leukopenia (WBC count <4000 cells
per cubic millimeter as a result of infection alone)
Thrombocytopenia (platelet count <100,000
cells per cubic millimeter)
Hypothermia (core temperature <36" C)
Hypotension requiring aggressive fluid resuscitation

8. Major Criteria
lnvasive mechanical ventilation
Septic shock with the need for
vasopressors
The pathogens most
commonly cause severe CAP

9. The pathogens most commonly
cause severe CAP :
The most common causes of severe
CAP in ICU patients are
(in order of decreasing incidence):
Streptococcus pneumoniae
Legionella sp
Haemophilus influenzae
Gram-negative rods (GNRs)
Staphylococcus aureus
Pseudomonas aeruginosa
Pathogens are identified in fewer than
50% of cases.

10. Specific therapy seems to
have no particular
advantage over empiric
therapy except in ICU
patients, where every effort
should be made to reach an
etiologic diagnosis and tailor
therapy accordingly.

11. A typical work-up for an ICU patient
would include sputum Gram stain in
addition to sputum and blood cultures.
In addition urinary antigen tests for
Legionella and pneumococcus should
be considered.
More invasive tests, such as
bronchoscopic bronchoalveolar lavage,
may be considered in individual
patients.

12. CAP is diagnosed on the basis of
the presence of a constellation of
signs and symptoms
(fever, cough, sputum production,
and pleuritic chest pain)
with radiographic evidence of lung
infiltrates.
Sputum Gram stain and culture can
be obtained noninvasively and are
inexpensive diagnostic tests.

13. A sputum Gram stain
specimen is considered
satisfactory for interpretation
when the neutrophil count
is >25
and the epithelial cell count is
<10 per low power field.

14. Gram staining
can have multiple benefits:
The results can be used to broaden
coverage to cover microorganisms that
are typically not covered by empiric
regimens, such as S. aureus and GNRs.
Conversely, the absence of characteristic
Gram stains and sputum culture is a
strong argument for presumptively
excluding S. aureus and GNRs as
probable etiologies for the pneumonia.

15. Gram staining
In addition, a positive Gram stain validates a
subsequent sputum culture.
Keep in mind the diagnostic limitations of
sputum Gram stain and culture, including the
inability to visualize atypical organisms,
contamination by oral flora, and the difficulty
encountered by some patients to provide
adequate specimens.

16. Determinants of the selection of empiric
antimicrobial therapy for patients with
severe CAP
Empiric treatment should cover the three
most common pathogens causing severe
CAP , all atypical pathogens, and most
relevant Enterobacteriaceae species.
Broader coverage may be considered
depending on epidemiologic considerations
Combination therapy is better than
monotherapy.

17. Recent data strongly suggest
that benefits of combination
therapy are maximal
when one of the agents is a
macrolide.
Therefore a macrolide should
be included in all regimens
unless a compelling reason exists not
to do so.

18. Risk factors that would prompt broader
antimicrobial coverage can be conveniently
considered by the type of organism to be
covered:
Pseudomonas:
Long-term oral steroids (>I0 mg prednisone
per day), underlying bronchopulmonary
disease (bronchiectasis), severe chronic
obstructive pulmonary disease, alcoholism,
frequent antibiotic use.

19. Note that the strongest justification for
beginning antipseudomonal coverage is
the presence of a consistent Gram stain of
blood or sputum.
A p-lactam (cefotaxime, ceftriaxone, or
ampicillin-sulbactam) PLUS Either
azithromycin
OR A respiratory fluoroquinolone
(levofloxacin [750 mg], moxifloxacin, or
gemifloxacin)

20. If Pseudomonas is a consideration:
An antipneumococcal, antipseudomonal
p-lactam (piperacillin-tazobactam,
cefepime, imipenem, or meropenem)
PLUS Either ciprofloxacin or
levofloxacin (750 mg)
OR
The previously mentioned p-lactam
plus an aminoglycoside and
azithromycin

21. If Pseudomonas is a consideration:
OR
The previously mentioned p-lactam
plus an aminoglycoside and an
antipneumococcal fluoroquinolone
(for penicillin-allergic patients, substitute
aztreonam for previously mentioned p-
lactam)

22. If CA-MRSA is a
consideration:
Add vancomycin or linezolid.
Penicillin allergy:
Substitute aztreonam for the
previously mentioned p-
lactams.

23. Community-acquired methicillin-resistant S.
aureus (CA-MRSA):
Patients with cavitary lesions, patients who
have had influenza, patients receiving long-
term dialysis, intravenous (IV) drug abusers,
and patients who have had recent antibiotic
treatment (particularly with fluoroquinolones).
Although a consistent sputum Gram stain is a strong
reason to cover for S. aureus, a blood Gram stain may
be falsely positive because of contamination.

24. Anaerobes:
Aspiration in the setting of alcohol or drug
intoxication or in the presence of gingival
disease or esophageal dysmotility.
Drug-resistant S. pneumoniae (DRSP):
Age >65 years, alcoholism,
immunosuppression, exposure to antibiotics
in the last 3 months (class-specific
resistance), comorbidities, and exposure to
children attending day care.
In most cases, typical empiric therapy for
CAP in the ICU should cover DRSP.

25. Initiation of antibiotics must be within 4
hours of diagnosis of CAP .
patients should receive their first dose of
antibiotics while in the ED.
Patients with CAP should be treated for a
minimum of 5 days, should be afebrile for
48 to 72 hours, and should not have more
than one CAP-associated sign of clinical
instability before stopping treatment.

26. Conversion to oral therapy
May be considered in the hemodynamically
stable patient who is improving clinically,
can take oral medications, and has a
normally functioning gastrointestinal tract.
Temperature <37.8" C -Heart rate < 100 beatslmin -
Respiratory rate <24 breaths/min
Systolic blood pressure >90 mm Hg
- Arterial oxygen saturation >90% or PO2
>60 mm Hg with room air .

27. CA-MRSA infections
An important trend in public health is the increasing
prevalence of CA-MRSA infections.
Here we will briefly discuss some of the salient
features caused by CA-MRSA, particularly with
reference to CAP.
CA-MRSA infections have reached epidemic
proportions in the United States and are now the
most common cause of infections in patients
coming to EDs.

28. Discuss CA-MRSA infections
The majority of infections are skin and soft
tissue infections; approximately 2% of CA-
MRSA infections present as CAP.
CAP caused by CA-MRSA tends to be
severe, with a high incidence of necrotizing
pneumonia, shock, respiratory failure, lung
abscess, and empyema.

29. Discuss CA-MRSA infections
CA-MRSA-induced pneumonia has typically
been more common in children but is being
increasingly seen in adults.
Risk factors that predispose to CA-MRSA
were mentioned earlier.
CA-MRSA differs from the more typical health
care-associated MRSA (HA-MRSA) at the
genomic, phenotypic, and epidemiologic
levels.

30. Discuss CA-MRSA infections
However, CA-MRSA strains are beginning to
be increasingly represented in nosocomial
infections, and the distinctions between them
may be blurring.
Two key features that distinguish CA-MRSA
from HA-MRSA are the production of more
virulence factors, including the
Panton-Valentine leukocidin (PVL) toxin,
and a greater susceptibility to non-p-lactam
antibiotics in vitro.

31. Discuss CA-MRSA infections
However, the role of PVL in human
disease is unclear.
First-line treatment for CA-MRSA CAP
remains vancomycin.
Alternatives may include linezolid or
clindamycin, which have the theoretic
advantage of having some efficacy
against CA-MRSA exotoxins.

32. Recent developments in CAP
Areas of active investigation in the field
include biomarkers for the diagnosis and
prognosis in CAP, using the genomic
bacterial load as a marker of disease
severity, and epidemiologic studies of long-
term health effects of CAP.

33. Biomarkers in CAP
The potential applications of biomarkers in
CAP include stratifying patients accurately
into high- and low-risk groups and guiding
antibiotic therapy
(both initiation and duration).
Examples of biomarkers
procalcitonin and proadrenomedullin.
Some studies have shown that combining
these markers with existing severity of
illness scores has resulted in improved
predictive capacity.

34. Quantitative bacterial load
Recently some investigators have been
studying the use of quantitative
bacterial load in blood as a marker of
severity of illness, analogous to the use
of viral load in the management of
diseases such as hepatitis C and
human immunodeficiency virus (HIV).

35. Quantification of S. pneumoniae DNA
in blood with use of real-time polymerase
chain reaction PCR was shown to be a
strong predictor of the risk for shock and the
risk for death in pneumococcal pneumonia.
This test is more sensitive than blood
cultures, with a specificity approaching
100%.
It is rapid (turnover time <3 hours), is
inexpensive, and can also determine
susceptibility to penicillin.
If validated by further studies, this test could have a major impact in the management of CAP.

36. Long-term consequences of CAP
An important change in our
understanding of the impact of CAP on
patients has been the realization that
the 2-year mortality of patients with an
episode of CAP was significantly
increased over that of controls, even in
the absence of comorbid diseases.

37. Although the cause of the increased
mortality is not completely clear, some
evidence suggests a predominantly
cardiovascular cause.
Epidemiologic data show a strong
association between acute respiratory tract
infections and subsequent acute myocardial
infarctions.

38. This gives rise to the possibility
that the acute inflammatory and
procoagulant state induced by
CAP can destabilize atheromatous
plaques and accelerate underlying
cardiovascular disease.

39. Further studies are needed to identify
patients most at risk for delayed mortality,
and potential treatments such as aspirin or
3-hydroxy-3-methyl-glutaryl (HMG)
coenzyme A reductase inhibitors (such as
statins) can perhaps be tried. It may
therefore be helpful to view CAP as an
acute illness with long-term health
implications rather than a self-limiting
process.

40. SAMIR EL ANSARY
ICU PROFESSOR
AIN SHAMS
CAIRO
elansarysamir@yahoo.com
GOOD LUCK
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