RISK FACTORS:Tobacco smoking, Recent/concurrent viral infections, Hospitalization to include mechanical ventilation, antecedent antibiotics, NG tubes, Age extremes, Alcoholism, AIDS or other immunosuppression, Renal failure, Cardiovascular disease
RISK FACTORS
β’ Tobacco smoking
β’ Recent/concurrent viral infections
β’ Hospitalization to include mechanical ventilation, antecedent antibiotics, NG tubes
β’ Age extremes
β’ Alcoholism
β’ AIDS or other immunosuppression
β’ Renal failure
β’ Cardiovascular disease
β’ Functional asplenia
β’ Chronic obstructive pulmonary disease
β’ Diabetes mellitus
β’ Malnutrition
β’ Malignancy
β’ Altered level of consciousness or gag (e.g., seizures, stroke, neuromuscular disease, etc.)
β’ Occupational exposure
β’ Poorly implemented infection control practices (poor handwashing)
β’ Postoperative atelectasis
Medical Care: The initial approach to treating patients with
CAP involves a determination of 3 factors. (1) Should the patient with pneumonia be treated in the hospital or as an outpatient? (2) Does the patient have a serious coexisting illness or is the patient elderly? (3) How severely ill is the patient at the time of the initial evaluation?
Once these assessments have been made, initial antimicrobial therapy can be selected based on to the recommendations given in Tables 1-7. The choices cover the most common pathogens for a given clinical setting. Evaluating the response to therapy is important. Patients who are not improving with initial empirical antibiotic therapy should be identified and re-examined.
" Risk stratification of CAP
o Patients with CAP can be categorized into 1 of 4 groups based on information collected at the time of the initial evaluation.
o The risk factors for stratification include the need for hospitalization, the severity of illness, the presence of coexisting disease, and the patient's age.
o Penicillin (penicillin G/amoxicillin) remains the drug of choice for strains that are fully sensitive or have a moderately decreased susceptibility to penicillin, whereas cefotaxime and ceftriaxone are the first-line alternatives in cases with higher levels of resistance.
o The 4 major categories not only speculate the microbial etiology but also predict ultimate prognosis and outcome. These categories are (1) CAP occurring in patients aged 60 years or younger who have no evidence of comorbidity and who can be treated in an outpatient setting, (2) CAP occurring in patients with evidence of comorbidity and/or who are aged 60 years or older who can be treated in an outpatient setting, (3) CAP requiring hospitalization but not admission to an ICU, and (4) severe CAP requiring ICU care.
" Nosocomial pneumonia
o Nosocomial pneumonia remains a prevalent hospital-acquired infection. The gaps in knowledge and controversies regarding diagnosis, treatment, and prevention of nosocomial pneumonia continue. The initial empiric therapy of nosocomial pneumonia in immunocompetent patients is directed at the core organisms. In immunocompromised hosts, the additional bacteria are targeted and therapy is modified based on the results of microbiologic investigations.
o Modifications to the empirical antibiotic therapy may be necessary after assessment of 3 factors; these are (1) the severity illness in the patient, (2) the presence of any conditions that can lead to infection with specific pathogens, and (3) the length of time the patient has been hospitalized before the development of nosocomial pneumonia.
o Following these determinations, patients are categorized into 1 of 3 groups because a different microbiologic spectrum is suggested in each group. These groups are (1) patients without unusual risk factors who present with mild-to-moderate nosocomial pneumonia any time during hospitalization or present with severe nosocomial pneumonia at early onset, (2) patients with risk factors who present with mild-to-moderate nosocomial pneumonia occurring any time during hospitalization, and (3) patients with severe nosocomial pneumonia either of early onset with specific risk factors or of late onset without risk factors.
o Patients belonging to risk group 1 usually are infected with E coli or S aureus; Klebsiella, Proteus, Serratia, or Haemophilus, species; or streptococci. Patients in risk group 2 have infection with the previous organisms, but anaerobes, S aureus, Legionella species, and P aeruginosa also may be present. In risk group 3, the core organisms are present and P aeruginosa, Acinetobacter species, and methicillin-resistant S aureus are the additional possibilities.
" Definition of severe hospital-acquired pneumonia
o Admission to the ICU is indicated.
o Respiratory failure is defined as the need for mechanical ventilation or the requirement for fraction of inspired oxygen to be greater than 35% in order to maintain oxygen desaturation of greater than 90%.
o Rapid radiographic progression, multilobar pneumonia, or cavitation of a lung infiltrate is present.
o Evidence of severe sepsis with hypotension and/or an organ dysfunction is present.
o Shock state is present, as indicated by a systolic blood pressure of less than 90 mm Hg or a diastolic blood pressure of less than 60 mm Hg.
o Vasopressors are required for more than 4 hours.
o Urine output is less than 20 mL/h, or total urine output is less than 80 mL in 4 hours.
o Acute renal failure is present that requires dialysis.
" Empiric therapy for community-acquired bacterial pneumonia - Based on recommendations by the American Thoracic Society (1993) and consensus guidelines by the Canadian Infectious Disease Society/Canadian Thoracic Society (2000)
Table 1. Outpatient Pneumonia Without Comorbidity in Patients Aged 60 Years or Younger*
Organisms β
S pneumoniae
M pneumoniae
C pneumoniae
H influenzae
Miscellaneous
Legionella species, S aureus,
aerobic gram-negative bacilli
Therapy
1st choice - Macrolide β‘
2nd choice - Doxycycline
*Excludes patients at risk for HIV
β In roughly one third to one half of the cases, no etiology was identified.
β‘ Erythromycin, clarithromycin, or azithromycin
Table 2. Outpatient Bacterial Pneumonia With Comorbidity in Patients Aged 60 Years or Older*
Organisms β
S pneumoniae
H influenzae
Aerobic gram-negative bacilli
S aureus
Miscellaneous
M catarrhalis, Legionella species, Mycoplasma
Therapy
COPD (no recent antibiotics or oral steroids within past 3 mo)
1st choice - Newer macrolides
2nd choice - Doxycycline
COPD (recent antibiotics or oral steroids in past 3 mo)
1st choice - Respiratory fluoroquinolone*
2nd choice - Amoxicillin/clavulanate + macrolide or second-generation cephalosporin + macrolide
Suspected microaspiration - Oral anaerobes
1st choice -Amoxicillin/clavulanate and/or macrolide or fourth-generation fluoroquinolone (eg, moxifloxacin)
2nd choice - Third-generation fluoroquinolone (eg, levofloxacin plus clindamycin or metronidazole
*Excludes patients at risk for HIV
β In roughly one third to one half of the cases, no etiology was identified.
Table 3. Hospitalized Patients With Community-Acquired Bacterial Pneumonia (admission to medical ward)*
Organisms β
S pneumoniae
H influenzae
Polymicrobial (including aerobic bacteria)
Aerobic gram-negative bacilli
Legionella species
S aureus
C pneumoniae
Miscellaneous
M pneumoniae, M catarrhalis
Therapy
1st choice - Respiratory fluoroquinolone
2nd choice - Second-generation or third-generation cephalosporin + macrolide
*Excludes patients at risk for HIV
β In roughly one third to one half of the cases, no etiology was identified.
Table 4. Severe Hospitalized Patients With Community-Acquired Bacterial Pneumonia (admission to ICU)*
Organisms β
S pneumoniae
Legionella species
Aerobic gram-negative bacilli
M pneumoniae
Miscellaneous
H influenzae
Therapy
1st choice - Antipseudomonal fluoroquinolone (eg, ciprofloxacin)
plus antipseudomonal beta-lactam (eg, ceftazidime, piperacillin-
tazobactam, carbapenem) or aminoglycoside (eg, gentamicin,
tobramycin, amikacin)
2nd choice - Triple therapy with antipseudomonal beta-lactam plus
aminoglycoside plus macrolide
*Excludes patients at risk for HIV
β In roughly one third to one half of the cases, no etiology was identified.
Table 5. Patients With Mild-to-Moderate Hospital-Acquired Bacterial Pneumonia, No Unusual Risk Factors, and Onset at Any Time; or, Patients With Severe Hospital-Acquired Pneumonia With Early Onset*
Core Organisms Core Antibiotics
Enteric gram-negative bacilli Cephalosporin
(Nonpseudomonal) Enterobacter species, E coli Second-generation or nonpseudomonal third-generation
Klebsiella species Beta-lactam/beta-lactamase
inhibitor combination
Proteus species
S marcescens If allergic to penicillin, fluoroquinolone or clindamycin + aztreonam
H influenzae
Methicillin-sensitive S aureus
S pneumoniae
*Excludes patients with immunosuppression
Table 6. Patients With Mild-to-Moderate Hospital-Acquired Bacterial Pneumonia With Risk Factors, Onset at Any Time*
Core Organisms, Plus the Following: Core Antibiotics, Plus the Following:
Anaerobes
(recent abdominal surgery, witnessed aspiration) Clindamycin or beta-lactam/beta-lactamase inhibitor (alone)
S aureus (coma, head trauma, diabetes mellitus, renal failure) +/-vancomycin (until methicillin-resistant S aureus is excluded)
Legionella
(high-dose steroids) Erythromycin +/- rifampin
P aeruginosa
(prolonged ICU stay, steroids, antibiotics, structural lung disease Treat as severe hospital-acquired pneumonia (see Table 7)
*Excludes patients with immunosuppression
Table 7. Patients With Severe Hospital-Acquired Bacterial Pneumonia With Risk Factors and Early Onset or Patients With Severe Hospital-Acquired Pneumonia and Late Onset*
Core Organisms, Plus the Following Therapy
P aeruginosa
Acinetobacter species
Consider methicillin-resistant S aureus Aminoglycoside or ciprofloxacin plus one of the following:
Antipseudomonal penicillin
Beta-lactam/beta-lactamase
inhibitor
Ceftazidime or cefoperazone
Imipenem
+/-vancomycin
*Excludes patients with immunosuppression
" To determine the impact of initial antimicrobial choice on 30-day mortality rate in patients with CAP due to S pneumoniae, a prospective, observational study was performed. The factors related to mortality were bilateral disease, suspected aspiration, shock, HIV infection, renal failure, and pneumonia severity index (PSI) score class IV versus class I-III and categories V versus categories I-III. The association of beta-lactams plus macrolides was not better than the use of beta-lactams alone. The benefit of adequate initial antimicrobial regimen and 30-day mortality in patients with community-acquired pneumococcal pneumonia was demonstrated for those with a higher PSI score.
PATIENT MONITORING
. If outpatient therapy, daily assessment of the patients progress, and reassessment of therapy if clinical
worsening or no improvement in 48-72 hours
. CXR take time to clear and may not show clearing, even though patient is improving. Repeat study about
6 weeks after recovery to verify the pneumonia was not caused by an obstructing endobronchial lesion in
selected patients (smokers and older patients).
. Repeating the cultures after treatment has been started is unnecessary unless there has been treatment failure or if treating TB
PREVENTION/AVOIDANCE
. Reduce risk factors where possible (quit smoking)
. Bedridden and postoperative patients - deep breathing and coughing exercises; prevent aspiration during
nasogastric tube feedings
. Avoid indiscriminate use of antibiotics during minor viral infections
. Annual infl uenza vaccine for high risk individuals
. Polyvalent pneumococcal vaccine
POSSIBLE COMPLICATIONS
. Empyema
. Pulmonary abscess
. Superinfections
. Multiple organ dysfunction syndrome (MODS)
. Adult respiratory distress syndrome (ARDS)
. Post-pneumonic atelectasis may occur in 5-10% of children
EXPECTED COURSE/PROGNOSIS
. Usual course - acute. In otherwise healthy individual, improvement seen and fever resolved in 1-3 days;
sometimes up to 1 week
. Overall attributable mortality is about 5% in community acquired; (.15% if hospitalized and < 1% if not hospitalized) 25-50% in nosocomial
. Poorest prognosis - age extremes, positive blood cultures, low WBC, presence of associated disease,
immunosuppression respiratory failure, inappropriate antecedent antibiotics, delayed treatment >8 hours