NOSOCOMIAL PNEUMONIA

Definition: pneumonia (new CXR infiltrate w/ fever, purulent sputum or leukocytosis) occurring > 48h after admission and excluding infection incubating at the time of admission. Up to 70% mortality, 1/3 to ½ directly attributable to pneumonia.

Pathogenesis:

1. Routes of entry

a. microaspiration of o/p secretions

b. aspiration of esophagel/gastric contents

c. aerosol inhalation

d. hematogenous spread

1. Risk factors

a. Patient-related: severe acute or chronic illness, coma, malnutrition, prolonged hospitalization, hypotension, metabolic acidosis, cigarette smoking, CNS dysfunction, COPD, DM, EtOH, azotemia, respiratory failure.

b. Intervention-related: sedatives, corticosteroids, cytotoxic agents, prolonged surgery, ETT, prior antibiotic exposure, antacids, NGT.

Diagnostic studies:

1. History and physical exam (see below)

2. CXR

3. Blood cxs X 2- diagnostic and prognostic value

4. ABG/oximetry

5. Thoracentesis if effusion present

6. Sputum Gram stain/cx- neither sensitive nor specific, but may help to tailor abx

Empiric therapy: three questions- 1) mild to moderate OR severe? 2) specific host or therapeutic factors predisposing to specific pathogens? 3) early onset (< 5d after admission) OR late onset (> 5d after admission)?

1. Definition of severe nosocomial pneumonia

a. Admission to ICU.

b. Respiratory failure, defined as the need for mechanical ventilation or the need for >35% oxygen to maintain an arterial oxygen saturation >90%.

c. Rapid radiographic progression, multilobar pneumonia, or a cavitation of a lung infiltrate.

d. Evidence of severe sepsis with hypotension and/or end-organ dysfunction:

i. SBP < 90, or DBP < 60.

ii. Requirement of pressors > 4h.

iii. U/O < 20ml/h or total <80ml in 4h w/o other explanation.

iv. ARF requiring dialysis.

MILD-TO-MOD, NO SPECIFIC RISK FACTORS, ONSET ANY TIME or SEVERE, EARLY ONSET

Core organisms	Core antibiotics
EGNR(non-pseudomonal) Enterobacter E coli Klebsiella Proteus Serratia marcescens H flu MSSA S pneumo	Cephalosporin 2nd generation Non-pseudomonal 3rd generation (do not use as monotherapy if Enterobacter suspected) Beta-lactam w/ inhibitor IF PCN allergic Fluoroquinolone Clinda + aztreonam

MILD-TO-MOD, SPECIFIC RISK FACTORS, ONSET ANY TIME

Risk factor	Core organisms PLUS	Core antibiotics PLUS
Recent abd surg, witnessed aspiration	Anaerobes	Clinda OR beta-lactam w/ inhibitor
Coma, head trauma, DM, renal failure	S aureus	Vancomycin (until MRSA ruled out)
High-dose steroids	Legionella	Erytho +/- rifampin
Prolonged ICU stay, steroids, antibiotics, structural lung disease	Pseudomonas	Treat as SEVERE (see below)

SEVERE, SPECIFIC RISK FACTORS, EARLY ONSET, or SEVERE, LATE ONSET

Core organisms PLUS:	Therapy
Pseudomonas Acinetobacter ?MRSA	Aminoglycoside or ciprofloxacin PLUS one of the following: Antipseudomonal PCN Beta-lactam w/ inhibitor Ceftaz or cefoperazone Imipenem Aztreonam +/- Vanco

Assessing resolution

1. Clinical endpoints: change in fever, sputum purulence, leukocytosis, oxygenation, radiographic appearance, resolution of organ failure.

2. Improvement usually not noted for 48-72h. Abx should generally NOT be changed during this time period UNLESS progressive clinical deterioration occurs or initial microbiologic studies dictate need to modify therapy.

3. Duration of therapy: depends on severity, rapidity of clinical response, pathogen. 7-10d sufficient UNLESS Pseudomonas or Acinetobacter, multilobar, malnutrition, severe debilitation, cavitation, necrotizing GNR.

4. Causes of nonresolution: noninfectious (atelectasis, CHF, PE w/ infarction, contusion, chemical pneumonitis, ARDS, pulmonary hemorrhage), inadequate abx (MTB, fungi, virus, PCP), other source of infection, drug fever.

Am J Resp CCM. 153: 1711-1725, 1995.