Hospital-Acquired and Ventilator-Associated Pneumonia (HAP/VAP)
Pneumonia developing ≥48 h after hospital admission or ≥48 h after intubation.
Also known as: HAP, VAP, nosocomial pneumonia, hospital-acquired pneumonia, ventilator-associated pneumonia
Overview
HAP: pneumonia occurring ≥48 hours after hospital admission not incubating at admission. VAP: pneumonia developing ≥48 hours after endotracheal intubation. Caused by hospital-flora organisms with frequent multidrug resistance.
Epidemiology
HAP is the second most common nosocomial infection. VAP develops in 10-20% of patients ventilated >48 h, with attributable mortality up to 13%. Resistant pathogens (MRSA, Pseudomonas, Acinetobacter, ESBL Enterobacterales) increasingly common.
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Risk factors
- Mechanical ventilation (single greatest risk for VAP)
- Prior IV antibiotic exposure (especially within 90 days)
- Hospitalization ≥5 days, ICU stay
- Aspiration risk, impaired consciousness, NG tube
- Reintubation, supine positioning, inadequate cuff pressure
- Immunocompromise, chronic lung disease
- Recent influenza or other respiratory viral infection
Pathophysiology
Aspiration of oropharyngeal secretions colonized with hospital flora past an endotracheal tube cuff. Biofilm on the ETT serves as a reservoir. Common pathogens: Pseudomonas aeruginosa, Staphylococcus aureus (including MRSA), Klebsiella, E. coli, Enterobacter, Acinetobacter, Stenotrophomonas. Anaerobes are LESS important than previously thought.
Clinical presentation
Symptoms
- New or worsening dyspnea, purulent tracheobronchial secretions
- Fever, chills
- Mental status change (especially in elderly)
- Often subtle in ventilated/sedated patients — recognize by changes in vent parameters
Signs / physical exam
- New fever or hypothermia, leukocytosis or leukopenia
- Hypoxia, increasing FiO2 or PEEP requirements
- Purulent endotracheal aspirate
- New crackles or focal lung findings
Differential diagnosis
- Atelectasis — Post-op or immobilized; rapid resolution with recruitment; no leukocytosis or fever pattern
- Pulmonary embolism — Acute dyspnea/hypoxia, elevated D-dimer, CTPA; RV strain on echo
- ARDS — Bilateral infiltrates within 1 week of insult, PaO2/FiO2 ≤300, no cardiac etiology
- Pulmonary edema (cardiogenic or volume overload) — Bilateral, gravity-dependent, responsive to diuresis; elevated BNP, S3
- Aspiration pneumonitis (chemical) — Witnessed aspiration; rapid radiographic improvement within 24-36 h without antibiotics
- Drug-induced lung injury — Temporal relation to amiodarone, nitrofurantoin, methotrexate, immune checkpoint inhibitors
- Tracheobronchitis without pneumonia — Purulent secretions without new infiltrate; signs and inflammatory markers less pronounced
Diagnostic workup
Diagnostic criteria
Clinical: new or progressive radiographic infiltrate + ≥2 of (fever >38°C, leukocytosis/leukopenia, purulent secretions, hypoxemia, increasing ventilator support). Microbiologic confirmation strongly preferred to guide therapy.
Labs
- CBC, BMP, lactate, blood cultures × 2
- Lower respiratory tract sampling BEFORE antibiotic change: endotracheal aspirate, bronchoalveolar lavage (BAL), or mini-BAL with quantitative culture (≥10⁴ CFU/mL BAL, ≥10⁶ tracheal aspirate)
- Multiplex PCR panels for rapid pathogen identification
- Procalcitonin trend can guide de-escalation/duration
Imaging
- CXR — new or progressive infiltrate (essential for diagnosis)
- CT chest if complicated (cavitation, empyema, abscess) or radiograph indeterminate
Diagnostic algorithm
| Risk Tier | Empiric Coverage |
|---|---|
| HAP, no risk factors for MDR or mortality | Single agent active against MSSA + Pseudomonas (e.g., piperacillin-tazobactam, cefepime, levofloxacin) |
| HAP with MRSA risk OR high mortality risk | Antipseudomonal beta-lactam + MRSA coverage (vancomycin or linezolid) |
| VAP — all patients | Antipseudomonal beta-lactam + MRSA coverage; add second antipseudomonal if high resistance risk or septic shock |
| Known prior MDR pathogen | Tailor to prior isolate and antibiogram |
Treatment
First-line
- Empiric therapy targets MRSA and Pseudomonas in most VAP and in HAP with risk factors
- Antipseudomonal beta-lactam: piperacillin-tazobactam 4.5 g IV q6h (extended infusion), cefepime 2 g IV q8h, ceftazidime 2 g IV q8h, meropenem 1 g IV q8h, imipenem
- MRSA coverage: vancomycin (trough 15-20 mg/L) OR linezolid 600 mg IV q12h
- Add second antipseudomonal (aminoglycoside — amikacin/gentamicin/tobramycin — or fluoroquinolone — ciprofloxacin/levofloxacin) ONLY if high risk of resistance, septic shock, or local resistance >10-20% to monotherapy
- Tailor based on local antibiogram and prior cultures within 90 days
Second-line / adjunct
- De-escalate to narrowest agent once culture and sensitivities return; stop MRSA coverage if MRSA not isolated
- Duration: 7 days for most HAP/VAP (ATS/IDSA 2016) — even with non-fermenting GNRs like Pseudomonas, provided clinical response
- Difficult organisms: Acinetobacter — ampicillin-sulbactam (high dose), polymyxins, cefiderocol; ESBL — carbapenem; CRE — ceftazidime-avibactam, meropenem-vaborbactam, cefiderocol; Stenotrophomonas — TMP-SMX or levofloxacin
- Source control: drain empyema, remove infected devices
- Adjuncts to prevent VAP: head of bed 30-45°, daily sedation interruptions and spontaneous breathing trials, oral chlorhexidine (controversial), subglottic suction ETTs, early mobilization, stress ulcer prophylaxis only when indicated
Complications
- Septic shock, multiorgan dysfunction
- ARDS, prolonged mechanical ventilation, tracheostomy
- Empyema, lung abscess, necrotizing pneumonia (especially S. aureus, Klebsiella)
- Antibiotic-associated complications: C. difficile, AKI, antimicrobial resistance
- Death — attributable mortality ~13% for VAP
PANCE pearls
- HCAP (healthcare-associated pneumonia) was eliminated from ATS/IDSA guidelines in 2016 — it overestimated resistance and led to overtreatment.
- Quantitative BAL has lower false-positive rate than endotracheal aspirate and can support de-escalation.
- 7-day course is appropriate for most HAP/VAP including Pseudomonas (PneumA trial), provided clinical response.
- Procalcitonin algorithms can shorten antibiotic duration without worsening outcomes (SAPS trial).
- Stenotrophomonas maltophilia — resistant to most beta-lactams and carbapenems; first-line is TMP-SMX.
References
- ATS/IDSA 2016 — Management of Adults with Hospital-acquired and Ventilator-associated Pneumonia (Kalil et al., Clin Infect Dis 2016)
- PneumA Trial — Comparison of 8 vs 15 Days of Antibiotic Therapy for VAP (Chastre et al., JAMA 2003)
- SAPS Trial — Efficacy and Safety of Procalcitonin Guidance in Reducing Duration of Antibiotic Treatment in Critically Ill Patients (de Jong et al., Lancet Infect Dis 2016)
- SHEA/IDSA 2022 — Strategies to Prevent Ventilator-Associated Pneumonia, Ventilator-Associated Events, and Nonventilator Hospital-Acquired Pneumonia (Klompas et al., Infect Control Hosp Epidemiol 2022)
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