Hospital-Acquired Pneumonia
Pneumonia developing ≥48 hours after hospital admission, not incubating at time of admission. Associated with Gram-negative organisms and MRSA, with higher mortality than CAP.
Key Facts
Definition: pneumonia developing ≥48 hours after hospital admission Early-onset (<5 days): similar organisms to CAP (S. pneumoniae, H. influenzae); late-onset (≥5 days): Gram-negatives, Pseudomonas, MRSA Risk factors: mechanical ventilation (VAP), reduced consciousness, NG tube, PPI/H2RA use, prolonged hospitalisation, immunosuppression NICE NG139: first-line for non-severe HAP is co-amoxiclav 625mg TDS PO for 5 days Severe/late-onset HAP: piperacillin-tazobactam 4.5g IV TDS or meropenem 1g IV TDS ± vancomycin (if MRSA risk) VAP (ventilator-associated pneumonia): develops ≥48 hours after intubation; incidence 10-20% of ventilated patients Mortality: 20-50% (significantly higher than CAP); HAP is the leading cause of death from nosocomial infection Prevention: hand hygiene, head-of-bed elevation, oral care, PPI review, ventilator care bundles
Overview
Key Facts
Hospital-acquired pneumonia (HAP) is a lower respiratory tract infection that develops ≥48 hours after hospital admission and was not incubating at the time of admission. It is the second most common nosocomial infection and the leading cause of death from hospital-acquired infection.
Epidemiology
- Affects 0.5-1% of all hospital inpatients
- VAP affects 10-20% of mechanically ventilated patients
- Mortality: 20-50% (varies with organism and patient factors)
- Adds 7-10 days to hospital stay
- Estimated £1-2 billion annual cost to NHS
Aetiology
Early-onset HAP (<5 days):
- Streptococcus pneumoniae
- Haemophilus influenzae
- Staphylococcus aureus (MSSA)
Late-onset HAP (≥5 days):
- Pseudomonas aeruginosa
- Enterobacteriaceae (E. coli, Klebsiella)
- Acinetobacter baumannii
- MRSA
- Stenotrophomonas maltophilia
- Anaerobes
Pathophysiology
- Micro-aspiration of colonised oropharyngeal or gastric secretions is the primary mechanism
- Hospital environment promotes oropharyngeal colonisation with Gram-negative organisms
- Impaired mucociliary clearance (intubation, sedation, post-operative)
- Biofilm formation on endotracheal tubes (VAP)
- Reduced immune defences (critical illness, immunosuppression, malnutrition)
Clinical Presentation
Typical Presentation
- New or worsening cough with purulent sputum
- Fever >38°C or hypothermia
- New radiographic infiltrate or consolidation
- Increasing oxygen requirements
- Rising inflammatory markers (CRP, WCC)
- Deterioration in general condition
Clinical Signs
- Pyrexia or hypothermia
- Tachypnoea, tachycardia
- New focal chest signs: crackles, bronchial breathing
- Increased volume/purulence of tracheal secretions (in ventilated patients)
Diagnostic Criteria (Clinical)
- New radiographic infiltrate PLUS at least 2 of: fever >38°C, leucocytosis/leucopenia, purulent secretions
Red Flags
- Sepsis (NEWS2 ≥5 or clinical concern)
- Requirement for new or increased ventilatory support
- Multi-organ dysfunction
- Known MDR organism colonisation
- Rapidly progressive infiltrates
- Immunocompromised patient
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Pulmonary oedema | Bilateral infiltrates, raised BNP, fluid overload | BNP, echo, fluid balance |
| Pulmonary embolism | Pleuritic pain, wedge-shaped infarct, risk factors | CTPA |
| Atelectasis | Post-operative, reduced breath sounds at base, no fever initially | CXR |
| ARDS | Bilateral infiltrates, PaO₂/FiO₂ <300, no cardiac cause | Berlin criteria, echo |
| Aspiration pneumonitis | Witnessed aspiration, rapid onset, chemical inflammation | Clinical, CXR |
| Drug-induced pneumonitis | Temporal relationship with drug (amiodarone, methotrexate, nitrofurantoin) | Drug history, HRCT |
| Pulmonary haemorrhage | Haemoptysis, dropping Hb, diffuse infiltrates | FBC, CT, bronchoscopy |
Diagnosis / Investigation
Bedside
- Pulse oximetry: new oxygen requirement or increasing FiO₂
- NEWS2 score: sepsis screening
- Sputum sample/tracheal aspirate: MC&S (before antibiotics)
Bloods
- FBC: leucocytosis or leucopenia
- CRP/procalcitonin: elevated; procalcitonin may guide antibiotic duration
- U&Es: renal function (antibiotic dosing)
- Blood cultures x2: before antibiotics
- Lactate: if sepsis suspected
Imaging
- Chest X-ray: new infiltrate, consolidation, cavitation
- CT chest: if CXR equivocal or non-resolving
Special Tests
- Bronchoalveolar lavage (BAL): gold standard for VAP diagnosis (≥10⁴ CFU/mL significant)
- Non-directed bronchial lavage: alternative if bronchoscopy not available
- Respiratory viral PCR: exclude viral cause
- Galactomannan/beta-D-glucan: if fungal infection suspected (immunocompromised)
Management
Non-pharmacological
- Oxygen therapy (target SpO₂ 94-98% or 88-92% if COPD)
- IV fluids and nutritional support
- VTE prophylaxis
- Chest physiotherapy and early mobilisation
- Source control (remove/replace lines, NG tubes)
Pharmacological
NICE NG139 empirical antibiotics:
Non-severe HAP (early-onset, no MDR risk):
- Co-amoxiclav 625mg TDS PO for 5 days
- Penicillin allergy: doxycycline 200mg then 100mg OD
Severe or late-onset HAP (MDR risk):
- Piperacillin-tazobactam 4.5g IV TDS or meropenem 1g IV TDS
- Add vancomycin 15-20mg/kg IV BD (trough-guided) if MRSA risk
- Guided by local antibiogram and previous culture results
VAP:
- Piperacillin-tazobactam or meropenem + anti-MRSA cover (vancomycin/linezolid)
- De-escalate based on culture results within 48-72 hours
- Duration: 7-8 days (shorter courses non-inferior; longer if Pseudomonas)
Surgical/Interventional
- Chest drain for empyema
- Percutaneous or surgical drainage of lung abscess
Referral Criteria
- Microbiology advice for MDR organisms
- ICU if respiratory failure requiring escalation
- Infectious diseases input for complex/resistant infections
Prognosis
- HAP mortality: 20-50% (higher for VAP, MDR organisms, immunocompromised)
- VAP mortality: 25-50%
- Pseudomonas/Acinetobacter HAP carries highest mortality (~40-60%)
- Appropriate early antibiotics reduce mortality significantly
- Delays in appropriate antibiotic therapy increase mortality by 20-30%
- VAP prevention bundles reduce incidence by 40-50%
- Prolonged hospitalisation: average additional 7-10 days
- Increased risk of readmission and subsequent infections
Other Relevant Information
VAP Prevention Bundle
| Intervention | Evidence |
|---|---|
| Head-of-bed elevation 30-45° | Reduces aspiration |
| Daily sedation hold and assessment of readiness to extubate | Reduces ventilation days |
| Oral chlorhexidine decontamination | Moderate evidence |
| Stress ulcer prophylaxis review | Balance bleeding vs infection risk |
| DVT prophylaxis | Prevents PE |
| Subglottic secretion drainage | Reduces VAP incidence |
HAP Antibiotic Summary
| Severity | First-line | Duration |
|---|---|---|
| Non-severe, early-onset | Co-amoxiclav 625mg TDS PO | 5 days |
| Severe / late-onset | Pip-taz 4.5g IV TDS | 5-7 days |
| VAP | Pip-taz or meropenem ± vancomycin | 7-8 days |
| MRSA risk | Add vancomycin or linezolid | Per MC&S |