Hospital-acquired pneumonia (HAP) Flashcards
What is HAP?
HAP is an acute lower respiratory infection that is acquired after at least 48 hours of admission to hospital and is not intubating at the time of admission.
Causes of HAP
Most cases are caused by bacteria especially aerobic gram-negative bacilli, such as pseudomonas aeruginosa, E.coli, Klebsiella pneumonia and acinetobacter species.
How do patients present with HAP?
Patients usually present with a combination of fever (or hypothermia), leukocytosis (or leukopenia), increased tracheal secretions and poor oxygenation.
Classification of HAP
Early-onset HAP occurs within 4-5 days of admission and is usually caused by antibiotic-sensitive community organisms.
Late-onset infection (> 5 days) is more likely to be caused by antibiotic-resistant hospital pathogens.
Enterobacteria causes of HAP
Enterobacteria: E. coli, Klebsiella sp., Enterobacter sp., Serratia sp.
GI tract commensals
Translocate to the respiratory tract in hospitalised patients with multiple underlying morbidities.
May be multi-drug resistant.
S.aureus in HAP
Staphylococcus aureus (including MRSA)
Gram-positive coccus
Upper respiratory tract commensal
Aspiration of upper respiratory secretions into the lower respiratory tract can result in pneumonia
Pseudomonas aeruginosa
Gram-negative bacillus.
Innately resistant to many antibiotics.
Can colonise moist areas (both inpatients and in the environment). Immunosuppressed or those previously exposed to antibiotics particularly at risk.
Gram-negative causes of HAP
Environmental Gram Negatives: Acinetobacter sp., Stenotrophomonas maltophilia.
Multi-drug resistant and difficult to treat.
Usually, cause infection in significantly immunosuppressed or ventilated patients.
How do pathogens get in the lungs in HAP?
The most common introduction of bacteria into alveoli is micro-aspiration of oropharyngeal pathogens or leakage of secretions containing bacteria around an endotracheal tube cuff.
Other pathways include macro-aspiration (e.g of vomit), inhalation, haematogenous spread and direct inoculation (thoracentesis)
Important risk factors of HAP
ICU stay, mechanical ventilation
Prolonged hospital or ICU stay (with increased risk of multi- drug resistant organisms)
Severe underlying illness, multiple co-morbidities
Underlying respiratory disease e.g. COPD, asthma
Abdominal surgery, vomiting/aspiration
Sources of pathogen in HAP
Dyspnoea Productive cough Fever Chest pain Asymmetrical expansion of the chest Diminished resonance Egophony Whisper pectoriloquy Crackles or rhonchi Tachycardia Malaise/anorexia
Investigations of HAP
CXR- opacity, blurring of diaphragm or heart border
WBC count with differential- elevated or decreased WBC count
Pulse oximetry- low value
Culture of lower respiratory tract sample.
ABG- low PO2
Diagnostic thoracentesis- positive gram stain or culture
CT chest- may shown an opacity
CRP- raised
Procalcitonin- raised
Differentials of HAP
Cardiogenic pulmonary oedema. ARDS. Pleural effusion. PE Atelectasis Pulmonary haemorrhage Lung cancer
Management of HAP
Prompt, correct and adequate therapy is critical for the treatment of HAP.
Regimens are based on whether RFs are present for MDR.
These RFs are:
antibiotic therapy in the preceding 90 days.
Septic shock at time of VAP
ARDS preceding the VAP
Current admission to hospital of 5 or more days.
Treatment if RFs are present in HAP
Combination therapy with broad-spectrum agents is indicated.
