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Aetiology of pneumonia following isolated closed head injury
A Cazzadori1, G Di Perri, S Vento
1Bronchoscopy Unit, University of Verona, Italy.
Abstract:
Patients undergoing mechanical ventilation (MV) after an isolated closed head injury (ICHI) have often been found to develop hospital-acquired pneumonia (HAP) well before subjects who require MV for different reasons. In a prospective study of patients receiving MV after an ICHI. 38 subjects (out of 65 with clinically suspected HAP) had a bacteriological diagnosis established on the basis of correspondence between cultures made from bronchoalveolar lavage and protected specimen brush (with quantitative thresholds of 10(4) and 10(3) cfu ml-1, respectively). Patients were separated according to the time of onset of HAP, with 20 subjects who developed HAP within 4 days of the start of MV (early onset pneumonia, EOP) and 18 subjects who developed HAP after the fourth day (late onset pneumonia, LOP). In those who had LOP, an expected spectrum of organisms was found, with Gram-negatives (especially Pseudomonas sp.) accounting for the majority of isolates. However, in EOP cases, Gram-positive bacteria (especially Staphylococcus sp. and Streptococcus pneumoniae) were found to largely predominate (P = 0.0000026). This confirms the high incidence of staphylococcal pneumonia in neurosurgery patients, and also provides evidence that the vast majority of such staphylococcal pneumonia are EOP. Unlike most previous reports, the microbiological findings from the present study suggest that a cut-off point of 4 days successfully distinguishes between EOP and LOP. Since these two clinical entities differ significantly in terms of pathogenesis and aetiology, preventive measures and therapeutical protocols have to be tailored accordingly.
Insights
Patients with head injuries on mechanical ventilation (MV) often develop hospital-acquired pneumonia (HAP). Early-onset pneumonia (EOP) is frequently caused by Gram-positive bacteria, unlike late-onset pneumonia (LOP).
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Neurosurgery
Background:
- Hospital-acquired pneumonia (HAP) is a common complication in patients requiring mechanical ventilation (MV) after isolated closed head injury (ICHI).
- The timing of HAP onset may indicate different etiological and pathogenic factors.
Purpose of the Study:
- To investigate the microbiological differences between early-onset pneumonia (EOP) and late-onset pneumonia (LOP) in patients with ICHI requiring MV.
- To determine if a 4-day cutoff effectively distinguishes EOP from LOP in this patient population.
Main Methods:
- Prospective study of 65 patients with clinically suspected HAP after ICHI and MV.
- Bacteriological diagnosis in 38 subjects using bronchoalveolar lavage and protected specimen brush cultures.
- Patients categorized into EOP (within 4 days of MV) and LOP (after 4 days).
Main Results:
- Gram-positive bacteria, particularly Staphylococcus and Streptococcus pneumoniae, predominated in EOP (20 cases).
- Gram-negative bacteria, especially Pseudomonas, were prevalent in LOP (18 cases).
- The 4-day cutoff significantly distinguished between EOP and LOP (P = 0.0000026).
Conclusions:
- EOP in ICHI patients on MV is often caused by Gram-positive bacteria, notably Staphylococcus.
- LOP typically involves Gram-negative organisms, consistent with other MV populations.
- Differentiating EOP and LOP based on a 4-day threshold is crucial for tailoring preventive and therapeutic strategies.