Re-evaluation of Pneumonia Requiring Admission to an Intensive Care Unit: a Prospective Study

Background: Appropriate treatment of severe community and hospital acquired pneumonias requiring admission to a medical intensive care unit depends on knowledge of the likely aetiological agents in any community. Little is known about the pattern and outcome of patients with such pneumonias in Saudi Arabia.

Methods: In a prospective study 113 patients with pneumonia were investigated in the medical intensive care unit at King Khalid University Hospital, Riyadh, Saudi Arabia between September 1991 and December 1992. The diagnosis was established by microscopy and culture of sputum, blood culture, or serological examination. A standard proforma was used to collect demographic, clinical, and laboratory data.

Results: A microbiological diagnosis was made in 80% of the cases with a single pathogen accounting for 69% of the isolates and multiple pathogens for 11%. Pseudomonas aeruginosa was the most common infecting agent (16%), followed by Streptococcus pneumoniae (12%), Staphylococcus aureus (9%), and Mycobacterium tuberculosis (8%). Pneumonia due to Legionella pneumophilia was diagnosed in three patients and infection due to Mycoplasma pneumoniae in two. These five cases were identified by serological examination. Gram negative rods were the predominant pathogens in both community and hospital acquired pneumonia. The aetiology of pneumonia was not identified in 20% of cases. The overall mortality was 37%. Patients with hospital acquired pneumonia had a higher mortality than those with a community acquired pneumonia. Similarly, a high mortality was found in patients who had a serious underlying disease, abnormal mental state, diastolic blood pressure < 60 mm Hg, blood urea > 7 mmol/l, abnormal liver function tests, serum albumin < 30 g/l, those who required mechanical ventilatory support, and those with APACHE II scores > 20.

Conclusions: This study highlights two major findings which differ from previous reports on the aetiology of pneumonia. Firstly, Gram negative rods were the predominant pathogens in community acquired pneumonia and secondly, M tuberculosis was an important cause of pneumonia in these patients, indicating that tuberculous pneumonia should be considered in the differential diagnosis of pneumonia in Saudi Arabia.