Multifactorial analyses in the diagnosis of pneumonia arising in the surgical intensive care unit.

The diagnosis of ventilator-associated pneumonia in the surgical intensive care unit continues to be problematic. The majority of intensive care units use clinical criteria based on chest x-ray; fever; leukocytosis; alterations in the pulse oximeter observations; the need to alter modes and amounts of ventilatory support; and more specific microbiologic studies, such as appropriate sputum, Gram stain, and culture to identify pneumonia. Diagnosing pneumonia based on clinical criteria alone is often difficult and inaccurate, which may lead to inappropriate use and choice of antibiotics. Invasive diagnostic techniques, such as protected specimen brush and bronchoalveolar lavage, provide an important microbiologic diagnosis. However, the cost and inconvenience limit broad usage. Furthermore, those results that return positive are often too late to dictate the need for, or direction of, therapy. Our use of a "pneumonia grid" may help identify patients likely to have a poor outcome. Until a readily available and cost-effective diagnostic study for pneumonia is developed, clinical criteria remain vital in routine practice.

Immunologic responses to pneumonia.

Pneumonia in the critically ill surgical patient often results from the bombardment of a previously normal pulmonary system with therapeutic foreign bodies, hospital pathogens, and impairment of the host defenses. Despite its long history as a significant clinical problem, a woefully inadequate amount of study has been directed toward therapy. We created an experimental model of a differential pulmonary infection using a strain of Klebsiella pneumoniae. We then compared the progressively affected pneumonic process versus the normal parenchyma. We measured neutrophil and monocyte complement antibody receptor expression and monocyte and macrophage class II major histocompatibility antigens (HLA-DR) via percent of cells and mean fluorescent intensity outcomes from flow cytometry. The main difference between infected versus noninfected tissues was monocyte DR expression, which was consistently depressed in cells from infected parenchyma. What follows is a discussion of the implications of this work as well as other work in the immunology of pneumonia and cytokine expression. Possible therapeutic modalities are included.