S J Pinto | PubMed Health

PubMed2000

Ventilator-associated pneumonia.

Ventilator-associated pneumonia is a common complication in intensive care units, occurring in 9% to 24% of patients intubated for longer than 48 hours. Because of this large disease burden and the resultant attributable morbidity and mortality, there is great interest in accurately diagnosing, treating, and preventing this complication. More severely ill patients tend to develop ventilator-associated pneumonia, and identified risk factors include prolonged mechanical ventilation, reintubation after failed extubation, and a few other clinical variables. The efficacy of diagnostic and preventive strategies is somewhat controversial. Diagnosis by invasive methods requires a considerable commitment of resources but can potentially reduce cost of care; however, mortality benefit from this approach has not been demonstrated. As such, in most institutions, ventilator-associated pneumonia is best diagnosed using traditional clinical criteria. Prompt administration of appropriate antibiotics seems to be the only intervention that alters outcome once the diagnosis is established. Several strategies seem to reduce pneumonia incidence; however, mortality and cost benefits have yet to be convincingly shown.

Anti-Bacterial Agents↗

PubMed1998

The electron microscopic morphology of the common carotid artery in rats.

The common carotid arteries of normal adult rats were investigated electron-microscopically after tannic acid fixation. This fixation technique yields a better demonstrability of the structures of the connective tissue, the basal laminae and the surface coat of the cell membrane. The common carotid artery represents a vessel of the elastic type. The intima consists of an endothelium and a narrow gap of connective tissue (0.1-1 micron) which contains single collagenous fibrils and small elastic structures. This space is only occasionally as wide as 3 microns, especially beneath gaps of the internal elastic membrane. In these areas, single cells and structures of densely packed filaments are additionally observed which can neither be attributed to collagenous fibrils nor to elastic fibres. The intima is demarcated from the outside by an internal elastic membrane (1 micron) which shows a number of gaps. The media exhibits 3 to 4 elastic membranes without gaps. Smooth muscle cells of the contractile type stretch in an oblique direction between these membranes, i.e. they are not arranged in a circular or spiral manner. Most of their process-rich ends are inserted directly into the elastic material and not via a basal lamina. Processes from these smooth muscle cells, collagenous fibrils and elastic fibres are seen in the intercellular spaces. The muscle cells are occasionally interlinked by gap junctions. The basal lamina does not surround the muscle cells continuously. The adventitia contains bundles of collagenous fibrils, fibrocytes, a few small vessels and nerves with a perineuronal envelope. Nerves could not be demonstrated in the media. The oblique course of the smooth muscle cells and the insertion into the elastic membranes indicate that these cells do not predominantly contribute to changes in the width of the lumen but also serve the stabilisation and resetting of the elastic membranes. Contraction is probably induced by an opening of stretch-dependent Ca2+ channels. Due to the interlinkage with gap junctions, the muscle cells of one layer respond as a functional unit. Our findings provide a morphological basis for elucidating commonly encountered changes, such as smooth muscle migration through a normally interrupted inner elastic lamina.

Animals↗