Role of selective digestive decontamination (SDD) in the prevention of nosocomial pneumonia (NP): is gastric decontamination necessary?

Ventilator-associated pneumonia: clinical significance and implications for nursing

Pneumonia is the second most common nosocomial infection in the United States and the leading cause of death from nosocomial infections. Intubation and mechanical ventilation greatly increase the risk of bacterial pneumonia. Ventilator-associated pneumonia (VAP) occurs in a patient treated with mechanical ventilation, and it is neither present nor developing at the time of intubation; it is a serious problem--with significant morbidity and mortality rates. Aspiration of bacteria from the oropharynx, leakage of contaminated secretions around the endotracheal tube, patient position, and cross-contamination from respiratory equipment and health care providers are important factors in the development of VAP. Nurses caring for patients treated with mechanical ventilation must recognize risk factors and include strategies for reducing these factors as part of their nursing care. This article summarizes the literature related to VAP: its incidence, associated factors, diagnosis, and current therapies, with an emphasis on nursing implications in the care of these patients.

Sinusitis in mechanically ventilated patients and its role in the pathogenesis of nosocomial pneumonia

Nosocomial sinusitis is a complication of endotracheal intubation and mechanical ventilation in critically ill patients. Its incidence is often underestimated because of a lack of clinical signs. It is suspected in patients with nasal discharge or unexplained fever. Its diagnosis is based on radiological examination, by radiograph or computed tomography scan, and microbiological cultures of maxillary sinus aspirate. Maxillary sinusitis is often associated with involvement of the sphenoid, ethmoid, and/or frontal sinuses. Its incidence varies greatly according to diagnostic criteria and the population studied. Infectious sinusitis is less frequent than noninfectious sinusitis, occurring in 20 to 30% of patients intubated for at least seven days. Its incidence is higher in nasotracheally than in orotracheally intubated patients. Other risk factors include nasogastric tubes and head trauma. The main causative agents are gram-negative bacilli, primarily Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae, but Staphylococcus aureus and yeasts are also common. Patients with nosocomial sinusitis are more likely to develop pneumonia than those without sinusitis. The sinus provides a bacterial reservoir from which organisms may seed the tracheobronchial tree. The association of sinusitis and pneumonia is mainly due to Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii. The treatment of sinusitis is based on the removal of all nasal tubes, topical decongestants, and maxillary sinus drainage and lavage. The role of intravenous antibiotics is controversial.

Prevention of nosocomial pneumonia

Prevention of nosocomial pneumonia becomes an achievable goal only to the extent that the mechanisms of infection are known. It is likely that there is variation among microorganisms, patients, type of care and intensive care, and practices that determines the relative efficacy of preventive measures. Certain procedures appear to be universally required and include adequate reprocessing of ventilation equipment and infection control measures in patient care. In contrast, many factors may affect the role of the stomach as a cause of nosocomial pneumonia, including enteral feeding procedures and gastric acidity. Differences in results between studies of preventive measures may reflect uncontrolled practice factors, which make the measures either more or less important. Selective decontamination of the digestive tract is a measure with potentially serious consequences, primarily cost and microbial resistance, and should be undertaken with care probably in selected high-risk patients. Other recommendations such as the use of sucralfate, which is effective in prevention of bleeding without clear side effects, are probably worth instituting based on existing evidence. The primary need may be for better reprocessing of equipment or hand washing and sterile gloves, or it may be several changes at once. Certainly an array of preventive measures is necessary, and there is probably no single procedure likely to solve such a complex problem. Use of the collective findings of many investigators needs to be made and strategies applied to each patient and setting. There has been a marked increase in our knowledge of nosocomial pneumonia, and effective measures for prevention are available. Application of these measures widely should reduce the frequency of respiratory complications. The microbiologic tools to compare bacterial isolates have been developed, and the course of events preceding infection of the patient can be demonstrated. The role of equipment, environment, other patients, personnel, colonization sites, and other factors can now be examined. Future studies should control for the many known factors that may predispose to nosocomial pneumonia to make the results meaningful. This would include definition of infection, patient risk factors, identification of microorganisms, details of enteral nutrition, type of stress ulcer prophylaxis, exposure to antimicrobial agents, and institutional resistance patterns. In some studies, surveillance cultures and molecular epidemiology techniques would be required. Large controlled multicenter studies are necessary to determine the significance of the results of promising smaller studies.(ABSTRACT TRUNCATED AT 400 WORDS)

[Selective digestive decontamination in patients under reanimation]

Nosocomial infections increase morbidity and mortality in hospitalized patients. ICU patients are at high risk of sustaining them, due to the high rate of invasive procedures and their poor health state. Conventional methods for decreasing the incidence of infection in ICU patients include handwashing, catheter care, strict antibiotic policy, and reduction of environmental sources of infection. Despite these measures, the colonization in these patients is always high, because of the presence of pathogens in the own patients' flora. Nosocomial pneumonia which is a major cause of mortality in ICU patients arises from retrograde colonization of the lung by pathogens originating from oro-pharyngeal and gastric secretions. Since 1984, selective decontamination of the digestive tract (SDD) has been advocated in ICUs to prevent from bacterial and fungal gastrointestinal/oropharyngreal colonization, nosocomial infection, subsequent multiple organ failure (MOF) and death. The SDD regimen is usually an extemporaneously prepared suspension of antimicrobial agents. Appropriate antibiotics for this regimen should ideally be nonabsorbable, to prevent from the development of resistant pathogens and avoid systemic toxicity. They should also be able to selectively eliminate enterobacteriaceae and yeasts, without decreasing the protective anaerobic flora. The most used combination is a suspension of colistin, amphotericin B and aminoglycoside, administered four times day through the nasogastric tube, in association with a paste consisting of 2 p. 100 colistin/amphotericin B/aminoglycoside, applied to the oropharynx. A parenteral antibiotic is also often co-administered during the first four days to prevent from early infections until the SDD regimen reaches its full effect; cefotaxime is usually used for this. SDD significantly decreases colonization rates in the oropharynx, gastrointestinal (GI) tract and trachea. This effects is primarily attributable to a decrease of Gram-negative bacilli (GNB) and yeasts, although several studies also reported decreased isolates of Gram-positive cocci (GPC). Oropharyngeal and GI colonization significantly decrease after four days of such a regimen, but tracheal decontamination in uncertain. Several studies recognized an emergence of GPC during or after SDD and resistance occurrence in GNB (especially against aminoglycosides). Recolonization occurs rapidly, about 4 to 8 days after the discontinuation of SDD. SDD decreases significantly the nosocomial infections, especially Gram-negative pneumonia. This benefit is most obvious in trauma patients, severely burned patients and after orthopic liver transplantation. Several studies reported a significant decrease in the overall rate of infections, especially extrapulmonary infections, including blood, urinary tract, wounds, abdominal, and catheter related infections. Despite a major decrease in infection rates with SDD, most studies did not show lowered mortality rates.(ABSTRACT TRUNCATED AT 400 WORDS)