Nosocomial pneumonia in intubated patients given sucralfate as compared with antacids or histamine type 2 blockers. The role of gastric colonization

Nosocomial pneumonia in patients receiving continuous mechanical ventilation. Prospective analysis of 52 episodes with use of a protected specimen brush and quantitative culture techniques

Epidemiologic studies of nosocomial bacterial pneumonia in patients requiring mechanical ventilation have been limited because of the poor reliability of diagnosis procedures in this setting. To determine prognostic and descriptive factors of ventilator-associated (V-A) pneumonia, we prospectively studied 567 patients who had been receiving mechanical ventilation for more than 3 days in our unit. Fiberoptic bronchoscopy using a protected specimen brush (PSB) was performed on each patient suspected of having pneumonia because of the presence of a new pulmonary infiltrate and purulent tracheal secretions. The diagnosis of V-A pneumonia was retained only if PSB specimens yielded greater than 10(3) cfu/ml of at least one microorganism, unless this result was established to be a false positive result on follow-up. V-A pneumonia developed in 49 patients for a total of 52 episodes (9%). The actuarial risk of V-A pneumonia was 6.5% at 10 days, 19% at 20 days, and 28% at 30 days of ventilation. Patients with pneumonia were significantly older (65 versus 57 yr of age, p less than 0.01) and more frequently had severe underlying illnesses (24 versus 10%, p less than 0.01) than did patients without pneumonia. A total of 84 microorganisms (51 gram-negative and 33 gram-positive) were isolated in significant concentrations from PSB specimens. Pseudomonas aeruginosa and Staphylococcus aureus were involved in 31 and 33% of these pneumonias, respectively. Forty percent of all specimens yielded a polymicrobial flora with more than one potential pathogen.(ABSTRACT TRUNCATED AT 250 WORDS)

Reducing the risk of aspiration pneumonitis

Regurgitation of gastric contents with subsequent aspiration into the lungs contributes significantly to morbidity and mortality in surgical and nonsurgical patients. The consequences of aspiration pneumonitis depend on the volume and the acidity of the aspirate, and the presence of particulate and bacteria in the aspirate. The occurrence of aspiration pneumonitis may be prevented by correction of risk factors, careful monitoring, and appropriate airway management. The goal of aspiration pneumonitis prophylaxis is to minimize pulmonary complications by controlling risk factors for gastric regurgitation, which include gastric pH less than or equal to 2.5, gastric volume greater than 25 mL, lower esophageal sphincter incompetence, and delayed peristalsis. Prophylactic techniques include nasogastric decompression, acid neutralization, acid suppression, and increased gastric peristalsis. The ability of drugs to alter risk factors does not guarantee that aspiration will not occur, but it does reduce the likelihood of secondary respiratory complications. The ideal prophylactic agent should consistently reduce all risk factors, produce a prompt and sustained response, and possess few adverse effects and drug interactions.

Patterns and routes of tracheobronchial colonization in mechanically ventilated patients. The role of nutritional status in colonization of the lower airway by Pseudomonas species

Tracheobronchial colonization by Gram-negative bacteria is common in mechanically ventilated patients. Pseudomonas sp are commonly isolated from the lower airways. We hypothesized that Pseudomonas sp would preferentially colonize the lower airway and would be more common in patients with poor nutritional status. We serially collected 75 pairs of upper and lower respiratory tract cultures from 14 patients treated with mechanical ventilation for at least one week, examined patterns of airway colonization and routes of bacterial entry for Pseudomonas sp and other enteric Gram-negative bacteria (EGNB), and related these findings to host-associated factors, including nutritional status. Pseudomonas sp were the most common species isolates taken from the lower airway, found in nine of 14 patients and in 41.3 percent of all cultures. In contrast to other EGNB, Pseudomonas sp were found significantly (p less than or equal to 0.05) more often in the tracheobronchial tree (31 of 75 cultures) than in the oropharynx (18 of 75 cultures). Primary colonization of the lower airway by Pseudomonas sp was found in four patients, while other EGNB never followed this pattern when subjects were studied with cultures taken every third day. A host-related factor related to lower airway colonization by Pseudomonas species was poor nutritional status, assessed by a multifactorial index (p less than or equal to 0.01). We conclude that in mechanically ventilated patients, Pseudomonas sp colonize the lower airway in a different pattern and by a different route from those of other EGNB. The findings that Pseudomonas sp preferentially colonize the tracheobronchial tree may be important for the design of strategies to prevent airway colonization. The recognition that poor nutritional status, a potentially modifiable host-related factor, favors lower airway growth of Pseudomonas sp suggests one direction for future infection-control efforts.

Nosocomial pneumonia in the intubated patient: role of gastric colonization

A high rate of nosocomial pneumonia exists among intubated patients receiving mechanical ventilation. Retrograde colonization of the oropharynx and trachea with bacteria from the stomach is not widely appreciated in the pathogenesis of pneumonia. Gastric colonization is affected by age, malnutrition, antibiotics, disease of the gastrointestinal tract, and changes in pH. The widespread use of antacids and/or histamine type 2 blockers as prophylaxis against stress bleeding in the ventilated patient may also increase gastric pH and the risk of colonization in the upper gastrointestinal tract. Migration of bacteria between the stomach, oropharynx and trachea in the intubated patient may be a dynamic system involving large numbers of bacteria. The high fatality rate of mechanically ventilated patients with pneumonia, which persists despite treatment of these patients with appropriate antimicrobial therapy, underscores the need for effective measures of prevention. Preventive measures include the appropriate use of antibiotics, proper decontamination of respiratory therapy equipment, the cautious use of drugs that alter the natural gastric acid barrier, or, possibly, the selective use of antibiotics to prevent or reduce gastric, oropharyngeal and tracheal colonization.

Hospital-acquired pneumonia: overview of the current state of the art for prevention and control

Hospital-acquired pneumonia affects at least 250,000 patients in U.S. acute care institutions each year and is associated with a crude mortality of approximately 30%. Cases occur at a rate of 0.5-1 per 100 admissions, constituting 10-15% of all nosocomial infections and directly accounting for approximately one-third (10%) of the total mortality. It is likely, therefore, that nosocomial pneumonia represents an important cause of death. No recent large-scale study has systematically examined the true bacterial etiology of hospital-acquired pneumonia utilizing reliable techniques that bypass the oral flora. In the absence of such data, the current approach to therapy based on the examination of sputum is not optimal. Studies that focus on pathogenesis point to the stomach as an important reservoir of infecting organisms. Recent studies suggest that rates of pneumonia can be reduced either by selective decontamination of the digestive tract with antibiotic prophylaxis or by utilizing stress ulcer prophylaxis, which maintains normally low gastric pH. It seems that the time is propitious to examine prehospital determinants of nosocomial infection, with the goal of further preventing these life-threatening events in the hospital.

[Digestive stress hemorrhage. Physiopathology and prevention]

Lesions of the gastroduodenal mucosa are seen very early on in virtually 100% of patients suffering from organ failure. Bleeding, even if it is only occult, defines acute stress-induced gastrointestinal tract bleeding (SGIB). The rates of SGIB vary according to the inclusion criteria: 13 to 100% microscopic SGIB, 2.3 to 9.5% haemorrhage with blood transfusion and/or shock. Gastrointestinal bleeding does not really influence the death rate of patients with SGIB (0 to 5% increase). Damage to the gastric mucosa may be due to an intraluminal aggression, and/or decreased mucosal and mural defence mechanisms. H+ ions and bile salts are mostly responsible for the former. Physiological quantities of H+ ions may be sufficient, as their abnormal diffusion into the gastric mucosa will reduce the mucosal pH (pHm), which is itself sensitive to microcirculatory modifications and systemic acidosis. There is a good correlation between bleeding and pHm. Bile salts are involved because of the usual increase in frequency and volume of gastric biliary reflux due to stress. Surfactant, mucosal alkaline layer and the microcirculation are all involved in gastric protection. The PGE2 synthetized by the gastric mucosa have a favourable influence on these 3 mechanisms. Changes in microcirculation and hypoxia are the predominant factors involved in stress-induced mucosal damage. The prevention of SGIB relies on the treatment of risk factors, a reduction of intraluminal aggression, and the support and/or stimulation of gastric defence mechanisms. Antacids and anti-H2 drugs aim to neutralize most of the H+ ions, being more efficient than placebo in increasing gastric pH greater than 4, although anti-H2 agents are responsible of a greater number of failures. The non-homogenous character of the patient groups studied and the diagnostic methods, as well as the increasing lack of placebo groups in the published studies make the interpretation of the results rather risky. Antacids and anti-H2 drugs are more efficient than placebo, and equally efficient, in preventing overt SGIB. Efficiency is increased by giving anti-H2 drugs continuously, and antacids hourly. Other agents are thought to protect mucosal cells, probably increasing mucosal defences. Amongst them are the prostaglandins, the most interesting of which are still being investigated, and sucralfate. The latter molecule is as efficient as antacids and anti-H2 drugs, and does not alter gastric pH, so reducing the number of nosocomial pneumonias. Its reduced cost and easy administration make it, at the present time, the treatment of choice of SGIB. The few rare contraindications of sucralfate will justify the infusion of anti-H2 drugs in those patients at risk.

Efficacy of oral sucralfate suspension in prevention and treatment of chemotherapy-induced mucositis

The efficacy of orally administered sucralfate suspension in preventing and treating chemotherapy-induced mucositis was evaluated in a double-blind trial. Forty-eight children and adolescents with newly diagnosed acute nonlymphocytic leukemia were randomized to receive suspensions of either sucralfate or placebo orally every 6 hours during the first 10 weeks of intensive remission-induction chemotherapy. Patients given sucralfate suspension were less likely than subjects receiving placebo to acquire colonization with potentially pathogenic microorganisms: 14 (58%) of 24 versus 22 (92%) of 24, respectively (p = 0.008). However, no effect on preexisting colonization was noted. Subjective reporting of discomfort, objective scoring of the severity of mucositis, and the maximal percent of body weight lost during therapy were similar; 58% of patients receiving sucralfate reported no oral pain compared with 25% receiving placebo (p = 0.06). Ten episodes of gastrointestinal bleeding, 25 documented infections, and 886 days with fever were also equally distributed between sucralfate and placebo groups. We conclude that sucralfate suspension is of limited, if any efficacy, in the prevention and treatment of chemotherapy-induced mucositis. Sucralfate administration can, however, reduce acquisition of alimentary colonization with potential pathogens, perhaps by interfering with adherence to mucosal membranes.

Stress ulcers: current understanding of pathogenesis and prophylaxis

Stress-related gastrointestinal bleeding is known to occur in approximately 25 percent of untreated seriously ill patients, but with appropriate prophylaxis is largely preventable. Since the treatment of stress bleeding is generally unsatisfactory and has a high mortality, routine prophylaxis should be instituted for susceptible patients. Multiple mechanisms contribute to stress ulcer formation, the most important of which appear to be mucosal ischemia and the inability to control back-diffused hydrogen. Antacids and histamine2-blocking agents are presently the cornerstone of effective prophylaxis, but because they have been implicated as contributors to nosocomial pneumonias due to bacterial overgrowth in the stomach, investigation is ongoing into such alternative prophylactic agents as sucralfate and prostaglandins that do not alter the normal gastric acidity. This article presents a review of the literature on the development and prevention of stress ulcer disease.

Prevention of stress bleeding with ranitidine or pirenzepine and the risk of pneumonia

In a prospective, controlled, randomized trial of stress bleeding prophylaxis, 400 patients in a surgical intensive care unit received 50 mg pirenzepine (n = 200) or 200 mg ranitidine (n = 200) daily. The drugs were administered continuously via an intravenous line. The mean duration of the treatment was 3.9 days. Patients were included in the study if no long-term ventilation was expected. In patients with a stomach tube in place, the intragastric pH was determined every eight hours. Bleeding was defined as macroscopically visible. Along with stress bleeding, the development of postoperative pneumonia was documented. The intragastric pH was less than 4 significantly more often in patients treated with pirenzepine. In patients treated with ranitidine, six stress bleedings were observed, while in the pirenzepine group three bleeding episodes occurred. Seven of the nine bleeding patients were found to have a very high bleeding risk. In mechanically ventilated patients, a significantly higher risk of pneumonia was observed compared with non-ventilated patients (18.0% vs 2.7%). Fourteen of the 20 pneumonias occurred in patients treated with ranitidine. In ventilated patients treated with ranitidine, the pneumonia rate was 28.6%, while in the pirenzepine group the pneumonia rate reached only 9.1% (p less than 0.05). The increased frequency of pneumonia in patients treated with ranitidine appears to be caused by overgrowth of gram-negative bacteria in the stomach. Pirenzepine provides adequate protection against stress bleeding while also minimizing the danger of pneumonia caused by infection via the gastropulmonary route.