_______________________________________________________________ Healthcare-Associated Infections
Prophylaxis of Deep-Vein Thrombosis There is no clear relation between prophylaxis of deep-vein thrombosis and ventilator-associated pneumonia, but the American College of Chest Physicians reported a decrease in the rate of ventilator-associated pneumonia when such prophy- laxis was implemented as part of a package of interventions and included this measure in its clinical practice guidelines [213]. Other Measures In addition to these interventions, other measures have been recommended to help prevent ventilator-associated pneumonia. One such measure is selective decontamination of the digestive tract, which involves the use of either topi- cal antiseptic, oral antibiotics, or a brief course of systemic antibiotics [194]. A meta-analysis (28 studies) showed that selective decontamination of the digestive or respiratory tract with use of topical antiseptic or antimicrobial agents helped reduce the frequency of ventilator-associated pneumonia in the ICU [214]. The estimate of efficacy in prevention was 27% for antiseptics and 36% for antibiotics. Neither had an effect on mortality. This intervention is recommended in the SHEA/IDSA guidelines, only in regions or ICUs that do not have a high prevalence of antibiotic-resistant organisms [38]. Other preventive measures are targeted primarily to the care and use of ventilator equipment and practices in direct patient care. Meticulous attention to aseptic care of the equipment is necessary, and all reusable components, such as nebulizers, should be disinfected or sterilized. Tubing circuits should be replaced after more than 48 hours, or earlier if there are signs of malfunction or contamination [27]. Changes in the design of the endotracheal tube have also been evaluated; for example, a tube with a suction port above the cuff allows for continu- ous aspiration of subglottic secretions. Use of this specially designed endotracheal tube has led to significantly lower rates of ventilator-associated pneumonia, as well as shorter durations of ventilation and shorter stays in the ICU [215; 216]. Among patients who had major cardiac surgery, the greatest benefit was found for patients who received ventilation for more than 48 hours [216]. The cost of the tube is higher than tra- ditional tubes but is offset by overall cost savings in preventing ventilator-associated pneumonia [215]. In one meta-analysis, subglottic secretion drainage was significantly associated with a decreased incidence of ventilator-associated pneumonia, shorter time on mechanical ventilation, and longer time to the development of ventilator-associated pneumonia [217]. The CDC, the ATS/IDSA, and the SHEA/IDSA guidelines recommend subglottic secretion drainage with this tube when possible [20; 27; 38]. The use of noninvasive ventilation is another measure that has reduced the incidence of ventilator-associated pneumonia [27; 218; 219]. In one study, the incidence decreased from 20% to 8% when noninvasive ventilation was used routinely for criti- cally ill patients with acute exacerbation of chronic obstructive pulmonary disease or severe cardiogenic pulmonary edema [220]. Again, the CDC, the ATS/IDSA, and the SHEA/IDSA
guidelines recommend the use of noninvasive ventilation when possible [20; 27; 38]. Diagnosis The difficulty in diagnosing hospital-acquired or ventilator- associated pneumonia has been well established [20; 196; 221]. The clinical signs can resemble those of other, noninfectious conditions, and the specificity of clinical criteria is low [193]. According to the CDC definition, the diagnosis in adults is made on the basis of clinical signs and symptoms and results of laboratory testing or imaging and must meet one of two criteria [129; 222]. Criterion 1 For any patient, at least one of the following : • Fever (>38°C or >100.4°F) • Leukopenia (<4,000 WBC/mm 3 ) or leukocytosis (≥12,000 WBC/mm 3 ) • For adults ≥70 years of age, altered mental status with no other recognized cause AND at least two of the following : • New onset of purulent sputum, or change in character of sputum, or increased respiratory secretions, or increased suctioning requirements • New onset or worsening cough, or dyspnea, or tachypnea • Rales or bronchial breath sounds • Worsening gas exchange (e.g., oxygen desaturations [e.g., PaO 2 /FiO 2 ≤240 mm Hg], increased oxygen requirements, or increased ventilator demand) Criterion 2 Two or more serial chest radiographs showing at least one of the following : • New or progressive and persistent infiltrate • Consolidation • Cavitation • Pneumatoceles, in infants 1 year of age or younger In patients without underlying pulmonary or cardiac disease (e.g., respiratory distress syndrome, pulmonary edema, chronic obstructive pulmonary disease), one definitive chest radiograph is acceptable. There are no compelling data to recommend a specific approach to diagnosing hospital-acquired or ventilator- associated pneumonia. For patients who are not receiving mechanical ventilation, collection of a sputum specimen should be attempted before antibiotic therapy is begun [198; 223]. Specimens for culture can be obtained by bronchoscopy with a protected specimen brush to limit contamination or by bronchoalveolar lavage. The latter method has been found to lead to higher rates of treatment than that based on the CDC definition, and one study showed that preferential sampling of
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