How to use an article on therapy or prevention: pneumonia prevention using subglottic secretion drainage

Evidence-based guidelines for the prevention of ventilator-associated pneumonia: results of a knowledge test among intensive care nurses

OBJECTIVE

To determine intensive care nurses' knowledge of evidence-based guidelines for the prevention of ventilator-associated pneumonia (VAP).

DESIGN

A survey using a validated multiple-choice questionnaire, developed to evaluate nurses' knowledge of VAP prevention. The questionnaire was distributed and collected during the annual congress of the Flemish Society for Critical Care Nurses (Ghent, November 2005). Demographic data included were gender, years of intensive care experience, number of critical beds, and whether respondents hold a special degree in emergency and intensive care.

MAIN RESULTS

We collected 638 questionnaires (response rate 74.6%). Nineteen percent of the respondents recognized the oral route as the recommended way for intubation. It was known by 49% of respondents that ventilator circuits should be changed for each new patient. Heat and moisture exchangers were checked as the recommended type of humidifier by 55% of respondents, but only 13% knew that it is recommended to change them once weekly. Closed suctioning systems were identified as recommended by 17% of respondents, and 20% knew that these must be changed for each new patient only. Sixty percent and 49%, respectively, recognized subglottic drainage and kinetic beds to reduce the incidence of VAP. Semi-recumbent positioning is well known to prevent VAP (90%). The average knowledge level was higher among more experienced nurses (> 1 year experience) and those holding a special degree in emergency and intensive care.

CONCLUSION

Nurses lack knowledge regarding recommendations for VAP prevention. Nurses' schooling and continuing education should include support from current evidence-based guidelines.

Impact of Humidification Systems on Ventilator-associated Pneumonia

RATIONALE AND OBJECTIVES

The respective influence on the incidence of ventilator-associated pneumonia of currently available systems used for warming and humidifying the gases delivered to mechanically ventilated patients, that is, heated humidifiers and heat and moisture exchanger filters, remains controversial.

METHODS

We addressed this question in a multicenter randomized study comparing heated humidifiers (with heated circuits) and filters in an unselected population of 369 intensive care patients receiving mechanical ventilation for more than 48 h.

MAIN MEASUREMENTS AND RESULTS

The diagnosis of pneumonia was confirmed according to strict microbiologic criteria. There was no difference in pneumonia rate between the two groups (53 of 184 [28.8%] versus 47 of 185 [25.4%] for humidifiers versus filters; p = 0.48), or in the incidence density of pneumonia (27.4/1,000 ventilatory days versus 25.3/1,000 ventilatory days for humidifiers versus filters; p = 0.76). The mean duration of mechanical ventilation did not differ between the two groups (14.9 +/- 15.1 versus 13.5 +/- 16.3 days for humidifiers versus filters, p = 0.36). Endotracheal tube occlusion occurred, respectively, in five patients and one patient in the humidifier and filter groups (p = 0.12). Intensive care mortality was identical in the two groups (about 33%).

CONCLUSION

These results suggest that both heated humidifiers and heat and moisture exchanger filters can be used with no significant impact on the incidence of ventilator-associated pneumonia and that other criteria may justify their choice.

Ensuring the comparability of comparison groups: is randomization enough?

BACKGROUND

It is widely believed that baseline imbalances in randomized trials must necessarily be random. In fact, there is a type of selection bias that can cause substantial, systematic and reproducible baseline imbalances of prognostic covariates even in properly randomized trials. It is possible, given complete data, to quantify both the susceptibility of a given trial to this type of selection bias and the extent to which selection bias appears to have caused either observable or unobservable baseline imbalances. Yet, in articles reporting on randomized trials, it is uncommon to find either these assessments or the information that would enable a reader to conduct them. Nevertheless, there have been a few published reports that contain descriptions of either this type of selection bias or indicators that it may have occurred.

OBJECTIVE

To document that the same type of selection bias has been described in numerous randomized trials and therefore that it represents a problem deserving of greater attention.

STUDY SELECTION

Computerized searches were not useful in locating trials with one or more elements that contribute to or are indicative of selection bias in randomized trials. We limit our treatment to trials that were previously questioned for susceptibility to selection bias or for large baseline imbalances.

RESULTS

We found 14 randomized trials that appear to be suspicious for selection bias. This may represent only the tip of the iceberg, because the status of other trials is inconclusive.

CONCLUSIONS

Authors of clinical trial reports should be required to disclose sufficient details to allow for an assessment of both allocation concealment and selection bias. The extent to which a randomized study was susceptible to selection bias should be considered in determining the relative contribution it makes to any subsequent meta-analysis, policy or decision.

A practical approach to evidence-based medicine: lessons learned from developing ventilator management protocols

Development of robust clinical protocols is a time-consuming process that requires allocation of sufficient time and resources. As outlined for the mechanical-ventilation protocol, the goals of the protocol must be clear before embarking on this journey. Critical appraisal of existing evidence is an essential first step to developing a draft protocol. The inclusion of a multidisciplinary team of clinicians, including nurses and respiratory therapists, is required to refine the logic and to ensure protocol acceptance. Extensive bedside testing of the protocol across the spectrum of patients in which it will be applied is essential for ensuring that the protocol works as intended. An effective, ongoing training program must be implemented to ensure protocol success. The final protocol should be carefully monitored in 50 to 100 patients to ensure that clinicians are complying with the protocol rules and that adverse events related to the protocol are not occurring. Finally, protocols must be tended to and updated when new evidence becomes available.

Improving the information content of categorical clinical trial endpoints

Because the severity of most diseases can be measured nonuniquely, different medical interventions with different mechanisms of action may be evaluated differently, even in the same patient population. Complicating this further is the fact that even for a given medical intervention, it may not be clear which endpoint, if any, will be most likely to show an intervention effect. For these and other reasons, clinical trials typically involve the evaluation of multiple safety and efficacy endpoints. As information accrues about diseases and patient populations, some endpoints may cease to be useful, but the trend would still likely be toward increasing numbers of potential endpoints. This trend would provide sponsors with increasing numbers of choices for the primary efficacy endpoint. If the endpoint selected as primary is not the optimal one for demonstrating the superiority of the experimental medical intervention, then a safe and effective medical intervention may be mistakenly found to be otherwise. On the other hand, the sponsor may find the endpoint that makes its case and not study other endpoints that would have shown the experimental intervention to be inferior, in some way, to the control intervention. As such, the reliance of medical decisions on narrow primary endpoints can lead to inflation of both the type I and type II error rates. To address these concerns, we propose that all endpoints, especially the primary endpoint, be as informative as possible. This could be accomplished by combining some endpoints into composite endpoints. To avoid losing information in this transformation, we define the concept of information-preserving composite endpoints and provide information concerning when this type of composite endpoint would be most useful. Specifically, we define the concept of joint fusibility of a set of endpoints and note that this property confers upon the derived information-preserving composite endpoint the greatest amenability to statistical analysis. We also point out that using composite endpoints allows sponsors the most discretion in selecting their primary between-group statistical analysis. We illustrate these ideas with examples from a variety of therapeutic areas.

Continuous subglottic suctioning for the prevention of ventilator-associated pneumonia : potential economic implications

STUDY OBJECTIVE

To determine the cost-effectiveness of continuous subglottic suctioning (CSS) as a strategy to decrease the incidence of ventilator-associated pneumonia (VAP).

DESIGN

Decision-model analysis of the cost and efficacy of endotracheal tubes that allow CSS at preventing VAP. The primary outcome was cases of VAP averted. Model estimates were based on data from published prospective trials of CSS and other prospective studies of the incidence of VAP.

SETTING AND PATIENTS

Hypothetical cohort of 100 patients requiring nonelective endotracheal intubation and management in an ICU.

INTERVENTIONS

In the model, patients were managed with either traditional endotracheal tubes (ETs) or ETs capable of CSS.

MEASUREMENTS AND MAIN RESULTS

The marginal cost-effectiveness of CSS was calculated as the savings resulting from cases of VAP averted minus the additional costs of CSS-ETs, and expressed as cost (or savings) per episode of VAP prevented. Sensitivity analysis of the impact of the major clinical inputs on the cost-effectiveness was performed. The base case assumed that the incidence of VAP in patients requiring > 72 h of mechanical ventilation (MV) was 25%, that CSS-ETs had no impact on patients requiring MV for < 72 h, and that CSS-ETs resulted in a relative risk reduction of VAP of 30%. Despite the higher costs of ETs capable of CSS, this tactic yielded a net savings of $4,992 per case of VAP prevented. For sensitivity analysis, model inputs were adjusted by 50% individually and then simultaneously. This demonstrated the model to be only moderately sensitive to the calculated cost of VAP. With the relative risk reduction at 50% of the base-case estimate, CSS resulted in $1,924 saved per case of VAP prevented. When all variables were skewed against CSS, total outlays were trivial (approximately $14 per patient in the cohort).

CONCLUSIONS

CSS represents a strategy for the prevention of VAP that may result in savings. Further studies are warranted to confirm the efficacy of CSS.

A randomized clinical trial of continuous aspiration of subglottic secretions in cardiac surgery patients

STUDY OBJECTIVES

To determine whether the application of continuous aspiration of subglottic secretions (CASS) is associated with a decreased incidence of ventilator-associated pneumonia (VAP).

DESIGN

Prospective clinical trial.

SETTING

Cardiothoracic ICU (CTICU) of Barnes-Jewish Hospital, St. Louis, a university-affiliated teaching hospital.

PATIENTS

Three hundred forty-three patients undergoing cardiac surgery and requiring mechanical ventilation in the CTICU.

INTERVENTIONS

Patients were assigned to receive either CASS, using a specially designed endotracheal tube (Hi-Lo Evac; Mallinckrodt Inc; Athlone, Ireland), or routine postoperative medical care without CASS.

RESULTS

One hundred sixty patients were assigned to receive CASS, and 183 were assigned to receive routine postoperative medical care without CASS. The two groups were similar at the time of randomization with regard to demographic characteristics, surgical procedures performed, and severity of illness. Risk factors for the development of VAP were also similar during the study period for both treatment groups. VAP was seen in 8 patients (5.0%) receiving CASS and in 15 patients (8. 2%) receiving routine postoperative medical care without CASS (relative risk, 0.61%; 95% confidence interval, 0.27 to 1.40; p = 0. 238). Episodes of VAP occurred statistically later among patients receiving CASS ([mean +/- SD] 5.6 +/- 2.3 days) than among patients who did not receive CASS (2.9 +/- 1.2 days); (p = 0.006). No statistically significant differences for hospital mortality, overall duration of mechanical ventilation, lengths of stay in the hospital or CTICU, or acquired organ system derangements were found between the two treatment groups. No complications related to CASS were observed in the intervention group.

CONCLUSIONS

Our findings suggest that CASS can be safely administered to patients undergoing cardiac surgery. The occurrence of VAP can be significantly delayed among patients undergoing cardiac surgery using this simple-to-apply technique.

Epidemiology and risk factors for nosocomial pneumonia. Emphasis on prevention

VAP is a complex nosocomial infection, the disease expression and resulting patient outcome of which is dependent on host factors, the causative organism, the timing and adequacy of treatment, and the presence of intrinsic or inducible antibiotic resistance. Significant improvements have been achieved in our ability to reduce the occurrence of VAP in the hospital setting. Clinicians caring for mechanically ventilated patients should strive to develop focused programs for the prevention of VAP, other nosocomial infections, and the occurrence of antibiotic-resistant infections at their institutions. The benefits of such programs are well demonstrated. The components of a PDSA (Plan-Do-STUDY-Act) model that can be simply employed to develop a VAP prevention program are as follows: Stages Plan: 1. Identify potentially modifiable risk factors for VAP at the institutional level. 2. Develop a strategy to modify or prevent the occurrence of these risk factors. [figure: see text] Do: 1. Carry out the planned intervention strategy. 2. Identify problems in the implementation of the designed intervention. 3. Update the intervention with solutions for the identified problems. 4. Collect basic data (e.g., VAP rates, severity of illness).

STUDY

1. Analyze data. 2. Summarize the results. Act: 1. Determine the overall success or failure of the intervention. 2. Identify potential modifications to improve the intervention strategy. 3. Prepare for next PDSA cycle. Inherent in the development and application of such programs is the concept that they are continuous processes striving to improve clinical performance over time (Fig. 3). At any given institution, the most likely approach to the prevention of NP and VAP will be a multifaceted one, employing interventions aimed at reducing the occurrence of aerodigestive tract colonization with pathogenic bacteria and aspiration. To be successful, such quality improvement programs must be embraced at the institutional level. Only in this way can hospitals hope to successfully reduce their rates of VAP and sustain or improve upon those efforts over time.

How to use the results of an economic evaluation

BACKGROUND

Given the high costs of delivering care to critically ill patients, practitioners and policymakers are beginning to scrutinize the costs and outcomes associated with intensive care. Health economics is a discipline concerned with determining the best way of using resources to maximize the health of the community. This involves addressing questions such as which procedure, test, therapy, or program should be provided, and to whom, given available resources.

PURPOSE

The purpose of this article is to review general economic principles that will help intensivists to better interpret published economic evaluations.

DATA SOURCES

Selected articles from the health economics and critical care literature.

RESULTS

In this article, we use an economic evaluation that examines sedation strategies in critically ill patients. We discuss how learning to critically appraise an economic evaluation is only part of the task for end users. Determining whether and how to apply the results of economic evaluations to local settings presents bigger challenges and remains largely a matter of judgment.

CONCLUSIONS

Economic evaluations use analytic techniques to systematically consider all possible costs and consequences of clinical actions. Although they should never form the sole basis for clinical decisions for individual patients, economic evaluations offer potentially useful information at different levels of decision-making.

Interpreting and using clinical trials

In 1754, aboard HMS Salisbury, James Lind conducted a simple, controlled clinical trial. He took 12 patients with "pale and bloated skin, listlessness, an aversion to exercise, swollen gums, halitosis, ecchymotic mucous membranes, and limb edema" and allocated them to receive treatment with one of six different therapies. Since the patients receiving two of his six chosen interventions had such a dramatic recovery, he felt ethically obligated to end his trial and administer these treatments to all the remaining sailors. Today we fully recognize the impact that the controlled clinical trial can have on the development of new interventions. Unfortunately, very few of these interventions are likely to have as dramatic an impact on outcomes as lemons and oranges did on scurvy. Because the interventions we study tend to have relatively small treatment effects, and because the design and reporting of published RCTs has consistently been documented to be less than perfect, there is a real need for us to develop critical appraisal skills. This article is by no means the only approach to critical appraisal, but hopefully it serves as an adequate starting point for the journey.

How to use a review article: prophylactic endoscopic sclerotherapy for esophageal varices. Evidence Based Critical Care Medicine Group

OBJECTIVE

To assess the validity of a meta-analysis about sclerotherapy for the primary prevention of bleeding from esophageal varices, to interpret the results, and discuss whether they apply in practice.

DATA SOURCES

Critical appraisal techniques for systematic reviews.

DATA EXTRACTION

Systematic reviews are distinct from narrative reviews in that they answer specific clinical questions, and have explicit and reproducible methods for searching, selecting, and appraising the primary studies, to create the most valid synthesis of the evidence.

DATA SYNTHESIS

Meta-analyses are systematic reviews containing a critical appraisal and statistical summary of individual study results and their confidence limits, whereas qualitative systematic reviews provide a narrative executive summary of study results.

CONCLUSIONS

High-quality systematic reviews are being used increasingly to guide practice, strengthening the link between research results and improved health outcomes. Understanding their strengths and limitations helps us to use them appropriately in practice.

How to use articles about harm: the relationship between high tidal volumes, ventilating pressures, and ventilator-induced lung injury

BACKGROUND

Intensivists commonly encounter patients who may be inadvertently harmed by critical care interventions. This article is designed to guide clinicians in the evaluations of an individual article assessing a question of harm, as well as the sum of multiple pieces of evidence.

OBJECTIVES

To assess the vaidity of a group of articles about the relationship between high tidal volumes and ventilating pressures on ventilator-induced lung injury; to interpret the results of these studies; and to consider whether they apply in practice.

DATA SOURCES

Issues of harm are sometimes measured in randomized trials, but are evaluated more often in myriad observational studies.

DATA EXTRACTION

We use critical appraisal guides for experimental studies (e.g., randomized trials) and observational studies (e.g., cohort studies, case-control studies and case series) that evaluate the potentially harmful exposure of high tidal volumes and ventilating pressures. This involves assessing the validity of the research, then determining the strength of association between the putative harmful exposure and adverse outcomes. These study designs and their interpretation using relative risks and odds ratios are reviewed. Finally, the relevance of this information (or lack thereof) to clinical practice needs to be determined.

DATA SYNTHESIS

Examining these studies individually and in totality, there appears to be a relationship between high tidal volumes and ventilating pressures, although the strength of inference from this research is limited by design issues and sample sizes.

CONCLUSIONS

Critically appraising a body of literature is more challenging than evaluating a single study, but often gives a broader view of the available evidence. Future large, rigorous, randomized trials of different approaches to mechanical ventilation will help to advance our understanding and to better inform our practice.