Effect of hospital-acquired ventilator-associated pneumonia on mortality of severe community-acquired pneumonia

Attributable mortality of ventilator-associated pneumonia

PURPOSE OF REVIEW

To critically discuss the attributable mortality of ventilator-associated pneumonia (VAP) and potential sources of variation.

RECENT FINDINGS

The review will cover the available estimates (0-50%). It will also explore the source of variation because of definition of VAP (being lower if inaccurate), case-mix issues (being lower for trauma patients), the severity of underlying illnesses (being maximal when the severity of underlying illness is intermediate), and on the characteristics and the severity of the VAP episode. Another important source of variation is the use of poorly appropriate statistical models (estimates biased by lead time bias and competing events). New extensions of survival models which take into account the time dependence of VAP occurrence and competing risks allow less biased estimation as compared with traditional models.

SUMMARY

Attributable mortality of VAP is about 6%. Accurate diagnostic methods are key to properly estimating it. Traditional statistical models should no longer be used to estimate it. Prevention efforts targeted on patients with intermediate severity may result in the most important outcome benefits.

Stress ulcer prophylaxis in mechanically ventilated patients: integrating evidence and judgment using a decision analysis

OBJECTIVE

Stress ulcer prophylaxis with a histamine-2 receptor antagonist can reduce the risk of gastrointestinal bleeding in mechanically ventilated patients but may also increase the risk of ventilator-associated pneumonia. We sought to clarify the tradeoffs involved in selecting a prophylactic strategy.

DESIGN

Decision analysis.

PATIENTS AND PARTICIPANTS

A decision tree was constructed for a hypothetical cohort of patients receiving mechanical ventilation for an expected duration of longer than 48 h, using probabilities estimated from the published literature.

INTERVENTIONS

Patients in the model could receive either prophylaxis with a histamine-2 receptor antagonist or no prophylaxis. Sensitivity analyses were preformed varying the estimated probabilities over their plausible ranges.

MEASUREMENTS AND RESULTS

Both strategies were associated with approximately the same baseline expected mortality (16.6% for histamine-2 receptor antagonists and 16.9% for no prophylaxis, risk difference 0.3%). Varying the estimated probabilities resulted in only small changes in both the expected mortality and the absolute risk reduction associated with the preferred treatment. At the extremes of assumptions the absolute mortality reduction ranged from 0.1% to 3.3%.

CONCLUSIONS

No single strategy of stress ulcer prophylaxis is preferred when mortality is used as the outcome. In the absence of a clinical trial demonstrating survival benefit the individual clinician's assumptions regarding the effect of prophylaxis on gastrointestinal bleeding and pneumonia and the attributable mortality of pneumonia vs. gastrointestinal bleeding will have a significant effect on the decision.

Hospital-Acquired Pneumonia in Critically Ill Patients

STUDY OBJECTIVES

To identify, in patients experiencing hospital-acquired pneumonia (HAP), prognostic factors present at disease onset and build an algorithm capable of stratifying mortality risk upon HAP onset.

DESIGN

Observational cohort from January 1994 to December 2001.

SETTING

One intensive care unit (ICU) from a university-affiliated, urban teaching hospital.

PATIENTS

All consecutive patients exhibiting bacteriologically documented HAP either on ICU admission or during ICU stay.

INTERVENTIONS

Data collection and multivariate analysis using Chi-Square Automatic Interaction and Detection technique.

RESULTS

168 patients were studied. The overall mean mortality rate was 49.4%. Upon onset of HAP, five independent variables allowed binary stratification of mortality risk. These consisted of underlying diseases (nonfatal versus ultimately and rapidly fatal diseases), Simplified Acute Physiology Score II (less than versus > or =37), platelet count (less than versus > or =150,000/mm3), chest x-ray involvement (1 versus >1 lobe), and PaO2/FiO2 (less than versus > or =167 mm Hg). A branching algorithm consisting of these five variables identified patients with HAP at both low (<35%) and high (>75%) risk of mortality.

CONCLUSION

Mortality in ICU patients with HAP may be predicted early, upon onset of HAP, by the cumulative use of prognostic factors in an algorithm.

Decision analysis of antibiotic and diagnostic strategies in ventilator-associated pneumonia

The optimal strategy for ventilator-associated pneumonia remains controversial. To clarify the tradeoffs involved, we performed a decision analysis. Strategies evaluated included antibiotic therapy with and without diagnostic testing. Tests that were explored included endotracheal aspirates, bronchoscopy with protected brush or bronchoalveolar lavage, and nonbronchoscopic mini-bronchoalveolar lavage (mini-BAL). Outcomes included dollar cost, antibiotic use, survival, cost-effectiveness, antibiotic use per survivor, and the outcome perspective of financial cost-antibiotic use per survivor. Initial coverage with three antibiotics was better than expectant management or one or two antibiotic approaches, leading to both improved survival (54% vs. 66%) and decreased cost (US dollars 55447 vs. US dollars 41483 per survivor). Testing with mini-BAL did not improve survival but did decrease costs (US dollars 41483 vs. US dollars 39967) and antibiotic use (63 vs. 39 antibiotic days per survivor). From the perspective of minimizing cost, minimizing antibiotic use, and maximizing survival, the best strategy was three antibiotics with mini-BAL.

Hospital-acquired pneumonia: risk factors for antimicrobial-resistant causative pathogens in critically ill patients

STUDY OBJECTIVES

To determine factors associated with antimicrobial-resistant hospital-acquired pneumonia (AR-HAP), to build an algorithm evaluating the risk for such a pneumonia, and to test this algorithm.

DESIGN

Combined observational and validation cohorts over two periods: January 1994 to December 1999, and January 2000 to March 2001.

SETTING

One ICU from a university-affiliated urban teaching hospital.

PATIENTS

One hundred twenty-four patients in the observational cohort and 26 patients in the validation cohort exhibiting bacteriologically documented hospital-acquired pneumonia (HAP).

INTERVENTIONS

Prospective data collection and multivariate analysis using the chi(2) automatic interaction and detection technique.

RESULTS

In the observational cohort, 39 antimicrobial-resistant bacteria were incriminated in 37 patients (30%). Multivariate analysis identified four independent variables allowing a binary stratification of risk. According to the presence or absence of prior antimicrobial treatment, neurologic disturbances on ICU admission, aspiration on ICU admission, and time elapsed between ICU admission and the onset of pneumonia, we were able to identify and separate patients at high, low, or even no risk for acquiring AR-HAP. In the validation cohort, nine antimicrobial-resistant bacteria were incriminated in nine patients (34.6%). In this cohort, the algorithm performed well allowing the identification of null risk categories: the absence of prior antimicrobial treatment, the presence of prior antimicrobial treatment with neurologic disturbances on ICU admission and an early-onset pneumonia, and the presence of prior antimicrobial treatment without neurologic disturbances but with aspiration on ICU admission were always associated with antimicrobial-susceptible HAP.

CONCLUSION

We developed and tested a binary algorithm allowing the identification of patients at low risk for acquiring AR-HAP. An antibiotic strategy including an initial antimicrobial treatment guided by such an algorithm, followed, if possible, by a de-escalation when antimicrobial data are available, could increase the administration of adequate initial antimicrobial treatment and help prevent the emergence of antibiotic resistance in the ICU.

Mortality due to ventilator-associated pneumonia: impact of medical versus surgical ICU admittance status

PURPOSE

The purpose of this study was to compare the prognosis of medical versus surgical patients developing ventilator-associated pneumonia (VAP).

MATERIALS AND METHODS

An observational cohort study included 125 consecutive patients exhibiting VAP. Incidence of death occurred at two different times: during intensive care unit (ICU) stay and during hospital stay.

RESULTS

Eighty-seven patients were included in the medical group and 38 in the surgical group. On ICU admission and at the time of VAP onset, most collected data, such as demographic parameters, severity of underlying diseases, and current illness, risk factors forVAP development andVAP characteristics were similar in the two groups. Mortality rates during ICU and hospital stays were not significantly different in medical (49%, 56%) and surgical (55%, 61%) groups. In multivariate logistic regression model adjusting for main factors of VAP mortality, surgical admittance status demonstrated no significant impact on mortality assessed during ICU stay (AOR = 1.6; 0.6 - 4.3 CI) and during hospital stay (AOR = 1.6; 0.6 - 4.2 CI).

CONCLUSIONS

In this series, after adjustment for mortality confounding factors, medical versus surgical admittance status was not a significant determinant of VAP mortality.

Diagnosis and Treatment of Opportunistic Infections in Immunocompromised Surgical Patients

The advent of successful therapy for patients who suffer many types of organ dysfunction and failure, malignancies, and acquired immunodeficiency syndrome has led to the concurrent threat of infection due to a wide array of pathogens, particularly opportunistic microbes that rarely cause disease under routine circumstances. Among patients who are subjected to extreme degrees of immunosuppression, almost any type of bacterial, fungal, viral, protozoal, or parasitic organism can exhibit pathogenic potential and lead to devastating consequences for the host. Immunosuppressive drug therapy for the purpose of organ allograft maintenance, cancer chemotherapy, or the human immunodeficiency virus exerts potent effects upon cellular immunity. Therefore, although these groups of patients are more susceptible to all types of infectious disease processes, infections due to those pathogens that require a component of cellular immunity for their eradication, such as fungi and viruses, occur at a higher frequency than that observed among normal individuals. Of critical importance, all types of infections are associated with higher rates of morbidity and mortality in immunosuppressed patients. Currently, improved diagnostic techniques and new treatment modalities have rendered many serious infections, for which suitable therapy previously did not exist, amenable to treatment. Because of the large number of immunosuppressed patients who now lead highly productive lives, it is important for the surgical practitioner to become familiar with the modalities currently available to precisely diagnose and effectively treat opportunistic infections in immunocompromised surgical patients.