Why are clinicians not embracing the results from pivotal clinical trials in severe sepsis? A bayesian analysis

Optimizing Fluid Resuscitation and Preventing Fluid Overload in Patients with Septic Shock

Intravenous fluid administration remains an important component in the care of patients with septic shock. A common error in the treatment of septic shock is the use of excessive fluid in an effort to overcome both hypovolemia and vasoplegia. While fluids are necessary to help correct the intravascular depletion, vasopressors should be concomitantly administered to address vasoplegia. Excessive fluid administration is associated with worse outcomes in septic shock, so great care should be taken when deciding how much fluid to give these vulnerable patients. Simple or strict "recipes" which mandate an exact amount of fluid to administer, even when weight based, are not associated with better outcomes and therefore should be avoided. Determining the correct amount of fluid requires the clinician to repeatedly assess and consider multiple variables, including the fluid deficit, organ dysfunction, tolerance of additional fluid, and overall trajectory of the shock state. Dynamic indices, often involving the interaction between the cardiovascular and respiratory systems, appear to be superior to traditional static indices such as central venous pressure for assessing fluid responsiveness. Point-of-care ultrasound offers the bedside clinician a multitude of applications which are useful in determining fluid administration in septic shock. In summary, prevention of fluid overload in septic shock patients is extremely important, and requires the careful attention of the entire critical care team.

Clinical trials in critical care: can a Bayesian approach enhance clinical and scientific decision making?

Recent Bayesian reanalyses of prominent trials in critical illness have generated controversy by contradicting the initial conclusions based on conventional frequentist analyses. Many clinicians might be sceptical that Bayesian analysis, a philosophical and statistical approach that combines prior beliefs with data to generate probabilities, provides more useful information about clinical trials than the frequentist approach. In this Personal View, we introduce clinicians to the rationale, process, and interpretation of Bayesian analysis through a systematic review and reanalysis of interventional trials in critical illness. In the majority of cases, Bayesian and frequentist analyses agreed. In the remainder, Bayesian analysis identified interventions where benefit was probable despite the absence of statistical significance, where interpretation depended substantially on choice of prior distribution, and where benefit was improbable despite statistical significance. Bayesian analysis in critical care medicine can help to distinguish harm from uncertainty and establish the probability of clinically important benefit for clinicians, policy makers, and patients.

A likelihood-based approach to P-value interpretation provided a novel, plausible, and clinically useful research study metric

OBJECTIVES

Interpretation of clinical research findings using the paradigm of null hypothesis significance testing has a number of limitations. These include arbitrary dichotomization of results, lack of incorporation of study power and prior probability, and the confusing use of conditional probability. This study aimed to describe a novel method of P-value interpretation that would address these limitations.

STUDY DESIGN AND SETTING

Published clinical research was reinterpreted using the delta likelihood ratio. The delta likelihood ratio is an application of Bayes' rule incorporating the P-value and study power. Calculation of the delta likelihood ratio allows the determination of the most likely effect size using the maximum likelihood principle.

RESULTS

We showed that the delta likelihood is easily calculated and produces plausible results using the example of several previously published research studies. Empirical evidence of validity was demonstrated by simulation.

CONCLUSION

The delta likelihood ratio and most likely effect size are simple and intuitive metrics to summarize research findings. The delta likelihood ratio incorporates study power and provides a continuous measure of the probability that the research result is a true effect. The most likely effect size is an easily understood metric that should aid the interpretation of research.

Updating Evidence for Using Hypothermia in Pediatric Severe Traumatic Brain Injury: Conventional and Bayesian Meta-Analytic Perspectives

OBJECTIVE

To evaluate clinical trials of hypothermia management on outcome in pediatric patients with severe traumatic brain injury using conventional and Bayesian meta-analyses.

DATA SOURCES

Screening of PubMed and other databases to identify randomized controlled trials of hypothermia for pediatric severe traumatic brain injury published before September 2016.

STUDY SELECTION

Four investigators assessed and reviewed randomized controlled trial data.

DATA EXTRACTION

Details of trial design, patient number, Glasgow Coma Scale score, hypothermia and control normothermia therapy, and outcome of mortality were collated.

DATA SYNTHESIS

In conventional meta-analysis, random-effects models were expressed as odds ratio (odds ratio with 95% credible-interval). Bayesian outcome probabilities were calculated as probability of odds ratio greater than or equal to 1. In seven randomized controlled trials (n = 472, patients 0-17 yr old), there was no difference in mortality (hypothermia vs normothermia) with pooled estimate 1.42 (credible-interval, 0.77-2.61; p = 0.26). Duration of hypothermia (24, 48, or 72 hr) did not show difference in mortality. (Similar results were found using poor outcome.) Bayesian analyses of randomized controlled trials ordered by time of study completed recruitment showed, after the seventh trial, chance of relative risk reduction of death by greater than 20% is 1-in-3. An optimistic belief (0.90 probability that relative risk reduction of death > 20% hypothermia vs normothermia) gives a chance of relative risk reduction of death by greater than 20% of 1-in-2.

CONCLUSIONS

Conventional meta-analysis shows the null hypothesis-no difference between hypothermia versus normothermia on mortality and poor outcome-cannot be rejected. However, Bayesian meta-analysis shows chance of relative risk reduction of death greater than 20% with hypothermia versus normothermia is 1-in-3, which may be further altered by one's optimistic or skeptical belief about a patient.

Vasopressors During Sepsis: Selection and Targets

Clinicians have greatly improved care for septic shock. Urgent resuscitation using intravenous fluids and vasopressors as well as rapid administration of broad spectrum antibiotics are probably the most basic and universally accepted interventions. Various trials have compared different types of vasopressors, associations of vasopressors and inotropes, and pressure targets. End goal-directed therapy algorithms are designed to optimize oxygen delivery by use of fluids, vasopressors, inotropes, and blood products. Patients who have a poor response to resuscitation and patients with known severe ventricular dysfunction might merit advanced hemodynamic monitoring. This review examines important vasopressor and septic shock trials.

Bayes to the Rescue: Continuous Positive Airway Pressure Has Less Mortality Than High-Flow Oxygen

OBJECTIVES

The merits of high-flow nasal cannula oxygen versus bubble continuous positive airway pressure are debated in children with pneumonia, with suggestions that randomized controlled trials are needed. In light of a previous randomized controlled trial showing a trend for lower mortality with bubble continuous positive airway pressure, we sought to determine the probability that a new randomized controlled trial would find high-flow nasal cannula oxygen superior to bubble continuous positive airway pressure through a "robust" Bayesian analysis.

DESING, SETTING, PATIENTS, AND INTERVENTIONS

Sample data were extracted from the trial by Chisti et al, and requisite to "robust" Bayesian analysis, we specified three prior distributions to represent clinically meaningful assumptions. These priors (reference, pessimistic, and optimistic) were used to generate three scenarios to represent the range of possible hypotheses. 1) "Reference": we believe bubble continuous positive airway pressure and high-flow nasal cannula oxygen are equally effective with the same uninformative reference priors; 2) "Sceptic on high-flow nasal cannula oxygen": we believe that bubble continuous positive airway pressure is better than high-flow nasal cannula oxygen (bubble continuous positive airway pressure has an optimistic prior and high-flow nasal cannula oxygen has a pessimistic prior); and 3) "Enthusiastic on high-flow nasal cannula oxygen": we believe that high-flow nasal cannula oxygen is better than bubble continuous positive airway pressure (high-flow nasal cannula oxygen has an optimistic prior and bubble continuous positive airway pressure has a pessimistic prior). Finally, posterior empiric Bayesian distributions were obtained through 100,000 Markov Chain Monte Carlo simulations.

MEASUREMENTS AND MAIN RESULTS

In all three scenarios, there was a high probability for more death from high-flow nasal cannula oxygen compared with bubble continuous positive airway pressure (reference, 0.98; sceptic on high-flow nasal cannula oxygen, 0.982; enthusiastic on high-flow nasal cannula oxygen, 0.742). The posterior 95% credible interval on the difference in mortality identified a future randomized controlled trial would be extremely unlikely to find a mortality benefit for high-flow nasal cannula oxygen over bubble continuous positive airway pressure, regardless of the scenario. Interpreting these findings using the "range of practical equivalence" framework would recommend rejecting the hypothesis that high-flow nasal cannula oxygen is superior to bubble continuous positive airway pressure for these children.

CONCLUSIONS

For children younger than 5 years with pneumonia, high-flow nasal cannula oxygen has higher mortality than bubble continuous positive airway pressure. A future randomized controlled trial in this population is unlikely to find high-flow nasal cannula oxygen superior to bubble continuous positive airway pressure.

Therapeutic Targets in Sepsis: Past, Present, and Future

Antibiotics and fluids have been standard treatment for sepsis since World War II. Many molecular mediators of septic shock have since been identified. In models of sepsis, blocking these mediators improved organ injury and decreased mortality. Clinical trials, however, have failed. The absence of new therapies has been vexing to clinicians, clinical researchers, basic scientists, and the pharmaceutical industry. This article examines the evolution of sepsis therapy and theorizes about why so many well-reasoned therapies have not worked in human trials. We review new molecular targets for sepsis and examine trial designs that might lead to successful treatments for sepsis.

Trials in adult critical care that show increased mortality of the new intervention: Inevitable or preventable mishaps?

Several promising therapies assessed in the adult critically ill in large, multicenter randomized controlled trials (RCTs) were associated with significantly increased mortality in the intervention arms. Our hypothesis was that there would be wide ranges in sponsorship (industry or not), type(s) of intervention(s), use of DSMBs, presence of interim analyses and early stopping rules, absolute risk increase (ARI), and whether or not adequate prior proof-of-principle Phase II studies were done of RCTs that found increased mortality rates of the intervention compared to control groups. We reviewed RCTs that showed a statistically significant increased mortality rate in the intervention compared to control group(s). We recorded source of sponsorship, sample sizes, types of interventions, mortality rates, ARI (as well as odds ratios, relative risks and number needed to harm), whether there were pre-specified interim analyses and early stopping rules, and whether or not there were prior proof-of-principle (also known as Phase II) RCTs. Ten RCTs (four industry sponsored) of many interventions (high oxygen delivery, diaspirin cross-linked hemoglobin, growth hormone, methylprednisolone, hetastarch, high-frequency oscillation ventilation, intensive insulin, NOS inhibition, and beta-2 adrenergic agonist, TNF-α receptor) included 19,126 patients and were associated with wide ranges of intervention versus control group mortality rates (25.7–59 %, mean 29.9 vs 17–49 %, mean 25 %, respectively) yielding ARIs of 2.6–29 % (mean 5 %). All but two RCTs had pre-specified interim analyses, and seven RCTs were stopped early. All RCTs were preceded by published proof-of-principle RCT(s), two by the same group. Seven interventions (except diaspirin cross-linked hemoglobin and the NOS inhibitor) were available for use clinically at the time of the pivotal RCT. Common, clinically available interventions used in the critically ill were associated with increased mortality in large, pivotal RCTs even though safety was often addressed by interim analyses and early stopping rules.

Lung protective ventilation in patients undergoing major surgery: a systematic review incorporating a Bayesian approach

OBJECTIVE

Protective ventilation (PV) has been validated in patients with acute respiratory distress syndrome. However, the effect of PV in patients undergoing major surgery is controversial. The study aimed to explore the beneficial effect of PV on patients undergoing a major operation by systematic review and meta-analysis.

SETTING

Various levels of medical centres.

PARTICIPANTS

Patients undergoing general anaesthesia.

INTERVENTIONS

PV with low tidal volume.

PRIMARY AND SECONDARY OUTCOME MEASURES

Study end points included acute lung injury (ALI), pneumonia, atelectasis, mortality, length of stay (LOS) in intensive care unit (ICU) and hospital.

METHODS

Databases including PubMed, Scopus, EBSCO and EMBASE were searched from inception to May 2015. Search strategies consisted of terms related to PV and anaesthesia. We reported OR for binary outcomes including ALI, mortality, pneumonia, atelectasis and other adverse outcomes. Weighted mean difference was reported for continuous outcomes such as LOS in the ICU and hospital, pH value, partial pressure of carbon dioxide, oxygenation and duration of mechanical ventilation (MV).

MAIN RESULTS

A total of 22 citations were included in the systematic review and meta-analysis. PV had protective effect against the development of ALI as compared with the control group, with an OR of 0.41 (95% CI 0.19 to 0.87). PV tended to be beneficial with regard to the development of pneumonia (OR 0.46, 95% CI 0.16 to 1.28) and atelectasis (OR 0.68, 95% CI 0.46 to 1.01), but statistical significance was not reached. Other adverse outcomes such as new onset arrhythmia were significantly reduced with the use of PV (OR 0.47, 95% CI 0.48 to 0.93).

CONCLUSIONS

The study demonstrates that PV can reduce the risk of ALI in patients undergoing major surgery. However, there is insufficient evidence that such a beneficial effect can be translated to more clinically relevant outcomes such as mortality or duration of MV.

TRIAL REGISTRATION NUMBER

The study was registered in PROSPERO (http://www.crd.york.ac.uk/PROSPERO/) under registration number CRD42013006416.

Bayesian methodology for the design and interpretation of clinical trials in critical care medicine: a primer for clinicians

OBJECTIVES

To review Bayesian methodology and its utility to clinical decision making and research in the critical care field.

DATA SOURCE AND STUDY SELECTION

Clinical, epidemiological, and biostatistical studies on Bayesian methods in PubMed and Embase from their inception to December 2013.

DATA SYNTHESIS

Bayesian methods have been extensively used by a wide range of scientific fields, including astronomy, engineering, chemistry, genetics, physics, geology, paleontology, climatology, cryptography, linguistics, ecology, and computational sciences. The application of medical knowledge in clinical research is analogous to the application of medical knowledge in clinical practice. Bedside physicians have to make most diagnostic and treatment decisions on critically ill patients every day without clear-cut evidence-based medicine (more subjective than objective evidence). Similarly, clinical researchers have to make most decisions about trial design with limited available data. Bayesian methodology allows both subjective and objective aspects of knowledge to be formally measured and transparently incorporated into the design, execution, and interpretation of clinical trials. In addition, various degrees of knowledge and several hypotheses can be tested at the same time in a single clinical trial without the risk of multiplicity. Notably, the Bayesian technology is naturally suited for the interpretation of clinical trial findings for the individualized care of critically ill patients and for the optimization of public health policies.

CONCLUSIONS

We propose that the application of the versatile Bayesian methodology in conjunction with the conventional statistical methods is not only ripe for actual use in critical care clinical research but it is also a necessary step to maximize the performance of clinical trials and its translation to the practice of critical care medicine.

Severe sepsis: are PROWESS and PROWESS-SHOCK trials comparable? A clinical and statistical heterogeneity analysis

Despite the same manufacturer, the same drotrecogin alfa activated dose, and the same placebo-controlled design, the negative result from the PROWESS-SHOCK trial contradicted the survival benefit observed in the PROWESS trial. We hypothesize that the different results were due to factors other than the experimental therapy and performed an analysis of the clinical heterogeneity (differences related to the trials' clinical aspects) and the statistical heterogeneity (differences related to the trials' statistical aspects) between these trials. Baseline characteristics and co-interventions were analyzed by chi-square testing and mortality was analyzed by random-effects modeling and I². Our findings show that clinical variables presented significant heterogeneity, and that up to 90% of the mortality differences between both trials were not due to chance. These results demonstrate that PROWESS and PROWESS-SHOCK are not comparable trials due to the highly significant clinical and statistical heterogeneity. We propose a new and pragmatic solution.

Beneficial effects of stress-dose corticosteroid therapy in canines depend on the severity of staphylococcal pneumonia

PURPOSE

The effects of stress-dose corticosteroid therapy were studied in a canine staphylococcal pneumonia model of septic shock.

METHODS

Immediately following intrabronchial bacterial challenge, purpose-bred beagles were treated with stress doses of desoxycorticosterone (DOC), a mineralocorticoid agonist, and dexamethasone (DEX), a glucocorticoid agonist, or with placebo for 96 h. Oxacillin (30 mg/kg every 8 h) was started 4 h after infection onset. Bacterial dose was titrated to achieve 80-90 % lethality (n = 20) using an adaptive design; additional animals (n = 18) were investigated using the highest bacterial dose.

RESULTS

Initial analysis of all animals (n = 38) demonstrated that the effects of DOC + DEX were significantly altered by bacterial dose (p = 0.04). The treatment effects of DOC + DEX were different in animals administered high or relatively lower bacterial doses in terms of survival (p = 0.05), shock reversal (p = 0.02), interleukin-6 levels (p = 0.02), and temperature (p = 0.01). DOC + DEX significantly improved the above parameters (p ≤ 0.03 for all) and lung injury scores (p = 0.02) after high-dose bacterial challenges, but not after lower challenges (p = not significant for all). Oxacillin trough levels were below the minimum inhibitory concentration of the infecting organism, and DOC + DEX increased the frequency of persistent staphylococcal bacteremia (odds ratio 3.09; 95 % confidence interval 1.05-9.11; p = 0.04).

CONCLUSIONS

Stress-dose corticosteroids were only beneficial in cases of sepsis with high risk for death and even short courses may interfere with host mechanisms of bacterial clearance.

Low-dose steroids in adult septic shock: results of the Surviving Sepsis Campaign

OBJECTIVE

The Surviving Sepsis Campaign (SSC) developed guidelines and treatment bundles for the administration of steroids in adult septic shock. However, it is not clear how this has affected clinical practice or patient outcome.

DESIGN AND SETTING

The SSC has developed an extensive database to assess the overall effect of its guidelines on clinical practice and patient outcome. This analysis focuses on one particular element of the SSC's management bundle, namely, the administration of low-dose steroids in adult septic shock. This analysis was conducted on data submitted from January 2005 through March 2010 including 27,836 subjects at 218 sites.

MAIN RESULTS

A total of 17,847 (of the total 27,836) patients in the database required vasopressor therapy despite fluid resuscitation and therefore met the eligibility criteria for receiving low-dose steroids. A total of 8,992 patients (50.4 %) received low-dose steroids for their septic shock. Patients in Europe (59.4 %) and South America (51.9 %) were more likely to be prescribed low-dose steroids compared to their counterparts in North America (46.2 %, p < 0.001). The adjusted hospital mortality was significantly higher (OR 1.18, 95 % CI 1.09-1.23, p < 0.001) in patients who received low-dose steroids compared to those who did not. There was still an association with increased adjusted hospital mortality with low-dose steroids even if they were prescribed within 8 h (OR 1.23, 95 % CI 1.13-1.34, p < 0.001).

CONCLUSIONS

Steroids were commonly administered in the treatment of septic shock in this subset analysis of the Surviving Sepsis Campaign database. However, this was associated with an increase in adjusted hospital mortality.

Effectiveness and safety of drotrecogin alfa (activated) for severe sepsis: a meta-analysis and metaregression

BACKGROUND

Drotrecogin alfa (activated) was approved for use in severe sepsis in 2001 on the basis of the Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) trial, but controversies about its effectiveness remain. We aimed to assess effectiveness and safety of use of this drug in the past 10 years and compare them with the original PROWESS results.

METHODS

We searched PubMed, Embase, Ovid, Cochrane Library, Evidence-Based Medicine, and the American College of Physicians Journal Club databases for experimental and analytical studies of drotrecogin alfa (activated) in adults with severe sepsis until Jan 31, 2012. We calculated adjusted risk ratios for effectiveness and safety outcomes with random-effects models. We did a metaregression to assess the effect of severity of illness on the risk of death and the risk of bleeding associated with drotrecogin alfa (activated).

FINDINGS

We included nine controlled trials (41,401 patients) and 16 single-group studies (5822 patients) in effectiveness analyses and 20 studies (8245 patients) in safety analyses. Hospital mortality was reduced by 18% with drotrecogin alfa (activated) compared with controls (relative risk 0·822, 95% CI 0·779-0·867; p<0·0001; I(2)=40%). This mortality reduction was much the same as was noted in PROWESS (0·851, 0·740-0·979), but smaller than that of patients in PROWESS with high disease severity (0·708, 0·590-0·849). Propensity-adjusted studies also showed a significant mortality reduction with lower heterogeneity (0·844, 0·800-0·891; p<0·0001, I(2)=18%). These findings were not changed by the addition of PROWESS-SHOCK results. Metaregression showed greater benefits of drotrecogin alfa (activated) with increasing control mortality (p=0·01) and more severe disease (p=0·04). Hospital mortality for single-group studies of drotrecogin alfa (activated) was 41% (95% CI 35-48), and was higher than that noted in PROWESS at 31% (27-36; p<0·0001). The serious bleeding rate with drotrecogin alfa (activated) was 5·6% (4·5-6·9), which was higher than the 3·5% (2·5-5·0) noted in PROWESS (p=0·003), but similar to that reported in PROWESS high disease severity (p=0·073).

INTERPRETATION

Real-life use of drotrecrogin alfa (activated) was associated with significant reduction in hospital mortality and increased rates of bleeding in patients with severe sepsis. Our effectiveness findings were in line with the PROWESS trial but not with the PROWESS-SHOCK trial.

FUNDING

None.

Bayesian cohort and cross-sectional analyses of the PINCER trial: a pharmacist-led intervention to reduce medication errors in primary care

Background

Medication errors are an important source of potentially preventable morbidity and mortality. The PINCER study, a cluster randomised controlled trial, is one of the world’s first experimental studies aiming to reduce the risk of such medication related potential for harm in general practice. Bayesian analyses can improve the clinical interpretability of trial findings.

Methods

Experts were asked to complete a questionnaire to elicit opinions of the likely effectiveness of the intervention for the key outcomes of interest - three important primary care medication errors. These were averaged to generate collective prior distributions, which were then combined with trial data to generate Bayesian posterior distributions. The trial data were analysed in two ways: firstly replicating the trial reported cohort analysis acknowledging pairing of observations, but excluding non-paired observations; and secondly as cross-sectional data, with no exclusions, but without acknowledgement of the pairing. Frequentist and Bayesian analyses were compared.

Findings

Bayesian evaluations suggest that the intervention is able to reduce the likelihood of one of the medication errors by about 50 (estimated to be between 20% and 70%). However, for the other two main outcomes considered, the evidence that the intervention is able to reduce the likelihood of prescription errors is less conclusive.

Conclusions

Clinicians are interested in what trial results mean to them, as opposed to what trial results suggest for future experiments. This analysis suggests that the PINCER intervention is strongly effective in reducing the likelihood of one of the important errors; not necessarily effective in reducing the other errors. Depending on the clinical importance of the respective errors, careful consideration should be given before implementation, and refinement targeted at the other errors may be something to consider.

Influence of severity of illness on the effects of eritoran tetrasodium (E5564) and on other therapies for severe sepsis

Disease severity varies widely in patients with severe sepsis. Eritoran tetrasodium (E5564), a TLR4 antagonist, blocks the binding of endotoxin and is being evaluated as a novel therapy for severe sepsis. This analysis aimed to assess the efficacy of eritoran based on severity of illness and similar effects in other recent sepsis trials. Prospective covariates from a randomized, double-blind, placebo-controlled, phase 2 trial were analyzed for treatment interaction measured by 28-day mortality. Five statistical interaction methodologies were used. The modified intent-to-treat population (n = 292), all-cause 28-day mortality was as follows: placebo, 33.3% (32/96); eritoran 45 mg/105 mg, 29.6% (58/196). Logistic regression analysis identified Acute Physiology and Chronic Health Evaluation II scores, predicted-risk-of-mortality scores, IL-6, age, sex, race, and eritoran use as associated with survival. Significant treatment interactions were observed (eritoran vs. placebo) for baseline covariates: Acute Physiology and Chronic Health Evaluation II (P = 0.035), predicted-risk-of-mortality scores (P = 0.008), number of organ failures (P = 0.079), international normalized ratio (P = 0.05), and acute physiology score (P = 0.039). I analysis showed that 38% of the total eritoran treatment variance was explained by the severity-of-illness heterogeneity rather than by chance. No interactions observed with other variables. Consistent with the finding in this eritoran trial, other sepsis trials (IL-1 receptor antagonist, TNFsr-p55, antithrombin, drotrecogin alfa-activated) also demonstrated significant treatment by severity interaction. Potential survival benefits of eritoran in severe sepsis patients were associated with high severity of illness. These findings were used to design a phase 3 trial. Similar treatment by severity-of-illness interaction was found in most recent sepsis trials.

Is (1→3)-β-D-glucan the missing link from bedside assessment to pre-emptive therapy of invasive candidiasis?

Invasive candidiasis is a frequent life-threatening complication in critically ill patients. Early diagnosis followed by prompt treatment aimed at improving outcome by minimizing unnecessary antifungal use remains a major challenge in the ICU setting. Timely patient selection thus plays a key role for clinically efficient and cost-effective management. Approaches combining clinical risk factors and Candida colonization data have improved our ability to identify such patients early. While the negative predictive value of scores and predicting rules is up to 95 to 99%, the positive predictive value is much lower, ranging between 10 and 60%. Accordingly, if a positive score or rule is used to guide the start of antifungal therapy, many patients may be treated unnecessarily. Candida biomarkers display higher positive predictive values; however, they lack sensitivity and are thus not able to identify all cases of invasive candidiasis. The (1→3)-β-D-glucan (BG) assay, a panfungal antigen test, is recommended as a complementary tool for the diagnosis of invasive mycoses in high-risk hemato-oncological patients. Its role in the more heterogeneous ICU population remains to be defined. More efficient clinical selection strategies combined with performant laboratory tools are needed in order to treat the right patients at the right time by keeping costs of screening and therapy as low as possible. The new approach proposed by Posteraro and colleagues in the previous issue of Critical Care meets these requirements. A single positive BG value in medical patients admitted to the ICU with sepsis and expected to stay for more than 5 days preceded the documentation of candidemia by 1 to 3 days with an unprecedented diagnostic accuracy. Applying this one-point fungal screening on a selected subset of ICU patients with an estimated 15 to 20% risk of developing candidemia is an appealing and potentially cost-effective approach. If confirmed by multicenter investigations, and extended to surgical patients at high risk of invasive candidiasis after abdominal surgery, this bayesian-based risk stratification approach aimed at maximizing clinical efficiency by minimizing health care resource utilization may substantially simplify the management of critically ill patients at risk of invasive candidiasis.

Is cefepime safe for clinical use? A Bayesian viewpoint

Cefepime hydrochloride is approved for pneumonia, empirical therapy for febrile neutropenia, uncomplicated and complicated urinary tract infections, uncomplicated skin and skin structure infections and complicated intra-abdominal infections. A recent meta-analysis by Yahav et al. (Lancet Infect Dis 2007; 7: 338-48) concluded that cefepime was associated with a statistically significant increase in mortality (risk ratio 1.26, 95% confidence interval 1.08-1.49) when compared with other antibiotics. The US FDA decided to re-evaluate the meta-analysis data in collaboration with the drug sponsor. Two years later the FDA Alert summarized that 'data do not indicate a higher rate of death in cefepime-treated patients. Cefepime remains an appropriate therapy for its approved indications.' However, a thorough evaluation of the 52-page FDA report still shows that safety remains an unresolved issue. A Bayesian re-appraisal of the findings by the FDA and by Yahav et al. indicates that there is a 90.9% (by FDA trial-level meta-analysis), 80.8% (by FDA patient-level meta-analysis) and 99.2% (by Yahav et al. meta-analysis) probability that cefepime raises mortality in neutropenic fever patients, which translates into the following numbers needed to harm (NNH), i.e. to cause one extra death with the use of cefepime: FDA trial-level meta-analysis, NNH = 109; FDA patient-level meta-analysis, NNH = 76; Yahav et al. meta-analysis, NNH = 54. A similar harmful probability was observed with skin structure infections but not with pneumonias, intra-abdominal infections and urinary tract infections. In conclusion, cefepime should be avoided in patients with neutropenic fever or with skin structure infections.

Low-dose steroids for septic shock and severe sepsis: the use of Bayesian statistics to resolve clinical trial controversies

PURPOSE

Low-dose steroids have shown contradictory results in trials and three recent meta-analyses. We aimed to assess the efficacy and safety of low-dose steroids for severe sepsis and septic shock by Bayesian methodology.

METHODS

Randomized trials from three published meta-analyses were reviewed and entered in both classic and Bayesian databases to estimate relative risk reduction (RRR) for 28-day mortality, and relative risk increase (RRI) for shock reversal and side effects.

RESULTS

In septic shock trials only (Marik meta-analysis; N = 965), the probability that low-dose steroids decrease mortality by more than 15% (i.e., RRR > 15%) was 0.41 (0.24 for RRR > 20% and 0.14 for RRR > 25%). For severe sepsis and septic shock trials combined, the results were as follows: (1) for the Annane meta-analysis (N = 1,228), the probabilities were 0.57 (RRR > 15%), 0.32 (RRR > 20%), and 0.13 (RRR > 25%); (2) for the Minneci meta-analysis (N = 1,171), the probability was 0.57 to achieve mortality RRR > 15%, 0.32 (RRR > 20%), and 0.14 (RRR > 25%). The removal of the Sprung trial from each analysis did not change the overall results. The probability of achieving shock reversal ranged from 65 to 92%. The probability of developing steroid-induced side effects was as follows: for gastrointestinal bleeding (N = 924), there was a 0.73 probability of steroids causing an RRI > 1%, 0.70 for RRI > 2%, and 0.67 for RRI > 5%; for superinfections (N = 964), probabilities were 0.81 (RRI > 1%), 0.76 (RRI > 2%), and 0.70 (RRI > 5%); and for hyperglycemia (N = 540), 0.99 (RRI > 1%), 0.97 (RRI > 2%), and 0.94 (RRI > 5%).

CONCLUSIONS

Based on clinically meaningful thresholds (RRR > 15-25%) for mortality reduction in severe sepsis or septic shock, the Bayesian approach to all three meta-analyses consistently showed that low-dose steroids were not associated with survival benefits. The probabilities of developing steroid-induced side effects (superinfections, bleeding, and hyperglycemia) were high for all analyses.

Implementing a collaborative protocol in a sepsis intervention program: lessons learned

The objective of this prospective cohort study was to see the effect of the implementation of a Sepsis Intervention Program on the standard processes of patient care using a collaborative approach between the Emergency Department (ED) and Medical Intensive Care Unit (MICU). This was performed in a large urban tertiary-care hospital, with no previous experience utilizing a specific intervention program as routine care for septic shock and which has services and resources commonly available in most hospitals. The study included 106 patients who presented to the ED with severe sepsis or septic shock. Eighty-seven of those patients met the inclusion criteria for complete data analysis. The ED and MICU staff underwent a 3-month training period followed by implementation of a protocol for sepsis intervention program over 6 months. In the first 6 months of the program's implementation, 106 patients were admitted to the ED with severe sepsis and septic shock. During this time, the ED attempted to initiate the sepsis intervention protocol in 76% of the 87 septic patients who met the inclusion criteria. This was assessed by documentation of a central venous catheter insertion for continuous SvO(2) monitoring in a patient with sepsis or septic shock. However, only 48% of the eligible patients completed the early goal-directed therapy (EGDT) protocol. Our data showed that the in-hospital mortality rate was 30.5% for the 87 septic shock patients with a mean APACHE II score of 29. This was very similar to a landmark study of EGDT (30.5% mortality with mean APACHE II of 21.5). Data collected on processes of care showed improvements in time to fluid administration, central venous access insertion, antibiotic administration, vasopressor administration, and time to MICU transfer from ED arrival in our patients enrolled in the protocol versus those who were not. Further review of our performance data showed that processes of care improved steadily the longer the protocol was in effect, although this was not statistically significant. There was no improvement in secondary outcomes, including total length of hospital stay, MICU days, and mortality. Implementation of a sepsis intervention program as a standard of care in a typical hospital protocol leads to improvements in processes of care. However, despite a collaborative approach, the sepsis intervention program was underutilized with only 48% of the patients completing the sepsis intervention protocol.

Global utilization of low-dose corticosteroids in severe sepsis and septic shock: a report from the PROGRESS registry

INTRODUCTION

The benefits and use of low-dose corticosteroids (LDCs) in severe sepsis and septic shock remain controversial. Surviving sepsis campaign guidelines suggest LDC use for septic shock patients poorly responsive to fluid resuscitation and vasopressor therapy. Their use is suspected to be wide-spread, but paucity of data regarding global practice exists. The purpose of this study was to compare baseline characteristics and clinical outcomes of patients treated or not treated with LDC from the international PROGRESS (PROmoting Global Research Excellence in Severe Sepsis) cohort study of severe sepsis.

METHODS

Patients enrolled in the PROGRESS registry were evaluated for use of vasopressor and LDC (equivalent or lesser potency to hydrocortisone 50 mg six-hourly plus 50 microg 9-alpha-fludrocortisone) for treatment of severe sepsis at any time in intensive care units (ICUs). Baseline characteristics and hospital mortality were analyzed, and logistic regression techniques used to develop propensity score and outcome models adjusted for baseline imbalances between groups.

RESULTS

A total of 8,968 patients with severe sepsis and sufficient data for analysis were studied. A total of 79.8% (7,160/8,968) of patients received vasopressors, and 34.0% (3,051/8,968) of patients received LDC. Regional use of LDC was highest in Europe (51.1%) and lowest in Asia (21.6%). Country use was highest in Brazil (62.9%) and lowest in Malaysia (9.0%). A total of 14.2% of patients on LDC were not receiving any vasopressor therapy. LDC patients were older, had more co-morbidities and higher disease severity scores. Patients receiving LDC spent longer in ICU than patients who did not (median of 12 versus 8 days; P <0.001). Overall hospital mortality rates were greater in the LDC than in the non-LDC group (58.0% versus 43.0%; P <0.001). After adjusting for baseline imbalances, in all mortality models (with vasopressor use), a consistent association remained between LDC and hospital mortality (odds ratios varying from 1.30 to 1.47).

CONCLUSIONS

Widespread use of LDC for the treatment of severe sepsis with significant regional and country variation exists. In this study, 14.2% of patients received LDC despite the absence of evidence of shock. Hospital mortality was higher in the LDC group and remained higher after adjustment for key determinates of mortality.

Serum lipopolysaccharide binding protein levels predict severity of lung injury and mortality in patients with severe sepsis

Background

There is a need for biomarkers insuring identification of septic patients at high-risk for death. We performed a prospective, multicenter, observational study to investigate the time-course of lipopolysaccharide binding protein (LBP) serum levels in patients with severe sepsis and examined whether serial serum levels of LBP could be used as a marker of outcome.

Methodology/Principal Findings

LBP serum levels at study entry, at 48 hours and at day-7 were measured in 180 patients with severe sepsis. Data regarding the nature of infections, disease severity, development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), and intensive care unit (ICU) outcome were recorded. LBP serum levels were similar in survivors and non-survivors at study entry (117.4±75.7 µg/mL vs. 129.8±71.3 µg/mL, P = 0.249) but there were significant differences at 48 hours (77.2±57.0 vs. 121.2±73.4 µg/mL, P<0.0001) and at day-7 (64.7±45.8 vs. 89.7±61.1 µg/ml, p = 0.017). At 48 hours, LBP levels were significantly higher in ARDS patients than in ALI patients (112.5±71.8 µg/ml vs. 76.6±55.9 µg/ml, P = 0.0001). An increase of LBP levels at 48 hours was associated with higher mortality (odds ratio 3.97; 95%CI: 1.84–8.56; P<0.001).

Conclusions/Significance

Serial LBP serum measurements may offer a clinically useful biomarker for identification of patients with severe sepsis having the worst outcomes and the highest probability of developing sepsis-induced ARDS.

Effectiveness of treatments for severe sepsis: a prospective, multicenter, observational study

RATIONALE

Several Surviving Sepsis Campaign Guidelines recommendations are reevaluated.

OBJECTIVES

To analyze the effectiveness of treatments recommended in the sepsis guidelines.

METHODS

In a prospective observational study, we studied all adult patients with severe sepsis from 77 intensive care units. We recorded compliance with four therapeutic goals (central venous pressure 8 mm Hg or greater for persistent hypotension despite fluid resuscitation and/or lactate greater than 36 mg/dl, central venous oxygen saturation 70% or greater for persistent hypotension despite fluid resuscitation and/or lactate greater than 36 mg/dl, blood glucose greater than or equal to the lower limit of normal but less than 150 mg/dl, and inspiratory plateau pressure less than 30 cm H(2)O for mechanically ventilated patients) and four treatments (early broad-spectrum antibiotics, fluid challenge in the event of hypotension and/or lactate greater than 36 mg/dl, low-dose steroids for septic shock, drotrecogin alfa [activated] for multiorgan failure). The primary outcome measure was hospital mortality. The effectiveness of each treatment was estimated using propensity scores.

MEASUREMENTS AND MAIN RESULTS

Of 2,796 patients, 41.6% died before hospital discharge. Treatments associated with lower hospital mortality were early broad-spectrum antibiotic treatment (treatment within 1 hour vs. no treatment within first 6 hours of diagnosis; odds ratio, 0.67; 95% confidence interval, 0.50-0.90; P = 0.008) and drotrecogin alfa (activated) (odds ratio, 0.59; 95% confidence interval, 0.41-0.84; P = 0.004). Fluid challenge and low-dose steroids showed no benefits.

CONCLUSIONS

In severe sepsis, early administration of broad-spectrum antibiotics in all patients and administration of drotrecogin alfa (activated) in the most severe patients reduce mortality.