Katherine J. Deans

Meta-Analysis: The Effect of Steroids on Survival and Shock during Sepsis Depends on the Dose

Despite effective antibiotics, septic shock remains the most common cause of death in the intensive care unit, incurring a mortality rate of 30% to 50% (1, 2). Several therapies targeting the upregulated inflammatory pathways of sepsis have been studied to improve survival. However, few therapies have proven beneficial (3-10). In the 1960s, preclinical studies reported that high doses of glucocorticoids in models of Escherichia coli and endotoxic shock improved survival. These studies prompted the initiation of human sepsis trials (11-13). Subsequently, more than 50 human trials have examined the role of high-dose steroid therapy in sepsis. These trials administered doses of methylprednisolone as high as 30 to 120 mg/kg of body weight over 24 hours. Because the reported results of these trials were inconsistent, there was little consensus on the appropriate use of steroids in patients with septic shock. To clarify the treatment effects of high-dose steroids, 3 meta-analyses performed in the 1990s examined the more rigorously conducted randomized, controlled clinical trials of sepsis (7, 14, 15). The meta-analysis by Lefering and colleagues (14) incorporated 10 trials and found no overall beneficial effect of glucocorticoid therapy on mortality in septic patients (absolute difference in mortality rates between treatment and control groups, 0.2 percentage point [95% CI, 9.2 percentage points to 8.8 percentage points]). A second meta-analysis by Cronin and colleagues (15) examined 9 trials with variable effects (P= 0.02) and reported no evidence of a beneficial effect of high-dose steroids on mortality from sepsis (relative risk for death with treatment, 1.13 [CI, 0.99 to 1.29]). A third meta-analysis, performed by our group (7), examined the trials included in the previous meta-analyses. Nine trials, which were the same as those investigated by Cronin and colleagues (15), met inclusion criteria for that analysis (7). In this group of trials, we identified 1 study (16) as a statistical outlier that accounted for the variability reported by Cronin and colleagues. After exclusion of this outlier, our analysis revealed a homogenous group of 8 studies (P> 0.2) that demonstrated an overall increase in mortality associated with the use of high-dose steroids in septic patients (odds ratio of survival with treatment, 0.70 [CI, 0.55 to 0.91]; P= 0.008) (7). The increased mortality in these studies may have been due to the immunosuppressive effects of steroids, which led to more severe secondary infections (17-19). In response to these overall discouraging results, the use of high-dose glucocorticoids in septic patients decreased in the late 1980s and 1990s. Recently, interest in examining the role of the adrenal axis in sepsis has been renewed. Briegel and colleagues (20) reported that septic patients have an attenuated response to corticotropin stimulation testing during their acute illness. Furthermore, Annane and colleagues (21) demonstrated that a high cortisol level and an attenuated response to corticotropin stimulation indicate relative adrenal insufficiency during sepsis that may increase mortality. On the basis of these findings, several clinical trials have been performed to determine whether administering glucocorticoids in dosages similar to the amount produced physiologically during a stressful state (that is, 300 mg of cortisol per day) affects outcome in septic patients. We performed the current study to update our previous meta-analysis and compare recent clinical trials with previous clinical trials of steroid use in patients with sepsis (22). Methods Literature Search We searched MEDLINE for medical literature published from 1988 to December 2003 by using the following keywords: steroids and sepsis, steroids and septic shock, glucocorticoids and sepsis, glucocorticoids and septic shock, corticosteroids and sepsis, and corticosteroids and septic shock. Studies were included if they met all of the following criteria: randomized, controlled trial design; enrollment of adult patients who met criteria for sepsis or septic shock; and a primary end point, including either the discontinuation of vasopressor therapy or a change in survival comparing glucocorticoid treatment with a control group with or without placebo. Included studies must have administered similar treatments to both the control and steroid groups, with the exception of the administration of a predetermined glucocorticoid regimen. Criteria for sepsis or septic shock needed to be clearly defined in each study and be consistent with the American College of Chest Physicians and Society of Critical Care Medicine Consensus Conference (23) definition for sepsis (including documented site or strong suspicion of infection, temperature > 38 C or < 36 C, heart rate > 90 beats/min, respiratory rate > 20 breaths/min, and leukocyte count > 12 109 cells/L), severe sepsis (sepsis plus organ dysfunction; hypotension or hypoperfusion, including oliguria, altered mental status, or lactate acidosis), and septic shock (hypotension despite fluid resuscitation plus hypoperfusion abnormalities) (23). Data Collection Two investigators trained in critical care medicine independently reviewed the included studies by using a standardized protocol and data collection form. A third author trained in critical care medicine evaluated and resolved discrepancies. We collected data on patient characteristics, study characteristics, treatment interventions, and treatment outcomes. Abstracted data included the presence of sepsis, severe sepsis, or septic shock; type, dose, and duration of glucocorticoid administered; incidence and severity of secondary infections; response to corticotropin stimulation testing; the number of patients with shock reversal; and the number of patient deaths. We evaluated the quality of the included trials by assessing the method and adequacy of randomization, blinding protocols, completeness of follow-up, adherence to treatment protocols, and co-interventions or treatments to each group in the studies. Our primary goal was to compare the effect of glucocorticoid administration on survival in the recent studies with the effects reported in the previously analyzed trials (22). Since the glucocorticoid regimen differed among the trials, we converted all dosages to hydrocortisone equivalents (24). Statistical Analysis Survival data were analyzed by using a Cochran-Mantel-Haenszel test to estimate the pooled effect of steroids (25). The similarity of the effect across studies was assessed by using a Breslow-Day test and reported with an I2 value (26, 27). When statistically significant heterogeneity of treatment effects was observed, studies were partitioned (for example, early vs. late studies) to decrease the heterogeneity of studies in a particular partition and increase the differences among the partitions, which can be seen when the I2 value is substantially lower in each partition as compared with the overall I2 value (28). One study increased the I2 value substantially in the set of early studies and was removed from all subsequent analyses. Partitioning variables were determined by regressing study characteristics (for example, steroid dose in first 24 hours) on mortality, specifically the log relative survival benefit (29). Regression was performed by using an inverse-variance-weighted restricted maximum likelihood random-effects method. When the regression was performed by using log steroid dose in the first 24 hours as the independent variable, 1 study was observed to be both a statistical outlier and influential. An indicator variable for this study was included in the regression analysis. Similar estimates of the slope associated with the effect of log steroid dose in the first 24 hours were observed when the influential study was removed and for early and late studies separately. A regression analysis that included control group mortality rate as an additional independent variable did not change the relationship between steroid dose in the first 24 hours and relative survival benefit. All pooled relative survival benefits are reported with associated 95% CIs by using a fixed-effects model. Random-effects estimates of survival were also calculated and reported. Statistically significant differences in characteristics between early and late studies were assessed by using analysis of variance (ANOVA) (when a weighted analysis was needed) or a 2-sample Wilcoxon test (when an unweighted analysis was performed). To analyze the different types of severity of illness scores used in the studies, we computed an effect size for each. This effect size was calculated by determining the difference between the mean steroid severity score and the mean control severity score, divided by the control standard deviation in each study. Role of the Funding Sources The Warren G. Magnuson Clinical Center at the National Institutes of Health, Bethesda, Maryland, provided intramural funds for this study. The funding source played no role in the design, conduct, or reporting of the study or decision to submit the manuscript for publication. Data Synthesis Comparison of Study Methods Since 1988, more than 1300 articles on steroids and sepsis have been published. Five randomized, controlled trials, all published after 1997, met inclusion criteria and were included in our analysis (30-34) (Figure 1). Four of these studies were published manuscripts, and 1 study was reported in abstract form (33). Figure 1. Flow diagram of the published articles evaluated for inclusion in this meta-analysis. The 5 studies published after 1997 were randomized, double-blind, placebo-controlled trials (Table 1). Each study listed specific inclusion and exclusion criteria that were consistent with American College of Chest Physicians and Society of Critical Care Medicine Consensus Conference definitions of sepsis and septic shock (23). Each study used a severity of illness score (Simplified Ac

Hemolysis-associated endothelial dysfunction mediated by accelerated NO inactivation by decompartmentalized oxyhemoglobin.

During intravascular hemolysis in human disease, vasomotor tone and organ perfusion may be impaired by the increased reactivity of cell-free plasma hemoglobin (Hb) with NO. We experimentally produced acute intravascular hemolysis in a canine model in order to test the hypothesis that low levels of decompartmentalized or cell-free plasma Hb will severely reduce NO bioavailability and produce vasomotor instability. Importantly, in this model the total intravascular Hb level is unchanged; only the compartmentalization of Hb within the erythrocyte membrane is disrupted. Using a full-factorial design, we demonstrate that free water-induced intravascular hemolysis produces dose-dependent systemic vasoconstriction and impairs renal function. We find that these physiologic changes are secondary to the stoichiometric oxidation of endogenous NO by cell-free plasma oxyhemoglobin. In this model, 80 ppm of inhaled NO gas oxidized 85-90% of plasma oxyhemoglobin to methemoglobin, thereby inhibiting endogenous NO scavenging by cell-free Hb. As a result, the vasoconstriction caused by acute hemolysis was attenuated and the responsiveness to systemically infused NO donors was restored. These observations confirm that the acute toxicity of intravascular hemolysis occurs secondarily to the accelerated dioxygenation reaction of plasma oxyhemoglobin with endothelium-derived NO to form bioinactive nitrate. These biochemical and physiological studies demonstrate a major role for the intact erythrocyte in NO homeostasis and provide mechanistic support for the existence of a human syndrome of hemolysis-associated NO dysregulation, which may contribute to the vasculopathy of hereditary, acquired, and iatrogenic hemolytic states.

Randomization in clinical trials of titrated therapies: unintended consequences of using fixed treatment protocols.

Objective:Clinical trial designs that randomize patients to fixed treatment regimens may disrupt preexisting relationships between illness severity and level of therapy. The practice misalignments created by such designs may have unintended effects on trial results and safety. Methods:To illustrate this problem, the Transfusion Requirements in Critical Care (TRICC) trial and the Acute Respiratory Distress Syndrome Network low tidal volume (ARMA) trial were analyzed. Results:Publications before TRICC indicated that clinicians used higher transfusion thresholds in patients with ischemic heart disease compared with younger, healthier patients (p = .001). The trial, however, randomized patients (n = 838) to liberal (10 g/dL hemoglobin) or restrictive (7 g/dL) transfusion thresholds. Thirty-day mortality was different and opposite in the liberal compared with the restrictive arm depending on presence (21 vs. 26%) or absence (25 vs. 16%) of ischemic heart disease (p = .03). At baseline in ARMA, consistent with prior publications, physicians set ventilator volumes lower in patients with high airway pressures and poor compliance (8.4–10.6 mL/kg interquartile range) than patients with less severe abnormalities (9.6–12 mL/kg) (p = .0001). In the trial, however, patients (n = 861) were randomized to low (6 mL/kg) or high (12 mL/kg) tidal volumes. In patients with low compliance (<0.6 mL/kg), 28-day mortality was higher when tidal volumes were raised rather than lowered (42 vs. 29%), but this effect was reversed in patients with higher compliance (21 vs. 37%; p = .003). Conclusions:In TRICC and ARMA, randomization to fixed treatment regimens disrupted preexisting relationships between illness severity and therapy level. This created noncomparable subgroups in both study arms that received care different and opposite from titrated care, that is, practice misalignments. These subgroups reduced the interpretability and safety of each trial. Characterizing current practice, incorporating current practice controls, and using alternative trial designs to minimize practice misalignments should improve trial safety and interpretability.

Mechanical ventilation in ARDS: One size does not fit all.

In this issue of Critical Care Medicine, Dr. Kallet and colleagues (1) report a significant improvement in mortality in patients with adult respiratory distress syndrome (ARDS) and acute lung injury (ALI) who received lung protective ventilation based on the recommendations of the ARDS Network trial

The effects of steroids during sepsis depend on dose and severity of illness: an updated meta-analysis

A previous meta-analysis determined that the effects of steroids during sepsis were dose-dependent; since then, additional trials have been published. The current analysis updates our previous analysis examining the effects of steroids during sepsis. A literature search from 2004 to 2008 identified seven randomized controlled trials in adult patients; these were added to 14 previously identified trials. The effects of steroids on mortality were highly variable among the 21 trials (p <0.001, I(2) = 60%). In trials published before 1989, which involved short courses of high-dose steroids, steroids increased mortality (n = 8, I(2) = 14%, OR of death 1.39 (95% CI 1.04-1.86), p 0.03). In trials published after 1997, which involved longer courses of lower-dose steroids, steroids consistently improved shock reversal (n = 7, I(2) = 0%, OR of shock reversal 1.66 [95% CI 1.25-2.20), p <0.001), but demonstrated a more heterogeneous beneficial effect on mortality (n = 12, I(2) = 25%, OR of death 0.64 (95% CI 0.45-0.93), p 0.02). An inverse linear relationship between severity of illness and the effects of steroids on mortality was identified across all trials (p 0.03) and within the subgroup of trials published after 1997 (p 0.03); steroids were harmful in less severely ill patient populations and beneficial in more severely ill patient populations. There was no effect of response to adrenocorticotrophic hormone (ACTH) stimulation testing concerning the effects of steroids and no increase in steroid-associated adverse events. Low-dose steroids appear to improve mortality rates in patients with septic shock who are at high risk of death; however, additional trials in this subpopulation are necessary to definitively determine the role of low-dose steroids during sepsis.

Nitrite reductase activity of hemoglobin as a systemic nitric oxide generator mechanism to detoxify plasma hemoglobin produced during hemolysis

Hemoglobin (Hb) potently inactivates the nitric oxide (NO) radical via a dioxygenation reaction forming nitrate (NO(3)(-)). This inactivation produces endothelial dysfunction during hemolytic conditions and may contribute to the vascular complications of Hb-based blood substitutes. Hb also functions as a nitrite (NO(2)(-)) reductase, converting nitrite into NO as it deoxygenates. We hypothesized that during intravascular hemolysis, nitrite infusions would limit the vasoconstrictive properties of plasma Hb. In a canine model of low- and high-intensity hypotonic intravascular hemolysis, we characterized hemodynamic responses to nitrite infusions. Hemolysis increased systemic and pulmonary arterial pressures and systemic vascular resistance. Hemolysis also inhibited NO-dependent pulmonary and systemic vasodilation by the NO donor sodium nitroprusside. Compared with nitroprusside, nitrite demonstrated unique effects by not only inhibiting hemolysis-associated vasoconstriction but also by potentiating vasodilation at plasma Hb concentrations of <25 muM. We also observed an interaction between plasma Hb levels and nitrite to augment nitroprusside-induced vasodilation of the pulmonary and systemic circulation. This nitrite reductase activity of Hb in vivo was recapitulated in vitro using a mitochondrial NO sensor system. Nitrite infusions may promote NO generation from Hb while maintaining oxygen delivery; this effect could be harnessed to treat hemolytic conditions and to detoxify Hb-based blood substitutes.

Mortality increases with recurrent episodes of nonaccidental trauma in children

BACKGROUND Nonaccidental trauma (NAT) is a leading cause of childhood traumatic injury and death. Our objectives were to compare the mortality rates of children who experience recurrent episodes of NAT (rNAT) with children who experience a single episode of NAT and to identify factors associated with rNAT and increased mortality from rNAT. METHODS Patients of NAT and rNAT in the Ohio State Trauma Registry were identified by matching date of birth, race, and sex between records of patients younger than 16 years between 2000 and 2010 with an DRG International Classification of Diseases—9th Rev. e-code for child abuse (E967–E967.9). Statistical comparisons were made using Fisher’s exact and Wilcoxon rank-sum tests. RESULTS A total of 1,572 patients of NAT were identified, with 53 patients meeting criteria for rNAT. Compared with patients with single-episode NAT, patients with rNAT were more commonly male (66% vs. 52%, p = 0.05), were white (83% vs. 65%, p = 0.02), were evaluated at a pediatric trauma center (87% vs. 69%, p = 0.008), and had higher mortality (24.5% vs. 9.9%, p = 0.002). Compared with rNAT patients who did not die, those who died with rNAT had a longer interval from initial episode to second episode (median [interquartile range], 527 days [83–1,099] vs. 166 days [52–502]; p = 0.07) and were older during their second episode (1 year [<6 months to 3 years] vs. <6 months [<6 months to 1 year]; p = 0.06). At initial presentation, lower-extremity fractures (p = 0.09) and liver injuries (p = 0.06) were reported more commonly in nonsurvivors of rNAT. CONCLUSION Mortality is significantly higher in children who experience rNAT. Therefore, it is critically important to effectively intervene with appropriate resources and follow-up after a child’s initial episode of NAT to prevent a future catastrophic episode. LEVEL OF EVIDENCE Prognostic/epidemiologic study, level IV.

Activated protein C in sepsis: emerging insights regarding its mechanism of action and clinical effectiveness

Purpose of review Dysregulation of endogenous coagulant and anticoagulant systems is now believed to play an important role in the pathogenesis of sepsis and septic shock. Reductions in host activated protein C levels and resultant microvascular thrombosis provided a basis for the use of recombinant human activated protein C in sepsis. Although controversial, the findings from an initial phase III trial testing this agent resulted in its approval for use in patients with severe sepsis and high risk of death. This review highlights emerging insights into the biology of protein C and activated protein C in sepsis, summarizes additional analysis growing out of the phase III trial testing recombinant human activated protein C, and assesses the cost-effectiveness that the clinical use of the agent has had thus far. Recent findings Binding of activated protein C to the endothelial cell protein C receptor is recognized to result in a growing number of actions including increased activity of activated protein C itself and inhibition of both nuclear factor-κB, a central regulator in the host inflammatory response, and apoptosis. Additional analysis of the original phase III trial testing recombinant human activated protein C appears to emphasize one of the US Food and Drug Administrations original concerns regarding an association between severity of sepsis and this agents effects. Postmarketing analysis and growing experience with other anticoagulant agents and corticosteroids in sepsis raise questions regarding the ultimate cost-effectiveness of activated protein C. Summary The protein C pathway is important both to coagulant and inflammatory pathways during sepsis. Based on emerging investigations, its actions appear to be increasingly complex ones. Despite potentially promising results in an initial phase III trial, the role of recombinant human activated protein C in the treatment of septic patients must continue to be evaluated.

Increasing the Efficacy of Anti-Inflammatory Agents Used in the Treatment of Sepsis

Excessive production of inflammatory mediators during invasive infection plays a key role in the pathogenesis of septic shock. In an attempt to improve survival of patients with this lethal syndrome, agents were developed to selectively inhibit mediators in this inflammatory response. Despite promising preclinical results, several different mediator-specific anti-inflammatory agents failed to demonstrate significant benefit in patients. There was, however, a significant difference in mortality between preclinical and clinical trials. The median control mortality in preclinical trials, performed almost uniformly in highly lethal sepsis models, was 88%. In clinical trials however, the median control mortality rate was much lower, at 41%. A recent meta-regression analysis of these preclinical and clinical trials in combination with prospective confirmatory studies demonstrated that risk of death as assessed by control group mortality rate significantly altered the treatment effect of these agents in both humans and animals. While anti-inflammatory agents were very beneficial in groups with high control mortality rates, they were ineffective or harmful in groups with low control mortality rates. Thus, variation in the risk of death due to sepsis provides a basis for the marked difference in the efficacy of these anti-inflammatory agents in preclinical and clinical trials over the last decade. In contrast to mediator-specific anti-inflammatory agents, glucocorticoids and activated protein C have recently demonstrated significant beneficial effects in individual clinical trials. However, glucocorticoids were studied only in patients with vasopressor-dependent septic shock, which is associated with a high control mortality rate (i.e. 61%) similar to the level at which mediator-specific agents would have been expected to be markedly beneficial. Furthermore, consistent with earlier findings for mediator-specific anti-inflammatory agents, analysis of the activated protein C study also demonstrated a relationship between risk of death and effect of treatment. Developing better methods to define high-risk septic populations for treatment with anti-inflammatory agents will increase the efficacy of this therapeutic approach and minimize its potential for harm.

Antithrombotic therapies for sepsis: A need for more studies*

I n this issue of Critical Care Medicine, Dr. Wiedermann and colleagues (1) performed a retrospective analysis of the phase III Kybersept trial and demonstrated a beneficial effect of antithrombin (AT) III in the subgroup of patients with a moderate risk of death (40–70% mortality rate) (2). However, over the past 2 decades, beneficial effects of new sepsis therapies identified by such subgroup analysis have not been confirmed in subsequent clinical trials (3). To maximize predictive ability, subgroup analysis of clinical trials should include all patients enrolled in the trial and should test whether treatment effects are altered by important variables. In addition, p values should be corrected for those factors tested that could potentially alter the treatment effect of an agent. Finally, findings should be consistent with known pathophysiologic mechanisms. The analysis by Dr. Wiedermann and colleagues does not meet these requirements. However, their report represents an intriguing application of a previous hypothesis by Knaus and Wagner (4). They postulated that treatments which alter the host inflammatory response, such as AT III, should be beneficial in septic patients with intermediate mortality rates but not the extremes (4). These therapies would have no effect in very low risk patients because host responses are appropriate and of limited harm, and they would be ineffective in very high risk patients because the overall likelihood of death is so great that no treatment would be beneficial. To further test this hypothesis for AT III, we examined the clinical sepsis trials of AT III and two other antithrombotic agents: recombinant human activated protein C (rhAPC) and tissue factor pathway inhibitor (TFPI, Table 1) (2, 5, 6). Examining these three agents separately and combined, we attempted to provide insights into how these agents act as a class, to improve our understanding of the similarities and differences in these agents, and to potentially identify factors that alter their efficacy. This analysis explores additional data not available in prior review of these agents (7).