A trial of antioxidants N-acetylcysteine and procysteine in ARDS. The Antioxidant in ARDS Study Group

Randomized clinical trial of activated protein C for the treatment of acute lung injury

RATIONALE

Microvascular injury, inflammation, and coagulation play critical roles in the pathogenesis of acute lung injury (ALI). Plasma protein C levels are decreased in patients with acute lung injury and are associated with higher mortality and fewer ventilator-free days.

OBJECTIVES

To test the efficacy of activated protein C (APC) as a therapy for patients with ALI.

METHODS

Eligible subjects were critically ill patients who met the American/European consensus criteria for ALI. Patients with severe sepsis and an APACHE II score of 25 or more were excluded. Participants were randomized to receive APC (24 microg/kg/h for 96 h) or placebo in a double-blind fashion within 72 hours of the onset of ALI. The primary endpoint was ventilator-free days.

MEASUREMENTS AND MAIN RESULTS

APC increased plasma protein C levels (P = 0.002) and decreased pulmonary dead space fraction (P = 0.02). However, there was no statistically significant difference between patients receiving placebo (n = 38) or APC (n = 37) in the number of ventilator-free days (median [25-75% interquartile range]: 19 [0-24] vs. 19 [14-22], respectively; P = 0.78) or in 60-day mortality (5/38 vs. 5/37 patients, respectively; P = 1.0). There were no differences in the number of bleeding events between the two groups.

CONCLUSIONS

APC did not improve outcomes from ALI. The results of this trial do not support a large clinical trial of APC for ALI in the absence of severe sepsis and high disease severity.

Formic acid: a rare but deadly source of carbon monoxide poisoning

INTRODUCTION

Formic acid decomposes upon contact with strong acids producing carbon monoxide. Carbon monoxide poisoning from such a source, however, is extremely rare.

CASE REPORT

A 26-year-old man committed suicide by mixing 2.5 L of formic acid and 2.5 L of sulfuric acid in three beakers and staying in a closed room. The 53-year-old father performed cardiopulmonary resuscitation on his son but soon lost consciousness. In hospital, he initially manifested coma, hypoxemia, metabolic acidosis, and a carboxyhemoglobin level of 45.8%. He was treated with hyperbaric oxygen but developed acute respiratory distress syndrome on day four despite an early improvement. He was successfully weaned from the ventilator on day 8. The 53-year-old mother felt dizziness, headache and had a carboxyhemoglobin level of 23.0%. Her symptoms improved after oxygen therapy.

DISCUSSION AND CONCLUSIONS

Formic acid is a highly fatal source of carbon monoxide poisoning when mixed with sulfuric acid. In addition to the toxicities of carbon monoxide, concomitant inhalation of formic acid fumes can cause severe lung injury, which may complicate the management of carbon monoxide poisoning.

A double-blind placebo-controlled study to evaluate the safety and efficacy of L-2-oxothiazolidine-4-carboxylic acid in the treatment of patients with acute respiratory distress syndrome

OBJECTIVE

Acute respiratory distress syndrome is an abrupt inflammatory illness that involves damage from reactive oxygen species. We examined the efficacy and safety of oxothiazolidine-4-carboxylic acid (OTZ), a free radical scavenger, in treating acute respiratory distress syndrome.

DESIGN

Double-blind, placebo-controlled trial.

SETTING

Multicentered study.

PATIENTS

Patients with a PaO2/FiO2 < or = 200 and bilateral infiltrates on chest radiograph, and requiring mechanical ventilation.

INTERVENTIONS

We randomized 215 patients to receive OTZ, 210 mg/kg per day every 8 hrs for 14 days or placebo.

MEASUREMENTS AND MAIN RESULTS

Ventilator-free days (the number of days alive and free from ventilator requirement) during the first 30 days of study were 8.3 vs. 13.5 days for the OTZ and placebo groups, respectively (p < .001). Mortality was 30/101 (29.7%) in the OTZ group and 18/114 (15.8%) in the placebo group during the 30-day study period (p = .014). This study was terminated prematurely for safety reasons after 215 of the planned 352 patients were enrolled.

CONCLUSIONS

OTZ does not improve survival or reduce ventilator time in patients with acute respiratory distress syndrome and may worsen outcome, although mortality in the OTZ group was similar or lower than most similar trials. Alternatively, our results may be best explained by the unusually excellent outcome in the placebo group.

Roles of oxidants and redox signaling in the pathogenesis of acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a disease process that is characterized by diffuse inflammation in the lung parenchyma and resultant permeability edema. The involvement of inflammatory mediators in ARDS has been the subject of intense investigation, and oxidant-mediated tissue injury is likely to be important in the pathogenesis of ARDS. In response to various inflammatory stimuli, lung endothelial cells, alveolar cells, and airway epithelial cells, as well as alveolar macrophages, produce reactive oxygen species (ROS) and reactive nitrogen species (RNS). In addition, the therapeutic administration of oxygen can enhance the production of these toxic species. As the antioxidant defense system, various enzymes and low-molecular weight scavengers are present in the lung tissue and epithelial lining fluid. In addition to their contribution to tissue damage, ROS and RNS serve as signaling molecules for the evolution and perpetuation of the inflammatory process, which involves genetic regulation. The pattern of gene expression mediated by oxidant-sensitive transcription factors is a crucial component of the machinery that determines cellular responses to oxidative stress. This review summarizes the recent progress concerning how redox status can be modulated and how it regulates gene transcription during the development of ARDS, as well as the therapeutic implications.

Vasopressin versus norepinephrine infusion in patients with septic shock

BACKGROUND

Vasopressin is commonly used as an adjunct to catecholamines to support blood pressure in refractory septic shock, but its effect on mortality is unknown. We hypothesized that low-dose vasopressin as compared with norepinephrine would decrease mortality among patients with septic shock who were being treated with conventional (catecholamine) vasopressors.

METHODS

In this multicenter, randomized, double-blind trial, we assigned patients who had septic shock and were receiving a minimum of 5 microg of norepinephrine per minute to receive either low-dose vasopressin (0.01 to 0.03 U per minute) or norepinephrine (5 to 15 microg per minute) in addition to open-label vasopressors. All vasopressor infusions were titrated and tapered according to protocols to maintain a target blood pressure. The primary end point was the mortality rate 28 days after the start of infusions.

RESULTS

A total of 778 patients underwent randomization, were infused with the study drug (396 patients received vasopressin, and 382 norepinephrine), and were included in the analysis. There was no significant difference between the vasopressin and norepinephrine groups in the 28-day mortality rate (35.4% and 39.3%, respectively; P=0.26) or in 90-day mortality (43.9% and 49.6%, respectively; P=0.11). There were no significant differences in the overall rates of serious adverse events (10.3% and 10.5%, respectively; P=1.00). In the prospectively defined stratum of less severe septic shock, the mortality rate was lower in the vasopressin group than in the norepinephrine group at 28 days (26.5% vs. 35.7%, P=0.05); in the stratum of more severe septic shock, there was no significant difference in 28-day mortality (44.0% and 42.5%, respectively; P=0.76). A test for heterogeneity between these two study strata was not significant (P=0.10).

CONCLUSIONS

Low-dose vasopressin did not reduce mortality rates as compared with norepinephrine among patients with septic shock who were treated with catecholamine vasopressors. (Current Controlled Trials number, ISRCTN94845869 [controlled-trials.com].).

N-acetylcysteine attenuates acute lung injury induced by fat embolism

OBJECTIVES

Fat embolism syndrome is a clinical issue in subjects with long-bone fracture. It may lead to acute lung injury. The mechanisms and therapeutic regimen remain unclear. The present study was designed to investigate the pathologic and biochemical changes after fat embolization in isolated rat lungs, and to test the effects of posttreatment with N-acetylcysteine (NAC).

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

A total of 36 perfused lungs isolated from Sprague-Dawley rats.

INTERVENTIONS

The isolated lungs were randomly assigned to receive physiologic saline solution (vehicle group), fat embolism (FE group), or FE with NAC posttreatment (FE + NAC group). There were 12 isolated lungs in each group. FE was produced by introduction of corn oil micelles. NAC at a dose 150 mg/kg was given 10 mins after FE.

MEASUREMENTS AND MAIN RESULTS

The extent of acute lung injury was evaluated by lung weight change, protein concentration in bronchoalveolar lavage, and exhaled nitric oxide. We also measured the pulmonary arterial pressure and capillary filtration coefficient and determined the nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate. Histopathologic changes of the lung were examined and quantified. The levels of neutrophil elastase and myeloperoxidase were determined. The expression of inducible nitric oxide synthase was detected. FE caused acute lung injury as evidenced by the lung weight changes, increases in exhaled nitric oxide and protein concentration in bronchoalveolar lavage, pulmonary hypertension, increased capillary filtration coefficient, and lung pathology. The insult also increased nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate, increased neutrophil elastase and myeloperoxidase levels, and upregulated inducible nitric oxide synthase expression. Posttreatment with NAC abrogated these changes induced by FE.

CONCLUSION

FE caused acute lung injury and associated biochemical changes. Posttreatment with NAC was effective to alleviate the pathologic and biochemical changes caused by FE.

Immunonutrition in surgical and critically ill patients

Surgery, trauma, burns and injury induce an inflammatory response that can become excessive and damaging in some patients. This hyperinflammation can be followed by an immunosuppressed state which increases susceptibility to infection. The resulting septic syndromes are associated with significant morbidity and mortality. A range of nutrients are able to modulate inflammation (and the associated oxidative stress) and to maintain or improve immune function. These include several amino acids, antioxidant vitamins and minerals, long-chain n-3 fatty acids and nucleotides. Experimental studies support a role for each of these nutrients in surgical, injured or critically ill patients. There is good evidence that glutamine influences immune function in such patients and that this is associated with clinical improvement. Evidence is also mounting for the use of long-chain n-3 fatty acids in surgical and septic patients, but more evidence of clinical efficacy is required. Mixtures of antioxidant vitamins and minerals are also clinically effective, especially if they include selenium. Their action appears not to involve improved immune function, although an anti-inflammatory mode of action has not been ruled out. Enteral immunonutrient mixtures, usually including arginine, nucleotides and long-chain n-3 fatty acids, have been used widely in surgical and critically ill patients. Evidence of efficacy is good in surgical patients. However whether these same mixtures are beneficial, or should even be used, in critically ill patients remains controversial, since some studies show increased mortality with such mixtures. There is a view that this is due to a high arginine content driving nitric oxide production.

Recent developments in the management of acute respiratory distress syndrome in adults

PURPOSE

Recent developments in the management of acute respiratory distress syndrome (ARDS) in adults are reviewed.

SUMMARY

Corticosteroids have been extensively studied in ARDS; however, they have not demonstrated clear benefit in patients with ARDS. Some trials have found increased complications and mortality related to corticosteroid use. The use of conservative fluid management has been associated with significant reductions in morbidity, highlighting the need to avoid fluid over-administration in patients with ARDS. A number of ventilatory strategies have also been studied. Studies have found that higher positive end-expiratory pressure settings do not appear to be harmful in patients with ARDS. In an effort to prevent alveolar overdistention, low tidal volume and plateau pressure ventilation is increasingly being used in patients with acute lung injury (ALI). Given the increasing evidence supporting the use of lower tidal volume ventilation, this strategy has become the new standard of care in patients with suspected ALI and ARDS. No clear benefit has been shown in the treatment of ARDS with nitric oxide and surfactant. Prostaglandins and acetylcysteine are not considered useful in the treatment of ARDS, while no conclusions can be drawn regarding the benefits of albuterol on mortality in patients with ARDS. The use of prone positioning should be discouraged in the treatment of ARDS based on its associated risks.

CONCLUSION

Early administration of moderate-dosage corticosteroids likely helps decrease the time of ventilator dependence and duration of intensive care unit stay. Conservative fluid management and low tidal volume ventilation are becoming increasingly widespread in the management of patients with ARDS. Nitric oxide, surfactant, prostaglandins, albuterol, acetylcysteine, and prone positioning have not been shown to be beneficial in the treatment of ARDS.

Redox imbalance and ventilator-induced lung injury

Mechanical ventilation (MV) is an indispensable therapy in the care of critically ill patients with acute lung injury and the acute respiratory distress syndrome; however, it is also known to further lung injury in certain conditions of mechanical stress, leading to ventilator-induced lung injury (VILI). The mechanisms by which conventional MV exacerbates lung injury and inflammation are of considerable clinical significance. Redox imbalance has been postulated, among other mechanisms, to enhance/perpetuate susceptibility to VILI. A better understanding of these pathologic mechanisms will help not only in alleviating the side effects of mechanical forces but also in the development of new therapeutic strategies. Here, we review the relevance of oxidative stress in VILI from human studies as well as cellular and mouse models of mechanical stress. Potential therapeutic avenues for the treatment of VILI with exogenous administration of antioxidants also are discussed.

High dose N-acetylcysteine to prevent pulmonary complications in partial or total transthoracic esophagectomy: results of a prospective observational study

Cancer of the esophagus has a poor long-term prognosis and a high peri-operative morbidity in which pulmonary complications play a major role. The combination of the surgical approach, pre-existing pulmonary disorders, poor nutritional status and the release of pro-inflammatory cytokines may be contributing factors. N-acetylcysteine ((NAC) has been shown to have oxygen scavenging abilities. In severe sepsis and acute respiratory distress syndrome, positive effects of NAC on morbidity and mortality were discovered. In this observational study peri-operative high dose NAC was administered in 22 patients. The effects of this treatment on respiratory function, morbidity and survival were studied. These prospectively collected data were compared with data of a matched, retrospective group without NAC treatment. There were no significant differences between the groups in terms of socio-demographic data, preoperative pulmonary function, intra-operative course and oncologic characteristics. The oxygenation indices at the postoperative hours 2 (P = 0.019), 4 (P < 0.001), 8 (P = 0.035), 12 (P = 0.035) and 24 (P = 0.046) were significantly higher in the NAC group. After 36 h, the difference between groups was no longer significant (P = 0.064). NAC-treated patients showed significant lower overall pulmonary morbidity, 45.5% versus 81.8% (P = 0.027). Surgical morbidity, intensive care unit and hospital stay were not significantly different between groups, mortality was zero. Kaplan-Meier curves showed no significant difference in survival 12 months postoperatively. These data indicate that postoperative oxygenation can be improved and rate of overall pulmonary complications is reduced using peri-operative high dose NAC in transthoracic esophagectomy.

Emerging therapies for treatment of acute lung injury and acute respiratory distress syndrome

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a life-threatening form of respiratory failure that affects a heterogeneous population of critically ill patients. Although overall mortality appears to be decreasing in recent years due to improvements in supportive care, there are presently no proven, effective pharmacological therapies to treat ARDS and prevent its associated complications. The most common cause of death in ARDS is not hypoxemia or pulmonary failure, but rather multiple organ dysfunction syndrome (MODS), suggesting that improving survival in patients with ARDS may be linked to decreasing the incidence or severity of MODS. The key to developing novel treatments depends, in part, on identifying and understanding the mechanisms by which ARDS leads to MODS, although the heterogeneity and complexity of this disorder certainly poses a challenge to investigators. Novel therapies in development for treatment of ALI/ARDS include exogenous surfactant, therapies aimed at modulating neutrophil activity, such as prostaglandin and complement inhibitors, and treatments targeting earlier resolution of ARDS, such as beta-agonists and granulocyte macrophage colony-stimulating factor. From a clinical perspective, identifying subpopulations of patients most likely to benefit from a particular therapy and recognising the appropriate stage of illness in which to initiate treatment could potentially lead to better outcomes in the short term.

Acute lung injury and the acute respiratory distress syndrome: a clinical review

Acute respiratory distress syndrome and acute lung injury are well defined and readily recognised clinical disorders caused by many clinical insults to the lung or because of predispositions to lung injury. That this process is common in intensive care is well established. The mainstay of treatment for this disorder is provision of excellent supportive care since these patients are critically ill and frequently have coexisting conditions including sepsis and multiple organ failure. Refinements in ventilator and fluid management supported by data from prospective randomised trials have increased the methods available to effectively manage this disorder.

The biochemical basis of antioxidant therapy in critical illness

During critical illness free radical production may increase as a result of, for example, sepsis or tissue trauma. In addition, because of a potential for increased losses, and the possibility of inadequate nutrition, the antioxidant defences of the body may become compromised. Thus, the delicate balance between free radicals and antioxidants may be disturbed. Various nutritional and pharmacological strategies to enhance antioxidant defences have been proposed, which aim either to maintain or enhance endogenous antioxidant stores or to provide alternative antioxidant agents. Trace elements and amino acids are particularly important, and their synergistic role in the maintenance of the body's antioxidant defence network will be discussed.

Protein C -1641 AA is associated with decreased survival and more organ dysfunction in severe sepsis

OBJECTIVE

Protein C contains an A/G polymorphism at position -1641 and a C/T polymorphism at -1654 associated with risk of deep venous thrombosis. We tested the hypothesis that these polymorphisms are associated with altered outcome in patients having severe sepsis, in which protein C is a central molecule.

DESIGN

Prospective cohorts, gene-association study.

SETTING

Tertiary care medical/surgical intensive care unit.

PATIENTS

We first recruited a derivation cohort of patients having severe sepsis (n = 62). A second replication cohort was similarly defined but larger (n = 402). We tested for biological plausibility in a third cohort of post-cardiopulmonary bypass patients (n = 61).

INTERVENTIONS

Patients were genotyped at protein C -1641 and -1654.

MEASUREMENTS AND MAIN RESULTS

The primary outcome variable was survival in cohorts 1 and 2 and postoperative serum interleukin-6 concentration in cohort 3. Severity of individual organ dysfunctions and systemic inflammation were secondary outcome variables. In the first derivation cohort, the protein C -1641 AA genotype was associated with decreased 28-day survival (p < .05). This finding was confirmed in the much larger replication cohort of patients having severe sepsis (p = .028). In addition, the protein C -1641 AA genotype was associated with significantly more organ dysfunction and more clinical evidence of systemic inflammation (p < .05). Furthermore, the -1641 AA genotype was associated with increased serum interleukin-6 at 4 and 24 hrs after cardiopulmonary bypass (p = .024). There was no association of -1654 A/G with phenotype in any cohort.

CONCLUSIONS

Protein C -1641 AA genotype is associated with decreased survival, more organ dysfunction, and more systemic inflammation in patients having severe sepsis and with increased interleukin-6 levels after cardiopulmonary bypass surgery.

Acute lung injury and the acute respiratory distress syndrome: challenges in clinical trial design

Despite significant advances in the understanding of the complex pathophysiology, only a limited number of new treatments for acute lung injury (ALI) have emerged in the last 2 decades. This article discusses some of the challenges that remain in conducting clinical research in patients who have ALI and acute respiratory distress syndrome. New definitions that incorporate prognostic measures and reduce patient heterogeneity will allow more efficient enrollment of patients. Delineating outcomes attributable to the lung injury will improve the power of studies to detect significant treatment effects. Future collaborative studies will be needed to investigate longer-term clinical outcomes.

Adjunctive therapy to mechanical ventilation: surfactant therapy, liquid ventilation, and prone position

Acute lung injury and acute respiratory distress syndrome are associated with significant morbidity and mortality in critically ill patients. Although lung protective mechanical ventilation is the only therapy shown to reduce mortality and development of organ failure, several biologic pathways have been identified and provided an opportunity for therapeutic interventions. No pharmacologic or adjunctive treatments are available. Clinical studies demonstrated that prone position results in significant and clinically relevant improvement in oxygenation and ventilation, which persist when patients are returned to supine position; the beneficial response is not limited to patients turned early in disease course. Few complications are associated with prone ventilation. Clinical experience suggests that prone ventilation may protect the lung from potential detrimental effects of mechanical ventilation. Further studies are needed.

From bench to bedside: a review of the clinical trial development plan of drotrecogin alfa (activated)

OBJECTIVE

To provide a comprehensive overview of the various clinical trials of drotrecogin alfa (activated) (DrotAA) completed by Eli Lilly and Company over the past 10 years.

METHODS

Eli Lilly and Company data from phase 1 through phase 4 trials, observational studies, and compassionate-use studies of DrotAA were reviewed. Safety, efficacy, and pharmacokinetic data were included. The review excluded pediatric studies and studies recently concluded where the manuscript was in press. All studies included in the review were approved by the ethical review boards at the participating institutions.

RESULTS

Over 9000 adults with severe sepsis have been enrolled in DrotAA clinical trials through December 2005 and the results of the clinical evaluation of DrotAA have been widely disseminated in publications. Analyses of the data indicate that the pharmacokinetics of DrotAA are both linear and dose-proportional. The phase 2 and phase 3 studies of administration of DrotAA to patients with severe sepsis demonstrated a significant reduction in mortality and were associated with a favorable benefit/risk profile. Three of these trials (a phase 2 and two phase 3, PROWESS and ENHANCE) evaluated the effect of DrotAA in adult patients with sepsis associated with acute organ dysfunction (severe sepsis) while another phase 3 trial (ADDRESS) was conducted in the non-indicated population of adult patients with severe sepsis associated with a lower risk of death. A phase 4 trial demonstrated no significant difference in steady-state plasma concentrations or elimination half-life of DrotAA between patients < or =135 kg and >135 kg, indicating that DrotAA should be dosed by actual body weight.

DISCUSSION

The challenges and limitations of the clinical development plan for DrotAA are discussed.

CONCLUSION

DrotAA is indicated for the reduction of mortality in adult patients with severe sepsis (sepsis associated with acute organ dysfunction) who have a high risk of death. DrotAA is not indicated in adult patients with severe sepsis and low risk of death. The clinical plan for DrotAA continues with a focus on tailored therapy and identifying the most appropriate patients for DrotAA treatment.

Reactive oxygen species: toxic molecules or spark of life?

Increases in reactive oxygen species (ROS) and tissue evidence of oxidative injury are common in patients with inflammatory processes or tissue injury. This has led to many clinical attempts to scavenge ROS and reduce oxidative injury. However, we live in an oxygen rich environment and ROS and their chemical reactions are part of the basic chemical processes of normal metabolism. Accordingly, organisms have evolved sophisticated mechanisms to control these reactive molecules. Recently, it has become increasingly evident that ROS also play a role in the regulation of many intracellular signaling pathways that are important for normal cell growth and inflammatory responses that are essential for host defense. Thus, simply trying to scavenge ROS is likely not possible and potentially harmful. The 'normal' level of ROS will also likely vary in different tissues and even in different parts of cells. In this paper, the terminology and basic chemistry of reactive species are reviewed. Examples and mechanisms of tissue injury by ROS as well as their positive role as signaling molecules are discussed. Hopefully, a better understanding of the nature of ROS will lead to better planned therapeutic attempts to manipulate the concentrations of these important molecules. We need to regulate ROS, not eradicate them.

N-acetylcysteine attenuates the acute lung injury caused by phorbol myristate acetate in isolated rat lungs

Acute lung injury (ALI) caused by phorbol myristate acetate (PMA) is characterized by pulmonary edema and inflammatory cells infiltration. PMA-activated neutrophils in vivo and in vitro to release free radicals, pro-inflammatory cytokines, nitric oxide (NO) and other mediators. These mediators may be the causes of pulmonary hypertension and increased microvascular permeability. In the present study, we used isolated perfused rat lungs from Sprague-Dawley (SD) rats. The purpose was to evaluate the effects of pretreatment of N-acetylcysteine (NAC) on the PMA-induced ALI and associated changes. PMA (2 microg kg(-1)) was introduced into the lung perfusate. NAC (150 mg kg(-1)) was administered 10 min before PMA. Thirty isolated lungs were randomly assigned to receive vehicle (dimethyl sulfoxide, DMSO, the solvent for PMA, 100 microg g(-1)), PMA alone and PMA with NAC pretreatment. There were 10 lungs in each group. We measured the lung weight (LW) to body weight (BW) ratio (LW/BW), LW gain (LWG), exhaled nitric oxide (NO) and protein concentration in bronchoalveolar lavage (PCBAL). The pulmonary arterial pressure (PAP) and microvascular permeability (K(fc)) were assessed. The concentration of nitrate/nitrite, methyl guanidine (MG), tumor necrosis factor(alpha) (TNF(alpha)) and interleukin-1(beta) (IL-1(beta)) in lung perfusate were determined. In addition, we also evaluate the lung injury by histopathological examination and by grading system for the lung injury score (LIS). PMA caused severe ALI as evidenced by the marked increases in LW changes, exhaled NO, PCBAL, histopathological changes, and LIS. It also increased the nitrate/nitrite, MG, TNF(alpha), and IL-1(beta) in lung perfusate. Pretreatment with NAC significantly attenuated these changes and abrogated the extent of ALI. Our results suggest that NAC exerts strong protective effects on the PMA-induced ALI and associated alterations. The mechanisms are possibly attributable to its antioxidant actions, inhibition of pro-inflammatory cytokines, and restoration of glutathione enzymes.

Defining the research agenda for surgical infection: a consensus of experts using the Delphi approach

BACKGROUND

A substantial proportion of operative procedures are complicated by infections, either remote from or related to the surgical site. These infections account for substantive morbidity and health care costs. With limited research funds available to study interventions designed to either prevent or reduce the morbidity associated with infections in surgical patients, we developed a research agenda to develop priorities to aid in study design and to focus both human and capital resources more effectively.

METHODS

A Delphi survey approach was used. Consensus was developed among experts in the field of surgical infection and the membership of the Surgical Infection Society.

RESULTS

Thirty-six experts generated a total of 62 questions that were submitted for two rounds of consensus ranking. A total of 31 questions were ranked in the final round and are available at www.sisna.org. The most highly ranked question was "Does strict glycemic control compared with standard care reduce the risk of surgical site infection in patients undergoing abdominal surgery?" Most of the questions had little available data, suggesting these are both important and necessary areas for further research.

CONCLUSIONS

This research agenda, developed by a consensus of experts, provides direction and focus to the development of interventional trials geared toward reducing the morbidity associated with infections in surgical patients.

The effects of sulfur amino acid intake on immune function in humans

No direct data exist on the influence of supranormal intakes of sulfur amino acids on immune function in humans. However 3 major products of sulfur amino acids, glutathione (GSH), homocysteine (Hcy), and taurine (Tau), influence, mainly, inflammatory aspects of the immune response in vitro and in vivo. Methionine intakes above approximately 1 g/d transiently raise plasma Tau, Hcy, and GSH. Tau and GSH ameliorate inflammation. Hcy has the opposite effect. A biphasic relation, between cellular GSH and CD4+ and CD8+ numbers occurs in healthy men. How changes in sulfur amino acid intake influence this phenomenon is unknown. In animals, high Tau intakes are antiinflammatory. How immune function in humans is affected is unknown. A positive relation between plasma neopterin (a marker of a Th-1-type immune response) and Hcy indicates that Hcy may play a part in inflammatory aspects of Parkinson's disease and aging. In vitro, Hcy, at concentrations seen following consumption of approximately 6 g L-methionine/d in adults, increases the interactions among T lymphocytes, monocytes, and endothelium. Whether a similar phenomenon occurs in vivo is unknown. Polymorphisms in the methylenetetrahydrofolate reductase gene are associated with raised plasma Hcy in young but not old subjects. The relation of this observation to immune function is unknown. The relationships among Hcy, inflammatory aspects of disease, and in vitro alterations in immune cell behavior create a cautionary note about supplementation of diets with l-methionine to raise intake above approximately 1 g/d. Studies directly linking methionine intake, genetics, plasma Hcy, Tau, and GSH and immune function are needed.

Concomitant Administration of Mannitol and N-Acetylcysteine for the Prevention of Lung Reperfusion Injury

BACKGROUND

Mannitol (MN) and N- acetylcysteine (NAC) are partially successful in preventing lung reperfusion injury after liver ischemia reperfusion (IR). Their concomitant administration might enhance the individual effects of each.

METHODS

Rat isolated livers were perfused with Krebs-Henseleit solution (controls) or made globally ischemic (IR) for 2 hours. Separately isolated lungs were paired with livers and each pair was reperfused in-series for 15 minutes. During reperfusion, eight groups were treated with Krebs containing two low and two high doses of MN and/or NAC; one group received no treatment.

RESULTS

The tested lung parameters were unchanged in all control groups. Pulmonary perfusion or ventilatory pressures, weight gain and bronchoalveolar lavage volume increased by 30 to 70% of baseline in the nontreated IR-paired lungs and in the only IR-MN 0.44- and the IR-NAC 0.25 mmol (weight/body weight) treated lungs but remained preserved by the two higher monotherapies (MN 0.55 mmol and NAC 0.37 mmol) and by the four bitherapies. The reduced glutathione content in all lung tissue subgroups treated by the bitherapies was higher by 63 to 124% of the corresponding monotherapy values. Xanthine oxidase activity in the bitherapies-treated IR-lungs decreased 1.5 to twofold compared with the corresponding monotherapies.

CONCLUSIONS

Co-administration of MN and NAC augments the amount of lung protection afforded by each drug individually and enhances their antioxidant potentials.

Pharmacotherapy of acute lung injury and the acute respiratory distress syndrome

Acute lung injury and the acute respiratory distress syndrome are common syndromes with a high mortality rate that affect both medical and surgical patients. Better understanding of the pathophysiology of acute lung injury and the acute respiratory distress syndrome and advances in supportive care and mechanical ventilation have led to improved clinical outcomes since the syndrome was first described in 1967. Although several promising pharmacological therapies, including surfactant, nitric oxide, glucocorticoids and lysofylline, have been studied in patients with acute lung injury and the acute respiratory distress syndrome, none of these pharmacological treatments reduced mortality. This article provides an overview of pharmacological therapies of acute lung injury and the acute respiratory distress syndrome tested in clinical trials and current recommendations for their use as well as a discussion of potential future pharmacological therapies including beta(2)-adrenergic agonist therapy, keratinocyte growth factor, and activated protein C.

N-acetylcysteine abrogates acute lung injury induced by endotoxin

1. Acute lung injury (ALI) or acute respiratory distress syndrome is a serious clinical problem with high mortality. N-Acetylcysteine (NAC) is an anti-oxidant and a free radical scavenger. It has been reported recently that NAC ameliorates organ damage induced by endotoxin (lipopolysaccharide; LPS) in conscious rats. The present study was designed to evaluate the effects of NAC on LPS-induced ALI and other changes in anaesthetized rats. 2. Sprague-Dawley rats were anaesthetized with pentobarbital (40 mg/kg, i.p.). Endotracheal intubation was performed to provide artificial ventilation. Arterial pressure and heart rate were monitored. The extent of ALI was evaluated with the lung weight (LW)/bodyweight ratio, LW gain, exhaled nitric oxide (NO) and protein concentration in bronchoalveolar lavage (PCBAL). Haematocrit, white blood cells, plasma nitrate/nitrite, methyl guanidine (MG), tumour necrosis factor (TNF)-alpha and interleukin (IL)-1b were measured. Pathological changes in the lung were examined and evaluated. 3. Endotoxaemia was produced by injection of 10 mg/kg, i.v., LPS (Escherichia coli). Animals were randomly divided into three groups. In the vehicle group, rats received an i.v. drip of physiological saline solution (PSS) at a rate of 0.3 mL/h. The LPS group received an i.v. drip of PSS for 1 h, followed by LPS (10 mg/kg by slow blous injection, i.v., over 1-2 min). Rats in the LPS + NAC group received NAC by i.v. drip at a rate of 150 mg/kg per h (0.3 mL/h) for 60 min starting 10 min before LPS administration (10 mg/kg by slow blous injection, i.v., over 1-2 min). Each group was observed for a period of 6 h. 4. N-Acetylcysteine treatment improved the LPS-induced hypotension and leukocytopenia. It also reduced the extent of ALI, as evidenced by reductions in LW changes, exhaled NO, PCBAL and lung pathology. In addition, NAC diminished the LPS-induced increases in nitrate/nitrite, MG, TNF-a and IL-1b. 5. In another series of experiments, LPS increased the mortality rate compared with the vehicle group (i.v. drip of PSS at a rate of 0.3 mL/h) during a 6 h observation period. N-Acetylcysteine, given 10 min prior to LPS, significantly increased the survival rate. 6. The results of the present study suggest that NAC exerts a protective effect on the LPS-induced ALI. The mechanisms of action may be mediated through the reduction of the production of NO, free radicals and pro-inflammatory cytokines.

Vitamins and respiratory disease: antioxidant micronutrients in pulmonary health and disease

The lungs are continually exposed to relatively-high O(2) tensions, and as such, in comparison with other organs, they represent a unique tissue for the damaging effects of oxidant attack. At particular times during a lifetime this every day challenge may increase exponentially. The first oxidative insult occurs at birth, when cells are exposed to a sudden 5-fold increase in O(2) concentration. Thereafter, the human lung, from infancy through to old age, can be subjected to deleterious oxidative events as a consequence of inhaling environmental pollutants or irritants, succumbing to several pulmonary diseases (including infant and adult respiratory distress syndromes, asthma, chronic obstructive pulmonary disease, cystic fibrosis and cancer) and receiving treatment for these diseases. The present paper will review the concept that consumption of a healthy diet and the consequent ability to establish and then maintain adequate micronutrient antioxidant concentrations in the lung throughout life, and following various oxidative insults, could prevent or reduce the incidence of oxidant-mediated respiratory diseases. Furthermore, the rationale, practicalities and complexities of boosting the antioxidant pool of the respiratory-tract lining fluid in diseases in which oxidative stress is actively involved, by direct application to the lung v. dietary modification, in order to achieve a therapeutic effect will be discussed.

Lack of protection of N-acetylcysteine (NAC) in acute renal failure related to elective aortic aneurysm repair—a randomized controlled trial

BACKGROUND

N-acetylcysteine (NAC) is an antioxidant drug largely tested in different clinical situations. Recently, NAC has been employed with variable success in the prevention of radiocontrast nephropathy. Since aortic aneurysm surgical repair is a condition that is frequently accompanied by acute renal failure (ARF), we sought to investigate whether NAC has any role in preventing ARF in this scenario.

METHODS

A randomized, placebo-controlled, double-blind trial with the following inclusion criteria: elective aortic aneurysm repair in patients with stable renal function. The groups were randomly matched for age, gender, presence of diabetes and pre-existent renal failure. NAC or placebo (control) was administered p.o. for 24 h before operation and maintained i.v. for 48 h after operation. The dose of NAC was 1200 mg b.i.d. the day before surgery and 600 mg b.i.d. after. The primary endpoint was the development of ARF up to the third post-operative day, defined as an increase in SCr > or = 25% from baseline. Secondary endpoints were: ICU mortality and ICU length of stay.

RESULTS

Forty-two patients (n = 18 for NAC group and n = 24 for control) were studied. The baseline SCr and calculated GFR did not differ between the groups (1.19 +/- 0.33 vs 1.37 +/- 0.49 mg/dl; and 64.6 +/- 26.22 vs 65.7 +/- 28.32 ml/min, NAC vs control, respectively, P = 0.17 and P = 0.90). Need for suprarenal aortic cross-clamping and its duration, occurrence of major bleeding, intra-operative hypotension and the post-operative peak of CPK did not differ between NAC and control groups. The overall incidence of ARF in the study was 36% (13/36), but it was not significantly different between groups (7/14, 50% in NAC vs 6/22, 27.3% in control, P = 0.16). The overall mortality was 23% (10/42) and was not different (P = 0.209) in NAC group (33.3%) when compared with control (16.7%), the same occurring with the length of ICU stay (2.93 +/- 1.53 vs 2.52 +/- 1.36 days, P = 0.40).

CONCLUSION

This study suggests that the putative beneficial effects of NAC on radiocontrast nephropathy might not be applicable to other situations, such as ARF associated with elective aortic aneurysm repair.

The role of oxidative stress in adult critical care

Oxidative stress defines an imbalance in production of oxidizing chemical species and their effective removal by protective antioxidants and scavenger enzymes. Evidence of massive oxidative stress is well established in adult critical illnesses characterized by tissue ischemia-reperfusion injury and by an intense systemic inflammatory response such as during sepsis and acute respiratory distress syndrome. Oxidative stress could exacerbate organ injury and thus overall clinical outcome. We searched MEDLINE databases (January 1966 to June 2005). For interventional studies, we accepted only randomized trials. Several small clinical trials have been performed in order to reduce oxidative stress by supplementation of antioxidants alone or in combination with standard therapies. These studies have reported controversial results. Newer large multicenter trials with antioxidant supplementation should be performed, considering administration at an early stage of illness and a wider population of critically ill patients.

Pharmacological therapy for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is an Inflammatory process caused by a variety of direct and indirect injuries to the lungs. Despite improvements in supportive care and advances in ventilator management, mortality in patients with ARDS remains high. Multiple pharmacological interventions have been investigated but have not shown improved survival. Clinical trials using corticosterolds, prostaglandins, nitric oxide, prostacyclin, surfactant, lisofylline, ketoconazole, N-acetylcystelne, and fish oil have been unable to show a statistically significant Improvement in patient mortality. As more is understood about the pathophyslology of ARDS, treatment strategies such as increasing alveolar fluid clearance through activation of sodium channels, enhancing repair of alveolar epithelium with growth factors, inhibiting fibrin deposition, blocking proinflammatory transcription factors, preventing the effect of potent vasocontrictors such as endothelin, and using antibodies against key inflammatory cytokines are being explored. This review focuses on the pharmacological treatments studied clinically, proposed reasons for their lack of success, and new concepts emerging in ARDS therapy.

Inhaled beta-2 agonist salbutamol and acute lung injury: an association with improvement in acute lung injury

INTRODUCTION

Beta2 agonists have several properties that could be beneficial in acute lung injury (ALI). We therefore chose to study the effect of inhaled beta2 agonist use (salbutamol) on duration and severity of ALI.

METHODS

We undertook a retrospective chart review of 86 consecutive mechanically ventilated patients with ALI, who had varying exposure to inhaled salbutamol. The cohort was divided into two groups according to the average daily dose of inhaled salbutamol they received ('high dose' > or = 2.2 mg/day and 'low dose' < 2.2 mg/day). Severity of ALI and non-pulmonary organ dysfunction was compared between the groups by calculating the days alive and free of ALI and other organ dysfunctions.

RESULTS

The high dose and low dose groups received a mean of 3.72 mg and 0.64 mg salbutamol per day, respectively. The high dose salbutamol group had significantly more days alive and free of ALI than the low dose group (12.2 +/- 4.4 days versus 7.6 +/- 1.9 days, p = 0.02). There were no associations between dose of beta agonist and non-pulmonary organ dysfunctions. High dose salbutamol (p = 0.04), APACHE II score (p = 0.02), and cause of ALI (p = 0.02) were independent variables associated with number of days alive and free of ALI in a multivariate linear regression model.

CONCLUSION

Our retrospective study suggests that salbutamol, an inhaled beta2 agonist, is associated with a shorter duration and lower severity of ALI. A dose greater than 2.2 mg/day of inhaled salbutamol could be a minimal effective dose to evaluate in a randomized controlled trial.

Oral N-acetylcysteine administration does not stabilise the process of established severe preeclampsia

OBJECTIVE

To stabilise the disease process in women with early onset severe preeclampsia and/or HELLP syndrome by enhancing maternal antioxidants effects of glutathione.

STUDY DESIGN

In a randomised, double-blind, placebo-controlled trial, women with severe preeclampsia and/or HELLP syndrome received oral N-acetylcysteine. Primary outcome measures were disease stabilisation expressed as treatment-to-delivery interval and biochemical assessment of glutathione and parameters of oxidative stress. Secondary outcome measures were maternal complications, rate of caesarean section, stay at intensive care unit, postpartum hospital stay and neonatal morbidity and mortality. Analyses were done by intention-to-treat using Wilcoxon's two-sample test and regression analysis.

RESULTS

Median treatment-to-delivery interval was not significantly different between the N-acetylcysteine and placebo group. The whole blood and plasma levels of glutathione and other thiols were not affected by N-acetylcysteine administration, except for plasma homocysteine concentrations, which were lower in the N-acetylcysteine group. There were no differences found in maternal nor neonatal secondary outcome measures between both groups.

CONCLUSION

Oral N-acetylcysteine administration does not stabilise the disease process of early onset severe preeclampsia and/or HELLP syndrome.

The immuno-inflammatory response to trauma

The systemic inflammatory response syndrome is a well recognized physiological entity being part of our homeostatic mechanisms. It represents the cascade of inflammatory reactions initiated in the immediate aftermath following trauma reflecting the state of alertness that our body undergoes in order to fight for survival. A variety of inflammatory mediators and cellular elements are involved during this process interacting amongst each other. This allows communication between the different organ systems and thus regulating local and systemic responses. We have just begun to characterize and quantify the immuno-inflammatory response to trauma and this has opened new horizons in the way we understand the pathophysiological response to injury. As our knowledge evolves new therapeutic agents and innovative treatment plans will be developed contributing to increased survival rates in patients with multiple injuries.

Pathogenesis of multiple organ dysfunction syndrome--endotoxin, inflammatory cells, and their mediators: cytokines and reactive oxygen species

Multiple organ dysfunction syndrome (MODS) is caused by an overwhelming, uncontrolled systemic inflammatory response that is activated by a number of hostile stimuli including sepsis, hypovolemic shock, and severe trauma resulting in massive tissue injury. The indiscriminate activation of the inflammatory response due to these insults causes loss of the host's ability to localize the inflammation to the focus of the problem, leading to systemic inflammation and severe host tissue damage and subsequent MODS. While the major players, namely neutrophils, macrophages, endotoxin, cytokines, and oxidants have been known for some time, the disease processes responsible for the pathogenesis of MODS have only recently been elucidated. Our newly found knowledge has resulted in the development of novel therapeutic strategies to prevent or treat MODS, such as scavenging toxic oxygen species and inhibiting endotoxin, or cytokine production, or cytokine activity. Unfortunately, these strategies have not resulted in improved mortality rates among patients with MODS. The complex nature of the host response to severe insults combined with the fact that the host has multiple, redundant parallel systems to deal with various insults has made it difficult for clinical interventions to adequately ameliorate the disease process among patients at risk for MODS. The purpose of this article is to attempt to "dissect out" several individual components of the inflammatory response that play important roles in the development of MODS and to review some potentially beneficial approaches to combat these harmful processes.

Evolution of treatments for patients with acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are acute life-threatening forms of hypoxemic respiratory failure. ALI/ARDS patients require intensive care with prolonged mechanical ventilation. Despite advances in our understanding of the pathophysiology of ALI/ARDS, mortality rates remain > 30% and survivors suffer significant decrements in their quality of life. The evolving understanding of ALI/ARDS and the complex interactions involved in ALI/ARDS open the door for many potential targets for treatment. The condition is characterised by an acute inflammatory state that leads to increased capillary permeability and accumulation of proteinaceous pulmonary oedema. The changes that occur as a result of this inflammation clinically manifest themselves as hypoxemia, infiltrates on chest radiograph and reduced lung compliance. Many years have been dedicated to analysing the complexities involved in ALI/ARDS in order to improve current and future possibilities for treatment, with the aim of improving patient outcomes. Although some therapies have demonstrated benefits of improved oxygenation, such as surfactant and nitric oxide, these benefits have not translated into reductions in the duration of mechanical ventilation or mortality. Inflammatory mediator-targeted therapies were promising early on; however, larger trials have found therapies such as cytokine modulation, platelet-activating factor inhibition and neutrophil elastase inhibitors to be ineffective in the treatment of ALI/ARDS. Preclinical studies with beta2-agonists and granulocyte macrophage colony-stimulating factor have shown promise for restoring alveolar capillary barrier integrity or reducing pulmonary oedema, and further studies are being conducted to test for true clinical benefit. Despite previous therapeutic failures, newer surfactant formulations have shown promise, particularly in patients with direct forms of lung injury, and are currently in Phase III trials. Anticoagulant therapy with activated protein C has been shown to improve survival in sepsis, the most common risk factor for the development of ALI/ARDS, and is now being studied in ALI/ARDS. Until new data emerge, the focus must remain on supportive care, including optimised mechanical ventilation, nutritional support, manipulation of fluid balance and prevention of intervening medical complications.

Clinical Evaluation of Circulating Interleukin-6 and Interleukin-10 Levels after Surgery-induced Inflammation

BACKGROUND

It was previously reported that both pro- and anti-inflammatory cytokines are elevated in systemic inflammatory response syndrome (SIRS). Cytokine-mediated systemic neutrophil activation is a direct consequence of SIRS, and can lead to multiple organ dysfunction syndrome (MODS). This prospective study assessed the risk of SIRS and MODS after orthognathic surgery by measuring the circulating levels of inflammatory cytokines such as IL-6 and IL-10 as well as the neutrophil functions as a marker of organ failure.

MATERIALS AND METHODS

Blood samples for the measurement of IL-6, IL-10, CRP, neutrophil counts, and neutrophil function were drawn from 21 patients with mandibular prognathism at 2 days before, and at 1 and 3 days after orthognathic surgery. The neutrophil function was estimated by superoxide production and elastase release under the stimulation of FMLP.

RESULTS

Eight of the 21 patients were applicable to SIRS criteria 1 day postoperatively, and all of the subjects were excluded from SIRS criteria 3 days postoperatively. Although IL-6 and IL-10 levels were raised 1 day postoperatively, increased cytokine concentrations were decreased in most patients at 3 days postoperatively. The IL-6 concentration and the ratio of IL-6 to IL-10 were higher in the SIRS-matched group compared with the non-SIRS-matched group. Neutrophil priming for superoxide production and elastase release was discovered 1 day after orthognathic surgery, and differences in those values could not be distinguished between the groups.

CONCLUSIONS

These results suggest that a few patients in whom high levels of circulating inflammatory cytokine and neutrophil-derived toxic factor continue may have a possibility of contracting severe diseases such as SIRS and MODS after orthognathic surgery. We conclude that the ratio of IL-6 to IL-10 may be a predictive factor in SIRS.

N-acetylcysteine attenuates bacterial translocation after partial hepatectomy in rats

BACKGROUND

Translocating enteric bacteria have been suggested as playing a major role in the development of infections after partial hepatectomy. We investigated the effect of N-acetylcysteine (NAC) on bacterial translocation (BT) and intestinal mucosa as the first line of defense against BT.

MATERIALS AND METHODS

We compared four groups of eight Sprague-Dawley male rats each: sham, control (partially hepatectomized), partial hepatectomy plus preoperative single-dose NAC, and a fourth that received partial hepatectomy with a preoperative single-dose NAC plus treatment with NAC for 2 days. Microorganism counts of tissues, lung injury score, lung tissue glutathione, and malondialdehyde levels and microscopy of intestinal mucosa were studied at the end of 48 h.

RESULTS

Microorganism count in the lung and mesenteric lymph node cultures and lung injury score were significantly higher in the control group when compared with the sham, third, and fourth groups (lung: 9919.6 versus 0.0, 2912.9, 1550.0 cfu/g tissue; mesenteric lymph nodes: 8458.3 versus 0.0, 89.0, 88.9 cfu/g tissue; lung injury score: 3.25 versus 0.5, 1.13, 1.75). In the control group, the villous height of the distal ileal mucosa was significantly shorter than the sham group (65.25 versus 75.25 microm) and the difference from groups 3 and 4 was not statistically significant. Neutrophil infiltration in the distal ileal mucosa of the control group was significantly higher than the sham, third and fourth groups (3.13 versus 0.25, 0.38 and 1.0).

CONCLUSIONS

The parenteral use of NAC attenuates bacterial translocation after partial hepatectomy in rats. Attenuation of the lung injury after partial hepatectomy in NAC-treated groups might be attributable to both anti-inflammatory effect and the effect on BT.

Acute Respiratory Distress Syndrome

Acute lung injury is a syndrome diagnosed clinically and is one of the most common causes of respiratory failure seen in the intensive care unit. A consensus definition of this and its more severe form, acute respiratory distress syndrome (ARDS), has allowed for better consistency in determining the epidemiology and facilitates consistent clinical trial design to better find therapies to treat or prevent it. Patients who present with ARDS usually show signs of tachpnea or dyspnea and have underlying conditions that promote inflammatory responses. The pathogenesis involves an inflammatory insult that eventually destroys the pulmonary capillary vasculature as well as alveoli. Pathophysiologically, the patient with ARDS may progress through as many as 3 phases: exudative, proliferative, and fibrotic. Treatment options can be either nonpharmacologic or pharmacologic and are limited. Ventilator strategies such as low-tidal-volume ventilation have improved outcomes in these patients, while corticosteroid use is not as established to provide morbidity or mortality benefit. Other therapies have been investigated with inconclusive or disappointing results for the treatment of this fatal syndrome.

Contrast-induced nephropathy: a review

Contrast-induced nephropathy (CIN) is one of the leading causes of renal impairment in the United States and the third cause of hospital-acquired renal failure. Reduction in the incidence of CIN can lead to a decrease in the morbidity, mortality, and length of hospital stay. Although prophylactic hydration has been promising in decreasing the occurrence of CIN, other efforts such as diuretics, calcium channel blockers, theophylline, aminophylline, atrial natriuretic peptide, dopamine, and fenoldopam have been disappointing. The preventive effect of N-acetylcysteine on CIN has not been consistent in the literature. In a recent clinical trial, bicarbonate infusion was more effective than hydration in the prevention of CIN. Mechanical devices are in development to perfuse renal arteries with protective drugs during contrast exposure or for removal of contrast from coronary sinus during coronary angiography. In this article, we have reviewed available data in regards to CIN.

NF-κB: a therapeutic target in inflammatory diseases

The transcription factor NF-kappaB has been implicated in the pathogenesis of a variety of both acute and chronic inflammatory diseases. Many agents have shown promise and potential to abrogate NF-kappaB activity in both in vitro and in vivo systems. These include antioxidants, corticosteroids, proteasome inhibitors, arachadonic acid pathway metabolites, salicylates, molecular interventions and cell-permeable peptides. Unfortunately, therapies aimed at blocking its activation have not proven clinically feasible at this time. As the complex signal transduction pathways leading to NF-kappaB activation are further elucidated, more specific inhibitors of NF-kappaB are likely to be identified.

Therapeutic uses of antioxidant liposomes

This review will focus on the therapeutic uses of antioxidant liposomes. Antioxidant liposomes have a unique ability to deliver both lipid- and water-soluble antioxidants to tissues. This review will detail the varieties of antioxidants which have been incorporated into liposomes, their modes of administration, and the clinical conditions in which antioxidant liposomes could play an important therapeutic role. Antioxidant liposomes should be particularly useful for treating diseases or conditions in which oxidative stress plays a significant pathophysiological role because this technology has been shown to suppress oxidative stress. These diseases and conditions include cancer, trauma, irradiation, retinotherapy or prematurity, respiratory distress syndrome, chemical weapon exposure, and pulmonary infections.

N-acetylcysteine prevents endotoxin-induced degeneration of oligodendrocyte progenitors and hypomyelination in developing rat brain

Periventricular leukomalacia (PVL), the dominant form of brain injury in premature infants, is characterized by diffuse white matter injury and is associated with cerebral palsy (CP). Maternal and placental infections are major causes of prematurity and identifiable etiology of PVL and CP. Here we have evaluated the therapeutic efficacy of N-acetylcysteine (NAC), a potent antioxidant and precursor of glutathione, to attenuate lipopolysaccharide (LPS)-induced white matter injury and hypomyelination in the developing rat brain, an animal model of PVL. Intraperitoneal pretreatment of pregnant female rats with NAC (50 mg/kg), 2 hr prior to administration of LPS at embryonic day 18 (E18), attenuated the LPS-induced expression of inflammatory cytokines such as tumor necrosis factor-alpha, interleukin-1beta, and inducible nitric oxide synthase in fetal rat brains. There were significantly reduced numbers of TUNEL(+) nuclei coimmunostained for platelet-derived growth factor-alphaR(+) [a surface marker for oligodendrocyte progenitor cells (OPCs)] at E20 in the subventricular zone of fetal rat brain in the NAC + LPS group compared with the untreated LPS group. Interestingly, immunostaining for O4 and O1 as markers for late OPCs and immature oligodendrocytes demonstrated fewer O4(+) and O1(+) cells in the LPS group compared with the NAC + LPS and control groups. Consistent with O4(+)/O1(+) cell counts, the expression of myelin proteins such as myelin basic protein, proteolipid protein, and 2'3'-cyclic nucleotide phosphodiesterase, including transcription factors such as MyT1 and Gtx, was less in the LPS group at late postnatal days, indicating severe hypomyelination in the developing rat brain when compared with NAC + LPS and control groups. Collectively, these data support the hypothesis that NAC may provide neuroprotection and attenuate the degeneration of OPCs against LPS evoked inflammatory response and white matter injury in developing rat brain. Moreover, these data suggest the possible use of NAC as a treatment for pregnant women with maternal or placental infection as a means of minimizing the risk of PVL and CP.

Antioxidant nutrients: a systematic review of trace elements and vitamins in the critically ill patient

OBJECTIVE

Critical illness is associated with the generation of oxygen free radicals and low endogenous antioxidant capacity leading to a condition of oxidative stress. We investigated whether supplementing critically ill patients with antioxidants, trace elements, and vitamins improves their survival.

METHODS

We searched four bibliographic databases from 1980 to 2003 and included studies that were randomized, reported clinically important endpoints in critically ill patients, and compared various trace elements and vitamins to placebo.

RESULTS

Eleven articles met the inclusion criteria. When the results of all the trials were aggregated, overall antioxidants were associated with a significant reduction in mortality [Risk Ratio (RR) 0.65, 95% confidence intervals (CI) 0.44-0.97, p=0.03] but had no effect on infectious complications. Studies that utilized a single trace element were associated with a significant reduction in mortality [RR 0.52, 95% CI 0.27-0.98, p=0.04] whereas combined antioxidants had no effect. Studies using parenteral antioxidants were associated with a significant reduction in mortality [RR 0.56, 95% CI 0.34-0,92, p=0.02] whereas studies of enteral antioxidants were not. Selenium supplementation (alone and in combination with other antioxidants) may be associated with a reduction in mortality [RR 0.59, 95% CI 0.32-1.08, p=0.09] while nonselenium antioxidants had no effect on mortality.

CONCLUSIONS

Trace elements and vitamins that support antioxidant function, particularly high-dose parenteral selenium either alone or in combination with other antioxidants, are safe and may be associated with a reduction in mortality in critically ill patients.

Pharmacologic therapies for adults with acute lung injury and acute respiratory distress syndrome

BACKGROUND

Multiple pharmacologic treatments have been studied for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).

OBJECTIVES

Our objective was to determine the effects of pharmacologic treatments on clinical outcomes in adults with ALI or ARDS.

SEARCH STRATEGY

We searched OVID versions of CENTRAL (The Cochrane Library Issue 3, 2003), MEDLINE (1966 to week 2, January 2004), EMBASE (1980 to week 4, 2004), CINAHL (1982 to week 2, January 2004), and HEALTHSTAR (1995 to December 2003); proceedings from four conferences (1994 to 2003); and bibliographies of review articles and included studies.

SELECTION CRITERIA

Randomized controlled trials of pharmacologic treatments compared to no therapy or placebo for established ALI or ARDS in adults admitted to an intensive care unit, with measurement of early mortality (primary outcome), late mortality, duration of mechanical ventilation, ventilator-free days to day 28, or adverse events. We excluded trials of nitric oxide, partial liquid ventilation, fluid and nutritional interventions, oxygen, and trials in other populations reporting outcomes in subgroups of patients with ALI or ARDS.

DATA COLLECTION AND ANALYSIS

Two reviewers independently screened titles and abstracts, rated studies for inclusion, extracted data and assessed methodologic quality of included studies. Disagreements were resolved by consensus in consultation with a third reviewer. For each pharmacologic therapy, we quantitatively pooled the results of studies using random effects models where permitted by the available data. We contacted study authors when clarification of the primary outcome was required.

MAIN RESULTS

Thirty three trials randomizing 3272 patients met our inclusion criteria. Pooling of results showed no effect on early mortality of prostaglandin E1 (seven trials randomizing 697 patients; relative risk [RR] 0.95, 95% confidence interval [CI] 0.77 to 1.17), N-acetylcysteine (five trials randomizing 239 patients; RR 0.89, 95% CI 0.65 to 1.21), early high-dose corticosteroids (two trials randomizing 187 patients; RR 1.12, 95% CI 0.72 to 1.74), or surfactant (nine trials randomizing 1441 patients; RR 0.93, 95% CI 0.77 to 1.12). Two interventions were beneficial in single small trials; corticosteroids given for late phase ARDS reduced hospital mortality (24 patients; RR 0.20, 95% CI 0.05 to 0.81), and pentoxifylline reduced one-month mortality (RR 0.67, 95% CI 0.47 to 0.95) in 30 patients with metastatic cancer and ARDS. Individual trials of nine additional interventions failed to show a beneficial effect on prespecified outcomes.

REVIEWERS' CONCLUSIONS

Effective pharmacotherapy for ALI and ARDS is extremely limited, with insufficient evidence to support any specific intervention.

N-acetylcysteine reduces contrast-associated nephropathy but not clinical events during long-term follow-up

BACKGROUND

Contrast-associated nephropathy (CAN) is associated with increased morbidity and mortality following percutaneous coronary intervention (PCI). N-acetylcysteine (NAC) has been shown to reduce the risk of nephropathy; however, the impact of NAC on long-term clinical outcomes has not been assessed.

METHODS

This randomized, double-blind, placebo-controlled trial enrolled 180 patients with moderate renal dysfunction undergoing PCI or coronary angiography with a high likelihood of ad hoc PCI; 171 patients completed the clinical follow-up. Patients received oral NAC (2000 mg/dose, n = 95) or placebo (n = 85) twice a day for 3 doses if randomized the night prior to the procedure, and 2 doses if randomized the day of the procedure. The primary end point was the incidence of a > or =25% increase in serum creatinine level 48 to 72 hours after PCI. Secondary end points were the inhospital incidence of death, nonfatal myocardial infarction, or urgent dialysis, and the 9-month incidence of death, nonfatal myocardial infarction, need for dialysis, or repeat hospitalization for cardiac reasons.

RESULTS

CAN occurred in 9.6% of patients assigned to NAC and 22.2% of patients assigned to placebo (P =.04); 1 patient receiving NAC required urgent dialysis. The inhospital composite end point occurred in 7 (7.4%) NAC-treated and 3 (3.5%) placebo-treated patients, P = NS. At 9 months, the composite end point occurred in 23 (24.2%) NAC-treated patients and 18 (21.2%) placebo-treated, P = NS.

CONCLUSION

Although high-dose NAC prevented periprocedural CAN, this benefit did not translate into a decrease in adverse outcomes over 9 months. Further studies to determine the clinical utility of this drug are required.