Administration of dazoxiben, a selective thromboxane synthetase inhibitor, in the adult respiratory distress syndrome

Ketoconazole in the Prevention of Acute Respiratory Distress Syndrome

Objective:

To describe the pharmacology of ketoconazole and examine the use of ketoconazole in critically ill surgical patients to prevent the development of acute respiratory distress syndrome (ARDS).

Data Source:

An English-language literature search from 1985 to 1994 using MEDLINE-identified relevant articles. Search terms were adult, acute respiratory distress syndrome, ketoconazole, thromboxane, and leukotrienes.

Study Selection:

Two randomized, controlled, double-blind studies were identified that examined the use of ketoconazole in critically ill surgical patients. In vitro and animal studies were included to describe the mechanism of ketoconazole on inhibition of leukotriene and thromboxane synthesis.

Data Extraction:

Studies were evaluated for study design, efficacy, and toxicity.

Data Synthesis:

Two randomized, placebo-controlled clinical trials have been conducted in critically ill surgical patients. One study demonstrated a 6% incidence of ARDS in patients receiving ketoconazole 200 mg/d (n = 35) versus 31% on placebo (n = 36) (p < 0.01). Another study demonstrated a 15% incidence of ARDS in patients receiving ketoconazole 400 mg/d (n = 26) versus 64% on placebo (n = 28) (p < 0.002), and showed a statistically significant decrease in mortality in the ketoconazole group (15%) versus placebo (39%) (p < 0.05). There were no reports of serious adverse events, and patients in both treatment and placebo groups were discontinued for increased liver enzyme concentrations.

Conclusions:

Two studies conducted at single sites using prophylactic ketoconazole therapy in dosages of 200–400 mg/d in a small population of critically ill surgical patients at risk for ARDS have demonstrated a significant decrease in the incidence of ARDS. There are no ongoing multicenter trials that would provide the power to measure the true difference between the groups and minimize the selection bias inherent in these studies.

Cyclooxygenase inhibition in sepsis: is there life after death?

Prostaglandins are important mediators and modulators of the inflammatory response to infection. The prostaglandins participate in the pathogenesis of hemodynamic collapse, organ failure, and overwhelming inflammation that characterize severe sepsis and shock. In light of this, cyclooxygenase (COX) inhibiting pharmacological agents have been extensively studied for their capacity to ameliorate the aberrant physiological and immune responses during severe sepsis. Animal models of sepsis, using the systemic administration of pathogen-associated molecular patterns (PAMPs) or live pathogens, have been used to examine the effectiveness of COX inhibition as a treatment for severe sepsis. These studies have largely shown beneficial effects on mortality. However, human studies have failed to show clinical utility of COX inhibitor treatment in severely septic patients. Why this approach “worked” in animals but not in humans might reflect differences in the controlled nature of animal investigations compared to human studies. This paper contrasts the impact of COX inhibitors on mortality in animal models of sepsis and human studies of sepsis and examines potential reasons for differences between these two settings.

New management strategies in ARDS. Immunomodulation

Acute respiratory distress syndrome is a common condition among the critically ill and is associated with high morbidity and mortality [table: see text] rates. Improved understanding of the underlying inflammatory pathogenetics has encouraged the search for strategies that, by modifying this immune response, can improve outcome for this group of patients. Some agents are obviously anti-inflammatory. Others have been used primarily for other purposes; their immune effects are incidental, but no less important. Although immunomodulatory strategies have been discussed for many years, they now are beginning to show positive results, as in the study using activated protein C. Most patients with ARDS die with ARDS, rather than from ARDS. The approach to treatment must not be lung-limited but must take into account the systemic effects of the inflammatory response. The complex nature of the syndrome makes it likely that no single agent will provide the long-desired cure. Rather, it is probable that an individual patient will require a combination of several agents or different agents at different times during the disease process (Table 1). Mortality rates from ARDS already are beginning to fall with improved nutritional and ventilatory support. Positive results from trials using immunomodulatory agents are being reported, and soon such agents will form part of the routine management of patients with ARDS, further improving the outlook for these patients.

Pathophysiology and implications for treatment of acute respiratory distress syndrome

Acute respiratory distress syndrome is a complex group of signs and symptoms caused by direct or indirect lung injury. In spite of decades of research, it is still associated with a high mortality rate. Pathogenesis of this disease is related to alveolar endothelial and epithelial cell injury and associated release and sequestration of inflammatory mediators and cells, including cytokines and neutrophils, respectively. Pharmacologic interventions have been largely unsuccessful, and ventilation strategies to support oxygenation while limiting ventilator associated lung injury have not demonstrated any significant reductions in the mortality rate. However, novel therapies are in development, based on the knowledge of the pathologic processes of acute respiratory distress syndrome. In this article an overview of the disease process and mediator involvement is presented, followed by a review of pharmacologic and ventilation treatments currently in use or under study.

Lipid mediators in the pathophysiology of critical illness

Inflammatory lipid mediators are produced by the metabolism of membrane phospholipids following a number of different stimuli. These mediators lead to a variety of cellular and systemic responses which contribute to the manifestations of the systemic inflammatory response syndrome in the critically ill patient. These mediators include platelet-activating factor and the eicosanoids, including prostaglandins, thromboxanes, leukotrienes, and HETEs. This review seeks to evaluate the current role of these mediators in the pathophysiology of critical illness. We will focus on recent studies concerning the modulation of these pathways as a potential therapeutic strategy for management of these critically ill patients. This includes the gamut from nutritional strategies to alter the cellular membrane lipid composition, thereby effecting the substrate available to produce these lipid byproducts, to intracellular inhibitors to alter production of these mediators, to receptor blockage and enhanced clearance to inhibit their effects.

Pharmacologic adjuncts to mechanical ventilation in acute respiratory distress syndrome

This article reviews pharmacologic approaches to treating acute respiratory distress syndrome (ARDS). The authors discuss the therapeutic effects of ketoconazole, antioxidants, corticosteroids, surfactant, ketanserin, pentoxifylline, bronchodilators, and almitrine in ARDS. Current animal data and proposed mechanics which may foster future pharmacologic therapies are also examined.

Protective effects of a thromboxane synthetase inhibitor and continuous arteriovenous hemofiltration in rat endotoxic shock

We determined the efficacy of continuous arteriovenous hemofiltration (CAVH) and a thromboxane synthetase inhibitor (TSI) on survival and their effect on TXA2, PGI2, TNF alpha, and IL-1beta production in rat endotoxemia. Thirty-six endotoxemic rats were randomized to one of 4 groups: (A) no TSI, sham CAVH; (B) no TSI, CAVH; (C) TSI, sham CAVH; and (D) TSI, CAVH. Either CAVH (Group B) or pretreatment with TSI (Group C) resulted in increased survival time. CAVH did not prevent the rise in TX (Group B). TNF alpha levels at 2 h after LPS infusion were higher in Group D compared to Group B (26.1 +/- 3.7 vs 13.2 +/- 4.3 ng/mL, P < 0.05) respectively. IL-1beta was detected earlier in Groups C,D when compared to Groups A,B (P < 0.02). TNF alpha and IL-1beta were not ultrafiltered. CAVH and the inhibition of TX synthesis independently improved survival in endotoxemia, however, their beneficial effects were not additive. While TSI may improve survival by blocking TXA2 production, the salutary effects of CAVH appear to be from removal of an undetermined TXA2 dependent mediator. TNF alpha and IL-1beta concentrations do not appear to influence survival times in this model.

Ketoconazole to prevent acute respiratory distress syndrome in critically ill patients

Ketoconazole appears to be an effective prophylactic measure in surgical patients at risk of developing ARDS. The beneficial effects may be caused by thromboxane synthetase inhibition because thromboxane B2 concentrations were decreased by ketoconazole in both studies. Two studies were unable to demonstrate a beneficial effect with the selective thromboxane synthetase inhibitor dazoxiben. Both studies consisted of a small number of subjects with already established ARDS, not prophylaxis in patients at risk of ARDS. Although the effects of ketoconazole on mortality in patients at risk of ARDS are conflicting, there may be reduced mortality in patients with sepsis. Several issues must be considered before ketoconazole is used in this setting. First, the studies to date have excluded patients at risk of hepatotoxicity, which is probably wise considering the potential hepatotoxicity with ketoconazole and the unknown benefit/risk ratio in these patients. Also, therapies that reduce gastric acidity should be avoided to ensure bioavailability. If ketoconazole is administered through a jejunostomy tube, it probably should be given with a dilute acid to enhance absorption. Furthermore, ketoconazole is a known inhibitor of the cytochrome P450 system, which results in a number of drug interactions. If ketoconazole is used, the patient's current drug therapy should be reviewed for potential interacting drugs. In light of the current studies, ketoconazole may be considered for surgical patients at risk of developing ARDS (especially patients with sepsis) with the previously noted considerations. Future research should seek to confirm ketoconazole's role for the prevention of ARDS in all critically ill patients. Additional studies also should clarify the role of various inflammatory mediators in the pathophysiology and therapy of ARDS.

Systemic inflammatory response syndrome: septic shock

The systemic inflammatory response syndrome (SIRS) is the body's response to a multitude of chemical mediators. Conditions inciting the release of these mediators include bacterial sepsis, viremia, pancreatitis, trauma, neoplasia, heat stroke, and many others. The key to the successful management of SIRS lies in anticipation and not reaction. Resuscitation of the patient to supranormal levels, coupled with aggressive monitoring and support of target organs are essential.

Multiple Organ Failure Syndrome—Part I: Epidemiology, Prognosis, and Pathophysiology

The multiple organ failure syndrome (MOFS) is the leading cause of death in intensive care units. Although sepsis is an important cause of MOFS, it is clear that MOFS can occur in the absence of infection. The pathophysiology of MOFS is complex and multifactorial and includes derangements in oxygen delivery and consumption, the release of inflammatory and vasoactive mediators capable of inflicting tissue damage, and alterations in the barrier function of the intestinal mucosa. Although advances have been made in our understanding of MOFS, treatment remains nonspecific and largely supportive. Early and aggressive restoration of tissue perfusion, adequate treatment of infection, timely nutritional support, and support of individual failed organs remain the mainstay of therapy. Therapeutic agents directed against the various mediators associated with the pathophysiology of MOFS may prove useful in the future.

Role of thromboxane, prostaglandins and leukotrienes in endotoxic and septic shock

Intravenous bolus endotoxin elicits a marked but transient increase in plasma TxB2 and 6-keto-PGF1 alpha in a large number of species. A smaller, delayed and more prolonged increase in TxB2 and 6-keto-PGF1 alpha are reported in animals with septic shock, i.e., those with fecal peritonitis or cecal ligation. Thromboxane synthetase inhibitors or antagonists attenuate endotoxin-induced acute cardiopulmonary changes, the delayed increase in serum lysosomal enzymes, fibrin/fibrinogen degradation products and the thrombocytopenia in a number of species. While these drugs increase survival of rats or mice following endotoxin they do not alter survival of rats in septic shock. These results support the hypothesis that TxA2 exerts a pathophysiologic effect in shock following bolus endotoxin. In contrast, nonsteroidal antiinflammatory drugs (NSAID) and dietary essential fatty acid deficiency increase survival of rats subjected to endotoxin shock, and survival time in models of septic shock. These results also suggest that some other cyclooxygenase product(s) is involved in septic shock due to fecal peritonitis or cecal ligation. Preliminary experimental studies indicate salutary effects of leukotriene inhibitors and antagonists in endotoxin shock and in models of acute pulmonary injury. Clinical studies have demonstrated elevated plasma TxB2 and 6-keo-PGF1 alpha concentrations in patients with septic shock, and elevated LTD4 in pulmonary edema fluid of patients with the adult respiratory distress syndrome. In view of these clinical and experimental results, clinical trials of NSAID and/or leukotriene inhibitors/antagonists should be considered.