Endotoxin in Human Disease

Endotoxin in Human Disease* Part 1 : Biochemistry, Assay, and Possible Role in Diverse Disease States Constantine A. Manthous, M.D.; jesse B. Hall, M.D., F.C.C.P.; and Richard W Samsel, M.D.

(Chest 1993; 104:1572-81) ARDS =adult respiratory distress syndrome; BSA =body surface area; cAMP=cyclic adenosine monophosphate; cGMP=: cyclic guanosine monophosphate; EDRF =endothelium-derived relaxation factor; FHF =fulminant hepatic failure; IBD=inftammatory bowel disease; IL=interleuldn; LAL= Limulus amoebocyte lysate; LBP =lipopolysaccharide-binding protein; LPS = lipopolysaccharides; MSOF =multiple systems organ failure; PAF =platelet activating factor; SIRS.= systemic inftammatory response syndrome; TNF =tumor necrosis factor.

infections occur in as many as 500,000 Serious hospitalized patients each year in the United States.• Of these, one third to one half develop shock related to their infection, 2 ·3 and these have a subsequent mortality rate of 40 to 50 percent. 4 When a source of infection is identified, the responsible organisms are gram-negative bacteria in about half the cases. 5 In these gram-negative infections, bacterial endotoxins (lipopolysaccharides, LPS) appear to play a central pathogenetic role . Bacterial endotoxins are complex compounds located in the cell walls of gram-negative bacteria. While diverse in detail, their structures share a common design conserved across bacterial speciesantigenic sugar moieties are bound to the hydrophobic lipid A (Fig 1). Their common structure and location on bacterial cell walls render endotoxins suitable for recognition by host defenses. Mammals have evolved sensitive means to detect endotoxin as a sign of gramnegative ba<;terial growth; hence, endotoxin triggers powerful defensive responses which mediate its toxic effects. Miyamoto et al6 and Staub' have suggested that there may be significant variations between species in macrophage processing of foreign antigens, potentially explaining differences observed between various models of endotoxemic shock. Understanding the pathophysiologic effects of en*From the Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago. RePrint requests: Dr. Hall, Section oj fulmonary and Critical Care Medicine , 5841 South Maryland, Chicago 60637

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dotoxin in human disease requires an understanding of the physiology of host responses. We begin with a brief overview of the biochemistry and pharmacology of endotoxin, and then discuss evidence that it plays a role in several human disease states: sepsis, liver failure, burns, bowel diseases, and pancreatitis. We then review the protean physiologic abnormalities in these diverse conditions that may result from the initiation of host defenses by endotoxin. Finally, we discuss therapeutic interventions intended to attenuate the exaggerated and sometimes lethal consequences of the endotoxin-triggered cascade. BIOCHEMISTRY AND PHARMACOLOGY OF ENDOTOXINS

Endotoxin (Fig 1) is a lipopolysaccharide composed of a variably antigenic series of sugars8 attached to a lipid A moiety. The polysaccharide portion of the molecule consists of an 0-specific chain and a core oligosaccharide. The 0-specific chain consists of up to 70 repeating oligosaccharide units. Each unit contains up to seven sugar residues and is characteristic for each different bacterial species. The core is an heterooligosaccharide consisting of two components. The inner core sugars are similar between species while the outer core differs between and within species. Lipid A is a structurally complex molecule with a hydrophilic complex sugar and lipophilic fatty acid moieties but is very similar between species. 9 When injected into mammals, neither the core nor the 0specific chains themselves elicit physiologic responses characteristic of sepsis. Wild type (smooth) microbes

Bacterial Lipopolysaccharide

O·Speclflc Chan

Outer Core

Inner Core

Upid A

FIGURE 1. Endotoxin is a lipopolysaccharide mmposed of a variably antigenic series of sugars attached to a lipid A moiety. Endotoxin in Human Disease: Part 1 (Manthous, Hall, Samsel)

may lose their 0-antigen, becoming rough mutants. 8 Loss of the 0-antigen renders the bacteria more sensitive to opsonization and clearance.8 In contrast to the core and 0-specific chain, lipid A does initiate the host responses associated with sepsis, and these responses can be reproduced with injection of synthetic lipid A. 10 When injected into animals, endotoxin binds to a number of different proteins, including albumin, lipoproteins, complement and globulins, 11 as well as to a specific binding factor, lipopolysaccharide binding protein. 12 Endotoxin clearance and physiologic responses may be related to the degree of protein binding. When radioactively-labeled endotoxin is injected into rats, 80 percent appears in the liver within 5 hours of injection, but significant concentrations also appear in the spleen and adrenal glands. While some degradation occurs in the macrophages of the liver, the majority of injected endotoxin is eliminated in the bile. 13 In rats, the biologic activity of excreted endotoxin is essentially unchanged 13 while in humans there may be some detoxification. 14

Detection of Endotoxin Endotoxin is measured utilizing the hemolymph of amoebocytes from the Limulus horseshoe crab. 15•16 This substance contains a proenzyme which is directly activated by endotoxin. The activated enzyme cleaves peptide bonds in a second protein, also present in the hemolymph, leading to coagulation and visible gelling of the mixture. This Limulus amoebocyte lysate (LAL) assay can detect nanogram per deciliter concentrations of endotoxin. The gelatin method has been modified by the use of enzyme substrate that can be measured spectrophotometrically. 15• 17 This semiquantitative chromogenic assay detects endotoxin to less than 10 pwdL Unfortunately, the accuracy of the chromogenic assay may be affected by numerous circulating plasma proteins including antithrombin III and antiendotoxin antibodies. Furthermore, endotoxins from different bacterial species differentially activate the proenzyme. Numerous methods have been described to neutralize the effects of interfering proteins, but these logistic difficulties have prevented standardization between patients and institutions. 18 Some studies have suggested that the assay may be of adequate sensitivity but questionable specificity, since it can be positive in patients with gram-positive bacterial or fungal infections. 19 A positive LAL in such conditions could either represent a false-positive or may be a true-positive if endotoxemia related to gut leak accompanies these infections. Furthermore, sensitivities and specificities are dependent upon the development of reliable control curves that may vary between institutions and studies. The LAL assays, despite inadequacies, remain

the only practical means of detecting and quantitating endotoxin. Insofar as it is an imperfect tool for the detection of endotoxin, the studies to be discussed, which utilize the LAL must be viewed with some skepticism. A specific and sensitive assay that could reproducibly quantitate endotoxin would have enormous clinical and experimental utility. DoEs ENDOTOXIN MEDIATE CLINICAL SEPSis?

Sepsis is intimately linked with endotoxin. Classified and defined below, sepsis is a constellation of pathophysiologic phenomena arising from many different infections in many different settings. Clinicians often recognize this constellation without knowing the responsible etiologic diagnosis, so they must manage the physiology of sepsis as clinically defined. Endotoxin administration in animals or human volunteers reproduces many of the clinical manifestations of sepsis, and endotoxin is often detectable in sepsis. To provide standards for comparing observations, Bones differentiation between sepsis, the sepsis syndrome, and septic shock has been widely adopted (Table 1). 211 Sepsis is defined as an identifiable active infection with systemic manifestations including tachycardia, tachypnea, and abnormal thermoregulation. The sepsis syndrome is defined as sepsis with signs of hypoperfusion or end-organ injury, specifically lactic acidosis, oliguria, impaired mental status, or hypoxemic respiratory failure . Septic shock is the sepsis syndrome plus volume-refractory hypotension, often treated with vasoactive drugs. These details are semantic and are useful merely as a rough grading system for severity. They are nonetheless critical to standardizing interpretations for clinical studies. By general agreement, a diagnosis of sepsis, sepsis Table 1-DiagfiOIItic Criteria for Sepm and Related Disorder.* Disorder

Diagnostic Criteria

Bacteremia Sepsis

Positive blood cultures Evidence of infection and all of following: • RR>201min or MV> 101/min • HR>9Cimin • T>38.4°C or T<35.6°C Sepsis and impaired tissue function, one of following: • Lactate>normal • Urine < .5 mllkg for> 1 h • Altered mental status • Pa0/Fio1 Sepsis syndrome plus hypotension, one of following for >1 h: • SBP<90 mm Hg • Drop in SBP>40 mm Hg

Sepsis syndrome

Septic shock

*RR =respiratory rate; MV =minute ventilation; HR-heart rate; T = temperature; Pa02 =arterial partial pressure of oxygen; Flo1 = fraction of oxygen in inspired air; SBP =systolic blood pressure. CHEST I 104 I 5 I NOVEMBER, 1993

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syndrome, or septic shock requires the identification of an infective process. In practice, it is often difficult to demonstrate a specific infectious focus, and in many cases of sepsis, the source of infection remains obscure. While culture of bacteria from blood can establish the existence of infection, it is not necessary to meet a definition of sepsis; many patients with sepsis lack this marker. Under these conditions, cultures from other body sites are adequate to support the diagnosis of sepsis. The differential diagnosis of sepsis is further confounded by a number ofconditions (eg, hepatic failure, pancreatitis, bums, salicylate overdose) that yield a similar constellation of signs in the absence of infection. 21 This constellation of clinical findings has been termed the systemic inftammatory response syndrome (SIRS), an inclusive rubric meant to subsume sepsis. 22 Sepsis is also closely related to the multiple systems organ failure (MSOF, also termed multiple organ dysfunction, MOD), which may reftect nothing more than chronic progression of the septic or inftammatory process, with end-organ failure. We will not further differentiate among these syndromes or address a specific role for endotoxin in them . Demonstrating a role for endotoxin in sepsis requires three observations: endotoxin should be detected in sepsis, endotoxin administration should produce a physiologic state resembling sepsis, and endotoxin blockade should ameliorate clinical sepsis, Below, we will examine whether these requirements have been met. The first requirement is that endotoxin should be detectable in septic patients. A variety of studies have reported endotoxin in the blood of a substantial fraction of patients with sepsis. For example, Danner et al 19 reported that a quantitative LAL assay detected increased levels of circulating endotoxin in 43 of 100 patients with septic shock. Of these 43, gram-negative bacteremia was documented in only 10. Endotoxemia correlated with the development of renal insufficiency and adult respiratory distress syndrome (ARDS). This and other studies (Table 2) 19·23-27 show that endotoxin is often present in sepsis and that its presence correlates with severity of clinical manifestations and with Table 2-Studiea ofEndotuDn in Sepm First Author Danner" Shinnep"' Tubbs14 Levin15 McCartney., Brandtzaeg"'

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Entrance Criteria

Total

Endotoxemic

Bacteremic

Sepsis Sepsis Meningococcemia Suspected sepsis Septic shock with bacteremia Meningococcal disease

100

43

10 9 16

16 281 31

12 13 39 31

31

45

24

6

26

34

end-organ dysfunction. However, the same literature consistently finds that endotoxemia, as detected by amebocyte assay, is not invariably present in clinical sepsis. What accounts for the inconstancy of detecting endotoxin in sepsis? Methodologically, endotoxin is hard to measure, so clinically important forms of endotoxin may have been missed: the assays lacked sensitivity to low but biologically important levels. Alternatively, endotoxin could have exerted its effect at extravascular sites, or brief endotoxemia could have occurred at times other than when blood samples were drawn. More likely still is that endotoxin is not the only initial pathway into sepsis. Gram-positive bacterial and fungal infections can appear clinically indistinguishable from gram-negative bacterial sepsis. It seems likely that the physiology of sepsis can be triggered by a variety of stimuli, and one common important stimulus is endotoxin. These measurements alone do not preclude the possibility that endotoxin could be an innocent bystander, occasionally present but of no specific consequence. The second requirement directly addresses the question of whether endotoxin could be a passive bystander: if endotoxin is a central trigger for sepsis, then its administration should produce a sepsis-like syndrome. Endotoxin administration in animals effects dramatic physiologic changes; these vary with the species, the dose, the method of administration, and the origin of the endotoxin. A typical response is dilation of both resistance and capacitance vascular beds, and development of a low cardiac output, hypovolemic state. Fluid administration restores filling pressures of the right and left heart and generates a high cardiac output, but blood pressure remains very low as systemic vascular resistance falls further. This latter "ftuid resuscitated endotoxic shock" state bears a close similarity to human septic shock. Endotoxin has also been administered to human volunteers. Suffredini et al28 gave Escherichia coli endotoxin at a dose of 4 nglkg to 23 healthy volunteers. All subjects experienced a "ftu-like" illness with hyperthermia and chills. Pulmonary artery catheter measurements revealed a hyperdynamic state with increased cardiac index and heart rate, and reduced mean arterial pressure and vascular resistance. These changes are clinically compatible with mild sepsis and resemble the changes observed with low-dose endotoxin administration in animals. Thus, there is moderate evidence in favor of the first two requirements: endotoxemia has been found in human sepsis, and exogenous endotoxin produces a sepsis-like syndrome in animals and humans. In view of these data, endotoxin could be a clinically unimportant initiator of the septic host response, and detectable endotoxemia could be an unimportant late event Endoloxin In Human Disease: Part 1 (Menthous, Hall, Sam8el)

or an epiphenomenon. The pivotol test for a direct role of endotoxin in sepsis requires removing endotoxin in authentic clinical sepsis and demonstrating improvement. The closest available studies consider passive immunization against endotoxin. Several studies in man have suggested decreased mortality when antibodies to endotoxin are administered to patients with gram-negative bacteremia. 5 •29 •30 Importantly, these published results have not been confirmed by large, prospective trials, a controversy to be discussed in detail later. Endotoxin is thus sufficient but probably not necessary for initiation of the septic response, and its role as one of several mediators remains to be more fully delineated. ENDOTOXIN IN 0rHER DISEASE STATES

Endotoxin may contribute to the pathogenesis of several noninfectious disease processes including liver failure, burns, ischemic/inflammatory bowel diseases, and pancreatitis. Studies examining the role of endotoxin in these processes have used the LAL assay to detect endotoxin. Accordingly, the same cautions and limitations to data interpretation cited above regarding the role of endotoxin in sepsis pertain.

Liver Failure A number of investigations31 .;w have identified circulating endotoxin in patients with cirrhotic disease. Bigatello et al35 found it in 92 percent of those studied. The mechanism is not known, but increased gut passage, decreased clearance by a malfunctioning liver, and portosystemic shunting probably contribute.32·36 Patients with cirrhosis often exhibit high cardiac outputs with low systemic vascular resistance,37.JII a hemodynamic profile similar to that seen in many patients with sepsis. As in sepsis, the reninangiotensin system is activated in advanced liver disease, leading to salt and water retention. 37·40-42 As mean arterial pressure and systemic vascular resistance decline, a significant reduction of glomerular filtration rate, filtration fraction, and urinary output occur which can lead to acute renal failure . Patients with cirrhosis also exhibit intrapulmonary shunting, which may involve loss of hypoxic vasoconstriction43 and consequent ventilation/perfusion inhomogeneities which also occur in endotoxemic models of acute respiratory failure . An encephalopathy occurs in both sepsis and cirrhosis, and serum endotoxin levels have been demonstrated to correlate with mental status abnormalities in cirrhosis. 35 In fulminant hepatic failure {FHF), endotoxemia results from diminished clearance of endotoxin delivered to the portal circulation.44 As in patients with cirrhosis, those with FHF often have a high cardiac output with low peripheral vascular resistance ..-, Adult respiratory distress syndrome occurs in upwards

of 40 percent of cases, 46 and acute tubular necrosis with renal insufficiency is also frequently seen. 411.46 Cerebral edema with intracranial hypertension is a common cause of death in these patients and may relate to alterations in the blood brain barrier. 46 One case repoft47 suggested hemodynamic improvement in a patient with FHF who was treated with an antibody to endotoxin. However, no prospective studies have examined the role of antiendotoxin therapy in the supportive management of patients with FHF. Lastly, patients undergoing liver transplantation may represent an extreme of endotoxin-related phenomena among the various liver diseases. Yokayama et al48 reported increased serum endotoxin levels in liver transplant recipients, especially during the anhepatic phase of transplantation. Furthermore, they showed that the degree of endotoxemia during the peritransplant period correlated with both graft survival and patient survival after transplantation. If endotoxin adversely affects the hemodynamic or humoral milieu of the newly transplanted liver, antiendotoxin therapy may provide therapeutic benefit.

Thermal Injuries From days 2 to 6 after a burn, patients often enter a hypermetabolic phase which resembles sepsis: oxygen consumption is high, cardiac output is elevated with a low systemic vascular resistance, and fever and leukocytosis are common. 49 Dobke et al50 reported elevated levels of LAL-measured endotoxin in ten burned patients, also suggesting that early burn wound excision attenuated endotoxin levels. Winchurch et al51 studied 39 human burn patients with injuries ranging in severity from 1 to 88 percent of body surface area (BSA). Those with less than 20 percent BSA burns had minimally increased endotoxin levels when compared by LAL assay to healthy control subjects. Those with 21 to 40 percent burns had levels 3.5 times above those of normal subjects, while those with burns of greater than 40 percent BSA had endotoxin levels 5 times the control subjects. To determine if altered gut permeability might underlie endotoxemia in burn patients, Ziegler et al52 gave labeled lactulose enterally to 11 healthy control subjects and 15 patients with major burns. The burned patients had threefold higher urine excretion of this ordinarily nonabsorbed sugar, suggesting an increased gut permeability. Such increased gut permeability may itself result in an increase in endotoxin absorption.

Bowel Diseases Endotoxin may play a role in ischemic and inflammatory bowel diseases. As noted above, one manifestation of hypoperfusion of the gut may be increased permeability to luminal contents. Bowel infarction related to mesenteric occlusion carries a mortality of CHEST I 104 I 5 I NOVEMBER, 1993

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upwards of90 percent, and some of the early systemic effects of ischemia may be related to endotoxemia, prior to frank peritonitis. Inflammatory bowel diseases (IBD) may also lead to increased absorption of endotoxin, though few studies have examined this issue. One case report has described increased portal and systemic levels of LAL-measured endotoxin in a patient with ulcerative colitis. 53 Apparent sepsis often occurs in IBD without detectable infection. Conceivably, the inflammatory process itself can trigger a septic response or IBD permits translocation of bacteria or endotoxin into the portal blood. Antiendotoxin therapy might be useful in such clinical settings if this latter hypothesis is substantiated.

lbncreatitis Severe pancreatitis can produce many of the clinical signs of sepsis in the absence of infection. 54 Some data implicate endotoxin in the pathophysiology of these systemic manifestations of pancreatic inflammation. Foulis et al55 studies 24 patients with acute pancreatitis. Of26 episodes of acute pancreatitis, 13 were associated with LAL-positivity, and this measurement correlated with severity of illness, degree of hypoxemia, and mortality. Thus, endotoxemia may contribute to the appearance of "noninfectious sepsis" and MSOF in severe cases of pancreatitis. PATHOPHYSIOLOGY OF ENDOTOXIN-HOST INTERAGnON

The phenomenon of sepsis results from the systemic effects of processes that likely evolved as local responses to injury or microbial infection. These inflammatory mechanisms serve a protective function when activated locally. Because a variety of different organisms may invade mammalian tissues, mammals likely possess multiple pathways to these systemic effects, and it is therefore reasonable to suspect that endotoxin detection is only one way of triggering a septic response. In sepsis, the behavior of inflammatory and defensive cells changes, with cytokine release, initiation of multiple intracellular and extracellular processes, with eventual activation of granulocytes and macrophages. The changes to the milieu interieure wrought by inflammatory cell activity expose many cells to a potentially damaging environment, with activation of clotting and complement systems, generation of free radicals, and deprivation of oxygen and other substrates. At the systemic level, the septic state reflects these changes affecting many cells across many organs, with the myriad physiologic interconnections that a complex organism permits. The Humoral Cascade

In mammals, endotoxin produces a coordinated sequence of physiologic changes, which are largely 1576

humorally mediated. In fact, endotoxin administration increases blood concentration of many known signaling substances, including kallikrein,!56,SJ bradykinin,- endorphins,64-67 histamine, 66 •68 •69 complement/0 catechols,71-74 prostanoids,75•76 and cortisol.76 Hageman factor is known to decrease with activation of the coagulation cascade. 77-79 The sequence of activation of these mediators remains incomplete, and one cannot delimit precise roles for any of them. Nevertheless, a general schema is emerging. Endotoxin initiates host responses by binding to a receptor with subsequent activation of various intracellular processes. A soluble lipopolysaccharide binding protein (LBP) has been reported as a trace constituent of plasma (<500 nglml) in many species, and its presence reduces the dose of E coli endotoxin required for macrophage production of tumor necrosis factor (fNF, cachectin) by two orders of magnitude. 12 It seems likely that LBP provides a central initial detection mechanism for endotoxin's presence. The soluble endotoxin-LBP complex binds to CD 14 receptors on leukocytes, 80 thereby triggering synthesis and release of TNF, one of several cytokines which plays an important role in the genesis of a septic response. 81 Other important cytokines synthesized during the septic response include interleukins 1 and 6 (ILl, IL6). Cytokines activate neutrophils, increasing free radical generation and triggering degranulation. 82 Chemotaxis is decreased and neutrophil adhesion increases.83 Activated neutrophils have a higher likelihood oflodging in peripheral vessels, where they mediate cell damage by releasing toxic intermediates and altering microcirculatory flow. Thmor Necrosis Factor

Tumor necrosis factor is a macrophage protein consisting of 157 amino acids. Endotoxin elicits its synthesis and accelerates its release; serum levels peak at 90 to 129 min after endotoxin administration in rabbits. 84 Clearance ofTNF occurs by receptor binding and internalization. Injected TNF has a 6 to 7 min half life in mice, longer in humans. Experimentally, TNF induces synthesis of other cytokines, particularly ILl and IL6. 85•86 It is pyrogenic, and its administration can reproduce many of the features of septic shock in animal models, 87-811 including hypotension, early hyperglycemia followed by hypoglycemia, severe acidosis, and ultimately, death. These changes parallel those seen in animals treated with endotoxin. Importantly, physiologic changes continue long after TNF has been cleared. Like endotoxin, TNF acts to initiate a cascade of subsequent events. Passive immunization against TNF attenuates the endotoxin-induced septic response in pretreated rabbits and primates,80•91 provided that the antibody is given prior tothe endotoxin Endotoxin in Human Disease: Part 1 (Manthous, Hall, SatnNI)

challenge. Steroids have long been known to attenuate mortality in endotoxin-treated animals, 92 •93 but not in septic humans. 4 •94 •95 Glucocorticoids prevent TNF release by macrophages, and blunt the endotoxin-induced rise in TNF levels in vivo. Extended exposure to glucocorticoids is necessary to exert these effects; glucocorticoids limit TNF synthesis in part at a translational level. 84 It is not surprising that steroids failed to ameliorate sepsis in human trials: in humans, cytokine release precedes clinical signs of sepsis, so steroids are not given until it is too late. Pretreatment with steroids might conceivably be effective, but steroid treatment is hardly reasonable in patients at risk of developing an oveiWhelming infection. Similar reasoning suggests that any therapy aimed at preventing TNF release or activity may prove disappointing. Lipid-Derived Mediators

Arachidonic acid metabolites play an important role in the septic cascade. Increased levels ofthromboxane ~ and prostacyclin are found in the sera of sheep,

rodents, and dogs injected with endotoxin. 96-11!1 Furthermore, pretreatment with prostaglandin synthesis inhibitors attenuates physiologic responses to injected endotoxin or TNF in dogs and rodents.99 However, ibuprofen does not prevent the TNF rise following endotoxin infusion. These observations suggest that production of prostanoids is largely due to TNF, and TNF release does not depend on prostanoid signaling. These animal results have been extended to humans by Michie et al, 100 who studied 13 volunteers given endotoxin. Ibuprofen prevented the typical hyperthermia and tachycardia but did not attenuate the leukocytosis or increased TNF levels in these subjects. A similar study demonstrated improvement in hemodynamic and respiratory parameters in healthy adults pretreated with ibuprofen before endotoxin administration.101 Bernard and coworkers 102 reported increased urinary excretion of thromboxane and prostacyclin metabolites in patients with the sepsis syndrome; rectal ibuprofen attenuated this increased synthesis, and reduced temperature, heart rate, and peak aiiWay pressure. Platelet activating factor (PAF) has also been implicated in the hemodynamic changes and in lung injury in endotoxin-exposed rats: blood levels rise within 20 min of administration of endotoxin. Pretreatment with PAF inhibitors suppressed the hypotensive response, while preserving vascular function and improving survival in endotoxin-treated rats. 103·104 I nterleukins

Interleukins are synthesized by macrophages, endothelial cells, and fibroblasts and appear to play a vital early role in the humoral cascade of endotoxin-

induced sepsis. Interleukin 1 has been the best studied. 105 Serum levels increase shortly after elevations in TNF levels in endotoxin-induced sepsis in animal models. 100·105·106 Interleukin 6 levels also peak with or after ILl levels and may be modulated by ILl levels. 107 Injection of ILl into experimental animals leads to many of the abnormalities of sepsis. 105 Furthermore, pretreatment of rabbits with ILl receptor antagonist (ILl-RA) attenuates the hemodynamic abnormalities and decreases mortality 1011 in animals injected with endotoxin. The roles of interleukins 2, 6, and 8, which are also increased in sepsis, are under investigation. Neither TNF nor ILl can be the "single common mediator" of endotoxin's effect, for physiologic responses to TNF, ILl, and endotoxin differ. Administration of TNF in dogs led to MSOF and death in a large percentage of animals, whereas ILl administration did not. 109 The TNF frequently resulted in severe noncardiogenic pulmonary edema, 109 whereas this is a relatively rare event when endotoxin is given to dogs (personal observations from several studieslH._ 112 suggest less than 10 percent incidence over 8 h after endotoxin administration). Similarly, canine endotoxin administration causes immediate splanchnic pooling and a rise in aiiWay and pulmonary artery pressures. The TNF infusion does not share these immediate effects. It follows that TNF likely represents only one of several parallel pathways. If concordance of effects from multiple pathways is necessary to produce the septic syndrome, then blocking any of the pathways may be sufficient to block hemodynamic changes in experimental studies. Alternatively, if these various factors act in a complementary, self-amplifying fashion, interruption of multiple pathways may be necessary to reverse the abnormal physiologic effects. Clotting Cascade Endotoxin also activates the clotting cascade, likely by activating Hageman factor, and by increasing monocyte and endothelial expression of tissue factor, a potent procoagulant. Recently, Taylor et al 113 studied the effects of passive immunization against tissue factor in baboons with E coli bacteremia, comparing mortality and tissue histologic condition. All five placebotreated baboons were dead at 24 h, while the immunized baboons survived to the end of the study period (7 days). When killed, tissues from the antibodytreated animals exhibited little of the thrombosis, neutrophil infiltration, and tissue congestion present in the placebo-treated animals. Other studies show pretreatment with activated protein C 114 or antithrombin 111' 15 also attenuate severity of organ injury in similar models. Nitric Oxide While cytokine activation produces many of the CHEST I 104 I 5 I NOVEMBER, 1993

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untoward effects of endotoxin, these effects persist long after the cytokines have been cleared from the circulation. It follows that exposure to these cytokines produces lasting changes in cellular behavior, due either to continued generation of humoral intermediates, or to changes in cellular response, or both. In endotoxemia, vascular smooth muscle tone is decreased, resulting in hypotension despite a high cardiac output. Correspondingly, vascular smooth muscle has decreased tone in sepsis. Vasodilation is ordinarily an active process, and cytosolic production of either cyclic adenosine monophosphate (cAMP) or cyclic guanosine monophosphate {cGMP) can produce relaxation of vascular smooth muscle. The cAMP synthesis is stimulated by prostacyclin, beta-agonists, and other agents, while cGMP is stimulated by nitrovasodilators and atrial natriuretic peptide. 116 The cGMP system, activated by the endogenous nitrovasodilator nitric oxide {NO), appears to play a major role in vasodilation in models of sepsis. The free radical nitric oxide, generated from arginine, oxygen, and NADPH, is the essential element in endothelium-derived relaxation factor (EDRF), 117•118 a soluble paracrine mediator released in response to a broad variety of endothelium-dependent vasodilators, including acetylcholine and bradykinin. Excessive release of nitric oxide contributes to the diminished vascular tone in models of sepsis. 119•1210 Vessels taken from endotoxin-treated animals show diminished vasoconstriction, but direct blockade of nitric oxide synthase or of vascular guanylate cyclase restores normal vasoconstriction. 121 Moreover, blockade of NO synthesis with N-methyl arginine can partially reverse vasodilation and restore blood pressure in endotoxin-treated animals. 122 Unlike other pharmacologic agents {prostaglandin synthesis inhibitors, anti-TNF antibodies, steroids, etc.), inhibitors of nitric oxide biosynthesis have a recognizable effect on fully developed sepsis. Overall, this information suggests that excessive production of nitric oxide is a late event in the septic cascade and contributes importantly to the hypotension and vasodilation seen in sepsis. While nitric oxide synthesis may be an important contributor to sepsis, EDRF is an important physiologic mechanism for vascular control. Despite the systemic excess release of NO in sepsis, endotheliumdependent relaxation is impaired in canine femoral, renal, and mesenteric arteries. 110 Blocking NO synthesis to increase blood pressure may produce more harm than good, if it limits normal vascular regulation in a situation where vascular control mechanisms are already stressed. Umans and Samsel'23 recently reported that canavanine, a selective inhibitor of the macrophage isoform of NO synthase, partially restores contractility in aortas from endotoxin-treated rats 1578

without impairing endothelium-dependent relaxation. Thus, selective inhibitors may appear that can improve blood pressure without contravening the physiologic control of vascular tone afforded by native EDRF. REFERENCES 1 Centers for Disease Control. Increase in national hospital discharge survey rates for septicemia - United States, 19791987. MMWR 1990; 39:31-4 2 Bone RC , Fisher CJ Jr, Clemmer TP, Slotman GJ, Metz CA, Balk RA. Sepsis syndrome: a valid clinical entity. Crit Care Med 1989; 17:389-93 3 Kreger BE, Craven DE, McCabe WR. Gram-negative bacteremia: rv. Re-evaluation of clinical features and treatment in 612 patients. Am J Med 1980; 68:344-55 4 Bone RC, Fisher CJ, Clemmer IP, Slotman GJ, Metz CA, Balk RA. Acontrolled clinical trial of high-dose methylprednisolone in the treatment of severe sepsis and septic shock. N Engl J Med 1987; 317:659-67 5 Ziegler EJ, Fisher CJ, Sprung CL, Straube RC, Sadoff JC, Fouke GE, et al. Treatment of gram-negative bacteremia and septic shock with HA-lA human monoclonal antibody against endotoxin. N Engl J Med 1991; 324:429-36 6 Miyamoto K, Schultz E , Heath T, Mitchell MD, Albertine KH, Staub NC. Pulmonary intravascular macrophages and hemodynamic effects of liposomes in sheep. Physiol 1986; 29:117-20 7 Staub NC. Pulmonary intravascular macrophages. Chest 1988; 93:84S-85S 8 Westphal 0, Hann K, Himmelspach K. Chemistry and immunochemistry of bacterial lipopolysaccharide as cell wall antigens and endotoxins. Prog Allergy 1983; 33:9-39 9 Brade H, Brade L, Schade U, Zahringer U, Holst 0 , Kuhn H, et al. Structure, endotoxicity, immunogenicity and antigenicity of bacterial lipopolysaccharides. Prog Clin Bioi Res 1988; 272:17-45 10 Galanos C, Luderitz 0, Reitschel ETh, Westphal 0, Brade H, Brade L, et al. Synthetic and natural Escherichia coli free lipid A express identical endotoxic activities. Eur J Biochem 1985; 148:1-5 11 Tesh VL, Vukajlovich SW, Morrison DC. Endotoxin interactions with serum proteins and relationships to biological activity. Prog Clin Bioi Res 1988; 272:47-61 12 Schumann RR, Leong SR, Flaggs GW, Gray PW, Wright SD, Mathieson JC, et al. Structure and function of lipopolysaccharide binding protein. Science 1990; 249:1429-31 13 Freudenberg MA, Galanos C . The metabolic fate of endotoxins. Prog Clin Bioi Res 1988; 272:63-75 14 Munford RS , Hall CL. Detoxification of bacterial lipopolysaccharides by a human neutrophil enzyme . Science 1986; 234:203-05 15 Harris Rl, Stone PCW, Stuart J. An improved chromogenic substrate endotoxin assay for clinical use. J Clin Pathol 1983; 36: 1145-49 16 Vanhaecke E, Pijck J, Vuye A. Endotoxin testing. J Clin Pharmacal Therap 1987; 12:223-35 17 Philippe JJ, DeBuyzere MR. Endotoxin: detection and clinical significance. Acta Clin Belg 1988; 43:429-35 18 Webster C. Principles of a quantification assay for bacterial endotoxin in blood that uses limulus lysate and chromogenic substrates. J Clin Microbioll980; 12:644-50 19 Danner RL, Elin RJ, Hosseini JM, Wesley RA, Reilly JM , Parillo JE . Endotoxemia in human septic shock. Chest 1991; 99:169-76 20 Bone RC. The pathogenesis of sepsis. Ann Intern Med 1991; ll5:457-69 Endotoxin in Human Disease: Part 1 (Manthous. Hall, Samsel)

21 Pei YP, Thompson DA. Severe salicylate intoxication mimicking septic shock. Am J Med 1987; 82:381-82 22 Bone RC, Balk RA, Cerra FB, Dellinger RP, Fein AM, Knauss WA, et al. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Chest 1992; 101:1644-55 23 Shinnep JL, Flynn PM, Barrett FF, Stidham GL, Westenkirchner OF. Serial quantitation of endotoxemia and bacteremia during therapy for gram negative bacterial sepsis. J Infect Dis 1988; 157:565-68 24 Tubbs HR. Endotoxin in meningococcal infections. Arch Dis Child 1980; 55:808-19 25 Levin J, Poore TE, Young NS, Margolis S, Zauber NP, Townes AS, et al. Gram-negative sepsis: detection of endotoxemia with the limulus test. Ann Intern Med 1972; 76:1-7 26 McCartney AC, Banks JG, Clements GB, Sleigh JD, Tehrani M, Ledingham IM. Endotoxemia in septic shock: clinical and post-mortem correlations. lnt Care Med 1983; 9:117-22 27 Brandtzaeg PP, Keirulf P, Gaustad P, Skulberg A, Bruun JN, Halvorsen S, et al. Plasma endotoxin as a predictor of multiple organ failure and death in systemic meningococcal disease. J Infect Dis 1989; 159:195-204 28 Suffredini AF, Fromm RE, Parker MM, Brenner M, Kovacs JA, Wesley RA, et al. The cardiovascular response of normal humans to administration of endotoxin. N Eng! J Med 1989; 321:280-87 29 Zeigler EJ, McCutchan JA, Fierer J, Glauser MP, Sadoff JC, Douglas H, et al. Treatment of gram negative bacteremia and shock with human antiserum to a mutant Escherichia coli. N Eng! J Med 1982; 307:1225-30 30 Greenman RL, Schein RMH, Martin MA, Wenzell RP, MacIntyre NR, Emmanuelle G, et al. Acontrolled clinical trial of E-5 murine monoclonal lgM antibody to endotoxin in the treatment of gram-negative sepsis. JAMA 1991; 266:1097-1102 31 Lumdsen AB, Henderson JM, Kutner MH. Endotoxin levels measured by a chromogenic assay in portal, hepatic and peripheral venous blood in patients with cirrhosis. Hepatology 1988; 8:232-36 32 Tachiyama G. Endogenous endotoxemia in patients with liver cirrhosis: a quantitative analysis of endotoxin in portal and peripheral blood. Jap J Surg 1988; 18:403-08 33 Yajima Y, Fukuda I , Otsuki M, Suzuki H, Mork T, Gato Y. Nonseptic endotoxemia in cirrhotic patients. Gastroenterol Jap 1989; 24:262-69 34 Prytz H, Holst-Christensen J, Komer B, Liehr H . Portal venous and systemic endotoxemia in patients without liver disease and systemic endotoxemia in patients with cirrhosis. Scand J Gastroenteroll976; 11:857-63 35 Bigatello LM , Broitman SA, Fattori L, DiPaoli M, Pontello M, Bevilacqua G, et al. Endotoxemia, encephalopathy and mortality in cirrhotic patients. Am J Gastroenterol1987; 82:11-15 36 Yamamoto Y. The study of endotoxin levels in portal venous systems in liver cirrhosis. Jpn J Gastroenterol 1990; 87:997-

42

43 44 45 46

47

48

49

50

51

52

53 54

55

56

57

58

59

1002 37 Ring-Larsen H, Henriksen JH. Pathogenesis of ascites formation and hepatorenal syndrome: humoral and hemodynamic factors. Sem Liver Dis 1986; 6:341-52

60

38 Murray JF. Circulatory changes in chronic liver disease. Am J Med 1985; 24:358-67 39 Henriksen JH, Ring-Larsen H. Circulating noradrenaline and central hemodynamics in patients with cirrhosis. Scand J Gastroenteroll985; 20:1185-90 40 Lieberman FL. The relationship of plasma volume, portal hypertension, ascites, and renal sodium retention in cirrhosis: the overflow theory of ascites formation. Ann NY Acad Sci 1970; 170:202-12 41 Henriksen JH . Protein-kinetics and hemodynamic studies in

61 62

63

patients with liver cirrhosis: evidence of lymph-imbalance theory of ascites formation. Clin Physiol1981; 1:565-78 Arroyo V, Bernardi M, Epstein M, Henriksen JH, Schrier Rw, Rodes J. Pathophysiology of ascites and functional renal failure in cirrhosis. J Hepatol1988; 6:239-57 Krowka MJ, Cortese DA. Pulmonary aspects of liver disease and liver transplantation. Clin Chest Med 1989; 10:5~16 Trewby PN, Williams R. Pathophysiology of hypotension in patients with fulminant hepatic failure. Gut 1987; 18:1021-26 Payne J. Pathogenesis and treatment of fulminant liver failure. Compr Ther 1989; 15:42-4 Katelaris P, Jones B. Fulminant hepatic failure. Med Clin North Am 1989; 73:956-70 Manthous CA, Schmidt G, Kemp R, Wood LDH. Treatment of fulminant hepatic failure with anti-endotoxin antibody. Crit Care Med 1992; 20:1617-19 Yokayama I, Todo S, Miyata T, Selby R, Tszakis AG, Stan! TE. Endotoxin and human liver transplantation. Transplant Proc 1989; 21:3833-41 Demling R. Burns: resuscitation phase (0-36 H). In: Hall JB, Schmidt GA, Wood LDH, eds. Principles of critical care. New York: McGraw Hill, 1992; 797-811 Dobke MK, Simoni J, Nennemann JL, Barrett J, Harnar TJ. Endotoxemia after burn injury: effect of early excision on circulating endotoxin levels. J Burn Care Rehab 1989; 10:10711 Winchurch RA, Tupari JN, Munster AM . Endotoxemia in burn patients: levels of circulating endotoxins are related to burn size. Surgery 1987; 102:808-12 Ziegler TR, Smith RT, O'Dwyer ST, Demling RH, Wilmore OW. Increased intestinal permeability associated with infection in burn patients. Arch Surg 1988; 123:1313-19 Jacob Jl, Goldberg PK, Bloom N. Endotoxin and bacteria in portal blood. Gastroenterology 1977; 72:1268-70 Taylor BR. Acute pancreatitis in the critically ill. In: Hall JB, Schmidt GA, Wood LDH, eds. Principles of critical care. New York: McGraw Hill, 1992; 2028-36 Foulis AK, Murray WR, Galloway D, McCartney AC, LangE, Veitch J, et al. Endotoxemia and complement activation in acute pancreatitis in man. Gut 1982; 23:656-61 Mason JW. Kleesberg U, Dolan P, Colman Rw. Plasma kallikrein and Hageman factor in gram-negative bacteremia. Ann Intern Med 1970; 73:545-51 Smith-Erichsen N. Studies of components of the coagulation systems in normal individuals and septic shock patients. Circ Shock 1982; 9:491-97 Katori M, Najima M, Odoi-Adome R, Sunahara N, Yasuharo U. Evidence for the involvement of a plasma kallikrein-kinin system in immediate hypotension produced by endotoxin in anaesthetized rats. Br J Pharmacol1989; 98:1383-91 Naess T, Roeise 0, Pilgram-Larsen J, Ruud TE, Stadaas JO, Aasen AO. Plasma proteolysis and circulating cells in relation to varying endotoxin concentrations in porcine endotoxaemia. Circ Shock 1989; 28:89-100 Miller RL, Reichgott MJ, Melmon KL. Biochemical mechanisms of generation of bradykinin by endotoxin. J Infect Dis 1!173; 128(suppl):144-56 Kimball HR, Melmon KL, Wo!IJSM. Endotoxin-induced kinin production in man. Proc Soc Exp Bioi Med 1972; 139:1078-81 Reichgott MJN. Forsyth RP, Melmon KL. Effects of bradykinin and autonomic nervous system inhibition on systemic and regional hemodynamics in the unanesthetized rhesus monkey. Circ Res 1971; 29:367-74 Wilson DO, de-Garavilla L, Kuhn W, Togo J, Burch RM, Steronka LR. D-Arg-9Hyp3-D-Phe7-bradykinin, a bradykinin antagonist, reduces mortality in a rat model of endotoxic shock. Circ Shock 1989; 27:93-101 CHEST I 104 I 5 I NOVEMBER, 1993

1579

64 Casale IB, Ballas ZK, Kaliner MA, Keahey TN . The effects of intravenous endotoxin on various host-effector molecules. J Allergy Clin Immunol1990; 85:45-51 65 Gurll NJ, Reynolds DC, Holaday JW. Evidence for a role of endorphins in the cardiovascular pathophysiology of primate shock. Crit Care Med 1988; 16:521-30 66 Naess T, Roeise 0, Stadaas JO, Aasen AO. Combined drug therapy in procine endotoxaemia: hemodynamic and proteolytic effect of antagonists against histamine, serotonin and endorphin. Eur Surg Res 1990; 22:160-69 67 Hamilton AJ, Carr DB, LaRovere JM, Black PM . Endotoxic shock elicits greater endorphin secretion than hemorrhage. Circ Shock 1986; 19:47-54 68 Brackett UJ, Hamburger SA, Lerner MR, Jones SB, Schaffer CF, Henry DP, et al. An assessment of plasma histamine concentrations during documented endotoxic shock. Agent Actions 1990; 31:263-74 69 Vick JA, Hehlman B, Heilfer MH . Early histamine release and death due to endotoxin. Proc Soc Exp Bioi Med 1971; 137:90206 70 Fearon DT, Ruddy S, Shur PH , McCabe WR. Activation of the properidin pathway in patients with gram negative bacteremia. N Eng) J Med 1975; 292:937-40 71 Jones SB, Romano PD. Dose- and time-dependent changes in plasma catecholamines in response to endotoxin in conscious rats. Circ Shock 1989; 28:59-68 72 Spitzer JJ, Bagby GJ, Meszaros K, Lang CH . Altered control of carbohydrate metabolism in endotoxaemia. Prog Clin Bioi Res 1989; 286:145-65 73 Zhou ZZ, Wurster RD, Qi M. Sympathoadrenal activation in sinoaortic-denervated rats following endotoxin. Am J Physiol 1991; 260:739-46 74 Boosman R, Mutsaers CW, Dielman SJ. Sympathico-adrenal effects of endotoxemia in cattle. Vet Res 1990; 127:11-14 75 Cook JA, Olanoff WC, Wise GE. Role of eicosanoids in endotoxic and septic shock. In: Janssen HF, Barnes CD. Circulatory shock: basic and clinical implications. Orlando, Fla: Academic Press, 1985; 101-32 76 Giri SN, Amau P, Cullor JS. Effects of endotoxin infusion on circulating levels of eicosanoids, progesterone, cortisol, glucose and lactic acid and abortion in pregnant cows. Vet Microbiol 1990; 21 :211-31 77 Rapaport SI, Tatter D, Coeur-Barron N, Hjort PF. Pseudomonas septicemia with intravascular clotting leading to the generalized Schwartzman reaction. N Eng) J Med 1964; 271 : 80-4 78 Brozna JP. Schwartzman reactions. Semin Thromb Hemost 1990; 16:326-32 79 Morrison DC, Cochrane CG. Direct evidence for Hageman factor (factor XII) activation by bacterial lipopolysaccharides (endotoxins). J Exp Med 1974; 140:797-811 80 Wright SD, Ramos RA, Tobias PS, Ulevitch RJ, Mathison JC. CD14, a receptor for complexes of lipopolysaccharide (LPS) and LPS binding protein. Science 1990; 249:1431-33 81 Fong Y, Lowry SF. Tumor necrosis factor in the pathophysiology of infection and sepsis. Clin Immunol Immunopathol 1990; 55:157-70 82 Ferrante A, Nandoskar A, Waltz D, Goh DH, Kowanko IC. Effects of tumor necrosis factor alpha and interleukin-1 alpha and beta on human neutrophil migration, respiratory burst, and degranulation. Int Arch Allergy Appl Immunol1988; 86:8291 83 Sayler JL, Bohnsak JF, Knape WA, Shigeoka AO, Ashwood ER, Hill HR. Mechanisms of tumor necrosis factor alpha alteration of PMN adhesion and migration. Am J Pathol 1990; 136:831-41 84 Beutler B, Milsark I, Cerami A. Cachectin/tumor necrosis

1580

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

factor: production, distribution and metabolic fate in vivo. J Immunol1986; 135:3972-77 Dinarello CA, Cannon JG, Bernheim SM, Buetler B, Cerami A, Figari IS, et al. Tumor necrosis factor {cachectin) is an endogenous pyrogen and induces production of interleukin 1. J Exp Med 1986; 163:1433-50 Jablons DM, Mule JJ, Mcintosh JK, Sehgal PB, May LT, Huang CM. IL-6/IFN-B-2 as a circulating hormone: induction by cytokine administration in humans. Immunol 1989; 142:1542-47 Tracey KJ, Lowry SF, Fahey TJ III, Albert JD, Fong Y, Hess D, et al. Cachectin/tumor necrosis factor induces lethal shock and stress hormone responses in the dog. Surg Gynecol Obstet 1987; 104:415 Tracey KJ, Beutler B, Lowry SF, Merryweather J, Nolpe S, Milsark IW, et al. Shock and tissue injury induced by recombinant human cachectin. Science 1987; 234:47Q-74 Natanson C , Eichenholz PW, Danner RL, Eichacker D, Hoffman WD, Kuo GC, et al. Endotoxin and tumor necrosis factor challenges in dogs simulate the cardiovascular profile of human septic shock. J Exp Med 1989; 169:823-32 Tracey KJ, Fong Y, Hesse DC, Manogue KR, Lee AT, Kuo GC, et al. Anticachectin/TNF monoclonal antibodies prevent septic shock during lethal bacteraemia. Nature 1987; 330:662-64 Mathison JC, Wolfson E, Ulevitch RJ. Participation of tumor necrosis factor in the mediation of gram-negative bacterial lipopolysaccharide-induced injury in rabbits. J Clin Invest 1988; 81:1925-37 Thomas CS, Brockman SK. The role of adrenal corticosteroid therapy in Escherichia coli endotoxin shock. Surg Gynecol Obstet 1968; 126:61-9 White GI, Archer LJ, Beller BK, Hinshaw LB. Increased survival with methylprednisolone treatment in canine endotoxin shock. JSurg Res 1978; 25:357-64 Sprung CL, Caralis PV, Marcial EH , Pierce M, Gelbard MA, Long WM, et al. The effects of high-dose corticosteroids in patients with septic shock. NEng) J Med 1984; 311:1137-43 Veterans Administration Systems Sepsis Cooperative Study Group. Effect of high dose glucocorticoid therapy on mortality in patients with clinical signs of systemic sepsis. N Eng) J Med 1987; 317:659-65 CookJA, Wise WC, Halushka PV. Elevated thromboxane levels in the rat during endotoxic shock. J Clin Invest 1980; 65:22730 Demling RH, Smith M, Gunther R, Flynn JT, Gee MH . Pulmonary injury and prostaglandin production during endotoxaemia in conscious sheep. Am J Physiol1981; 240:348-53 Yellin SA, Nguyen D, Quinn JY, Buchard KW, Crowley JP, Slotman GJ. Prostacyclin and thromboxane A2 in septic shock: species differences. Circ Shock 1986; 20:291-97 Fink MP, Macvittie JJ, Casey LC. Inhibitors of prostaglandin synthesis restore normal hemodynamics in canine hyperdynamic sepsis. Ann Surg 1984; 200:619-26 Michie HR, Manogue KR, Spriggs DR, Revhaug A, O'Dwyer S, Dinarello CA, et al. Detection of circulating tumor necrosis factor after endotoxin administration. N Engl J Med 1988; 310:1461-66 Revhaug A, Michie HR, Manson JM, Watters JM, Dinarello CA, Wolf SM, et al. Inhibition of cyclo-oxygenase attenuates the metabolic response to endotoxin in humans. Arch Surg 1988; 123: 162-70 Bernard GR, Reines HD, Halushka PV, Higgins SB, Metz CA, Swindell BB, et al. Prostacyclin and thromboxane A2 formation is increased in human sepsis syndrome. Am Rev Respir Dis 1991; 144:1095-1101 Chang SW, Feddersen CO, Henson PM , Voelkel NF. Platelet activating factor mediates hemodynamic changes and lung Endoloxin in Human Disease: Part 1 (Manthous, Hall, Samsel)

104

105 106

107

108

109

110

111

112 113

injury in endotoxin-treated rats. J Clin Invest 1987; 79:14981509 Doebber Tw, Wu MS, Robbins JC, Choy BM, Chang MN, Shen TY. Platelet activating factor involvement in endotoxininduced hypotension in rats: studies with PAF~receptor antagonist kadsurenone. Biochem Biophys Res Common 1985; 127:799-808 Dinarello CA. Interleukin-1 and interleukin-1 antagonism. Blood 1991; 77:1627-52 Cannon JG, Tomkins RG, Gelfand JA, Michie HR, Stanford GG. Circulating interleukin-1 and tumor necrosis factor in septic shock and experimental endotoxin fever. J Infect Dis 1990; 161:79-84 Gershenwald JE, Fong YM, Fahey TJ III, Calvano SE, ChizzoniteR, Killian PL, et al. Interleukin-1 blockage attenuates the host in8ammatory response. Proc Nat! Acad Sci USA 1990; 87:4966-70 Wakabayashi G, Gelfand JA, Burke JF, Thompson RC, Dinarello CA. A specific receptor antagonist for interleukin-1 prevents E coli-induced shock. FASEB 1991; 5:338-43 Eichacker B, Hoffman WD, Farese A, Banks SM, Kuo GC, MacVittie TJ, et al. TNF but not IL-l in dogs causes lethal lung injury and multiple organ dysfunction similar to human sepsis. J Appl Physiol1991; 71:1979-89 Wylam ME, Samsel Rw, Mitchell Rw, Umans JG, Letr A, Schumacker PT. Endotoxin in oioo impairs endotheliumdependent relaxation of canine arteries in vitro. Am Rev Respir Dis 1990; 142: 1~7 Nelson D , Samsel R, Wood LDH, Schumacker PT. Pathological supply dependence of systemic and intestinal 02 uptake during endotoxemia. J Appl Physiol1988; 64:2410-19 Samsel R, Nelson D, Sanders W, Wood LDH, Schumacker PT. Effect of endotoxin on systemic and skeletal muscle 02 extraction. J Appl Physiol1988; 65:1377-82 lilylor FB, Chang A, Ruf W, Morrissey JH, Hinshaw LB, Catlett R, et al. Lethal E coli septic shock is prevented by blocking tissue factor with monoclonal antibody. Circ Shock

~ 1991; 33:127-34 114 lilylor FB, Chang A, Esmon CT, D'Angelo A, Vigano-D'Angelo S, Blick KE. Protein C prevents the coagulopathic and lethal effects of Escherichia coli infusion in the baboon. JClin Invest 1987; 79:918-25 115 Emerson TE, Fournel MA, Redens TB, Thylor FB. Efficacy of antithrombin III supplementation in animal models of fulminant Escherichia coli endotoxaemia or bacteremia. Am J Med 1989; 87:275-335 116 Vane JR, Anggard EE, Botting RM. Mechanisms of disease: regulatory functions of the vascular endothelium . N Eng) J Med 1990; 323:27-36 117 Palmer RMJ, Ferrige AG, Moncada S. Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor. Nature 1987; 524:327{6122) 118 Meyers PR, Minor RL, Guerra R. Vasorelaxant properties of the endothelium-derived relaxing factor more closely resemble S-nitrosocysteine than nitric oxide. Nature 1990; 345:161~ 119 Kilbourn RG, Gross SS, Jubran A, Adams J, Griffith AW, Levi R, et al. NG-methyi-L-arginine inhibits tumor necrosis factorinduced hypotension: Implications for the involvement of nitric oxide. Proc Nat! Acad Sci USA 1990; 8:3639-42 120 Kilbourn RG, Jubran A, Gross SS, Adams J, Griffith OW, Levi R, et al. Reversal of endotoxin-mediated shock by NG-methyiL-arginine, an inhibitor of nitric oxide synthesis. Biochem Biophys Res Commun 1990; 172:1132-38 121 Julou-Schaetrer G, Gray GA, Fleming I, Schott C, Parratt JR, Stoclet JC. Loss of vascular responsiveness induced by endotoxin involves L-arginine pathway. Am J Physiol1990; 259:1038-

43

122 Thimermann C, Vane J. Inhibition of nitric oxide synthesis reduces the hypotension induced by bacterial lipopolysaccharides in the rat in oioo. Eur J Pharmacol1990; 182:591-95 123 Umans JG, Samsel Rw. L-canavanine selectively augments contraction in aortae from endotoxaemic rats. Eur J Pharmacol 1992; 210:343-46

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