Endotoxin (LPS) increases mesenteric vascular resistance (MVR) and bacterial translocation (BT)

Hepatic blood flow regulation but not oxygen extraction capability is impaired in prolonged experimental abdominal sepsis

Impaired oxygen utilization has been proposed to play a significant role in sepsis-induced liver dysfunction, but its magnitude and temporal course during prolonged resuscitation is controversial. The aim of this study is to evaluate the capability of the liver to increase oxygen extraction in sepsis during repeated acute portal vein blood flow reduction. Twenty anesthetized and mechanically ventilated pigs with hepatic hemodynamic monitoring were randomized to fecal peritonitis or controls (n = 10, each). After 8-h untreated sepsis, the animals were resuscitated for three days. The ability to increase hepatic O₂ extraction was evaluated by repeated, acute decreases in hepatic oxygen delivery (Do₂) via reduction of portal flow. Blood samples for liver function and liver biopsies were obtained repeatedly. Although liver function tests, ATP content, and Do₂ remained unaltered, there were signs of liver injury in blood samples and overt liver cell necrosis in biopsies. With acute portal vein occlusion, hepatic Do₂ decreased more in septic animals compared with controls [max. decrease: 1.66 ± 0.68 mL/min/kg in sepsis vs. 1.19 ± 0.42 mL/min/kg in controls; portal venous flow (Qpv) reduction-sepsis interaction: P = 0.028]. Hepatic arterial buffer response (HABR) was impaired but recovered after 3-day resuscitation, whereas hepatic oxygen extraction increased similarly during the procedures in both groups (max. increase: 0.27 ± 0.13 in sepsis vs. 0.18 ± 0.09 in controls; all P > 0.05). Our data indicate maintained capacity of the liver to acutely increase O₂ extraction, whereas blood flow regulation is transiently impaired with the potential to contribute to liver injury in sepsis.NEW & NOTEWORTHY The capacity to acutely increase hepatic O₂ extraction with portal flow reduction is maintained in sepsis with accompanying liver injury, but hepatic blood flow regulation is impaired.

The generation of immune-induced fever and emotional stress-induced hyperthermia in mice does not involve brown adipose tissue thermogenesis

We examined the role of brown adipose tissue (BAT) for fever and emotional stress-induced hyperthermia. Wild-type and uncoupling protein-1 (UCP-1) knockout mice were injected with lipopolysaccharide intraperitoneally or intravenously, or subjected to cage exchange, and body temperature monitored by telemetry. Both genotypes showed similar febrile responses to immune challenge and both displayed hyperthermia to emotional stress. Neither procedure resulted in the activation of BAT, such as the induction of UCP-1 or peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) mRNA, or reduced BAT weight and triglyceride content. In contrast, in mice injected with a β₃ agonist, UCP-1 and PGC-1α were strongly induced, and BAT weight and triglyceride content reduced. Both lipopolysaccharide and the β₃ agonist, and emotional stress, induced UCP-3 mRNA in skeletal muscle. A β₃ antagonist did not attenuate lipopolysaccharide-induced fever, but augmented body temperature decrease and inhibited BAT activation when mice were exposed to cold. An α₁ /α_2b antagonist or a 5HT_1A agonist, which inhibit vasoconstriction, abolished lipopolysaccharide-induced fever, but had no effect on emotional stress-induced hyperthermia. These findings demonstrate that in mice, UCP-1-mediated BAT thermogenesis does not take part in inflammation-induced fever, which is dependent on peripheral vasoconstriction, nor in stress-induced hyperthermia. However, both phenomena may involve UCP-3-mediated muscle thermogenesis.

Is There a Role for the Enteral Administration of Serum-Derived Immunoglobulins in Human Gastrointestinal Disease and Pediatric Critical Care Nutrition?

Twenty years ago, there was profound, international interest in developing oral human, bovine, or chicken egg-derived immunoglobulin (Ig) for the prevention and nutritional treatment of childhood malnutrition and gastrointestinal disease, including acute diarrhea and necrotizing enterocolitis. Although such Ig products were shown to be effective, with both nutritional and antidiarrheal benefits, interest waned because of their cost and because of the perceived risk of bovine serum encephalitis (BSE). BSE is no longer considered a barrier to use of oral Ig, because the WHO has declared the United States to be BSE-free since the early 2000s. Low-cost bovine-derived products with high Ig content have been developed and are regulated as medical foods. These new products, called serum bovine Igs (SBIs), facilitate the management of chronic or severe gastrointestinal disturbances in both children and adults and are regulated by the US Food and Drug Administration. Well-established applications for use of SBIs include human immunodeficiency virus (HIV)-associated enteropathy and diarrhea-predominant irritable bowel syndrome. However, SBIs and other similar products could potentially become important components of the treatment regimen for other conditions, such as inflammatory bowel disease, by aiding in disease control without immunosuppressive side effects. In addition, SBIs may be helpful in conditions associated with the depletion of circulating and luminal Igs and could potentially play an important role in critical care nutrition. The rationale for their use is to facilitate intraluminal microbial antibody coating, an essential process in immune recognition in the gut which is disturbed in these conditions, thereby leading to intestinal inflammation. Thus, oral Ig may emerge as an important "add-on" therapy for a variety of gastrointestinal and nutritional problems during the next decade.

Noninvasive indocyanine green plasma disappearance rate predicts early complications, graft failure or death after liver transplantation

BACKGROUND

Early detection of graft malfunction or postoperative complications is essential to save patients and organs after orthotopic liver transplantation (OLT). Predictive tests for graft dysfunction are needed to enable earlier implementation of organ-saving interventions following transplantation. This study was undertaken to assess the value of indocyanine green plasma disappearance rates (ICG-PDRs) for predicting postoperative complications, graft dysfunction, and patient survival following OLT.

METHODS

Eighty-six patients undergoing OLT were included in this single-centre trial. ICG-PDR was assessed daily for the first 7 days following OLT. Endpoints were graft loss or death within 30 days and postoperative complications, graft loss, or death within 30 days.

RESULTS

Postoperative complications of 31 patients included deaths (12 patients) or graft losses. ICG-PDR was significantly different in patients whose endpoints were graft loss or death beginning from day 3 and in those whose endpoints were graft-loss, death, or postoperative complications beginning from day 4 after OLT. For day 7 measurements, receiver operating characteristic curve analysis revealed an ICG-PDR cut-off for predicting death or graft loss of 9.6% per min (a sensitivity of 75.0%, a specificity of 72.6%, positive predictive value 0.35, negative predictive value 0.94). For prediction of graft loss, death, or postoperative complications, the ICG-PDR cut-off was 12.3% per min (a sensitivity of 68.9%, a specificity of 66.7%, positive predictive value 0.57, negative predictive value 0.77).

CONCLUSIONS

ICG-PDR measurements on postoperative day 7 are predictive of early patient outcomes following OLT. The added value over that of routinely determined laboratory parameters is low.

Lack of therapeutic effects of gabexate mesilate on the hepatic encephalopathy in rats with acute and chronic hepatic failure

BACKGROUND AND AIM

Inflammation plays a pivotal role in liver injury. Gabexate mesilate (GM, a protease inhibitor) inhibits inflammation by blocking various serine proteases. This study examined the effects of GM on hepatic encephalopathy in rats with acute and chronic liver failure.

METHODS

Acute and chronic liver failure (cirrhosis) were induced by intraperitoneal TAA administration (350 mg/kg/day for 3 days) and common bile duct ligation, respectively, in male Sprague-Dawley rats. Rats were randomized to receive either GM (50 mg/10 mL/kg) or saline intraperitoneally for 5 days. Severity of encephalopathy was assessed by the Opto-Varimex animal activity meter and hemodynamic parameters, mean arterial pressure and portal pressure, were measured (only in chronic liver failure rats). Plasma levels of liver biochemistry, ammonia, nitrate/nitrite, interleukins (IL) and tumor necrosis factor (TNF)-alpha were determined.

RESULTS

In rats with acute liver failure, GM treatment significantly decreased the plasma levels of alanine aminotransferase (P = 0.02), but no significant difference of motor activity, plasma levels of ammonia, IL-1beta, IL-6, IL-10 and TNF-alpha or survival was found. In chronic liver failure rats, GM significantly lowered the plasma TNF-alpha levels (P = 0.04). However, there was no significant difference of motor activity, other biochemical tests or survival found. GM-treated chronic liver failure rats had higher portal pressure (P = 0.04) but similar mean arterial pressure in comparison with saline-treated rats.

CONCLUSIONS

Chronic GM treatment does not have a major effect on hepatic encephalopathy in rats with TAA-induced acute liver failure and rats with chronic liver failure induced by common bile duct ligation.

Evolution of portal-systemic collateral vasopressin response in endotoxemic portal hypertensive rats

Cirrhotic patients with portal hypertension and variceal hemorrhage are vulnerable to endotoxemia. However, the direct influence of endotoxemia on portal-systemic collateral vasculature remains unexplored. In this study, portal hypertension was induced in Sprague-Dawley rats by partial portal vein ligation. On the 7th day after portal vein ligation, at 0.5, 1.5, and 5 h post endotoxin (LPS; Escherichia coli serotype O111:B4, 3 mg/kg, i.p., E0.5, E1.5 and E5, respectively) or saline (control, C0.5, C1.5, and C5, respectively) injection, hemodynamic measurements and concentration-response relationships to arginine vasopressin (AVP; 10(-10)-10(-7) mol/L) in collateral vascular bed were obtained. In another six parallel groups, reverse-transcriptase-polymerase chain reaction of iNOS, eNOS, and endothelin 1 (ET-1) mRNA expressions for splenorenal shunt, the most prominent intra-abdominal collateral vessel, was performed. The results showed that E0.5 had lower perfusion pressure changes to AVP and higher splenorenal shunt eNOS expression than C0.5 group (P < 0.05). Compared with C1.5, tachycardia, higher perfusion pressure changes and enhanced splenorenal shunt iNOS and ET-1 expression were observed in E1.5 group (P < 0.05). In E5, systemic and portal hypotension with markedly enhanced collateral AVP responsiveness and splenorenal shunt iNOS and ET-1 expressions were noted (P < 0.05). In conclusion, vasoactive substances counterregulation participates, at least in part, the time-dependent changes of collateral AVP responsiveness in endotoxemic portal hypertensive rats.

[Burn: An inflammatory process]

Thermal injury induce a two-phase inflammatory response: first, a pro-inflammatory status, resulting in a systemic inflammatory response syndrome, then an anti-inflammatory phase characterized by a profound defect in cellular-mediated immunity. This inflammatory reaction proceeds from complex phenomenons in whom many cellular elements are involved (macrophage is the central one) and very complex molecular products interact (especially cytokines). These phenomenons promote significant physiopathologic consequences, especially on cardiovascular homeostasis and endothelial permeability, that lower the prognosis. The inflammatory reaction can be modified, enhanced or maintained by adverse events (i.e. infection) resulting in degradation of clinical situation. Despite a better comprehension of the phenomenons underlying this inflammatory process, diagnosis or therapeutic applications are at that time disappointing.

Plasma disappearance rate of indocyanine green: a tool to evaluate early graft outcome after liver transplantation

Indocyanine green clearance (Cl-ICG) has been used to assess liver function and hepatic blood flow mainly before and after hepatic surgery. Cl-ICG (invasive method) has been reported to be a good marker of early graft function after liver transplantation (LT). The goal of this study was to determine if the indocyanine green plasma disappearance rate (PDR-ICG), measured by a noninvasive technique (LiMON, Impulse Medical System, Munich, Germany), is predictive of complications and graft outcome after LT. From September 2005 to June 2006, 72 LT recipients were included in the study. PDR-ICG was measured daily (from day 0 to day 5 after LT) with a digital sensor after patients were injected with 0.25 mg/kg indocyanine green. A PDR-ICG cutoff level of 12.85%/minute was predictive of the development of a serious postoperative complication. The sequential changes of PDR-ICG enabled us to differentiate 2 groups: (1) patients with early severe complications (hepatic artery thrombosis, primary graft nonfunction, or sepsis) who had a low value of PDR-ICG during the first 5 posttransplantation days (average, 8.8 +/- 4.5%/minute) and (2) patients who developed acute rejection and who had a progressive reduction of PDR-ICG between days 0 and 5 (from 25.5 +/- 4.8 to 10.3 +/- 2.5%/minute; P < 0.002). In conclusion, after LT, PDR-ICG (a noninvasive technique), measured regularly during the first 5 postoperative days, is a safe technique that can predict early postoperative complications.

Liver perfusion in sepsis, septic shock, and multiorgan failure

Sepsis causes significant alterations in the hepatic macro- and microcirculation. Diverging views exist on global hepatic blood flow during experimental sepsis because of the large variety in animal and sepsis models. Fluid-resuscitated clinical sepsis is characterized by ongoing liver ischemia due to a defective oxygen extraction despite enhanced perfusion. The effects of vasoactive agents on the hepatosplanchnic circulation are variable, mostly anecdotal, and depend on baseline perfusion, time of drug administration, and use of concomitant medication. Microvascular blood flow disturbances are thought to play a pivotal role in the development of sepsis-induced multiorgan failure. Redistribution of intrahepatic blood flow in concert with a complex interplay between sinusoidal endothelial cells, liver macrophages, and passing leukocytes lead to a decreased perfusion and blood flow velocity in the liver sinusoids. Activation and dysfunction of the endothelial cell barrier with subsequent invasion of neutrophils and formation of microthrombi further enhance liver tissue ischemia and damage. Substances that regulate (micro)vascular tone, such as nitric oxide, endothelin-1, and carbon monoxide, are highly active during sepsis. Possible interactions between these mediators are not well understood, and their therapeutic manipulation produces equivocal or disappointing results. Whether and how standard resuscitation therapy influences the hepatic microvascular response to sepsis is unknown. Indirect evidence supports the concept that improving the microcirculation may prevent or ameliorate sepsis-induced organ failure.

Effects of glutamine supplementation on innate immune response in rats with gut-derived sepsis

The present study examined the effect of glutamine (Gln)-enriched diets before sepsis or Gln-containing total parenteral nutrition (TPN) after sepsis, or both, on the phagocytic activity and blood lymphocyte subpopulation in rats with gut-derived sepsis. Rats were assigned to a control group or one of four experimental groups. The control group and groups 1 and 2 were fed a semipurified diet; groups 3 and 4 had part of casein replaced by Gln. After feeding the diets for 10d, sepsis was induced by caecal ligation and puncture (CLP); TPN was maintained for 3d after CLP. The control group and groups 1 and 3 were infused with conventional TPN and groups 2 and 4 were supplemented with Gln in the TPN solution. All rats were killed 3d after CLP or sham operation to examine their immune responses. The results showed that compared with the control group, the phagocytic activities of peritoneal macrophages were enhanced in groups 3 and 4, but not in groups 1 and 2. The proportion of CD3+ cells in group 1 was significantly lower (P<0·05) than that of the control group, whereas no differences were observed among the control and Gln-supplemented groups. The CD4+ cell proportion was significantly lower (P<0·05) in group 1 compared with the control group and groups 3 and 4. These findings suggest that Gln-enriched diets before CLP significantly enhanced peritoneal macrophage phagocytic activity, preserved CD4+ cells and maintained blood total T lymphocytes in gut-derived sepsis. However, parenteral Gln administration after caecal ligation and puncture had no favourable effects on modulating immune response in septic rats.

Oral carbohydrate solution ameliorates endotoxemia-induced splanchnic ischemia

The purpose of this study was to investigate the effect of oral administration of a simple carbohydrate solution on splanchnic circulation and bacterial translocation in endotoxemia. Group 1 was sham control; group 2 was starved for 24 hours; in group 3, endotoxin was administrated at the end of starvation; in group 4, carbohydrate solution was administrated via orogastric route for 24 hours; and in group 5, carbohydrate solution was given and endotoxin was administrated at the end of 24 hours. Splanchnic blood flows were recorded and tissue samples were collected for microbiological analyses. There was a significant increase (P<.05) in the incidence of bacterial translocation in starvation. Endotoxemia decreased distal (P=.021) and midmesenteric (P=.046) flow in starved animals. Oral carbohydrate significantly increased ileal blood flow in starvation (P=.036) and endotoxemia (P=.008). In conclusion, oral carbohydrate solution prevents bacterial translocation during starvation and endotoxemia. The possible mechanism is the improvement in the mesenteric blood flow.

Beneficial effects of alkaline phosphatase in septic shock

OBJECTIVE

Alkaline phosphatase may decrease the harmful effects of lipopolysaccharide by detoxifying lipid A. The aim of this study was to investigate whether administration of alkaline phosphatase is beneficial in a clinically relevant septic shock model.

DESIGN

Interventional laboratory study.

SETTING

University hospital animal research laboratory.

SUBJECTS

Fourteen fasted, anesthetized, invasively monitored, mechanically ventilated, female sheep (27.6 +/- 3.9 kg).

INTERVENTIONS

Each animal received 1.5 g/kg body weight of feces intraperitoneally to induce sepsis. Ringer's lactate and a 6% hydroxyethyl starch solution were infused throughout the experiment to prevent hypovolemia. Two hours after feces injection, animals were randomized to alkaline phosphatase (60 units/kg intravenous bolus followed by a continuous infusion of 20 units/kg/hr for a total of 15 hrs) or no alkaline phosphatase (control group).

MEASUREMENTS AND MAIN RESULTS

All animals were studied until their spontaneous death or for a maximum of 30 hrs. Plasma alkaline phosphatase concentrations decreased in the control group but increased in the treatment group following alkaline phosphatase administration. In the treatment group, the Pao2/Fio2 ratio was higher (p < .05), blood interleukin-6 concentrations were lower (p < .05), and the survival time was longer (median time 23.8 vs. 17 .0 hrs, p < 0.05) than in the control group. There were no significant differences in systemic hemodynamics or diuresis.

CONCLUSIONS

In this clinically relevant septic shock model, alkaline phosphatase administration improved gas exchange, decreased interleukin-6 concentrations, and prolonged survival time.

Effects of arginine supplementation on mucosal immunity in rats with septic peritonitis

BACKGROUND

Supplemental Arginine (Arg) has been demonstrated to improve the immunologic response and reduce mortality in rodents with sepsis. However, the effects of Arg on gut-associated lymphoid tissue function after infection and sepsis are not clear. The aim of this study was to study the effect of Arg-supplemented diets before and Arg-enriched total parenteral nutrition (TPN) after sepsis or both on the intestinal immunity of rats with septic peritonitis.

METHODS

Rats were assigned to four groups. Groups 1 and 2 were fed a semipurified diet, while in the diets of groups 3 and 4, part of the casein was replaced with Arg. After feeding the experimental diets for 10 days, sepsis was induced by cecal ligation and puncture (CLP); at the same time, the internal jugular vein was cannulated. All rats were maintained on TPN for 3 days. Groups 1 and 3 were infused with conventional TPN, while groups 2 and 4 were given a TPN solution supplemented with Arg, which replaced 10% of the total amino acids. All rats were sacrificed 3 days after CLP. Intestinal immunoglobin (Ig) A levels, total lymphocyte yields, and lymphocyte subpopulations in Peyer's patches were analyzed. In vitro cytokine secretion by splenocytes and Peyer's patch lymphocytes were also measured.

RESULTS

Total lymphocyte yields in Peyer's patches, and small intestinal immunoglobulin A (IgA) secretion in group 4 were significantly higher than the groups 1 and 2. No differences were observed between groups 3 and 4. There were no differences in the interleukin (IL)-2 and interferon- gamma levels among all groups when splenocytes were stimulated with mitogen. However, in vitro splenocyte IL-10 production in group 4 was significantly higher than those of groups 1 and 2, and had no difference from group 3. There were no differences in the ratios of B and T lymphocyte subpopulations in Peyer's patches among all groups.

CONCLUSIONS

Enteral Arg supplementation before sepsis tended to enhance total lymphocyte yields in Peyer's patches and intestinal IgA secretion. Arg administered both before and after CLP had a synergistic effect on improving intestinal immunity, possibly by enhancing systemic IL-10 secretion. However, intravenous Arg administration after CLP had no favorable effects on mucosal immunity in rats with septic peritonitis.

Effects of glutamine supplementation on splenocyte cytokine mRNA expression in rats with septic peritonitis

AIM: To investigate the effects of glutamine (GLN)-enriched diets before and GLN-containing total parenteral nutrition (TPN) after sepsis or both on the secretion of cytokines and their mRNA expression levels in splenocytes of rats with septic peritonitis.

METHODS: Rats were assigned to a control group and 4 experimental groups. The control group and experimental groups 1 and 2 were fed a semipurified diet, while experimental groups 3 and 4 had part of the casein replaced by GLN which provided 25% of the total nitrogen. After rats were fed with these diets for 10 d, sepsis was induced by cecal ligation and puncture (CLP), whereas the control group underwent a sham operation, at the same time, an internal jugular vein was cannulated. All rats were maintained on TPN for 3 d. The control group and experimental groups 1 and 3 were infused with conventional TPN, while the TPN in experimental groups 2 and 4 was supplemented with GLN, providing 25% of the total nitrogen in the TPN solution. All rats were kiued 3 d after sham operation or CLP to examine their splenocyte subpopulation distribution and cytokine expression levels.

RESULTS: Most cytokines could not be detected in plasma except for IL-10. No difference in plasma IL-10 was observed among the 5 groups. The IL-2, IL-4, IL-10, and TNF-α mRNA expression levels in splenocytes were significantly higher in experimental groups 2 and 4 than in the control group and group 1. The mRNA expression of IFN-γ was significantly higher in the GLN-supplemented groups than in the control group and experimental group 1. The proportion of CD45Ra+ was increased, while those of CD3+ and CD4+ were decreased in experimental group 1 after CLP was performed. There were no differences in spleen CD3+ lymphocyte distributions between the control and GLN-supplemented groups.

CONCLUSION: GLN supplementation can maintain T-lymphocyte populations in the spleen and significantly enhance the mRNA expression levels of Th1 and Th2 cytokines and TNF-α in the spleen of rats with septic peritonitis.

A new therapeutic approach for the treatment of sepsis

Despite important advances in understanding its pathophysiology, therapy for septic shock remains largely symptomatic and supportive. Aiming to elevate the systemic arterial blood pressure by using vasoconstrictor manoeuvers are preferred without paying much attention to the ischaemia produced at the peripheral tissues. Since, these maneuvers proved no remarkable success in reducing the mortality up to date, we now propose a different perspective in this manuscript. Although it is not always easy to distinguish the different phases of septic shock, at least two fundamentally different phases can be distinguished, i.e. (i) hyperdynamic phase and (ii) hypodynamic phase mandating the adoption of vasodilative and vasoconstrictive interventions, consequently. Additionally, endothelium-derived vasodilator and vasoconstrictor substances such as nitric oxide and endothelin play key roles in systemic inflammatory response syndrome that lead to fatal multiple organ dysfunction. Therefore, we hypothesize that the inhibition of nitric oxide production during earlier phases of septic shock combined with the blockade of endothelin receptors at later stages appear feasible and a novel strategy for the therapy of septic shock.

Glutamine supplementation enhances mucosal immunity in rats with Gut-Derived sepsis

OBJECTIVE

Supplemental glutamine (Gln) has been demonstrated to improve the immunologic response and reduce mortality in rodents with sepsis. However, the effects of Gln on gut-associated lymphoid tissue function after infection and sepsis are not clear. We investigated the effects of Gln-supplemented diets before sepsis, Gln-enriched total parenteral nutrition (TPN) after sepsis, or both on the intestinal immunity in rats with gut-derived sepsis.

METHODS

Male Wistar rats were assigned to control and four experimental groups. The control and experimental groups 1 and 2 were fed a semi-purified diet; in experimental groups 3 and 4, part of the casein in the diets was replaced with Gln. After feeding rats the respective diets for 10 d, sepsis was induced by cecal ligation and puncture (CLP) in the experimental groups, whereas the control group underwent a sham operation; at the same time, the internal jugular vein of all rats was cannulated. All rats were maintained on TPN for 3 d. The control group and groups 1 and 3 were infused with conventional TPN, and groups 2 and 4 were given a TPN solution supplemented with Gln, which provided 25% of total amino acid nitrogen. All rats were killed 3 d after the sham operation or CLP. Intestinal immunoglobin A levels, total lymphocyte yields, and lymphocyte subpopulations in Peyer's patches were analyzed.

RESULTS

Total Peyer's patch lymphocyte numbers were significantly higher in the Gln-supplemented groups than in the control group. Distributions of CD3+ and CD4+ in group 1 were significantly lower than those in the control group, whereas no differences were observed among the control and Gln-supplemented groups. Plasma immunoglobulin A levels were higher in the Gln-supplemented groups than the control group and group 1. Intestinal immunoglobulin A levels were significantly higher in groups 2 and 4 than in the control group and group 1.

CONCLUSIONS

Preventive use of a Gln-supplemented enteral diet before CLP or intravenous Gln supplementation after CLP have similar effects in promoting proliferation of total lymphocyte in gut-associated lymphoid tissue, enhancing IgA secretion, and maintaining T-lymphocyte populations in Peyer's patches. Gln administered before and after CLP did not seem to have a synergistic effect on enhancing mucosal immunity in rats with gut-derived sepsis.

Isoflurane pretreatment supports hemodynamics and leukocyte rolling velocities in rat mesentery during lipopolysaccharide-induced inflammation

We hypothesized that the protective effects of isoflurane (ISO) pretreatment on the vasculature may be attributed, in part, to altered leukocyte-endothelial interactions. Rats were anesthetized with pentobarbital and then randomized into four groups: control, ISO-control (pretreatment with 30 min of 1.4% ISO), lipopolysaccharide (LPS; 10 mg/kg IV), and ISO-LPS (ISO pretreatment and then LPS). The mesentery was prepared for intravital videomicroscopy. Mean arterial blood pressure (MAP), along with microcirculatory variables that included postcapillary venular and arteriolar blood flow velocity and leukocyte dynamics (number of rolling and adherent leukocytes and individual rolling leukocyte velocities), were measured hourly (baseline and at 0-4 h). In LPS rats, ISO pretreatment significantly (P < 0.05) attenuated the decrease in MAP at 2 and 4 h after LPS and increased leukocyte rolling velocities after 2-4 h. Four hours after LPS, leukocyte rolling velocities were >200% more rapid (63.7 +/- 27.6 microm/s versus 19.8 +/- 6.4 micro m/s) in ISO-LPS versus LPS rats. In control rats, ISO pretreatment had no effect on MAP or leukocyte rolling velocities but increased the number of rolling leukocytes. ISO pretreatment had no effect on arteriolar and postcapillary venular blood flow velocity in LPS rats or leukocyte adherence in LPS or control rats. In conclusion, ISO pretreatment supported hemodynamics and increased leukocyte rolling velocities but did not alter the number of rolling or adherent leukocytes in the mesenteric microcirculation during LPS-induced inflammation.

IMPLICATIONS

Isoflurane pretreatment supported hemodynamics and increased leukocyte rolling velocities in the mesenteric microcirculation during lipopolysaccharide-induced inflammation. Faster rolling velocities may reduce the incidence of inflammation by decreasing leukocyte-endothelial interactions and cellular injury.

Role of the gut in the course of severe acute pancreatitis

INTRODUCTION

The pathogenesis of acute pancreatitis remains elusive. Sepsis and multiple organ failure continue to cause death (overall mortality rate, approximately 10%) despite immense improvements in supportive, radiologic, and surgical therapy. The gut appears to play a key role in the development of these complications.

AIM

To critically review the evidence implicating the gut in the pathogenesis of acute pancreatitis.

METHODS

Relevant English-language literature or abstracts cited in the MEDLINE database were reviewed.

RESULTS AND CONCLUSION

Gram-negative enteric organisms account for most infections of pancreatic necrosis and subsequent sepsis, which suggests the gut as a source. Intestinal permeability is increased early in patients with severe acute pancreatitis and correlates with endotoxemia, which suggests translocation as a possible mechanism. The pathogenesis of the deranged function of the gut mucosal barrier and the possible sites of increase in intestinal permeability are discussed. The gut also plays a role in priming neutrophils and the release of inflammatory cytokines, which initiate and propagate nearly all the detrimental consequences of severe inflammation and sepsis. Future research avenues and potential therapeutic measures that may restore and preserve gut barrier function are explored.

Relationship between lymphocyte apoptosis and endotoxin translocation after thermal injury in rats

AIM: To investigate the relationship between lymphocyte apoptosis in peripheral blood, spleen and mesenteric lymph nodes (MLN) and endotoxin translocation after thermal injury in rats.

METHODS: In a Wistar rat model inflicted with 30% TBSA III degree scalding, serum LPS levels in portal vein and vena cava were quantified by tachypleus amebocyte lysate (TAL) technique. The analysis of peripheral blood lymphocyte was employed in in situ Cell Death Detection Kit and evaluated by flow cytometry. Apoptotic lymphocytes in paraffin-embedded spleen and MLN sections were examined by histologic analysis, in situ deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) and peroxidase (POD) staining. The imagines were taken by Cooldccd camera system, and the count and optical density value (transmission light) of apoptotic lymphocytes were analyzed with software Spot and Imagine proplus 4.10a (IPP4.10a).

RESULTS: In the period of 3 to 48 postburn hours (PBHs) serum LPS level (× 10³ EU·L^-1) in portal vein (2.11 ± 0.02, 5.66 ± 0.20, 3.70 ± 0.22, 2.56 ± 0.28, 0.90 ± 0.11) was higher than that in vena cava (0.63 ± 0.01, 1.53 ± 0.18, 0.83 ± 0.32, 0.52 ± 0.12, 0.23 ± 0.02, P < 0.01), but both increased sharply in postburn rats (P < 0.01) and reached a peak at 6 PBH. Analysis of apoptotic lymphocytes showed that the proportion (%) of postburn apoptotic cells was much higher than that in healthy rats (8.34 ± 1.53, 8.13 ± 1.81, 20.77 ± 3.94, 23.90 ± 3.92, 11.23 ± 1.35 and 13.26 ± 2.09 at 3, 6, 12, 24, 48 and 72 PBH, respectively, vs 3.99 ± 1.72, P < 0.01), especially after 6 PBH. The concentrations of lymphocytic apoptosis at 12 and 24 PBH were markedly higher than that at other time points. Meantime, few apoptotic lymphocytes were found in normal MLN, but increased postburn obviously (3 ± 1 vs 546 ± 83, 285 ± 39, 149 ± 30, 58 ± 10, 36 ± 11 and 33 ± 9 in turn, P < 0.01), especially at 3 PBH, whereas apoptotic lymphocytes were concentrated in splenic cortex before the burn and decreased obviously during 72 PBHs (499 ± 186 vs 12 ± 8, 19 ± 15, 12 ± 7, 100 ± 15, 123 ± 25 and 226 ± 26 in turn, P < 0.01) though a slight rise was found in the medulla after 24 PBH. Optical density of apoptotic lymphocytes was significantly reduced in spleen in the 24 PBHs and raised in MLN during 48 PBHs than that prior to the burn, respectively.

CONCLUSION: Gut-origin LPS is a major cause of endotoxemia taken place early in rats following severe thermal injury and could induce extensive lymphocyte apoptosis in blood and MLN, which suggests an immunosuppression state could follow the initial injury and favores a septic state based on apoptotic mechanism.

Immune-modulatory actions of arginine in the critically ill

Current trials of immune-enhancing diets suggest several beneficial clinical effects. These products are associated with a reduction in infectious risk, ventilator days, ICU and hospital stay. However, methodological weaknesses limit the inferences we can make from these studies. Furthermore, improvements in outcomes were largely seen in surgical patients and in patients who tolerated critical amounts of formula. We propose that the beneficial findings cannot easily be extrapolated to other patient populations since there is suggestion from clinical trials that the sickest patients, especially those with severest appearances of sepsis, shock and organ failure may not benefit or may even be harmed. In these conditions we hypothesize that systemic inflammation might be undesirably intensified by immune-enhancing nutrients like arginine in critically ill patients. In this paper, we review the purported effects of arginine on the immune system and organ function to understand the scientific rationale for its inclusion into enteral feeding products. We conclude that patients with the most severe appearances of the systemic inflammatory response syndrome should not receive immune-enhancing substrates which may aggravate systemic inflammation and worsen clinical outcomes.

Hepatic response to sepsis: interaction between coagulation and inflammatory processes

OBJECTIVES

a) To review the hepatic response to sepsis and to establish how this response contributes to coagulation and inflammatory processes; b) to review the physiologic and biochemical mechanisms that suggest hepatic dysfunction may occur during sepsis, enhance procoagulant and proinflammatory activities, and participate in the potential evolution to multiple organ dysfunction syndrome.

DATA SOURCES

A summary of published medical literature from MEDLINE search files and published reviews on liver function in experimental and human sepsis.

DATA SUMMARY

In sepsis, the liver plays a major role in host defense mechanisms. Kupffer cells are responsible for bacterial scavenging, bacterial products inactivation, and inflammatory mediators clearance and production. Hepatocytes, via receptors for many proinflammatory cytokines, modify their metabolic pathway toward gluconeogenesis, amino-acid uptake, and increased synthesis of coagulant and complement factors and protease inhibitors. The acute-phase protein (APP) response also contributes to the procoagulant state, especially by enhancing the inhibition of protein C (alpha1-antitrypsin and alpha2-macroglobulin) and by decreasing liver synthesis of protein C and antithrombin (negative APPs). Elevated C-reactive protein levels (positive APPs) promote the expression of tissue factor by mononuclear cells. Increased liver production of thrombin-activatable fibrinolytic inhibitor (positive APPs) enhances fibrinolysis inhibition. Conversely, such hepatic inflammatory and coagulation processes in sepsis may alter the function of this organ. Indeed, the liver can be injured by activated Kupffer cells that release chemokines, attract blood neutrophils into the liver, and activate them. Neutrophils up-regulate their surface adhesion molecules, tissue factor, and Kupffer cells, whereas tissue factor pathway inhibitor and thrombomodulin are almost undetectable in endothelial cells. This may lead to microcirculatory disturbances, fibrin deposition, hepatocyte injury, endotoxin and bacteria spillover, and multiple organ failure.

CONCLUSIONS

In sepsis, the liver participates in host defense and tissue repair through hepatic cell cross-talk that controls most of the coagulation and inflammatory processes. When this control is not adequate, a secondary hepatic dysfunction may occur and may sometimes lead to bacterial products spillover, enhanced procoagulant and inflammatory processes, and in turn, multiple organ failure and death.

Indocyanine green elimination rate detects hepatocellular dysfunction early in septic shock and correlates with survival

OBJECTIVE

To determine whether indocyanine green clearance is an early indicator of hepatocellular injury in septic shock and to assess its predictive value.

DESIGN

Observational study with prospective data collection.

SETTING

Traumatology and critical care unit in a city hospital, staffed by traumatology and intensive care clinicians.

PATIENTS

Twelve patients in septic shock who survived at least 2 months (group S) and nine patients who died within 2 wks (group N).

INTERVENTIONS

Routine resuscitation from septic shock (surgery, fluid loading, and administration of catecholamines and antibiotic drugs).

MEASUREMENTS AND MAIN RESULTS

Pulmonary artery occlusion pressure, cardiac index, oxygen delivery index, oxygen consumption index, and the indocyanine green elimination rate constant (KICG; or the slope of the loge [indocyanine green concentration] vs. time curve) 3-9 mins after injection were measured within 12 hrs of the onset of hypotension, then at 24 hrs, and every 24 hrs thereafter. Alanine aminotransferase and total bilirubin were measured on day 0 and day 1. Volume of fluid administered and duration of shock were the same in survivors and nonsurvivors. The oxygen consumption index was higher in survivors at 12 hrs, but no intergroup difference in pulmonary artery occlusion pressure, cardiac index, or oxygen delivery index was significant at any time point. KICG in nonsurvivors was lower than in survivors both initially and after 24 hrs, and it was subnormal in all patients except one survivor (p <.05). The KICG increased between 24 and 120 hrs in 11 survivors but progressively decreased and remained below 0.05 in seven nonsurvivors. The remaining two nonsurvivors died within 24 hrs of the initial measurement of KICG, which was >0.05. Alanine aminotransferase and total bilirubin were less sensitive measures of hepatic dysfunction in the first 24 hrs than the KICG.

CONCLUSIONS

The KICG can identify reversible liver injury in septic shock, suggesting good prognosis. Either failure to increase the KICG within 120 hrs or an extremely low KICG is a poor prognostic sign.

Beneficial effects of low-dose prostacyclin on cat intestinal perfusion during endotoxemia as evaluated with microdialysis and oxygen transport variables

OBJECTIVE

To evaluate the effects of low-dose prostacyclin on intestinal perfusion during endotoxemia.

DESIGN

A randomized, blinded experimental study.

SETTING

A university laboratory.

SUBJECTS

Sixteen anesthetized cats.

INTERVENTIONS

The animals received endotoxin by continuous intravenous infusion (0.5 mg/kg plus 0.5 mg x kg(-1) x hr(-1)) and a continuous volume replacement throughout the experiment. Four hours after the start of endotoxin, the animals were randomized to receive an infusion of either prostacyclin at a dose of 1 ng x kg(-1) x min(-1) (prostacyclin group) or vehicle (control group) during the next 4 hrs.

MEASUREMENTS AND MAIN RESULTS

Intestinal vascular resistance was calculated from systemic arterial pressure, central venous pressure, and superior mesenteric artery blood flow, and intestinal oxygen delivery and uptake were calculated from superior mesenteric artery and vein blood samples and blood flow. Interstitial lactate, pyruvate, glucose, and glycerol in the ileal wall were measured by using microdialysis. There were no differences in baseline values between the groups. Systemic blood pressure decreased initially but recovered and remained stable in both groups. In the control group, intestinal vascular resistance increased from 10.9 +/- 1.0 to 24.7 +/- 5.3 mm Hg x mL x min(-1) x kg(-1) (p <.05) at 8 hrs, and oxygen delivery decreased from 2.6 +/- 0.2 to 1.3 +/- 0.3 mL x min(-1) x kg(-1) (p <.05). Simultaneously, microdialysis lactate increased from 1.6 +/- 0.1 to 3.6 +/- 0.5 mmol/L (p <.05) with concomitant pyruvate increase and unchanged lactate/pyruvate ratio. Blood lactate increased and pH decreased. In the prostacyclin group at 8 hrs, intestinal vascular resistance of 6.9 +/- 0.8 mm Hg x mL x min(-1) x kg(-1) was lower and intestinal oxygen delivery of 3.2 +/- 0.3 was higher (p <.05) than in the control group at 8 hrs. Intestinal oxygen uptake of 0.54 +/- 0.10 mL x min(-1) x kg(-1) was higher than in the control group, in which oxygen uptake was 0.26 +/- 0.04 mL x min(-1) x kg(-1). Lactate, pyruvate, and pH were normalized at 8 hrs in the prostacyclin group.

CONCLUSION

Low-dose prostacyclin has beneficial effects on small intestinal perfusion during endotoxemia in this experimental cat model.

Changes in gastrointestinal morphology associated with obstructive jaundice

Bacterial translocation has been consistently demonstrated in experimental models of obstructive jaundice. An important factor which promotes this phenomenon is physical injury of the intestinal mucosa. Some previous studies have presented suggestive evidence of this, following bile duct ligation. The aims of this study were to analyse objectively intestinal mucosal morphometric characteristics, to examine for evidence of bacterial translocation, and to assess enterocytes for ultrastructural abnormalities. Adult female Wistar rats were assigned to one of three groups: control (n=8), bile duct ligation (BDL; n=11), or sham operation (n=10). One week later, portal blood, mesenteric lymph nodes, liver, and spleen were harvested and cultured aerobically and anaerobically for evidence of bacterial translocation. Segments of jejunum, ileum, caecum, and large bowel were examined histologically, using light microscopy and morphometrically, using an image analysis system. Electron microscopy was performed on regions of the gastrointestinal tract where significant morphometric alterations had been identified. Significant bacterial translocation was identified following BDL (63. 6% BDL vs. 0% sham vs. 0% control, p<0.01, Fisher's exact test). There was a significant reduction in total mucosal thickness (standard error) [650 microm (23) BDL vs. 731 microm (27) sham vs. 744 microm (95) control] and villous height [451 microm (20) BDL vs. 515 microm (18) sham vs. 559 microm (79) control] in jaundiced animals, compared with sham-operated and control animals (p<0.02, Mann-Whitney U-test). Electron microscopy revealed oedematous change associated with mild inflammation, disruption of desmosomes, and the formation of lateral spaces between enterocytes. In addition, enterocytes showed vacuolation of their cytoplasm and mitochondrial swelling. Increased numbers of bacteria appeared to be attached to the mucosa. These data provide evidence of physical disruption of intestinal mucosa in jaundiced animals, most marked in the distal ileum. Significant bacterial translocation occurs following bile duct ligation and this supports the hypothesis of gut barrier dysfunction with obstructive jaundice.

Hypertonic saline-dextran improves intestinal perfusion and survival in porcine endotoxin shock

OBJECTIVE

To examine the effects of hypertonic (7.5%) saline-6% dextran 70 (HSD) and isotonic (0.9%) saline-6% dextran 70 (ISD) on cardiovascular function and intestinal perfusion in experimental endotoxin shock.

DESIGN

Experimental, randomized, unblinded, interventional study.

SETTING

University experimental animal laboratory.

SUBJECTS

Anesthetized and mechanically ventilated landrace pigs (n = 24).

INTERVENTIONS

Induction of endotoxin (ET) shock by infusion of Escherichia coil lipopolysaccharide endotoxin (serotype 0111: B4) followed by no fluid treatment (control; C) or small-volume (4 mL/kg) treatment with HSD or ISD.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure, central venous pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, cardiac output, portal vein blood flow, intestinal microcirculation, intramucosal (regional) P(CO2), intestinal-arterial gap of CO2, and intramucosal pH were monitored, and blood gases were analyzed. Infusion of ET resulted in hypokinetic shock, which in untreated animals led to cardiovascular deterioration and a survival rate of only 33% at 300 mins after start of ET infusion. ISD treatment transiently improved hemodynamic variables and mucosal blood flow but did not affect the survival rate vs. C. Significant beneficial, long-lasting effects of HSD infusion on hemodynamics, especially on mucosal blood flow and intramucosal pH, were demonstrable, resulting in a survival rate of 86%. The relative risk of death at 300 mins was 1.20 for ISD vs. C and 0.17 for HSD vs. C.

CONCLUSION

Small-volume HSD resuscitation is much more effective than ISD resuscitation. Variables that were improved include cardiac output, portal blood flow, and intestinal mucosal blood flow in ET shock, all of which improve survival. Such beneficial effects of HSD on splanchnic perfusion may be of value in treating critically ill septic patients in the intensive care unit.

Angiotensin II inhibitor DuP753 attenuates burn- and endotoxin-induced gut ischemia, lipid peroxidation, mucosal permeability, and bacterial translocation

OBJECTIVE

To investigate the role of angiotensin II as a mediator of burn- and sepsis-induced gut ischemia and reperfusion injury and to determine whether treatment with the angiotensin II inhibitor DuP753 can attenuate mucosal injury and bacterial translocation in a burn/endotoxemia porcine model.

SUMMARY BACKGROUND DATA

Thermal injuries and endotoxemia have been shown to induce ischemia and reperfusion injury to the intestine, leading to increased mucosal permeability and bacterial translocation. Angiotensin II, the production of which has been reported to increase after burn, is thought to be one of the primary mediators of postburn mesenteric vasoconstriction.

METHODS

An ultrasonic flow probe was inserted into the superior mesenteric artery and a catheter into the superior mesenteric vein in 21 female pigs. After 5 days, all animals were anesthetized, and 14 received 40% total body surface area third-degree burn. DuP753 was administered intravenously at 1 microg/kg to seven pigs immediately after burn. Eighteen hours after burn, 100 microg/kg Escherichia coli lipopolysaccharide (LPS) was intravenously administered. Systemic and splanchnic hemodynamics were measured and blood samples were drawn for blood gas analysis. Plasma conjugated dienes (PCDs), an index of lipid peroxidation, were measured every 6 hours. Intestinal permeability was assessed every 6 hours by measuring the lactulose/mannitol excretion ratio. At the end of the study (42 hours), tissue samples were harvested for bacteriologic cultures.

RESULTS

Burn caused a significant decrease in mesenteric blood flow, to approximately 58% of baseline. Postburn endotoxemia significantly reduced the blood flow in the superior mesenteric artery to 53% of baseline. Treatment with DuP753 prevented postburn vasoconstriction and subsequently abrogated the impact of postburn endotoxemia on blood flow in the superior mesenteric artery. Mesenteric oxygen supply was significantly reduced after burn and endotoxin to 60% and 51% of baseline levels, respectively. DuP753 administration significantly improved mesenteric oxygen supply after both insults. Burn- and LPS-induced mesenteric hypoxia, as indicated by decreased mesenteric oxygen consumption, was also ameliorated by DuP753 treatment. PCD levels were significantly elevated 8 hours after burn. LPS caused a higher and prolonged increase in PCD levels. Treatment with DuP753 significantly reduced PCD levels after burn and after LPS. Intestinal permeability, as assessed by the lactulose/mannitol ratio, showed 6-fold and 12-fold increases after thermal injury and LPS, respectively. In contrast, the lactulose/mannitol ratio was only doubled in DuP753-treated animals. Bacterial translocation was significantly increased after burn and endotoxin. The incidence of bacterial translocation in the DuP753-treated animals was similar to that in the sham group.

CONCLUSIONS

Angiotensin II appears to play a pivotal role in the burn- and endotoxin-induced intestinal ischemia and reperfusion injury, with subsequent increases in permeability and bacterial translocation. Postburn administration of the angiotensin II receptor antagonist DuP753 significantly reduces the extent of these events.

Effect of endotoxemia on hepatic portal and sinusoidal blood flow in rats

A decrease in liver blood flow leads to dysfunction of hepatocytes and Kupffer cells, with subsequent local and systemic liberation of proinflammatory mediators that may maintain systemic inflammatory response syndrome (SIRS) and may lead to multiple organ dysfunction syndrome (MODS). There is only limited knowledge on the hepatic micro- and macrocirculation during sepsis or endotoxemia. Therefore, the aim of our study was to investigate alterations in hepatic portal blood flow (PBF) and sinusoidal blood flow (SBF) during endotoxemia. In male Wistar rats endotoxemia was induced by continuous infusion of 2 mg/kg/h lipopolysaccharides from Escherichia coli 026:B6 immediately after baseline measurements (n = 8). The control group (n = 8) received an equivalent volume of Ringer's solution. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), PBF, and SBF were measured at baseline and 60 and 120 min after induction of endotoxemia. PBF was measured using an ultrasonic flow probe that was positioned around the portal vein. SBF was detected by in vivo videomicroscopy of the left liver lobe. In the LPS group MAP decreased, but CO remained at baseline values. During endotoxemia PBF decreased significantly from 23 +/- 3 to 15 +/- 4 mL/min (60 min) and 16 +/- 3 mL/min (120 min). SBF also significantly decreased to 68.5% (60 min) and 57.1% (120 min) of baseline value. Our results demonstrate that during early endotoxemia hepatic macro- and microcirculatory perfusion is significantly decreased despite unchanged CO. This early reduction of hepatic perfusion might be caused by an increased hepatic vessel resistance as a consequence of liberation of vasoconstrictive mediators or/and by a decrease in intestinal perfusion.

Dobutamine restores intestinal mucosal blood flow in a porcine model of intra-abdominal hyperpressure

OBJECTIVE

To assess the effects of dopamine and dobutamine administration on the systemic and mesenteric (macro- and microvascular) circulatory disturbances induced by intra-abdominal hyperpressure.

DESIGN

Prospective, randomized study.

SETTING

Animal research laboratory in a university hospital.

SUBJECTS

Twenty-five pigs of either gender, weighing 30-35 kg.

INTERVENTIONS

Animals were anesthetized, and their lungs were mechanically ventilated. Pulmonary artery flotation and carotid artery catheters were inserted for hemodynamic monitoring and blood sampling. A perivascular flow probe was placed around the superior mesenteric artery, and a laser Doppler probe was positioned in the lumen of the ileum to measure arterial and intestinal mucosal blood flows, respectively. CO2 was insufflated into the peritoneal cavity to reach an intra-abdominal pressure of 15 mm Hg, and 60 mins later, animals received dopamine (5 microg/kg/min; n = 10), dobutamine (5 microg/kg/min; n = 10), or saline (n = 5) for 30 mins.

MEASUREMENTS AND MAIN RESULTS

Peritoneal CO2 insufflation induced significant increases in heart rate, arterial pressure, and systemic vascular resistance with concomitant decreases in cardiac output and superior mesenteric arterial and intestinal mucosal blood flows. Although dobutamine infusion reversed the decrease in cardiac output, it failed to restore superior mesenteric artery blood flow; however, intestinal mucosal blood flow returned to baseline levels. Dopamine also attenuated the decrease in cardiac output, but it had no beneficial effect on splanchnic hemodynamic variables.

CONCLUSIONS

Low-dose infusion of dobutamine, but not dopamine, corrects the intestinal mucosal perfusion impairment induced by moderate increases in intra-abdominal pressure.

The 21-aminosteroid U74389G enhances hepatic blood flow and preserves sinusoidal endothelial cell function and structure in endotoxin-shocked dogs

BACKGROUND

21-Aminosteroids are potent anti-inflammatory and antioxidant drugs that provide remarkable endothelial protection in different models of tissue ischemia-reperfusion and inflammation. The effects of 21-aminosteroids in sepsis, a highly inflammatory condition leading to panendothelial activation and injury, are largely uninvestigated. We therefore explored the effects of the 21-aminosteroid U74386G on hepatic blood flow, endothelial cell function, and sinusoidal structure in a canine model of fluid-resuscitated, hyperdynamic endotoxic shock.

MATERIALS AND METHODS

Following invasive hemodynamic monitoring and placement of ultrasonic flow probes around the common hepatic artery and the portal vein, 12 anesthetized dogs received 2 mg/kg iv of Escherichia coli endotoxin, followed by generous saline infusion, before randomization into two groups. One group (N = 6) received U74389G as an iv bolus of 80 microg/kg, followed by a continuous infusion of 10 microg/kg. min. The other group (N = 6) received an equivalent volume of vehicle. Hyaluronic acid was measured in plasma for in vivo evaluation of endothelial cell function. Liver biopsies were taken after 4 h of endotoxic shock and prepared for light and electron microscopic examination.

RESULTS

Compared with the vehicle-treated controls, U74389G maintained a higher blood flow in the hepatic artery and in the portal vein, without markedly influencing the systemic hemodynamic response. The endotoxin-induced increase in plasma hyaluronic acid levels was significantly attenuated following U74389G treatment (70 +/- 14 vs 188 +/- 24 ng/mL after 3 h of endotoxic shock; P < 0.05). Morphological studies showed that the U74389G-treated group had less sinusoidal endothelial cell damage together with a dramatic reduction of neutrophil infiltration into the liver tissue.

CONCLUSION

U74389G can preserve the functional and structural integrity of endothelial cells in the hepatic sinusoid during hyperdynamic endotoxic shock. This endothelial-protective effect was associated with a better maintained hepatic blood flow and a significant attenuation of inflammatory liver injury.

Increase in endotoxin-induced mucosal permeability is related to increased nitric oxide synthase activity using the Ussing chamber

OBJECTIVE

To determine if nitric oxide production is associated with increased intestinal permeability after endotoxin challenge using the ex vivo Ussing chamber.

SUBJECTS

Ileal mucosal membranes harvested from normal rats weighing 300 to 420 g.

INTERVENTIONS

Endotoxin (lipopolysaccharide), 1, 10, 100 microg/ mL, or saline was placed on the serosal side of ileal mucosal membranes mounted in Ussing chambers after 10(9) Escherichia coli C-25 had been placed on the mucosal side of the ileal membranes (n = 6-7/group). In a second set of experiments, ileal membranes were exposed to 100 microg/mL lipopolysaccharide with or without the addition of the nitric oxide synthase inhibitor, N(G)-monomethyl-L-arginine at a concentration of 10 mM (n = 7-8/group).

MAIN OUTCOME MEASURE

Bacterial translocation of E. coli C-25 from the mucosal to the serosal side of the ileal membrane was measured every hour during the 3-hr experimental period, as were serial measurements of the potential difference and resistance values of the ileal membranes. At the conclusion of the 3-hr period, the ileal membranes were harvested and levels of inducible nitric oxide synthase and constitutive nitric oxide synthase activity were measured.

RESULTS

The incidence of E. coli C-25 passage across the ileal membranes mounted in the Ussing chambers was significantly increased in the ileal membranes exposed to 10 or 100 microg/mL of lipopolysaccharide (71% and 86%, respectively) vs. the control membranes (0%) or the membranes exposed to 1 microg/mL of lipopolysaccharide (0%) (p < .05). This increase in E. coli C-25 passage in the ileal membranes exposed to 10 or 100 microg/mL of lipopolysaccharide was associated with a decrease in ileal membrane resistance and an increase in inducible nitric oxide synthase activity (p < .05). The addition of N(G)-monomethyl-L-arginine protected against lipopolysaccharide-induced bacterial translocation and prevented the lipopolysaccharide-induced increase in ileal membrane inducible nitric oxide synthase activity.

CONCLUSION

These results indicate that lipopolysaccharide induction of increased ileal inducible nitric oxide synthase activity is necessary for lipopolysaccharide-induced E. coli C-25 translocation to occur in normal ileal mucosal membranes tested in the Ussing chamber system.

Early effect of low-dose endotoxin on rat cecal mucosa ex vivo

It has been suggested that endotoxin triggers translocation of intestinal bacteria in vivo, either by directly damaging intestinal mucosa or by inducing a systemic inflammatory reaction that leads to mucosal disruption. To address this issue, we examined the immediate effect of extraluminal endotoxin on structure and function of isolated rat cecal mucosa without other inflammatory cells in vitro. The cecal mucosa of 12 male Wistar rats was mounted in modified Ussing chambers filled with Dulbecco's modified Eagle's medium and the ampicillin-resistant Escherichia coli HB101:K12 incubated on the mucosal side. Endotoxin was added to the submucosal side at concentrations of 1 and 10 EU/ml, respectively. Under gassing with carbogene at 37 degreesC, the potential difference across the mucosa was measured continuously. Samples of the mucosal and submucosal solutions were removed at 60, 120, and 180 min and plated out on McConkey ampicillin-agar. After 180 min, the mucosal specimens were retrieved and examined by light and scanning electron microscopy. No significant change in potential difference was observed in control or endotoxin-incubated mucosa within the observation period. Neither light nor scanning electron microscopy showed a significant change in the structure of the epithelium, mucosa, or submucosa. No significant translocation of the E. coli across the mucosa was seen. We concluded that endotoxin alone does not induce immediate structural and functional damage to rat cecal mucosa in vitro. Therefore, it seems unlikely that a short endotoxemia alone directly triggers bacterial translocation by disrupting intestinal mucosa, but rather, entotoxin induces a local and systemic inflammatory reaction that leads to mucosal disruption.

Early effects of catecholamine therapy on mucosal integrity, intestinal blood flow, and oxygen metabolism in porcine endotoxin shock

OBJECTIVE

To determine the early effects of therapy of endotoxin (ET) shock with epinephrine, norepinephrine, or dopexamine on splanchnic circulation, oxygen metabolism, sigmoid mucosal pHi, bacterial translocation, and morphologic integrity of the ileal, colonic, and sigmoid mucosa.

SUMMARY BACKGROUND DATA

Conflicting concepts exist concerning the catecholamine therapy of septic shock, but little is known about the effects of catecholamine treatment on splanchnic circulation and mucosal integrity.

METHODS

ET shock was induced in pigs by ET infusion over 30 minutes, and animals were studied for 4 hours. All animals were resuscitated with fluid. To mimic the treatment of septic shock in humans, mean arterial pressure was maintained in two groups at >70 mm Hg with the administration of epinephrine or norepinephrine. A third group of animals received dopexamine at 7 microg/kg per minute. Systemic and splanchnic blood flow and oxygen metabolism were studied, sigmoid colon mucosal pHi was obtained tonometrically, and bacterial translocation was determined by culture of portal venous blood, mesenteric lymph nodes, liver, spleen, and lung specimens. Histologic sections of ileal, colonic, and sigmoid mucosa were morphometrically examined for therapy effects.

RESULTS

All investigated catecholamines increased cardiac output and systemic oxygen delivery, whereas intestinal blood flow and oxygen delivery remained unchanged. Sigmoid mucosal pHi decreased in all study animals, but the decrease was most pronounced in the epinephrine group. Pigs receiving epinephrine also showed >40% damage of the mucosa of the ileum and colon, whereas animals receiving ET alone, norepinephrine, or dopexamine showed only moderate lesions with signs of restitution. No animal showed bacterial translocation.

CONCLUSIONS

Systemic hemodynamics and oxygen metabolism data do not reflect intestinal perfusion. Norepinephrine or dopexamine administration in ET shock causes no additional impairment of intestinal integrity. Epinephrine therapy, in contrast, is associated with a significant reduction of mucosal pHi and considerable early mucosal damage. Its application in septic shock is hazardous.

The relationships among nitric oxide production, bacterial translocation, and intestinal injury after endotoxin challenge in vivo

BACKGROUND

This study examines the hypothesis that there is a relationship among endotoxin-induced bacterial translocation (BT) and increased nitric oxide (NO) production and that inhibition of excessive NO production with NG-monomethyl-L-arginine (L-NMMA) is beneficial.

METHODS

Rats received 0, 1, or 4 mg/kg endotoxin intraperitoneally, and 6 or 18 hours later, they were killed and BT, NO production (as reflected in nitrite/nitrate levels), and calcium-dependent nitric oxide synthase and calcium-independent nitric oxide synthase (iNOS) activities were measured in tissues (ileum, liver, and mesenteric lymph nodes) and blood. In a second set of experiments, the animals received the NOS inhibitor L-NMMA (100 mg/kg) intravenously either 15 minutes before or 2 hours after endotoxin challenge (4 mg/kg) and the same parameters were measured.

RESULTS

The incidence of BT was higher in rats receiving 4 mg/kg endotoxin (62.5%) than in the control group (0%, p < 0.05), and the 1 mg/kg endotoxin group had intermediate incidence (25%). The animals receiving 4 mg/kg endotoxin had higher tissue (mesenteric lymph nodes, liver) and blood nitrite/nitrate levels than the control or 1 mg/kg endotoxin groups. The increased NO production was mainly attributable to an elevated level of iNOS activity. The administration of L-NMMA before but not after endotoxin challenge reduced iNOS activity, NO production, and BT to control levels at 6 hours but not 18 hours after endotoxin administration.

CONCLUSION

Endotoxin-induced mucosal injury and BT are associated with iNOS activity and increased NO production. Inhibition of iNOS activity with L-NMMA before treatment prevented endotoxin-induced ileal mucosal injury and BT.

Origin of endotoxemia influences the metabolic response to endotoxin in dogs

Different routes of endotoxin administration have been used to mimic inflammatory and metabolic responses observed during sepsis. Because the origin of endotoxemia may affect the reactions to endotoxin, we compared the induction of tumor necrosis factor (TNF), interleukin-6 (IL-6), hormones, and glucose production after endotoxin (1.0 microg/kg Escherichia coli 0111:B4) administration into a peripheral (n = 8) versus the portal (n = 8) vein in anesthetized dogs. Prior to endotoxin, a laparotomy was performed for cannulation of hepatic vessels. To evaluate the effects of surgery and anesthesia, we also studied the effects of peripheral endotoxin administration in six awake dogs. The rate of appearance of glucose was measured by primed continuous infusion of [6,6-2H2]glucose. In anesthetized dogs, arterial concentrations of TNF and IL-6 increased after endotoxin administration (P < 0.01 vs basal; NS between groups). Net hepatic TNF production was increased after endotoxin administration (peripheral vs portal endotoxin administration: 533 +/- 177 vs 2135 +/- 1127 ng/min, both P < 0.05 vs basal; NS between groups). Net hepatic IL-6 production was stimulated only after portal endotoxin delivery (from 86 +/- 129 to 4740 +/- 1899 ng/min, P < 0.05; NS between groups). Although there were no differences in neuroendocrine activation, portal endotoxin administration resulted in decreased glucose production compared with peripheral administration (13.6 +/- 0.9 vs 16.8 +/- 1.2 micromol/kg.min, P < 0. 05). In contrast to anesthetized dogs, endotoxin increased glucose production considerably in awake dogs from 13.8 +/- 1.2 to 24.2 +/- 3.2 micromol/kg.min (P < 0.05; P < 0.05 vs anesthetized dogs). The contribution of anesthesia and surgery increased the endotoxin-induced IL-6 response by approximately 350% compared with the effect of endotoxin in awake dogs (P < 0.01). In conclusion, there are no major differences in the responses to endotoxin between peripherally treated and portally treated dogs, except for differences in glucose production. Portal delivery compared with systemic delivery of endotoxin alters hepatic metabolism through nonendocrine mechanisms, reflected in decreased glucose production. The inflammatory, endocrine, and metabolic effects of endotoxin are altered by the combination of surgery and anesthesia.

Effect of endotoxin administration on the severity of acute pancreatitis in two experimental models

CONCLUSIONS

Endotoxemia can transform acute pancreatitis (AP) into a more severe form of the disease in models of AP provoked by common pancreatico-biliary duct ligation or L-arginine injection.

BACKGROUND

It has been shown that systemic endotoxemia is a common feature in severe AP. The effect of endotoxemia on the course of experimental pancreatitis is unknown.

METHODS

AP was induced by common pancreatico-biliary duct ligation (experiment 1) and i.p. injection of 250 mg/100 g body wt of L-arginine (experiment 2). Test animals of both experiments received i.p. injections of 0.5 and 1.0 mg/100 g body wt of endotoxin at the induction of AP. Saline-treated and only endotoxin-dosed animals served as controls for both experiments. Mortality rates and pancreatic histology were investigated at 48 h.

RESULTS

The mortality rate was significantly elevated (60%, p < 0.05) in experiment 1 when 1.0 mg/100 g of endotoxin was given. In experiment 2, the mortality rate was also increased (30%) at this dose of endotoxin without reaching significance. Histologic changes were more severe in both groups of AP treated by the two doses of endotoxin than without it. Acinar necrosis and hemorrhage were highly elevated (p < 0.01) in both experiments when AP was combined with 1.0 mg/100 g body wt of endotoxin. The animals receiving only endotoxin showed only slight inflammatory and necrotic changes.

Dobutamine improves gastrointestinal mucosal blood flow in a porcine model of endotoxic shock

OBJECTIVE

To test the hypothesis that saline solution plus dobutamine increases gastrointestinal mucosal perfusion better than saline solution alone in a model of endotoxic shock.

DESIGN

Prospective, randomized, unblinded study.

SETTING

Animal research laboratory affiliated with a university teaching hospital.

SUBJECTS

Twelve female pigs, weighing 30 to 32 kg.

INTERVENTIONS

Animals were anesthetized, and their lungs were mechanically ventilated. Catheters were inserted into the right atrium, pulmonary artery, and carotid artery for blood sampling and blood pressure and cardiac output measurements. A tonometer and a laser Doppler probe were placed in the lumen of the stomach and the ileum for determination of mucosal acid-base status and measurement of mucosal blood flow. Group 1 animals (n = 6) received an infusion (T = 0 min) of 150 mcirog/kg Escherichia coli endotoxin and normal saline solution (0.3 mL/kg/min). Group 2 animals (n = 6) received an infusion of endotoxin and were resuscitated with the same method as used in group 1, but an infusion of dobutamine (5 microg/kg/min) was begun at T = 60 mins, and continued for the duration of the experiment.

MEASUREMENTS AND MAIN RESULTS

Both experimental regimens produced shock, with decreased mean arterial pressure and systemic vascular resistance, without change in cardiac output and oxygen delivery. Endotoxin plus saline infusion decreased gastrointestinal mucosal blood flow to <60% of baseline and decreased gastrointestinal pH. In contrast, gastrointestinal mucosal blood flow returned to baseline values, and intramucosal pH tended to normalize by the end of the saline solution plus dobutamine resuscitative protocol.

CONCLUSION

Compared with saline solution alone, saline solution plus dobutamine increased blood flow to the gastrointestinal mucosa, and may have partially improved oxygenation.

Effects of the stable prostacyclin analogue iloprost on mesenteric blood flow in porcine endotoxic shock

OBJECTIVE

To determine the effects of the stable prostacyclin analog, iloprost, in a porcine model of endotoxin-induced mesenteric ischemia.

DESIGN

Prospective, experimental, randomized, controlled study.

SETTING

Animal research laboratory at a university medical center.

INTERVENTIONS

Pigs were randomized to receive a constant infusion of iloprost (0.18 microg/kg/min) or an equivalent amount of carrier solution (normal saline) 30 mins before being infused with endotoxin (100 microg/kg over 1 hr). The infusion with iloprost or carrier solution was continued for the duration of the experiment.

MEASUREMENTS AND MAIN RESULTS

Twelve pigs (six per group), weighing between 20 and 22 kg, underwent laparotomy during which a magnetic flowprobe was placed around the superior mesenteric artery and an ileal tonometer was inserted. Thirty minutes before they were infused with endotoxin, the animals were randomized to receive intravenous iloprost or normal saline. Endotoxin was infused centrally over a 60-min period. Animals received normal saline at a rate of 1.2 mL/kg/min which was begun at the start of the endotoxin infusion. Data were measured at the end of the endotoxin infusion (E60) and 1 hr later (E120). Mean arterial pressure was not affected by the dosage of iloprost used in this experiment. After resuscitation, the cardiac output returned to baseline in the iloprost-treated group but remained decreased in the control group (2.6 +/- 0.5 vs. 1.6 +/- 0.4 L/min). Superior mesenteric blood flow increased 34% above baseline levels in animals pretreated with iloprost (from 363 +/- 85 to 485 +/- 81 mL/min). The superior mesenteric PCO2 was significantly higher (53 +/- 9 vs. 40 +/- 5 torr; 7.1 +/- 1.2 vs. 5.3 +/- 0.7 kPa) and the ileal intramucosal pH was significantly lower (7.07 +/- .28 vs. 7.44 +/- .23) in the control group than in the iloprost-treated group.

CONCLUSIONS

Pretreatment with intravenous iloprost effectively increased intestinal blood flow in this model of endotoxin-induced mesenteric ischemia. This action of the drug resulted in an attenuation of ileal intracellular acidosis. Since low-dose iloprost had no effect on mean arterial pressure, it may be a useful adjunct in the treatment of sepsis and septic shock.

Hemodynamic and metabolic effects of vasopressin blockade in endotoxin shock

BACKGROUND

Arginine vasopressin V1 receptor antagonist (AVPRA) was administered to investigate the influence of vasopressin blockade on hemodynamics and metabolism during endotoxin shock.

METHODS

Anesthetized rats were divided into four groups: control (0.9% saline solution, n = 5), drug control (AVPRA, n = 5), endotoxin (endotoxin, 5 mg/kg, n = 10), and pretreatment (AVPRA and endotoxin, n = 10). Hemodynamics and oxygen transport were evaluated for 2 hours. Terminal arterial and portal venous concentrations of endotoxin, pyruvate, lactate, and ketone bodies were determined.

RESULTS

The endotoxin group maintained blood pressure levels similar to those of control animals. AVPRA pretreatment decreased vascular resistance and resulted in lower blood pressure than endotoxin alone. Endotoxin decreased oxygen consumption and the oxygen extraction ratio and increased arterial lactate concentration and the lactate/pyruvate ratio. Endotoxin also decreased arterial ketone body concentration and markedly decreased ketone body availability in the mesenteric circulation. AVPRA pretreatment improved oxygen consumption, oxygen extraction ratio, and ketone body availability; arterial lactate concentration, lactate/pyruvate ratio, and arterial ketone body concentration were not affected. Pretreatment with AVPRA also decreased arterial and portal venous concentrations of endotoxin.

CONCLUSIONS

Vasopressin receptor blockade during endotoxemia resulted in lower blood pressure than endotoxin alone. Vasopressin receptor blockade also maintained oxygen extraction ratio and ketone body availability in the mesenteric circulation. Vasopressin may play a key role in the response to endotoxemia.

Introducing Critical Appraisal to studies of animal models investigating novel therapies in sepsis

OBJECTIVES

To discuss theoretical and practical aspects relating to the design of animal studies investigating the efficacy of novel therapeutic agents for the treatment of sepsis, and to make explicit the process whereby these studies can be evaluated for the purpose of designing clinical trials in humans.

DATA SOURCES

Relevant articles from the pertinent literature were reviewed.

STUDY SELECTION

Studies relevant to an evidence-based assessment of clinical studies on therapeutic efficacy, and studies relevant to the design of animal models of sepsis were selected.

DATA EXTRACTION

Concepts relevant to an evidence-based assessment of the animal literature were extracted.

DATA SYNTHESIS

Articles were reviewed and an evidence-based framework for the assessment of animal studies was developed. In this process, we discuss the steps that are necessary to assess the internal validity of an individual study and review topics relevant to the application of animal data to the design of clinical trials.

CONCLUSIONS

The success of clinical trials of sepsis therapies is predicated on the generation and interpretation of sound preclinical data. In this review, we have attempted to outline an evidence-based approach to the assessment of preclinical animal studies evaluating novel therapeutic interventions in sepsis.

Different effects of early endotoxaemia on hepatic and small intestinal oxygenation in pigs

OBJECTIVE

Study on simultaneous O2 supply/uptake relationships in liver and gut during endotoxaemia, to determine whether signs of dysoxia develop uniformly in the splanchnic region.

DESIGN

Animal study to assess the early effects of endotoxaemia on oxygenation of both liver and small intestine.

INTERVENTIONS

Eight anaesthetized pigs received a continuous portal venous infusion of lipopolysaccharide (0.5 microgram.kg-1.h-1) for 6 h. Systemic, pulmonary and splanchnic haemodynamics as well as systemic and splanchnic O2 supply/uptake relationships were determined.

RESULTS

There was a multiphasic haemodynamic response pattern characterized by an early (within the 1st h) and a subsequent more prolonged phase (between the 2nd and 6th h) of decreases and recovery of hepatic arterial, portal venous and superior mesenteric arterial blood flows (electromagnetic flow probes) and splanchnic O2 deliveries. Unrelated to perfusion pressure and O2 delivery, there were early and sustained decreases in ileal mucosal surface partial pressure of oxygen (PO2) (multiwire PO2 electrode) and pH (tonometry). This was not reflected by ileal serosal surface PO2, O2 uptake and arteriomesenteric venous pH and partial pressure of carbon dioxide (PCO2) gradients. There was little evidence of concomitant hepatic dysoxia as evaluated by surface PO2.

CONCLUSIONS

The study demonstrates early and sustained regional (mucosa) intestinal hypoxia with little evidence of simultaneous hepatic dysoxia during initial endotoxaemia.

Oxygen delivery and consumption during sepsis

This article discusses the oxygen consumption (VO2) and delivery (DO2) relationship as it pertains to animal models of sepsis and human sepsis syndrome and septic shock. Pathologic dependence of VO2 on DO2 is not present in resuscitated patients who have sepsis syndrome and septic shock. Defects in oxygen extraction and use at the individual organ level with maldistribution of blood flow probably do occur in sepsis; however, there is no clinical evidence that augmenting DO2 to supernormal levels decreases organ dysfunction or mortality in sepsis. We need improved techniques to assess tissue hypoxia at the organ level, and we need to test therapies directed at correcting the maldistribution of blood flow and O2 use defects of sepsis.

Hemodynamic changes and gut barrier function in sequential hemorrhagic and endotoxic shock

Multisystem organ failure (MSOF) is the major cause of late death following trauma. The gut is hypothesized to be the source of an ongoing systemic inflammatory response that drives MSOF. It has also been suggested that while a single physiologic insult might not reliably cause MSOF, the addition of a delayed second stress will. This is known as the "two-hit" theory. The purpose of this study was to investigate the two-hit theory by observing the hemodynamic and bacteriologic response to a second stress in a subacute pig model of hemorrhagic and endotoxic shock. Swine (n = 18, 30-40 kg) were fed an antibiotic-free diet for 14 days. During instrumentation and experimentation on days 1 and 3, all animals were anesthetized (ketamine, isofluorane). On day 1, all animals had placement of central venous and arterial catheters, a portal venous catheter, and superior mesenteric artery flow probe. Group E (n = 6) underwent instrumentation on day 1, then infusion of endotoxin (25 mcg/kg E. coli lipopolysaccharide) on day 3. Group HE (n = 7) underwent instrumentation then hemorrhagic shock (mean arterial pressure = 40 mm Hg for 4 hours) on day 1, then infusion of endotoxin on day 3. Group H (n = 5) were instrumented and hemorrhaged on day 1, and underwent anesthesia only on Day 3. Between periods of anesthesia the animals were allowed food and water ad lib and systemic blood was sampled for culture every 12 hours. On day 5, the animals were euthanized prior to organ sampling for bacterial culture. One animal from group HE died during endotoxic shock on day 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Splanchnic ischaemia and its role in multiple organ failure

Multiple organ failure remains the leading cause of death in the intensive care unit. Increasing numbers of investigators have focused their attention on the role of gastrointestinal tract in the pathogenesis of this syndrome. Their data indicate that inadequate gut perfusion leads to a measurable imbalance between oxygen delivery and the needs of the tissues, i.e., ischaemia. Gut ischaemia of sufficient duration impairs gastrointestinal tract barrier function, facilitating the passage of enteric bacterial endotoxin into the circulation. It has been hypothesized that production of tumor necrosis factor alpha, and other biologic mediators by endotoxin-stimulated macrophages, triggers a generalized and uncontrolled inflammatory response that ultimately leads to multiple organ failure. Preliminary evidence suggests that survival can be improved significantly if gut ischaemia is promptly identified and aggressively treated by administration of fluids and inotropic drugs, using gastric intramucosal pH as the therapeutic endpoint. Future studies are needed to determine whether additional treatment modalities can improve outcome once the inflammatory response has fully developed.