L.C.J.M. Lemaire

Thoracic Duct in Patients With Multiple Organ Failure: No Major Route of Bacterial Translocation

OBJECTIVE To determine whether translocation of bacteria or endotoxin occurred into the thoracic duct in patients with multiple organ failure (MOF). SUMMARY BACKGROUND DATA Translocation of bacteria or endotoxin has been proposed as a causative factor for MOF in patients without an infectious focus, although it has rarely been demonstrated in patients at risk for MOF. Most studies have investigated the hematogenic route of translocation, but it has been argued that lymphatic translocation of bacteria or endotoxin by the thoracic duct is the major route of translocation. METHODS The thoracic duct was drained for 5 days in patients with MOF caused either by generalized fecal peritonitis (n = 4) or by an event without clinical and microbiologic evidence of infection (n = 4). Patients without MOF who were undergoing a transthoracic esophageal resection served as controls. In lymph and blood, concentrations of endotoxin, proinflammatory cytokines, and antiinflammatory cytokines were measured. RESULTS Endotoxin concentrations in lymph and blood of patients with MOF ranged from 39 to 63 units per liter and were not significantly different from concentrations in patients without MOF. The quantity of endotoxin transported by the thoracic duct in the study group was small. In patients with MOF, low levels of proinflammatory cytokines and high levels of antagonists of these cytokines were found. CONCLUSION This study provides evidence that translocation (especially of endotoxin) occurs into the thoracic duct. However, these data do not support the concept that the thoracic duct is a major route of bacterial translocation in patients with MOF.

Prednisolone Dose-Dependently Influences Inflammation and Coagulation during Human Endotoxemia

The effects of steroids on the outcome of sepsis are dose dependent. Low doses appear to be beneficial, but high doses do not improve outcome for reasons that are insufficiently understood. The effects of steroids on systemic inflammation as a function of dose have not previously been studied in humans. To determine the effects of increasing doses of prednisolone on inflammation and coagulation in humans exposed to LPS, 32 healthy males received prednisolone orally at doses of 0, 3, 10, or 30 mg (n = 8 per group) at 2 h before i.v. injection of Escherichia coli LPS (4 ng/kg). Prednisolone dose-dependently inhibited the LPS-induced release of cytokines (TNF-α and IL-6) and chemokines (IL-8 and MCP-1), while enhancing the release of the anti-inflammatory cytokine IL-10. Prednisolone attenuated neutrophil activation (plasma elastase levels) and endothelial cell activation (von Willebrand factor). Most remarkably, prednisolone did not inhibit LPS-induced coagulation activation, measured by plasma concentrations of thrombin-antithrombin complexes, prothrombin fragment F1+2, and soluble tissue factor. In addition, activation of the fibrinolytic pathway (tissue-type plasminogen activator and plasmin-α2-antiplasmin complexes) was dose-dependently enhanced by prednisolone. These data indicate that prednisolone dose-dependently and differentially influences the systemic activation of different host response pathways during human endotoxemia.

Lipid composition and lipopolysaccharide binding capacity of lipoproteins in plasma and lymph of patients with systemic inflammatory response syndrome and multiple organ failure

BACKGROUND Lipopolysaccharide (LPS), the major glycolipid component of Gram-negative bacterial outer membranes, is a potent endotoxin responsible for many of the directly or indirectly induced symptoms of infection. Lipoproteins (in particular, high-density lipoproteins) sequester LPS, thereby acting as a humoral detoxification mechanism. PATIENTS Differences in the lipoprotein composition in human plasma and lymph of a control patient group (n = 5) without systemic inflammatory response syndrome (non-SIRS/MOF) and patients with SIRS and multiple organ failure (MOF, n = 9) were studied. The LPS binding capacity of the lipoproteins in SIRS/MOF and non-SIRS/MOF patients was investigated by rechallenge of the plasma and lymph with fluorescently labeled LPS ex vivo. The lipoprotein composition was analyzed using immunochemical techniques and high-performance gel permeation chromatography. RESULTS In the non-SIRS/MOF patient group, plasma and lymph levels of apolipoprotein A-I (600 and 450 mg/L, respectively), apolipoprotein B (440 and 280 mg/L, respectively), total cholesterol (2.88 and 1.05 mM, respectively), and total triglycerides (0.67 and 0.97 mM, respectively) were observed. In the SIRS/MOF group, a decrease of apolipoprotein A-I (-55% in plasma and lymph), a decrease of apolipoprotein B (-43% in plasma and -38% in lymph), and a decrease of total cholesterol levels (-54% in plasma and -37% in lymph) were demonstrated. However, the triglyceride levels in the SIRS/MOF group showed a 30% increase in plasma and a 47% decrease in lymph compared with the non-SIRS/MOF patients. In SIRS/MOF patients, a 2.8-fold increase in plasma and a 1.8-fold increase in lymph of the LPS low-density lipoprotein/high-density lipoprotein ratio was observed, indicating that the relative LPS binding capacity of the lipoproteins in the SIRS/MOF patient group showed a trend to be shifted mainly toward low-density lipoproteins. Furthermore, in plasma and lymph of four SIRS/MOF patients, a novel cholesterol-containing high-density lipoprotein-like particle was found that barely had LPS binding capacity (<5%). CONCLUSIONS In the SIRS/MOF patients, the changes in lipoprotein composition in lymph are a reflection of those in plasma, except for the triglyceride levels. In comparison with the non-SIRS/MOF patients, the SIRS/MOF patients show a shifted LPS binding capacity of high-density lipoproteins toward low-density lipoproteins in plasma and in lymph. Moreover, in plasma and lymph, novel cholesterol-containing particles, resembling high-density lipoprotein, were identified in the SIRS/MOF patient group.

Bacterial Translocation to the Thoracic Duct in a Setting of Ischemia, Partial Resection and Reperfusion of the Porcine Liver

Background/Aims: Bacterial translocation is postulated as a risk factor in the development of a systemic inflammatory response syndrome (SIRS). Research on this topic has focused on the detection of bacteria and endotoxin in blood or mesenteric lymph nodes (MLNs). We investigated whether bacterial translocation occurs beyond the MLNs into the thoracic duct in a setting of ischemia, partial resection and reperfusion of the porcine liver. Methods: A porcine model of severe, extra-intestinal tissue injury, consisting of prolonged hepatic ischemia and reperfusion, in combination with hemihepatectomy, was used (experimental group, n = 5 pigs). To prevent venous congestion of the gut during ischemia, a temporary portal-caval shunt was created. In 5 animals (sham group) a sham portal-caval shunt was constructed while liver ischemia, partial resection and reperfusion were not induced. Thoracic duct lymph, portal blood and systemic blood were collected, and analyzed for the presence of bacteria and endotoxin. Results: In the experimental group, the incidence of bacterial translocation to the thoracic duct was significantly higher during early reperfusion compared to the sham group (5/5 animals versus 1/5 animals, p < 0.05). Conclusion: This study demonstrates bacterial translocation into the thoracic duct. Translocation at this level leads to direct discharge of bacteria and endotoxin into the systemic circulation and therefore, may potentially enhance the development of SIRS.

Dobutamine does not influence inflammatory pathways during human endotoxemia

Objective:Catecholamines have anti-inflammatory and anticoagulant properties. Dobutamine is a synthetic catecholamine frequently used in patients with septic myocardial dysfunction. The objective was to determine whether a continuous infusion of dobutamine exerts immunomodulatory effects in healthy volunteers challenged with endotoxin. Design:Prospective, open-label study. Setting:Clinical research unit of a university hospital. Participants:Sixteen male healthy volunteers. Interventions:Volunteers received a constant infusion with dobutamine (10 &mgr;g·kg−1·min−1, n = 8) or physiologic saline (n = 8). All participants were challenged with a bolus injection of endotoxin prepared from Escherichia coli (4 ng/kg). Dobutamine infusion was commenced 1 hr before endotoxin challenge and was continued until 3 hrs thereafter. Measurements and Main Results:Dobutamine infusion was associated with an increase in mean arterial blood pressure (peak 122 ± 5 mm Hg) and heart rate (peak 84 ± 4 beats/min, both p < .05 vs. saline). Endotoxin injection induced the systemic release of cytokines (tumor necrosis factor-α, interleukins-6, -8, and -10) and secretory phospholipase A2, endothelial cell activation (increase in the plasma levels of soluble E-selectin and von Willebrand factor), activation of coagulation (increased plasma levels of soluble tissue factor, F1 + 2 prothrombin fragment, and thrombin-antithrombin complexes), and activation with subsequent inhibition of fibrinolysis (increased plasma concentrations of tissue-type plasminogen activator, plasminogen activator inhibitor type I, and plasmin-α2-antiplasmin complexes). None of these responses were influenced by dobutamine. Conclusions:Dobutamine, infused in a clinically relevant dose, does not influence inflammatory and coagulant pathways during human endotoxemia.

Differential dose-dependent effects of prednisolone on shedding of endothelial adhesion molecules during human endotoxemia.

Low dose prednisolone was shown to be beneficial in the treatment of the Acute respiratory distress syndrome (ARDS) and septic shock. One corticosteroid-induced effect, postulated to mediate corticosteroid-induced anti-inflammatory effects, is decreased expression of adhesion molecules on endothelial cells, thereby preventing leukocyte recruitment at inflammatory sites. The current study aimed to investigate the effect of increasing doses of prednisolone on the release of soluble adhesion molecules in healthy volunteers challenged with endotoxin. Therefore, 32 healthy, male volunteers received prednisolone orally at doses of 0mg, 3mg, 10mg or 30 mg at 2h before injection of endotoxin prepared from Escherichia coli (4 ng/kg) and levels of soluble E-selectin (sE-selectin), soluble VCAM-1 (sVCAM-1) and soluble ICAM-1 (sICAM-1) were measured. Levels of all markers were increased after induction of endotoxemia. Levels of sE-selectin were inhibited by a dose of 3mg prednisolone and levels of sVCAM-1 were decreased after a dose of 10mg. Maximal inhibition of both sE-selectin and sVCAM-1 levels was achieved by the highest dose of prednisolone 30 mg. Remarkably, prednisolone 3mg potentiated endotoxin-induced sVCAM-1 release. Levels of sICAM-1 were not affected by prednisolone. Together, the data suggest that prednisolone differentially and dose-dependently influences the release of soluble endothelial adhesion molecules during human endotoxemia.

Human thoracic duct lymph inhibits lipopolysaccharide-induced release of cytokines

Oral starvation causes gut atrophy and breakdown of barrier function, which can lead to transport of lipopolysaccharide (LPS) across the intestinal mucosa. Since triglyceride-rich lipoproteins can inhibit lipopolysaccharide-induced cytokine release, it can be hypothesized that enteral feeding protects the body against translocated LPS at the level of the thoracic duct by increasing the levels of triglycerides in thoracic duct lymph. We sought to determine the LPS-neutralizing capacity of human chyle by measuring LPS-induced cytokine production in vitro in the presence or absence of thoracic duct lymph. Moreover, we assessed whether enteral administration of triglyceride-rich lipoproteins changed the ability of lymph to influence LPS activity. Indeed, the presence of 10% and 100% triglyceride-poor and triglyceride-rich lymph induced a significant reduction in the TNF and IL-6 production elicited by LPS. However, there was no difference in the extent of inhibition of cytokine-release by triglyceride-poor and triglyceride-rich lymph. This study shows that lymph can inhibit LPS activity. This is not affected by prior enteral administration of triglycerides.

Immunomodulatory Effects of General Anesthetics

Postoperative patients are prone to develop infectious complications, and the phenomenon of immunoparalysis, defined as a diminished capacity of immunocompetent cells to respond to infectious agents, has been implicated as a major contributing factor. When inflammatory postoperative disorders are already established, intervention is difficult. However, if perioperative modulation of the inflammatory response were possible, this may influence postoperative outcome. General anesthetics exert a variety of effects, including sedation, amnesia, and analgesia. Current research focuses primarily on the effects of these compounds on membrane proteins in the central nervous system (CNS), to elucidate the molecular mechanism of their action. The (side-) effects of general anesthetics on other organ systems have been less extensively investigated. In this chapter, we will discuss the data available on the immunomodulatory effects of general anesthetics and the potential clinical implications of these effects on the development of (postoperative) infections.

Immunocytochemical Detection of Tumour Cells in the Thoracic Duct of Patients with an Adenocarcinoma of the Oesophagus

Background: Compared to other hollow viscus organs, the oesophagus has a unique anatomy in which lymphatic channels are abundantly present in the mucosa and submucosa. It has been hypothesized that tumour cells can directly disseminate from these superficial layers into the thoracic duct without passing juxta-tumoral lymph nodes. We investigated whether tumour cells of an oesophageal carcinoma could be detected in the thoracic duct during operative manipulation. Methods: In patients with an adenocarcinoma of the oesophagus and/or gastro-oesophageal junction, undergoing a transthoracic resection with two-field lymphadenectomy, lymph was collected and cells were immunostained. Results: Tumour cells could be detected in the thoracic duct lymph of only 1 out of 19 patients during operative manipulation. Conclusion: Peroperative data from this study do not support the hypothesis that oesophageal carcinoma readily metastasizes directly into the thoracic duct.