Endotoxemia and mediator release during cardiac surgery

Narrative review of systemic inflammatory response mechanisms in cardiac surgery and immunomodulatory role of anesthetic agents

Although surgical techniques and perioperative care have made significant advances, perioperative mortality in cardiac surgery remains relatively high. Single- or multiple-organ failure remains the leading cause of postoperative mortality. Systemic inflammatory response syndrome (SIRS) is a common trigger for organ injury or dysfunction in surgical patients. Cardiac surgery involves major surgical dissection, the use of cardiopulmonary bypass (CPB), and frequent blood transfusions. Ischemia-reperfusion injury and contact activation from CPB are among the major triggers for SIRS. Blood transfusion can also induce proinflammatory responses. Here, we review the immunological mechanisms of organ injury and the role of anesthetic regimens in cardiac surgery.

RAGE-dependent NF-kB inflammation processes in the capsule of frozen shoulders

BACKGROUND

The etiology of frozen shoulder (FS) remains uncertain. Advanced glycation end-products (AGEs) cause the cross-linking and stabilization of collagen and are increased in FS. The purpose of this study was to elucidate the pathogenesis of FS by evaluating the receptor of AGE (RAGE)-dependent pathways.

METHODS

Tissue samples of the coracohumeral ligament (CHL) and anterior inferior glenohumeral ligament (IGHL) were collected from 33 patients with FS, with severe stiffness, and 25 with rotator cuff tears (RCTs) as controls. Gene expression levels of RAGE, high-mobility group box 1 (HMGB1), Toll-like receptor 2 (TLR2), TLR4, nuclear factor-kappa B (NF-kB), and cytokines were evaluated using a quantitative real-time polymerase chain reaction. The immunoreactivities of carboxymethyllysine (CML), pentosidine, and RAGE were also evaluated. CML and pentosidine were further evaluated using high-performance liquid chromatography.

RESULTS

Gene expression levels of RAGE, HMGB1, TLR2, TLR4, and NF-kB were significantly greater in the CHLs and IGHLs from the FS group than in those from the RCT group. Immunoreactivities of RAGE and CML were stronger in the CHLs and IGHLs from the FS group than in those from the RCT group. Pentosidine was weakly immunostained in the CHLs and IGHLs from the FS group. CML using high-performance liquid chromatography was significantly greater in the CHLs and IGHLs from the FS group than in those from the RCT group.

CONCLUSIONS

AGEs and HMGB1 might play important roles in the pathogenesis of FS by binding to RAGE and activating NF-kB signaling pathways. Suppression of these pathways could be a treatment option for FS.

Alkaline Phosphatase in Infant Cardiopulmonary Bypass: Kinetics and Relationship to Organ Injury and Major Cardiovascular Events

OBJECTIVES

To determine the kinetics of alkaline phosphatase (AP) activity and concentration after infant cardiopulmonary bypass, including isoform-specific changes, and to measure the association between postoperative AP activity and major postoperative cardiovascular events, organ injury/dysfunction, and postoperative support requirements STUDY DESIGN: Prospective cohort study of 120 infants ≤120 days of age undergoing cardiopulmonary bypass. AP total and isoform-specific activity was assessed at 6 time points (preoperation, rewarming, 6, 24, 48, and 72 hours postoperation). Low AP activity was defined as ≤80 U/L. AP concentrations and biomarkers of organ injury/dysfunction were collected through 24 hours postoperation. Major cardiovascular events were defined as cardiac arrest, mechanical circulatory support, or death.

RESULTS

AP activity loss occurred primarily during the operation (median decrease 89 U/L; P < .0001) secondary to decreased bone and liver 2 isoforms. Activity declined through 24 hours in 27% of patients. AP activity strongly correlated with serum concentration (r = 0.87-0.91; P < .0001). Persistent low AP activity at 72 hours was associated independently with occurrence of a major cardiac event (OR 5.6; P < .05). Early AP activity was associated independently with subsequent vasoactive-inotropic score (P < .001), peak lactate (P < .0001), peak creatinine (P < .0005), N-terminal pro-brain natriuretic peptide (P < .05), and intestinal fatty acid binding protein (P < .005).

CONCLUSIONS

AP activity decreases during infant cardiopulmonary bypass and may continue to decrease for 24 hours. Activity loss is secondary to decreased bone and liver 2 isoform concentrations. Early low AP activity is associated independently with subsequent postoperative support and organ injury/dysfunction, and persistence of AP activity ≤80 U/L at 72 hours is associated independently with increased odds of major cardiovascular events.

Investigating the Impacts of Preoperative Steroid Treatment on Tumor Necrosis Factor-Alpha and Duration of Extubation Time underwent Ventricular Septal Defect Surgery

BACKGROUND

Cardiopulmonary bypass is known to cause inflammatory events. Inflammation occurs due to many known important biological processes. Numerous mechanisms are known to be responsible for the development of inflammatory processes. Currently, there are many defined mediators as a tumor necrosis factor-α (TNF-α) playing an active role in this process.

AIMS

This research was to investigate the effects of pre-operative steroid use on inflammatory mediator TNF-α and on time to extubation postoperatively in ventricular septal defect patients undergoing cardiopulmonary bypass surgery.

STUDY DESIGN

Controlled clinical study.

METHODS

This study included 30 patients. These patients were assigned into two groups, each containing 15 patients. 5 micrograms/kg methylprednisolone was injected intravenously 2 hours before the surgery to Group I, whereas there was no application to the patients in Group II. TNF-α (pg/mL) level was measured in arterial blood samples obtained at four periods including: the preoperative period (Pre TNF); at the 5(th) minute of cross-clamping (Per TNF); 2 hours after termination of cardiopulmonary bypass (Post TNF); and at the postoperative 24th hours in cardiovascular surgery intensive care unit (Post 24 h TNF).

RESULTS

The mean cross-clamp time was 66±40 and 55±27 minutes in Group I and Group II respectively. No significant difference was found between the groups in terms of cross-clamp time (p>0.05). The mean time to extubation was 6.1±2.3 hours in Group I and 10.6±3.4 hours in Group II. Group I extubation time was significantly shorter than Group II. Group I TNF-α levels at Post TNF and Post24h TNF was lower than Group II. These differences are also statistically significant (p<0.05).

CONCLUSION

There is a strong indication that preoperative steroid treatment reduced the TNF-α level together with shortens duration of postoperative intubation and positively contributes to extubation in ventricular septal defect patients operated in cardiac surgery with cardiopulmonary bypass. (ClinicalTrials.gov Identifier: TCTR20150930001).

Intestinal mast cells mediate gut injury and systemic inflammation in a rat model of deep hypothermic circulatory arrest

OBJECTIVE

Cardiac surgery, especially when employing cardiopulmonary bypass and deep hypothermic circulatory arrest, is associated with systemic inflammatory responses that significantly affect morbidity and mortality. Intestinal perfusion abnormalities have been implicated in such responses, but the mechanisms linking local injury and systemic inflammation remain unclear. Intestinal mast cells are specialized immune cells that secrete various preformed effectors in response to cellular stress. We hypothesized that mast cells are activated in a microenvironment shaped by intestinal ischemia/reperfusion, and investigated local and systemic consequences.

DESIGN

Rat model of deep hypothermic circulatory arrest.

SETTING

University research laboratory.

SUBJECTS

Twelve- to 14-week-old male Sprague-Dawley rats.

INTERVENTIONS

Rats were anesthetized and cooled to 16°C to 18°C on cardiopulmonary bypass before instituting deep hypothermic circulatory arrest for 45 minutes. Specimens were harvested following rewarming and 2 hours of recovery.

MEASUREMENTS AND MAIN RESULTS

Significant intestinal barrier disruption was found, together with macro- and microscopic evidence of ischemia/reperfusion injury in ileum and colon, but not in the lungs or kidneys. Immunofluorescence and toluidine blue staining revealed increased numbers of mast cells and their activation in the gut. In animals pretreated with the mast cell stabilizer, cromolyn sodium, mast cell degranulation was blocked, and intestinal morphology and barrier function were preserved following deep hypothermic circulatory arrest. Furthermore, cromolyn sodium treatment was associated with reduced intestinal neutrophil influx and blunted systemic release of proinflammatory cytokines.

CONCLUSION

Our data provide primary evidence that intestinal ischemia/reperfusion is a leading pathophysiologic process in a rat model of deep hypothermic circulatory arrest, and that intestinal injury, and local and systemic inflammatory responses are critically dependent on mast cell activation. This identifies intestinal mast cells as central players in deep hypothermic circulatory arrest-associated responses, and opens novel therapeutic possibilities for patients undergoing this procedure.

Microcirculation and its relation to continuous subcutaneous glucose sensor accuracy in cardiac surgery patients in the intensive care unit

OBJECTIVE

Continuous glucose monitoring could be helpful for glucose regulation in critically ill patients; however, its accuracy is uncertain and might be influenced by microcirculation. We investigated the microcirculation and its relation to the accuracy of 2 continuous glucose monitoring devices in patients after cardiac surgery.

METHODS

The present prospective, observational study included 60 patients admitted for cardiac surgery. Two continuous glucose monitoring devices (Guardian Real-Time and FreeStyle Navigator) were placed before surgery. The relative absolute deviation between continuous glucose monitoring and the arterial reference glucose was calculated to assess the accuracy. Microcirculation was measured using the microvascular flow index, perfused vessel density, and proportion of perfused vessels using sublingual sidestream dark-field imaging, and tissue oxygenation using near-infrared spectroscopy. The associations were assessed using a linear mixed-effects model for repeated measures.

RESULTS

The median relative absolute deviation of the Navigator was 11% (interquartile range, 8%-16%) and of the Guardian was 14% (interquartile range, 11%-18%; P = .05). Tissue oxygenation significantly increased during the intensive care unit admission (maximum 91.2% [3.9] after 6 hours) and decreased thereafter, stabilizing after 20 hours. A decrease in perfused vessel density accompanied the increase in tissue oxygenation. Microcirculatory variables were not associated with sensor accuracy. A lower peripheral temperature (Navigator, b = -0.008, P = .003; Guardian, b = -0.006, P = .048), and for the Navigator, also a higher Acute Physiology and Chronic Health Evaluation IV predicted mortality (b = 0.017, P < .001) and age (b = 0.002, P = .037) were associated with decreased sensor accuracy.

CONCLUSIONS

The results of the present study have shown acceptable accuracy for both sensors in patients after cardiac surgery. The microcirculation was impaired to a limited extent compared with that in patients with sepsis and healthy controls. This impairment was not related to sensor accuracy but the peripheral temperature for both sensors and patient age and Acute Physiology and Chronic Health Evaluation IV predicted mortality for the Navigator were.

High levels of S100A8/A9 proteins aggravate ventilator-induced lung injury via TLR4 signaling

Background

Bacterial products add to mechanical ventilation in enhancing lung injury. The role of endogenous triggers of innate immunity herein is less well understood. S100A8/A9 proteins are released by phagocytes during inflammation. The present study investigates the role of S100A8/A9 proteins in ventilator-induced lung injury.

Methods

Pulmonary S100A8/A9 levels were measured in samples obtained from patients with and without lung injury. Furthermore, wild-type and S100A9 knock-out mice, naive and with lipopolysaccharide-induced injured lungs, were randomized to 5 hours of spontaneously breathing or mechanical ventilation with low or high tidal volume (V_T). In addition, healthy spontaneously breathing and high V_T ventilated mice received S100A8/A9, S100A8 or vehicle intratracheal. Furthermore, the role of Toll-like receptor 4 herein was investigated.

Results

S100A8/A9 protein levels were elevated in patients and mice with lung injury. S100A8/A9 levels synergistically increased upon the lipopolysaccharide/high V_T MV double hit. Markers of alveolar barrier dysfunction, cytokine and chemokine levels, and histology scores were attenuated in S100A9 knockout mice undergoing the double-hit. Exogenous S100A8/A9 and S100A8 induced neutrophil influx in spontaneously breathing mice. In ventilated mice, these proteins clearly amplified inflammation: neutrophil influx, cytokine, and chemokine levels were increased compared to ventilated vehicle-treated mice. In contrast, administration of S100A8/A9 to ventilated Toll-like receptor 4 mutant mice did not augment inflammation.

Conclusion

S100A8/A9 proteins increase during lung injury and contribute to inflammation induced by HV_T MV combined with lipopolysaccharide. In the absence of lipopolysaccharide, high levels of extracellular S100A8/A9 still amplify ventilator-induced lung injury via Toll-like receptor 4.

RAGE regulation and signaling in inflammation and beyond

RAGE is a key molecule in the onset and sustainment of the inflammatory response. New studies indicate that RAGE might represent a new link between the innate and adaptive immune system. RAGE belongs to the superfamily of Ig cell-surface receptors and is expressed on all types of leukocytes promoting activation, migration, or maturation of the different cells. RAGE expression is prominent on the activated endothelium, where it mediates leukocyte adhesion and transmigration. Moreover, proinflammatory molecules released from the inflamed or injured vascular system induce migration and proliferation of SMCs. RAGE binds a large number of different ligands and is therefore considered as a PRR, recognizing a structural motif rather than a specific ligand. In this review, we summarize the current knowledge about the signaling pathways activated in the different cell types and discuss a potential activation mechanism of RAGE, as well as putative options for therapeutic intervention.

Endotoxemia related to cardiopulmonary bypass is associated with increased risk of infection after cardiac surgery: a prospective observational study

Introduction

Previous studies have documented a high frequency of endotoxemia associated with cardiopulmonary bypass (CPB). Endotoxemia may be responsible for some of the complications associated with cardiac surgery. The purpose of the study was to examine the prevalence of endotoxemia during cardiopulmonary bypass supported aortocoronary bypass grafting surgery (ACB) using a new assay, the Endotoxin Activity Assay (EAA), and explore the association between endotoxemia and post-operative infection.

Methods

The study was a single center prospective observational study measuring EAA during the perioperative period for elective ACB. Blood samples were drawn at induction of anesthesia (T1), immediately prior to release of the aortic cross-clamp (T2), and on the first post-operative morning (T3). The primary outcome was the prevalence of endotoxemia. Secondary outcomes assessed included infection rates, intensive care unit (ICU) and hospital length of stay. An EAA of < 0.40 units was interpreted as "low", 0.41 to 0.59 units as "intermediate", and ≥0.60 units as "high".

Results

A total of 57 patients were enrolled and 54 patients were analyzable. The mean EAA at T1 was 0.38 +/- 0.14, at T2 0.39 +/- 0.18, and at T3 0.33 +/- 0.18. At T2 only 13.5% (7/52) of patients had an EAA in the high range. There was a positive correlation between EAA and duration of surgery (P = 0.02). In patients with EAA ≥0.40 at T2, 26.1% (6/23) of patients developed post-operative infections compared to 3.5% (1/29) of those that had a normal EAA (P = 0.0354). Maximum EAA over the first 24 hours was also strongly correlated with risk of post-operative infection (P = 0.0276).

Conclusions

High levels of endotoxin occur less frequently during ACB than previously documented. However, endotoxemia is associated with a significantly increased risk of the development of post-operative infection. Measuring endotoxin levels during ACB may provide a mechanism to identify and target a high risk patient population.

Management of mechanical ventilation during laparoscopic surgery

Laparoscopy is widely used in the surgical treatment of a number of diseases. Its advantages are generally believed to lie on its minimal invasiveness, better cosmetic outcome and shorter length of hospital stay based on surgical expertise and state-of-the-art equipment. Thousands of laparoscopic surgical procedures performed safely prove that mechanical ventilation during anaesthesia for laparoscopy is well tolerated by a vast majority of patients. However, the effects of pneumoperitoneum are particularly relevant to patients with underlying lung disease as well as to the increasing number of patients with higher-than-normal body mass index. Moreover, many surgical procedures are significantly longer in duration when performed with laparoscopic techniques. Taken together, these factors impose special care for the management of mechanical ventilation during laparoscopic surgery. The purpose of the review is to summarise the consequences of pneumoperitoneum on the standard monitoring of mechanical ventilation during anaesthesia and to discuss the rationale of using a protective ventilation strategy during laparoscopic surgery. The consequences of chest wall derangement occurring during pneumoperitoneum on airway pressure and central venous pressure, together with the role of end-tidal-CO2 monitoring are emphasised. Ventilatory and non-ventilatory strategies to protect the lung are discussed.

The RAGE axis in systemic inflammation, acute lung injury and myocardial dysfunction: an important therapeutic target?

BACKGROUND

The sepsis syndromes, frequently complicated by pulmonary and cardiac dysfunction, remain a major cause of death amongst the critically ill. Targeted therapies aimed at ameliorating the systemic inflammation that characterises the sepsis syndromes have largely yielded disappointing results in clinical trials. Whilst there are many potential reasons for lack of success of clinical trials, one possibility is that the pathways targeted, to date, are only modifiable very early in the course of the illness. More recent approaches have therefore attempted to identify pathways that could offer a wider therapeutic window, such as the receptor for advanced glycation end-products (RAGE) and its ligands.

PURPOSE

The objectives of this study were to review the evidence supporting the role of the RAGE axis in systemic inflammation and associated acute lung injury and myocardial dysfunction, to explore some of the problems and conflicts that these RAGE studies have raised and to consider strategies by which they might be resolved.

METHODS

MEDLINE was searched (1990-2010) and relevant literature collected and reviewed.

RESULTS AND CONCLUSION

RAGE is an inflammation-perpetuating receptor with a diverse range of ligands. Evidence supporting a role of the RAGE axis in the pathogenesis of systemic inflammation, ALI and myocardial dysfunction is compelling with numerous animal experiments showing the beneficial effects of inhibiting the RAGE axis. Despite a number of unanswered questions that need to be further addressed, the potential for inhibiting RAGE-mediated inflammation in humans undoubtedly exists.

Prevalence of endotoxemia after surgery and its association with ICU length of stay

Introduction

The aim of this observational study was to investigate the prevalence of endotoxemia after surgery and its association with ICU length of stay.

Methods

102 patients admitted to a university ICU after surgery were recruited. Within four hours of admission, functional data were collected and APACHE II severity score calculated. Arterial blood samples were taken and endotoxemia was measured by chemiluminescence (Endotoxin Activity (EA)). Patients were stratified according to their endotoxin levels (low, intermediate and high) and according to their surgical procedures. Differences between endotoxin levels were assessed by ANOVA, accepting P < 0.05 as significant. Data are expressed as mean ± SD.

Results

EA levels were low in 68 (66%) patients, intermediate in 17 (17%) and high in 17 (17%). Age (61 ± 17 years) and APACHE II score 8.3 ± 3.7 (P = 0.542) were not significantly different in the three EA groups. Functional parameters on admission were similar between EA groups: white blood cells 11093 ± 4605 cells/mm³ (P = 0.385), heart rate 76 ± 16 bpm (P = 0.898), mean arterial pressure 88.8 ± 13.6 mmHg (P = 0.576), lactate 1.18 ± 0.77 mmol/L (P = 0.370), PaO₂/FiO₂ 383 ± 109 mmHg (P = 0.474). Patients with high levels of EA were characterized by longer length of stay in the ICU: 1.9 ± 3.0 days in the low EA group, 1.8 ± 1.4 days in intermediate and 5.2 ± 7.8 days in high group (P = 0.038).

Conclusions

17% of our patients were characterized by high levels of endotoxemia as assessed by EA assay, despite their low level of complexity on admission. High levels of endotoxin were associated with a longer ICU length of stay.

Epicardial adipose tissue as a source of nuclear factor-kappaB and c-Jun N-terminal kinase mediated inflammation in patients with coronary artery disease

CONTEXT

Visceral adipose tissue (AT) is known to confer a significantly higher risk of type 2 diabetes and cardiovascular disease. Epicardial AT has been shown to be related to cardiovascular disease and myocardial function through unidentified mechanisms. Epicardial AT expresses an inflammatory profile of proteins; however, the mechanisms responsible are yet to be elucidated.

OBJECTIVES

The objectives of the study were to: 1) examine key mediators of the nuclear factor-kappaB (NFkappaB) and c-Jun N-terminal kinase (JNK) pathways in paired epicardial and gluteofemoral (thigh) AT from coronary artery disease (CAD) and control patients and 2) investigate circulating endotoxin levels in CAD and control subjects.

DESIGN

Serums and AT biopsies (epicardial and thigh) were obtained from CAD (n = 16) and non-CAD (n = 18) patients. Inflammation was assessed in tissue and serum samples through Western blot, real-time PCR, ELISAs, and activity studies.

RESULTS

Western blotting showed epicardial AT had significantly higher NFkappaB, inhibitory-kappaB kinase (IKK)-gamma, IKKbeta, and JNK-1 and -2 compared with thigh AT. Epicardial mRNA data showed strong correlations between CD-68 and toll-like receptor-2, toll-like receptor-4, and TNF-alpha. Circulating endotoxin was elevated in patients with CAD compared with matched controls [CAD: 6.80 +/- 0.28 endotoxin unit(EU)/ml vs. controls: 5.52 +/- 0.57 EU/ml; P<0.05].

CONCLUSION

Epicardial AT from patients with CAD shows increased NFkappaB, IKKbeta, and JNK expression compared with both CAD thigh AT and non-CAD epicardial AT, suggesting a depot-specific as well as a disease-linked response to inflammation. These studies implicate both NFkappaB and JNK pathways in the inflammatory profile of epicardial AT and highlight the role of the macrophage in the inflammation within this tissue.

Bacterial translocation during liver transplantation: a randomized trial comparing conventional with venovenous bypass vs. piggyback methods

The aim of this study was to evaluate the bacterial translocation in liver transplantation (LT), comparing the conventional and the piggyback methods. A total of 32 patients were randomized into the 2 groups. Samples of blood were collected from the radial artery, portal vein (PV) and hepatic vein (HV), in up to 120 minutes postreperfusion. The samples were sent for endotoxin level, as well as samples up to 2 minutes post-perfusion were sent to culture. Hepatic artery and PV blood flows were measured at postreperfusion collection times. The results analyzed were: endotoxin concentration, its quantity, and hepatic clearance. The statistical treatment consisted of analyzing each group's mean profile. The analysis for endotoxin concentration in the radial artery was the deviation related to presurgery measure, and in the PV the deviation related to preclamping (PC) measure. The overall mean level of endotoxin concentration was 0.99 EU/mL in the artery, 1.30 EU/mL in the PV, and 1.22 EU/mL in the HV. The deviation was significant in the portal (P = 0.0031), but not in the artery samples (P = 0.2092). We detected a significant quantity of endotoxin in the artery and in the portal and the HVs (P < 0.001). There was no difference between the 2 groups and no hepatic clearance of endotoxin was detected either (P = 0.1515). All the cultures were negative. In conclusion, the study detected a significant translocation of endotoxin, but not of bacteria. The study also detected the absence of endotoxin hepatic clearance in both the piggyback and the conventional methods without any difference between them.

Renal dysfunction after thoracic aortic surgery requiring deep hypothermic circulatory arrest: definition, incidence, and clinical predictors

OBJECTIVE

The purpose of this study was to evaluate renal dysfunction (RD) after thoracic aortic surgery (TAS) requiring deep hypothermic circulatory arrest (DHCA), to determine the influence of definition on RD after TAS-DHCA, to determine univariate predictors of RD after TAS-DHCA, and to determine multivariate predictors for RD TAS-DHCA. RD was defined in 3 ways: (1) >25% reduction in creatinine clearance, (2) >50% increase in serum creatinine, and (3) >50% increase in serum creatinine with an abnormal peak serum creatinine (>1.3 mg/dL for men and >1.0 mg/dL for women).

STUDY DESIGN

Retrospective and observational.

STUDY SETTING

Single large university hospital.

PARTICIPANTS

All adults requiring TAS-DHCA in 2000 and 2001.

MAIN RESULTS

The cohort size was 144. Antifibrinolytic exposure was 100%: aprotinin 66% and aminocaproic acid 34%. The incidence of RD TAS-DHCA was 22.9% to 38.2%, depending on the definition. The incidence of renal replacement therapy was 2.8%. Multivariate predictors for RD after TAS-DHCA were sepsis, aprotinin exposure, preoperative hypertension, age, and donor exposures.

CONCLUSIONS

Although RD after TAS-DHCA varies substantially because of definition, it is still very common. Its multivariate predictors merit further focused research to enhance perioperative protection of the kidney.

Relationship of granulocyte colony stimulating factor with other acute phase reactants in man

The non-specific acute phase response in mice is associated with increased resistance to bacterial infection, which is critically mediated by granulocyte colony stimulating factor (G-CSF), but the behaviour of G-CSF in the human acute phase response is not known. Cardiothoracic surgery is a powerful acute phase stimulus and we show here that this procedure caused increased production of G-CSF, in addition to increases in the circulating concentrations of the proinflammatory cytokine interleukin (IL)-6 and the acute phase plasma proteins C-reactive protein (CRP) and serum amyloid A protein (SAA). Values of G-CSF correlated positively with IL-6 concentrations and circulating neutrophil counts, but not with CRP values. These results confirm that G-CSF is a physiological component of the acute phase response in humans that shares some of the same regulatory controls as IL-6, but its downstream effects are on neutrophils, not hepatic acute phase protein synthesis. Our observations are compatible with a protective role against bacterial infection for G-CSF in the human acute phase response, and support investigation of the prophylactic use of G-CSF in at-risk patients.

Pharmacodynamic evaluation of the neutralization of endotoxin by PMX622 in mice

Polymyxin B (PMB) binds to and neutralizes endotoxin, but its systemic clinical utility is limited by neuro- and nephrotoxicity. PMX622 is a covalent conjugate of PMB and Dextran-70 designed to retain the ability of PMB to neutralize endotoxin and to retain the favorable colloidal, pharmacokinetic, and metabolic properties of Dextran-70. PMX622 has demonstrated efficacy in a number of animal models and effectively neutralized endotoxin in phase I clinical trials. Here, we systematically evaluated the pharmacodynamic properties of PMX622 in a murine model of endotoxin-induced lethality in galactosamine-sensitized mice. PMX622 completely and dose dependently inhibited lethality in this model. A stoichiometric relationship was found between the endotoxin challenge dose and the dose of PMX622 needed for protection. PMX622 neutralized endotoxin from four different genera of gram-negative bacteria but not Neisseria meningitidis. PMX622 was significantly less toxic than PMB in the mouse, suggesting that PMX622 has a better margin of safety than PMB. The timing of PMX622 administration relative to endotoxin was crucial. PMX622 was active for several hours prior to the endotoxin challenge; however, PMX622 did not protect mice if administered >/=15 min after endotoxin challenge. This suggests that PMX622 would best be clinically used prophylactically rather than therapeutically. These studies will be crucial in designing and interpreting human clinical trials assessing PMX622 efficacy.

Catecholamines potentiate LPS-induced expression of MMP-1 and MMP-9 in human monocytes and in the human monocytic cell line U937: possible implications for peri-operative plaque instability

Plaque destabilization leading to myocardial infarction is observed after surgery even if the intervention is of noncardiovascular nature. Mediators of peri- or postoperative stress responsible for such events could include catecholamines and lipopolysaccharide (LPS). Monocytes may be involved in destabilization of atherosclerotic plaques by production of matrix metalloproteinases (MMP). We examined whether catecholamines could affect the expression of MMPs in human monocytes/macrophages and whether catecholamines could modulate LPS-stimulated expression of particular MMPs in these cells. Epinephrine and norepinephrine up-regulated MMP-1 and potentiated LPS-induced expression of MMP-1 in peripheral blood monocytes and monocyte-derived macrophages. We further characterized this effect employing the monocytic cell line U937 and showed that catecholamines potentiate LPS-induced effects on MMP-1 and MMP-9 antigen and activity. mRNA levels of the respective MMPs also increased. These effects did not result from higher mRNA stability but rather from increased transcription possibly induced by enhanced DNA binding of AP-1 and were mediated by either beta1- or beta 2-receptors. If this mechanism is also effective in vivo, our findings might, at least in part, help to explain the observation that cardiac events are important causes of morbidity and mortality after noncardiac surgery and support the findings that peri-operative beta-blockade has been shown to reduce postoperative mortality from cardiac events.

Influence of modest endotoxemia on postoperative antithrombin deficiency and circulating secretory immunoglobulin a levels

OBJECTIVE

To evaluate the influence of modest endotoxemia on postoperative antithrombin deficiency and cholestasis.

SUMMARY BACKGROUND DATA

It has not been determined whether endotoxin translocation in small amounts is a physiological phenomenon or whether it is a potential health hazard.

METHODS

Blood endotoxin, antithrombin III (ATIII), secretory immunoglobulin A (sIgA), which was selected as a marker of cholestasis, C-reactive protein (CRP), and alpha-1-antitrypsin (AAT) concentrations were measured from the 20 patients undergoing curative gastrectomy for gastric cancer preoperatively and postoperatively. Portal and systemic blood samples were taken for the analysis of endotoxin and interleukin-6 (IL-6) concentrations during surgery in these patients.

RESULTS

Although plasma endotoxin levels showed a significant increase during surgery, we did not find a correlation with ATIII, sIgA, CRP, and IL-6 levels. Systemic blood endotoxin levels during surgery correlated with a postoperative rise of serum AAT levels. Plasma ATIII levels transiently decreased on the first and third postoperative day, and sIgA levels were shown to increase on the seventh postoperative day. There was a weak relationship between the extent of postoperative endotoxemia and a reduction in ATIII concentrations.

CONCLUSIONS

The influence of modest endotoxemia on postoperative antithrombin deficiency and cholestasis was limited, and increased translocational endotoxemia during abdominal surgery may be a physiological phenomenon to trigger off an acute-phase protein response.

Different acute-phase response in newborns and infants undergoing surgery

In a prospective clinical study, we investigated the inflammatory response in 88 neonatal subjects (43 boys and 45 girls) who underwent major abdominal surgery owing to congenital malformation involving the gastrointestinal tract and compared it with the response in 20 infants (8 boys, 12 girls; mean age, 4 mo) who underwent elective surgery for resolution of an existing temporary stoma. In both groups, plasma levels of endotoxin, IL-6, and C-reactive protein as well as leukocyte counts were determined during and after surgery. Endotoxin was measured by the Limulus amebocyte test, IL-6 by ELISA, and C-reactive protein by nephelometry. Statistical analyses were performed using the Wilcoxon signed-rank test. A significant increase in circulating endotoxin and a leukocyte shift was observed in the infant group only. Postoperatively, IL-6 levels peaked between 2 and 6 h and C-reactive protein after 24 h in the infant group. In contrast, no significant increase in the levels of endotoxin, IL-6, and C-reactive protein in plasma were observed during and after surgery in the neonatal subjects, except those with gastroschisis. Newborns with gastroschisis developed an inflammatory response after surgery that was less pronounced than the response of infants older than 4 mo. The finding that endotoxemia in newborns does not follow surgical trauma is most likely because of the absence of bacterial colonization of the gastrointestinal tract.

Preoperative oral application of immunoglobulin-enriched colostrum milk and mediator response during abdominal surgery

Our objective was to evaluate the influence of pre-operative oral application of an immunoglobulin-enriched milk preparation on endotoxin translocation and mediator release during and after abdominal surgery. Forty patients who had been treated by partial (n = 4) or total gastrectomy (n = 8) or pancreatic resection (n = 28) were enrolled in a placebo-controlled pilot study. Pre-operatively, patients were randomly treated for 3 days by oral application of a bovine milk preparation (lactobin 56g/day, n = 20) or placebo (n = 20). In both groups, endotoxin translocation and mediator release was studied pre- and intraoperatively by measuring endotoxin, endotoxin-neutralizing capacity (ENC), interleukin 6, C-reactive protein, transferrin, alpha-2-macroglobulin, albumin, apoliprotein-A1/-B, IgG, IgA, and IgM. The clinical course was followed up by daily evaluation of the Apache-II-score. Clinical data were comparable in both groups. The lactobin group showed significantly lower levels of endotoxin and ENC compared to the placebo group. Acute phase response, endotoxin-binding proteins, and clinical outcome did not differ between both groups. We conclude that prophylactic oral application of lactobin reduces perioperative endotoxemia and prevents reduction of ENC, suggesting a stabilization of gut barrier during abdominal surgery.

Changes of gut barrier function during anesthesia and cardiac surgery

The aim of this clinical study was to investigate the time sequence between intraoperative and postoperative endotoxemia, changes in intramucosal pH(I), mediator release, and acute phase proteins and their relationship to postoperative infections. In 60 patients (median age 61 [33-72] years, male/female: 50/10) plasma levels of endotoxin, endotoxin neutralizing capacity (ENC), leukotriene-C4 (LTC4), 6-ketoprostaglandin-F-1alpha (PGF), thromboxane-B2 (TxB2), interleukin-6 (IL-6), and C-reactive protein (CRP) were measured before, during, and after cardiac surgery. The intraluminal pH(I) of the stomach was assessed as a marker of splanchnic blood circulation. Patients were divided in one group with postoperative infections (group A, n = 8) and another groups without infections (group B, n = 52). Among all measured parameters, endotoxin plasma levels showed the most rapid changes. A significant increase of endotoxin plasma levels and a decrease in ENC appeared after the induction of anesthesia, culminating in a peak after reperfusion. Endotoxin showed a significantly higher increase in group A (14fold) compared to group B (sixfold, p<0.001), whereas ENC decreased by eightfold in both groups. The parameters of the arachidonic cascade increased and pH(I) decreased, however, there were no significant differences between both groups. The latest increase was observed for the acute phase proteins IL-6 and CRP. IL-6 levels peaked 6 hours postoperatively with a 20fold (group B) and 30fold (group A) increase (p < 0.001 vs baseline; no differences between groups), whereas CRP rose at the first postoperative day with a 21 fold (group B) and 25fold (group A) increase at day 2 (p<0.001 vs baseline, no difference between groups). Differences between both groups appeared at the second postoperative day for IL-6 (median values group A/B: 421/219 pg/mL; p <0.05) and at the fifth postoperative day for CRP (median values group A/B: 321/81 mg/L; p < 0.05). In conclusion, endotoxin seems to be the earliest trigger of the mediator cascade in acute phase response and may indicate infections in the postoperative course.

Cardiovascular optimization for high-risk surgery

Controversy still exists concerning the strategy of targeting so-called supranormal levels of oxygen delivery as a means of improving outcome from high-risk surgery. The pathogenesis of postoperative morbidity is not fully defined; however, it seems likely that the gastrointestinal tract plays a pivotal role, particularly as a source of endotoxin, which is a potent stimulator of the inflammatory response. Delayed recovery of gastrointestinal function also is a major contributor to postoperative morbidity. Demonstration of a significant reduction in gut ischemia, endotoxemia, postoperative inflammatory response, and morbidity in a high-risk general surgical population as a result of perioperative hemodynamic optimization would be a highly worthwhile study.

Metabolic changes after cardiac surgery

The metabolic changes that occur after cardiac surgery result from a complex interaction between the effects of surgery and extracorporeal circulation per se, the inflammatory response to surgical trauma and extracorporeal circulation, perioperative use of hypothermia, the cardiovascular and neuroendocrine responses characteristic to cardiac surgery, and the drugs and blood products used to support circulation during and after operation. These changes include among others increased oxygen consumption and energy expenditure and increased secretion of insulin, growth hormone, adrenocorticotrophic hormone, cortisol, epinephrine and norepinephrine. Other changes include decreased total-Trijodthyronine levels, hyperglycemia, hyperlactatemia, increased glutamate, aspartate and free fatty acid concentrations, hypokalemia, an increased production of inflammatory cytokines and increased consumption of complement and adhesion molecules. There is evidence that better control of metabolic abnormalities improves the patients' outcome.