Bleeding induced interleukin-6 decreases blood loss via activation of coagulation

Role of Omega-6 Fatty Acid Metabolism in Cardiac Surgery Postoperative Bleeding Risk

Cardiac surgery is frequently associated with significant postoperative bleeding. Platelet-dysfunction is the main cardiopulmonary bypass (CPB)-induced hemostatic defect. Not only the number of platelets decreases, but also the remaining are functionally impaired. Although lipid metabolism is crucial for platelet function, little is known regarding platelet metabolic changes associated with CPB-dysfunction. Our aim is to explore possible contribution of metabolic perturbations for platelet dysfunction after cardiac surgery.

DESIGN

Prospective cohort study.

SETTING

Tertiary academic cardiothoracic-surgery ICU.

PATIENTS

Thirty-three patients submitted to elective surgical aortic valve replacement.

INTERVENTIONS

Samples from patients were collected at three time points (preoperative, 6- and 24-hr postoperative). Untargeted metabolic analysis using high-performance liquid chromatography-tandem mass spectrometry was performed to compare patients with significant postoperative bleeding with patients without hemorrhage. Principal component analyses, Wilcoxon matched-pairs signed-rank tests, adjusted to FDR, and pairwise comparison were used to identify pathways of interest. Enrichment and pathway metabolomic complemented the analyses.

MEASUREMENTS AND MAIN RESULTS

We identified a platelet-related signature based on an overrepresentation of changes in known fatty acid metabolism pathways involved in platelet function. We observed that arachidonic acid (AA) levels and other metabolites from the pathway were reduced at 6 and 24 hours, independently from antiagreggation therapy and platelet count. Concentrations of preoperative AA were inversely correlated with postoperative chest tube blood loss but were not correlated with platelet count in the preoperative, at 6 or at 24 hours. Patients with significant postoperative blood-loss had considerably lower values of AA and higher transfusion rates. Values of postoperative interleukin-6 were strongly correlated with AA variability.

CONCLUSIONS AND RELEVANCE

Our observations suggest that an inflammatory-related perturbation of AA metabolism is a signature of cardiac surgery with CPB and that preoperative levels of AA may be more relevant than platelet count to anticipate and prevent postoperative blood loss in patients submitted to cardiac surgery with CPB.

A conceptual time window-based model for the early stratification of trauma patients

Progress in the testing of therapies targeting the immune response following trauma, a leading cause of morbidity and mortality worldwide, has been slow. We propose that the design of interventional trials in trauma would benefit from a scheme or platform that could support the identification and implementation of prognostic strategies for patient stratification. Here, we propose a stratification scheme based on defined time periods or windows following the traumatic event. This 'time-window' model allows for the incorporation of prognostic variables ranging from circulating biomarkers and clinical data to patient-specific information such as gene variants to predict adverse short- or long-term outcomes. A number of circulating biomarkers, including cell injury markers and damage-associated molecular patterns (DAMPs), and inflammatory mediators have been shown to correlate with adverse outcomes after trauma. Likewise, several single nucleotide polymorphisms (SNPs) associate with complications or death in trauma patients. This review summarizes the status of our understanding of the prognostic value of these classes of variables in predicting outcomes in trauma patients. Strategies for the incorporation of these prognostic variables into schemes designed to stratify trauma patients, such as our time-window model, are also discussed.

Trauma in silico: Individual-specific mathematical models and virtual clinical populations

Trauma-induced critical illness is driven by acute inflammation, and elevated systemic interleukin-6 (IL-6) after trauma is a biomarker of adverse outcomes. We constructed a multicompartment, ordinary differential equation model that represents a virtual trauma patient. Individual-specific variants of this model reproduced both systemic inflammation and outcomes of 33 blunt trauma survivors, from which a cohort of 10,000 virtual trauma patients was generated. Model-predicted length of stay in the intensive care unit, degree of multiple organ dysfunction, and IL-6 area under the curve as a function of injury severity were in concordance with the results from a validation cohort of 147 blunt trauma patients. In a subcohort of 98 trauma patients, those with high-IL-6 single-nucleotide polymorphisms (SNPs) exhibited higher plasma IL-6 levels than those with low IL-6 SNPs, matching model predictions. Although IL-6 could drive mortality in individual virtual patients, simulated outcomes in the overall cohort were independent of the propensity to produce IL-6, a prediction verified in the 98-patient subcohort. In silico randomized clinical trials suggested a small survival benefit of IL-6 inhibition, little benefit of IL-1β inhibition, and worse survival after tumor necrosis factor-α inhibition. This study demonstrates the limitations of extrapolating from reductionist mechanisms to outcomes in individuals and populations and demonstrates the use of mechanistic simulation in complex diseases.

Influence of the slow infusion of a soybean oil emulsion on plasma cytokines and ex vivo T cell proliferation after an esophagectomy

BACKGROUND

Lipid emulsions have been suggested to reduce immune responses, particularly in severely stressed patients. The authors investigated the influence of the slow intravenous infusion of a soybean oil-based lipid emulsion on some immune parameters in patients who had undergone an esophagectomy for esophageal cancer.

METHODS

Thirty-two patients who had undergone an esophagectomy were randomly divided into a lipid emulsion (LPD)-treated group and a control group. All patients received parenteral feeding with a glucose-based solution. Patients in the LPD group received 100 mL of a 20% soybean oil emulsion for 7 days after the esophagectomy in addition to the glucose-based feeding. A slow infusion rate (0.09-0.12 g/kg/h) was adopted to take account of the intrinsic degradation of infused lipids. Immune responses were measured based on lymphocyte proliferation and serum concentrations of monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). The authors also measured levels of rapid turnover proteins (ie, transferrin, prealbumin, and retinol-binding protein).

RESULTS

Phytohemagglutinin- and concanavalin A-stimulated lymphocyte proliferation significantly decreased after the esophagectomy, but no significant difference was seen between the LPD and control groups. No significant difference in changes in plasma concentrations of MCP-1, IL-6 and TNF-α occurred between the 2 groups either. Plasma concentrations of rapid turnover proteins did not differ between the groups.

CONCLUSIONS

These results indicate that the lipid emulsion did not affect the immune parameters measured in patients who had undergone an esophagectomy when administered at a slow rate.

Neutralizing Antibody against Interleukin-6 Attenuates Posthemorrhagic Vasospasm in the Rat Femoral Artery Model

OBJECTIVE

The degree to which inflammation contributes to the development of posthemorrhagic vasospasm is controversial. In the present study, we investigated the relationship between various inflammatory cytokines (tumor necrosis factor-alpha, interleukin [IL]-1alpha, IL-1beta, and IL-6) and the development of experimental vasospasm.

METHODS

Posthemorrhagic vasospasm was produced in the rat femoral artery model. A latex pouch was placed around each femoral artery, and one pouch was injected with autologous blood and the other with saline as an internal control. Animals were killed at various time points (1 h to 16 d) after surgery (blood exposure), and the degree of vasospasm was assessed by image analysis of artery cross sectional area. Levels of inflammatory cytokines were determined by enzyme-linked immunosorbent assay, and the ability of a polyclonal antibody against rat IL-6 to inhibit vasospasm was tested.

RESULTS

The rat femoral artery model produced a biphasic vasospasm response, with maximal chronic delayed vasospasm occurring at 8 days after hemorrhage. Enzyme-linked immunosorbent assay revealed a significant increase in IL-6 concentrations in blood-exposed arteries relative to saline-exposed arteries at multiple time points (6, 12, 24, and 48 h) after hemorrhage (P < 0.0001). A relative increase in IL-1alpha levels was noted at 24 hours (P < 0.01). IL-1beta levels were similarly elevated in both blood- and saline-exposed arteries, and tumor necrosis factor-alpha levels were not detectable. Administration of a neutralizing polyclonal antibody against rat IL-6 directly into the blood-exposed periarterial pouch at the time of initial surgery resulted in a dose-dependent reduction in the degree of vasospasm compared with vehicle-treated controls at 8 days after hemorrhage (P < 0.05).

CONCLUSIONS

These results indicate that cytokine-mediated inflammation is active in the setting of posthemorrhagic vasospasm produced by the rat femoral artery model. In particular, the profound increase in IL-6 levels after exposure to hemorrhage and the ability of a polyclonal antibody against IL-6 to reduce vasospasm suggest that IL-6 may play a prominent role in the development of vasospasm in this model.

Intraoperative detection of traumatic coagulopathy using the activated coagulation time

Traumatic coagulopathy manifests as a hypocoagulable state associated with hypothermia, acidosis, and coagulation factor dilution. The diagnosis must be made clinically because traditional coagulation tests are neither sensitive nor specific and take too long to be used for intraoperative monitoring. We hypothesized that the activated coagulation time (ACT) would reflect the global coagulation status of traumatized patients and would become elevated as coagulation reserves become exhausted. A prospective protocol was used to study 31 victims of major trauma who underwent immediate surgical Intervention. Victims of major head trauma were excluded and patients were selected at random over an 8-month period. At least two serial intraoperative blood samples were obtained at 15-min intervals via indwelling arterial catheters. A Hemochron model 801 coagulation monitor was used to measure the ACT. Of the 31 patients studied, 7 became clinically coagulopathic and 24 did not. The ACT measurements of coagulopathic and noncoagulopathic trauma patients were significantly different by multiple statistical comparisons. Both groups differed from normal, nontraumatized patients. The coagulopathic trauma patients had significantly elevated values when compared with other trauma patients or to normal values. We conclude that a low ACT reflects the initial hypercoagulability associated with major trauma and an elevated ACT is an objective indicator that the coagulation system reserve is near exhaustion. An elevated ACT may represent an indication for considering damage control maneuvers or more aggressive resuscitation.

Effects of isolated limb perfusion with tumor necrosis factor-alpha on circulating levels of proinflammatory cytokines

Hyperthermic isolated limb perfusion (ILP) with tumor necrosis factor-a (TNFalpha) and cytotoxic drugs is currently used for treatment of melanoma and sarcoma of the limbs. Tumor necrosis factor-alpha is involved in the systemic inflammatory response syndrome as a result of activation of inflammatory cells and production of bioactive substances. The goal of this study was to determine the circulating levels of proinflammatory cytokines and soluble adhesion molecules in 19 patients with limb melanoma or sarcoma undergoing ILP with (n = 9) or without TNFalpha (n = 10). The results obtained demonstrated that ILP with TNFalpha was responsible for a leakage of TNFalpha in the systemic circulation, followed by a rise in interleukin (IL)-6 and IL-8 levels within I h. Elevated soluble (s)P-selectin levels were found 1-3 h after ILP. Plasma sE-selectin peaked 6-9 h after ILP, and soluble vascular cell adhesion molecule (sVCAM) levels reached a maximum after 24 h. Significant correlations were observed among these variables, confirming the interdependence of all changes observed. On the other hand, ILP with cytotoxic drugs alone induced only a modest release of TNFalpha, which was not followed by an immediate rise in IL-6 and IL-8. Four of the 9 patients undergoing ILP with TNF had severe systemic toxicity. No association was found between systemic TNF levels and the clinical outcome, whereas elevated TNF perfusion levels as well as systemic IL-6 and IL-8 levels were constantly elevated in patients with severe toxicity. These results are suggestive of an important role of TNFalpha levels in the perfusion system (more than leakage of perfusate) in causing postoperative toxicity, although other ILP-related factors should not be excluded.

Endogenous heparin decreases the thrombotic response to hemorrhagic shock in rabbits

PURPOSE

The purpose of this study was to determine if endogenous heparin release would modulate the hemostatic response to hemorrhagic shock in rabbits.

MATERIALS AND METHODS

Anesthetized rabbits (n = 13) underwent hemorrhagic shock (MAP 30-40 mm Hg) for 60 minutes. Blood samples obtained before and 60 minutes after hemorrhagic shock had thrombelasto-graphic variables (R, reaction time [min]; angle, alpha [ degrees ]; and G [dynes/cm(2)]) determined. Hemostatic function was assessed by modified thrombelastography under four conditions: (1) unmodified sample; (2) platelet inhibition with cytochalasin D; (3) heparinase I exposure; and (4) platelet inhibition and heparinase I exposure.

RESULTS

Thrombelastographic variable values in samples without platelet inhibition or heparinase exposure did not significantly change after hemorrhage (before hemorrhage: R = 22.01 +/- 0.7 min, alpha 43.6 +/- 1.3 degrees, G 7,089 +/- 379 dyne/cm(2); after hemorrhage: R 22.1 +/- 2.4, alpha 41.6 +/- 3.9, G = 5,662 +/- 564; mean +/- SEM). However, blood samples exposed to heparinase after hemorrhage demonstrated enhanced hemostatic function with thrombelastographic values (R = 13.4 +/- 1.5, alpha 56.0 +/- 3.4, G = 7012 +/- 565) significantly different (P <.05) from samples not exposed to heparinase. Samples with platelet inhibition demonstrated a similar pattern.

CONCLUSION

Hemorrhagic shock significantly increased circulating endogenous heparin activity, attenuating the thrombotic response to hemorrhage in rabbits. Heparin-mediated regulation of hemostasis may serve as a protective mechanism in shock states.