Quantifying the Effects of Prior Acetyl-Salicylic Acid on Sepsis-Related Deaths: An Individual Patient Data Meta-Analysis Using Propensity Matching.

OBJECTIVE: The primary objective was to conduct a meta-analysis on published observational cohort data describing the association between acetyl-salicylic acid (aspirin) use prior to the onset of sepsis and mortality in hospitalized patients. STUDY SELECTION: Studies that reported mortality in patients on aspirin with sepsis with a comparison group of patients with sepsis not on prior aspirin therapy were included. DATA SOURCES: Fifteen studies described hospital-based cohorts (n = 17,065), whereas one was a large insurance-based database (n = 683,421). Individual-level patient data were incorporated from all selected studies. DATA EXTRACTION: Propensity analyses with 1:1 propensity score matching at the study level were performed, using the most consistently available covariates judged to be associated with aspirin. Meta-analyses were performed to estimate the pooled average treatment effect of aspirin on sepsis-related mortality. DATA SYNTHESIS: Use of aspirin was associated with a 7% (95% CI, 2-12%; p = 0.005) reduction in the risk of death as shown by meta-analysis with considerable statistical heterogeneity (I = 61.6%). CONCLUSIONS: These results are consistent with effects ranging from a 2% to 12% reduction in mortality risk in patients taking aspirin prior to sepsis onset. This association anticipates results of definitive studies of the use of low-dose aspirin as a strategy for reduction of deaths in patients with sepsis.

Preserved Expression of mRNA Coding von Willebrand Factor-Cleaving Protease ADAMTS13 by Selenite and Activated Protein C.

In sepsis, the severity-dependent decrease of von Willebrand factor (VWF)-inactivating protease, a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13), results in platelet aggregation and consumption, leading to sepsis-associated thrombotic microangiopathy (TMA) and organ failure. Previous reports assessing its functional deficiency have pinpointed involvement of autoantibodies or mutations to propagate thrombotic thrombocytopenic purpura (TTP). However, mechanisms of acquired ADAMTS13 deficiency during host response remain unclear. To enhance understanding of ADAMTS13 deficiency in sepsis, we evaluated changes in expression of mRNA coding ADAMTS13 during septic conditions using primary cellular sources of the protease. We hypothesized that proinflammatory cytokines and constituents of serum from septic patients affect the transcriptional level of ADAMTS13 in vitro, and previously recommended therapeutic agents as adjunctive therapy for sepsis interact therewith. Cultured hepatic stellate cells (HSCs), endothelial cells (HMEC) and human precision-cut liver slices as an ex vivo model were stimulated with sepsis prototypic cytokines, bacterial endotoxin and pooled serum obtained from septic patients. Stimulation resulted in a significant decrease in ADAMTS13 mRNA between 10% and 80% of basal transcriptional rates. Costimulation of selenite or recombinant activated protein C (APC) with serum prevented ADAMTS13 decrease in HSCs and increased ADAMTS13 transcripts in HMEC. In archived clinical samples, the activity of ADAMTS13 in septic patients treated with APC (n = 5) increased with an accompanying decrease in VWF propeptide as surrogate for improved endothelial function. In conclusion, proinflammatory conditions of sepsis repress mRNA coding ADAMTS13 and the ameliorating effect by selenite and APC may support the concept for identification of beneficial mechanisms triggered by these drugs at a molecular level.

Benefit of low-dose aspirin and non-steroidal anti-inflammatory drugs in septic patients.

Analyzing medical records of 979 patients with severe sepsis or septic shock provided some evidence that the use of low-dose aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) was associated with decreased hospital mortality. However, the benefit was abolished when aspirin and NSAIDs were given together.

Effects of low-dose acetylsalicylic acid and atherosclerotic vascular diseases on the outcome in patients with severe sepsis or septic shock.

Sepsis and its sequelae of multiple organ failure is one of the leading causes of death in the industrial countries. Several studies have shown that patients who are treated with low-dose acetyl salicylic acid (ASA) for secondary prevention of atherothrombosis may have a lower risk to develop organ failure in the case of critical illness. The benefit of ASA is probably due to an inhibition of platelet activation as well as an increase in the formation of anti-inflammatory lipoxin A4. On the other hand, the effect of ASA could be - at least partially - an indirect one, caused by atherosclerotic vascular diseases as the cause of ASA treatment. Atherosclerosis is considered as a moderate systemic inflammation and we hypothesise that this chronic condition could have an impact on the outcome in sepsis. To get more information on the benefit of ASA in critically ill patients and on possible interference with atherosclerotic vascular diseases, we analysed the medical records of 886 septic patients who were admitted to the surgical intensive care unit (ICU) of a university hospital. Logistic regression analysis indicated that patients who were treated during the ICU stay with ASA (100 mg/d) had a significantly lower mortality. Odds ratios (ORs; with 95% confidential intervals) of 0.56 (0.37-0.84) and 0.57 (0.39-0.83) were calculated for ICU and hospital mortality, respectively. In contrast, statin treatment did not have significant effect on mortality. Diagnosis of atherosclerotic vascular diseases according to ICD classification did not influence ICU mortality but lowered hospital mortality (OR = 0.71 (0.52-0.99)). Subgroup analysis provided preliminary evidence that clopidogrel when given as only anti-platelet drug may have a similar benefit as ASA, but the combination of ASA and clopidogrel failed to improve the outcome. The time course of plasma fibrinogen and procalcitonin levels indicate that ASA seems to reduce the activation of haemostasis and increase the resolution of inflammation. It is concluded that prospective interventional studies should be done to test the use of ASA as novel therapeutic approach in critically ill patients.

Characteristics of clinical sepsis reflected in a reliable and reproducible rodent sepsis model.

BACKGROUND: Sepsis models are frequently based on induction of peritonitis, with cecal ligation and puncture reflecting the prototypical model. However, there is an ongoing discussion about the limitations of these models due to their variability in progression and outcome. Since standardization is a cornerstone of experimental models, we aimed to develop a reliable and reproducible procedure for induction of peritonitis. MATERIALS AND METHODS: A human stool batch was processed for -80° storage. For induction of peritonitis in fluid-resuscitated rats, a defined volume of stool suspension from this batch was injected intraperitoneally. For characterization of the model, physiologic and inflammatory changes were evaluated after sepsis induction. Survival analyses with the same batch were repeated in four independent experiments over a time period of 16 mo. RESULTS: The polymicrobial infection resulted in severe peritoneal inflammation with a systemic increase in cytokines. The mortality rate at 15 h was 29% and this was reproducible over a 16 mo time period. If antibiotic treatment was applied, a 50% survival was achieved. Laboratory markers indicated a progressive multi-organ dysfunction, while blood gas analysis showed respiratory compensation of a metabolic acidosis, and maintenance of PaO(2). Intravital microscopy of the liver revealed an impaired microcirculation. A decreased hemostatic potential was demonstrated by rotational thromboelastometry. Despite clinical recovery within 3 d, surviving animals showed laboratory and histologic signs of persisting inflammation even after 2 wk. CONCLUSIONS: This model reflects many features of human sepsis. Application of an infectious focus that is both quantitatively and qualitatively defined assures high reproducibility. Moreover, the procedure is simple and can be easily standardized.

Antiplatelet drugs and outcome in mixed admissions to an intensive care unit.

OBJECTIVE: Platelet activation has been implicated in microvascular thrombosis and organ failure. We tested the hypothesis that antiplatelet drugs favorably affect outcome in patients nonelectively admitted to an intensive care unit. DESIGN: Retrospective cohort study. SETTING: A 22-bed intensive care unit of a tertiary care center. PATIENTS: Six hundred fifteen consecutive patients admitted to an intensive care unit within 24 hrs after hospitalization were enrolled, approximately 25% of whom received antiplatelet drugs (acetylsalicylic acid, clopidogrel) for secondary prevention of vascular disease. Impact of antiplatelet drugs and established risk factors on mortality were assessed by logistic regression and 2 x 2 table analysis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients on antiplatelet drugs were markedly older and presented higher Acute Physiology and Chronic Health Evaluation II scores on intensive care unit admission. There was no significant difference in injury severity scores in trauma patients with (21 [range, 13-29]) or without antiplatelet drugs (18 [range, 12-29]). Using logistic regression analysis, a significant reduction of mortality was estimated for the use of antiplatelet drugs in various subgroups of patients with normal or high bleeding risk (odds ratios, 0.04-0.34). Significant benefit was also estimated by 2 x 2 table analysis of Acute Physiology and Chronic Health Evaluation II-matched samples (Acute Physiology and Chronic Health Evaluation II >20) of internal medicine patients and/or patients receiving medical treatment. No significant benefit but also no harm of antiplatelet drugs was estimated in Acute Physiology and Chronic Health Evaluation II-matched samples of patients with increased bleeding risk: patients from surgery departments overall, patients with surgical treatment, trauma, active bleeding, or transfusion (odds ratios, 0.51-0.88). CONCLUSIONS: Our data are consistent with prevention of organ dysfunction by antiplatelet drugs, which may be masked in some patients by concomitant bleeding risk. Antiplatelet drugs might offer a novel therapeutic option to prevent organ failure, at least in the absence of active bleeding. This hypothesis warrants testing in a prospective trial.

Individual variability of response and non-response to acetyl salicylic acid after cardiac surgery.

Insufficient inhibition of platelet function by acetyl salicylic acid (ASA) or other platelet inhibitors is a risk factor for arterial thrombosis in cardiovascular patients. We wanted to collect and analyse information on the frequency and probable causes of non-response to ASA in patients prior to and after cardiac surgery. One hundred and one patients (mean age 68 ± 9 years) undergoing cardiac surgery (98 patients with coronary bypass grafting, 18 cases had combined valve replacement, and three patients with only valve replacement) were enrolled. Post-operatively all patients received metamizole for analgesia. Platelet aggregation in platelet-rich plasma was induced by arachidonic acid (AA; 1.6 mM) or ADP (3 mM) in the absence and presence of exogenous ASA (100 µM). ASA non-response was defined as a maximum AA-induced aggregation of >30%. Eighty eight patients had pre-operative medication with ASA (100 mg/d), and ASA non-response was found in 24%. Irrespective of whether or not ASA medication was continued immediately after surgery, incidence of non-response increased to 55% at the first post-operative day. During continuous post-operative ASA medication (100 mg/d), 65% of patients were non-responder at fifth-7th post-operative day. When estimated on the basis of exogenously added ASA, non-response was observed pre-operative in 10%, at first post-operative day in 53% and at fifth-7th post-operative day in 39% of the patients. Twenty six of the 52 patients who did not adequately respond to exogenous ASA at the first post-operative day became responders when tested at the fifth-7th post-operative day, and 13 of the 46 responders became non-responders. The conversions were not due to small changes around the threshold of 30% aggregation but due to a highly significant decrease or increase in the extend of aggregation. Neither extracorporal circulation nor co-medication with clopidogrel had any significant influence on the platelet response to ASA medication or exogenously added ASA. Some non-steroidal analgesics, including metamizole, have been suggested to prevent inhibition of platelet cylcooxygenase by ASA. However, in 10 healthy volunteers we did not observe any interference of metamizole with the response to ASA. In conclusion, platelet response to ASA is markedly decreased after cardiac surgery. The underlying mechanisms and the clinical consequences of the post-operative instability of non-response to ASA need further evaluation.

Variations in the ratio between von Willebrand factor and its cleaving protease during systemic inflammation and association with severity and prognosis of organ failure.

Von Willebrand factor (VWF) and related parameters as well as the protease activity regulating its biological activity were measured in plasma of healthy controls and patients with different cause and severity of systemic inflammation to examine the efficacy of the measures to detect highly prothrombotic states including thrombotic microangiopathy (TMA), one of the sequelae of sepsis. Plasma levels of VWF increased with increasing severity of systemic inflammation, probably due to activation of the endothelium. In parallel, the proteolytic activity of VWF inactivating protease, ADAMTS13, stepwise declined with the severity of inflammation, emphasizing the role of VWF-triggered platelet aggregation on the endothelium subsequently followed by development of TMA. As a consequence, the ratio of VWF antigen level and ADAMTS13 activity was significantly higher in patients with inflammation and sepsis, suggesting that this ratio might be more useful for the diagnosis of highly prothrombotic states including TMA than VWF multimer analysis alone. These findings suggest that ADAMTS13, VWF and related parameters, even in a combined approach, might be useful for the diagnosis and the therapeutic monitoring of patients with sepsis associated thrombotic microangiopathy.

HES 130/0.4 impairs haemostasis and stimulates pro-inflammatory blood platelet function.

INTRODUCTION: Hydroxyethyl starch (HES) solutions are widely used for volume replacement therapy but are also known to compromise coagulation, impair renal function and increase long-term mortality. To test the hypotheses that HES 130/0.4 has fewer adverse effects than HES 200/0.5 and exerts anti-inflammatory properties, we compared the effects of HES 130/0.4, HES 200/0.5 and saline on in vitro haemostasis and pro-inflammatory platelet function. METHODS: Whole blood samples from healthy volunteers were mixed with 6% HES 130/0.4, 10% HES 200/0.5, or normal saline to achieve a final haemodilution rate of 10% or 40%. Haemostatic capacity was characterised by thromboelastography (ROTEM) and measurement for FXIIIa activity. Platelet activation and pro-inflammatory platelet functions were characterised by flow cytometry measuring the platelet activation marker CD62P and binding of fibrinogen to platelets as well as the formation of heterotypic platelet-leukocyte conjugates. RESULTS: Compared with saline, HES 130/0.4 dose-dependently impaired formation and firmness of the fibrin clot but did not affect the fibrin crosslinking activity of FXIIIa. At 40% but not at 10% haemodilution rate, HES 200/0.5 also increased platelet fibrinogen binding and both HES solutions increased expression of CD62P, the main receptor for platelet-leukocyte adhesion. HES 130/0.4 but not HES 200/0.5 increased formation of platelet-neutrophil conjugates and, to a lesser degree, platelet-monocyte conjugates. CONCLUSIONS: Our data demonstrate that HES 130/0.4 has similar adverse effects as HES 200/0.5. In particular, both types of HES impair coagulation capacity and stimulate, rather than attenuate, pro-inflammatory platelet function.

Anti-platelet drugs and outcome in severe infection: clinical impact and underlying mechanisms.

Platelet activation contributes to microvascular thrombosis and organ failure in systemic inflammation. We tested the hypothesis whether anti-platelet drugs might favourably affect outcome in patients at risk for organ failure as well as in a mouse model of endotoxin shock. Two hundred twenty-four consecutive patients who were admitted for community acquired pneumonia over a time period of 5 years to a University Hospital were enrolled; about 20% of whom received anti-platelet drugs (acetylsalicylic acid, thienopyridines) for secondary prevention of cardiovascular disease. Patients with anti-platelet drugs were about 12 years old but did not differ in SOFA score and routine laboratory parameters at admission. Logistic regression and 2 x 2 table analysis in age-matched subgroups indicated that anti-platelet drugs may reduce the need of intensive care treatment (odds ratio (OR) 0.32 [95% confidential interval: 0.10-1.00] and 0.19 [0.04-0.87], respectively). In age-matched subgroups, the use of anti-platelet drugs was also associated with a shorter stay in hospital (13.9 +/- 6.2 vs. 18.2 +/- 10.2 days; p < 0.02). In the animal model Balb/c mice were pre-treated with clopidogrel (added to drinking water) for 4 days prior to intraperitoneal (i.p.) administration of endotoxin (lipopolsaccharide (LPS) from Escherichia coli 0111:B4). Within the first 48 hours after LPS there were no differences between clopidogrel and control animals (n = 26 each) in macro-haemodynamics. However, clopidogrel abolished the LPS-induced drop in platelet count and reduced fibrin deposition in lung tissue. Using DNA microarray technology, we could show that clopidogrel suppressed endotoxin-induced up-regulation of inflammation-relevant genes, including arachidonate-5-lipoxygenase activating protein and leukotriene B4 receptor 1. According to our data a possible benefit of anti-platelet drugs in patients on risk for systemic inflammation and organ failure should be tested in a prospective trial.

Inflammation-associated ADAMTS13 deficiency promotes formation of ultra-large von Willebrand factor.

In a prospective, longitudinal study, we investigated the association between decreased ADAMTS13 activity and impaired hemostasis, as well as organ dysfunctions in patients with systemic inflammation due to extracorporeal cardiopulmonary circuit or with severe sepsis. Similar to negative acute phase proteins, ADAMTS13 activity declined stepwise according to the extent of inflammatory responses. A marked imbalance between ADAMTS13 activity and VWF antigen level was associated with the appearance of ultra-large VWF multimers in plasma, with organ dysfunction and lethality. Our data support the view that systemic inflammation results in an ADAMTS13 deficiency which activates hemostasis.

The value of rotation thromboelastometry to monitor disturbed perioperative haemostasis and bleeding risk in patients with cardiopulmonary bypass.

Rotation thromboelastometry (ROTEM) performed on whole-blood samples provides information on the contribution of fibrinogen and platelets to clot formation. Such measurements are believed superior to classical plasma coagulation measurements as a means of monitoring disturbed haemostasis. On-pump cardiac surgery is associated with high bleeding risk. The study objective was to obtain information on the frequency of abnormal values of ROTEM variables and to assess their value in estimating bleeding risk in such patients. We studied 150 patients undergoing elective on-pump cardiac surgery. We found a significant surgery-induced decrease in haemostatic potential, with more abnormal ROTEM values in intrinsically activated coagulation (up to 50%) than in extrinsically activated coagulation (up to 27%) or the maximum clot firmness in FIBTEM (10%), a test measuring the contribution of fibrinogen. All ROTEM variables tend to normalize within 14-18 h postoperatively. Best positive predictive values and specificity for a postoperative blood loss above 600 ml were found for the clot formation time in extrinsically activated coagulation (71%/94%) and the maximum clot firmness in FIBTEM (73%/95%); these values were superior to the activated partial thromboplastin time or prothrombin time (56%/72% and 43%/5%, respectively). There was no relation between preoperative or early postoperative ROTEM values and intraoperative bleeding. ROTEM recorded a benefit of administration of platelet concentrates or fresh-frozen plasma, particularly when given postoperatively, on haemostasis. In contrast, intraoperative administration of red blood cells impaired haemostasis. ROTEM can provide a more detailed diagnostic basis enabling a focused therapy to cardiac surgery patients with high bleeding risk.

Acute short-term hyperglycemia impairs platelet receptor expression even in healthy adults in vitro.

BACKGROUND: Platelet function is crucial in intensive care patients. Several factors like hyperglycemia may influence this function. Recently, it was demonstrated that the prevention of hyperglycemia could reduce mortality even in non-diabetic individuals. The aim of the present study was to examine effects of an acute hyperglycemia on platelet receptor expression in non-diabetic healthy individuals in vitro. MATERIAL/METHODS: Citrated blood samples were drawn from twenty-five healthy blood donors and adjusted to final concentrations of 10 mmol l(-1) and 15 mmol l(-1) glucose, respectively. The control group with blood glucose of 5 mmol l(-1) received no additional glucose. Expression of CD62P, CD41, CD36, and CD42b on the surface of resting or agonist-stimulated platelets was determined by whole blood flow cytometry using fluorescence-labeled monoclonal antibodies. Platelet aggregation in platelet rich plasma was induced with ADP and collagen and recorded using a turbidimetric coagulation analyzer. RESULTS: Hyperglycemia had no significant influence on the expression of CD62P and CD36. At glucose concentration of 15 mmoles l(-1) the expression of both CD42b and CD41 was decreased in resting platelets a well as in platelets stimulated with 5 microM ADP or 6 microM TRAP-6. The addition of 10 mmoles l(-1) glucose caused a significant inhibition of CD41 expression in ADP-stimulated samples. The results of platelet aggregation showed no significant differences between the groups. CONCLUSIONS: Short term hyperglycemia up to 15 mmoles l(-1) may decrease the expression of CD41 and CD42b, but not that of CD62P and CD36 on platelets in healthy adults. However functional abilities tested by aggregation are not affected.

Role of increased sphingomyelinase activity in apoptosis and organ failure of patients with severe sepsis.

Numerous studies support the notion that an activation of sphingomyelinases and a subsequent increase of the concentration of the bioactive lipid mediator ceramide are critical in the concert of inflammatory stimuli and to the induction of apoptosis during inflammation. Here we show that patients with severe sepsis exhibit an enhanced sphingolytic activity in comparison with controls [262 pmol/(mlxh) vs. 123.6 pmol/(mlxh), P<0.005]. During the clinical course, a further increase was paralleled by the severity of illness and by fatal outcome. Moreover, we show that oxidative stress may partially account for the increased activity through posttranslational modification of the enzyme. In a murine endotoxic shock model, administration of a low molecular weight inhibitor diminished the rise in enzymatic activity and improved the survival rate. In liver specimen, inhibition of activity correlated with a reduced rate of hepato-cellular apoptosis. Our data support the concept that activation of the plasmatic isoform of sphingomyelinase may play a critical role in the development of apoptosis and organ failure in sepsis. An inhibition of the secreted isoform of sphingomyelinase should be explored further as a potential target in the complicated puzzle of sepsis.

Transcriptional regulation of ADAMTS13.

The metalloproteinase ADAMTS13 cleaves VWF multimers instantaneously when they are released from endothelial cells. Absent or manifestly diminished proteolytic activity of ADAMTS13 results in the appearance and accumulation of ultralarge VWF multimers (ULVWFM) in plasma, characterised by the manifestation of Thrombotic Thrombocytopenic Purpura (TTP). Despite congenital defects, infections and the actions of drugs such as cyclosporine A, doxycycline and corticosteroids apparently are involved in its development. To examine the possibility of transcriptional regulation of ADAMTS13 activity, we analyzed RNA levels in various cell culture systems and the response to known and assumed modulators of gene expression. We demonstrate the expression of ADAMTS13 in liver homogenates and a parenchyma liver cell culture system Hep3B, supporting the hypothesis that liver is an important source of plasma ADAMTS13, whereas there was no alteration in gene expression after stimulation of liver cells with proinflammatory stimuli such as endotoxin, TNF-alpha, IL-6, IL-1beta as well as immuno-suppressive agents, such as cyclosporine A, a variety of steroids as well as doxycycline. Therefore, we analysed the ADAMTS13 gene for binding sites of transcription factors in silico and compared the data with those found in two sets of 24 genes considered either as differentially regulated by prototypic inflammatory regulation or as unvaried under various conditions. On the basis of these data, the promotor of ADAMTS13 features the characteristics of a gene, which remains unvaried under a variety of conditions. To our knowledge, the current data demonstrate for the first time, that an alteration in transcriptional activity is negligible in accounting for diminished proteolytic activity as observed under various experimental and, in particular, clinical conditions.

Transfer of tissue factor from platelets to monocytes: role of platelet-derived microvesicles and CD62P.

Tissue factor (TF) is the most important initiator of intravascular coagulation. Platelets contribute to TF exposure on monocytes, but the mechanism is not completely understood. Here we examined the possibility that platelets may release TF that can be transferred to monocytes by platelet-derived microvesicles. When human citrated platelet-rich plasma was incubated with collagen there was an increase in the plasma levels of TF and CD62P. Incubation of plasma obtained from collagen-stimulated PRP with a sediment of red and white blood cells resulted in an increase in the number of monocytes that express TF, CD62P and the platelet-specific antigen CD42a on their surface. This transfer of platelet-derived antigens to monocytes was reduced when CD62P was blocked by a specific antibody or when platelet-derived microvesicles were removed from the plasma either by high speed centrifugation (17,500 x g for 30 min) or by filtration (pore size 0.2 microm). The data indicate that platelet-derived microvesicles that are released from collagen-stimulated platelets may carry TF, CD62P and CD42a and may transfer these antigens to the surface of monocytes. The interaction of platelet-derived microvesicles with monocytes and the transfer of TF to monocytes strongly depend on CD62P.

Platelet and leukocyte activation correlate with the severity of septic organ dysfunction.

This study was conducted to investigate the extent of platelet-leukocyte adhesion and platelet, monocyte, and neutrophil activation in septic patients and to analyze whether these variables correlate with the severity of sepsis. Forty-seven patients consecutively admitted to the operative ICU of a University Medical Centre and 12 control patients prior to elective surgery were included in this prospective cohort study. Patients were evaluated daily for sepsis criteria and sepsis-associated organ failure assessment (SOFA) score was used to describe the extent of sepsis-associated organ failure. Indicators for cell activation (CD62P on platelets and CD11b on neutrophils and monocytes) and binding of platelets to neutrophils and monocytes were analyzed by flow cytometry. CD62P was increased on platelets from patients with sepsis compared with patients who did not have sepsis. Patients with sepsis also had higher CD11b expression on neutrophils and monocytes. Statistical analyses revealed a positive correlation between platelet CD62P expression and severity of sepsis, as well as a positive correlation between the SOFA score and CD11b on monocytes. No correlation was found between the SOFA score and CD11b on neutrophils. Higher values for platelet-neutrophil adhesion were observed in patients with uncomplicated sepsis compared either with controls or to patients with septic shock. An inverse relation between severity of sepsis and extent of platelet-neutrophil adhesion was also obvious from correlation analysis. The results indicate that flow cytometry can be used to measure these parameters of cell activation in sepsis and that activation of platelets and monocytes as well as adhesion of platelets to neutrophils does play a role in the development of organ dysfunction.

The effects of GPIIb-IIIa antagonists and a combination of three other antiplatelet agents on platelet-leukocyte interactions.

The effects of the GPIIb-IIIa antagonists abciximab and MK-852 on platelet-leukocyte interactions in vitro were studied and the results compared with those obtained with a combination of aspirin, dipyridamole and AR-C69931 (Asp/Dip/AR-C). Platelet-monocyte (P/M) and platelet-neutrophil (P/N) conjugate formation increased when blood was stirred or a platelet agonist was added. Leukocyte activation also occurred as judged by expression of surface tissue factor antigen and CD11b. Abciximab and MK-852 potentiated P/M, especially when collagen was used. They also increased the amount of tissue factor on the monocytes, but not CD11b. The Asp/Dip/AR-C did not enhance P/M or tissue factor exposure. Augmented tissue factor expression on monocytes in the presence of a GPIIb-IIIa antagonist may be relevant to the increased mortality associated with trials of such antagonists when given orally in patients with vascular disease. The Asp/Dip/AR-C was superior to abciximab and MK-852 in inhibiting platelet and leukocyte function.