Platelet-neutrophil interactions in sepsis--platelet guilt by association?

Can Coagulation System Disorders and Cytokine and Inflammatory Marker Levels Predict the Temporary Clinical Deterioration or Improvement of Septic Patients on ICU Admission?

Although coagulation disorders and immune/inflammatory response have been associated with the final outcome of patients with sepsis, their link with thetemporaryclinical deterioration or improvement of patients is unknown. We aimed to investigate this link. We prospectively included consecutive patients admitted to the intensive care unit (ICU) with a suspected diagnosis of infection and evaluated within the first 24 h from admission. Blood levels of many cytokines and inflammatory and coagulation factors were measured and their predictive value was assessed by calculating the Area Under the Receiver Operating Characteristic (AUROC) curves. Patients (n = 102) were allocated in five groups, i.e., sepsis (n = 14), severe sepsis (n = 17), septic shock (n = 28), Systemic Inflammatory Response Syndrome (SIRS) without infection (n = 17), and trauma/surgery without SIRS or infection (n = 26). In septic shock, coagulation factors FVII and FIX and Protein C had AUROCs 0.67-0.78. In severe sepsis, Antithrombin III, Protein C, C-reactive protein, Procalcitonin and Thrombopoietin had AUROCs 0.73-0.75. In sepsis, Tumor Necrosis Factor a, and Interleukins 1β and 10 had AUROCs 0.66-0.72. In patients admitted to the ICU with a suspected diagnosis of infection, coagulation factors and inhibitors, as well as cytokine and inflammatory marker levels, have substantial predictive value in distinct groups of septic patients.

Platelet activation and prothrombotic properties in a mouse model of peritoneal sepsis

Sepsis is associated with thrombocytopenia and microvascular thrombosis. Studies have described platelets implication in this pathology but their kinetics of activation and behavior remain poorly known. We show in a mouse model of peritonitis, the appearance of platelet-rich thrombi in organ microvessels and organ damage. Complementary methods are necessary to characterize platelet activation during sepsis as circulating soluble markers and platelet-monocyte aggregates revealed early platelet activation, while surface activation markers were detected at later stage. A microfluidic based ex-vivo thrombosis assay demonstrated that platelets from septic mice have a prothrombotic behavior at shear rate encountered in microvessels. Interestingly, we found that even though phosphoinositide-3-kinase β-deficient platelet mice formed less thrombi in liver microcirculation, peritoneal sepsis activates a platelet alternative pathway to compensate the otherwise mandatory role of this lipid-kinase to form stable thrombi at high shear rate. Platelets are rapidly activated during sepsis. Thrombocytopenia can be attributed in part to platelet-rich thrombi formation in capillaries and platelet-leukocytes interactions. Platelets from septic mice have a prothrombotic phenotype at a shear rate encountered in arterioles. Further studies are necessary to unravel molecular mechanisms leading to this prothrombotic state of platelets in order to guide the development of future treatments of polymicrobial sepsis.

Similar change in platelets and leucocytes 24 h after injury is associated with septic shock a week later

BACKGROUND

Septic shock is a severe complication in polytrauma patients. Early identification of patients at risk can guide future prevention strategies. Platelets (PLTs) and leucocytes presumably play an important role in the post-injury inflammatory response. The role of early changes in PLT and leucocyte counts was investigated in search for the aetiology of the development of septic complications.

METHODS

Polytrauma patients (aged 16-80 years) admitted to the intensive care unit with an expected stay of at least 3 days were included. PLT and leucocyte counts were measured on a daily basis for 14 days.

RESULTS

A total of 41 patients were included, of whom nine (22%) developed septic shock. There was no difference in (New) Injury Severity Score or Acute Physiology and Chronic Health Evaluation II scores between patients who developed septic shock and patients who did not. Three patients died, one of them in septic shock. Patients who developed septic shock during hospital stay had lower PLTs and a slower recovery to normal PLT counts than patients without septic shock. Patients who developed either a decrease in both PLTs and leucocytes or an increase in PLTs and leucocytes in the first 24 h after trauma were more likely to develop septic shock. This correlation was not found in patients who did not develop septic shock.

CONCLUSION

A similar change in PLT and leucocyte counts in the first 24 h after trauma is associated with the development of septic shock after a week. This indicates an early interaction between PLTs and leucocytes, which needs further investigation to gain more insight in the aetiology of post-injury septic complications.

Prehospital statin and aspirin use and the prevalence of severe sepsis and acute lung injury/acute respiratory distress syndrome

OBJECTIVES

To determine whether prehospital statin use is associated with a lower risk of sepsis, acute lung injury/acute respiratory distress syndrome, and mortality in critically ill patients. We also investigated the effect of combined prehospital use of both statins and aspirin.

DESIGN

Cross-sectional analysis of a prospective cohort.

PATIENTS

A total of 575 critically ill patients admitted to the medical or surgical intensive care unit of an academic tertiary-care hospital.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 575 patients, 149 (26%) were on statin therapy before hospitalization. A multivariable analysis including age, gender, current tobacco use, prehospital aspirin use, race, and Acute Physiology and Chronic Health Evaluation II score revealed that patients on statin therapy before hospitalization were less likely to have or develop severe sepsis (odds ratio 0.62, 95% confidence interval 0.40-0.96) or acute lung injury/acute respiratory distress syndrome (odds ratio 0.60, 95% confidence interval 0.36-0.99) during the first four intensive care unit days. In-hospital mortalities for patients with and without prehospital statin use (odds ratio 1.06, 95% confidence interval 0.62-1.83) were similar. Patients who had prehospital use of both statins and aspirin had the lowest rates of severe sepsis, acute lung injury/acute respiratory distress syndrome, and mortality.

CONCLUSIONS

Prehospital use of statins may be protective against sepsis and acute lung injury. This effect may be potentiated by prehospital aspirin use.

Hypertonic saline, mannitol and hydroxyethyl starch preconditioning of platelets obtained from septic patients attenuates CD40 ligand expression in vitro

BACKGROUND

Because platelet CD40 ligand (CD40L) expression plays an important role in inflammatory conditions, reduction of CD40L expression may be beneficial for patients with sepsis. Although hypertonic saline, mannitol, and hydroxyethyl starch (HES) solutions have been shown to modulate inflammatory responses, their effects on platelet CD40L expression are unclear. We assessed the effects of hypertonic saline, mannitol, and HES solutions on platelet CD40L expression.

METHODS

Platelet-rich plasma samples were obtained from septic patients and diluted to 1%, 2.5%, 5%, or 7.5% (vol/vol) with 7.5% saline, 3% saline, 0.9% saline, 20% mannitol, 10% HES (200/0.5), or Ringer's solution. Twenty-five samples were used per dilution. To determine platelet CD40L expression, platelet samples were stimulated with thrombin (0.1 U/mL), incubated with fluorochrome-conjugated platelet antibodies, and analyzed using flow cytometry.

RESULTS

Preconditioning of platelet-rich plasma with hypertonic saline, mannitol, and HES attenuated CD40L expression at dilution ratios of 5%, 1%, and 1%, respectively. The decreases were concentration dependent. The effects of mannitol and HES on CD40L expression were almost identical and were superior to those of 3% saline. In contrast, 0.9% saline and Ringer's solution had no effect on CD40L expression.

CONCLUSIONS

Our data show that resuscitation fluids, such as hypertonic saline, mannitol, and HES, inhibit agonist-induced CD40L expression on platelets. These resuscitation fluids may have an anti-inflammatory action when administered to septic patients.

Implications of thrombocytopenia and platelet course on pediatric intensive care unit outcomes

INTRODUCTION

Thrombocytopenia has been shown to be an independent predictor of mortality and prolonged hospital length of stay in critically ill adults. Studies are lacking in the pediatric intensive care unit population. We evaluated the relationship between platelet counts at admission, platelet course, and outcomes.

HYPOTHESES

1) Thrombocytopenia at the time of admission to the pediatric intensive care unit is a risk factor for increased mortality and prolonged length of stay. 2) Thrombocytopenia at any point during pediatric intensive care unit stay is associated with increased mortality and length of stay. 3) Falling platelet counts during a pediatric intensive care unit course are associated with greater mortality and longer length of stay.

METHOD

Prospective observational study.

STUDY POPULATION

All patients admitted to a multidisciplinary tertiary care pediatric intensive care unit in a University Hospital over the course of a year. ANALYSIS OF DATA: Data were analyzed using logistic and linear regression.

RESULTS

Thrombocytopenia (platelet count <150 x 10/L) was present in 17.3% of pediatric intensive care unit patients on admission. Mortality was higher in thrombocytopenic patients (17.6% vs. 2.47%, p < 0.001). The median length of stay in the thrombocytopenia and nonthrombocytopenia groups was 4 days vs. 1.6 days, respectively (p < 0.001). The pediatric intensive care unit patients (25.3%) were thrombocytopenic at some point in their stay. They had higher mortality (17.1% vs. 0.9%, odds ratio [OR] 23.8, 95% confidence interval [CI] 5.2-108.6, p < 0.0005) and longer length of stay (median 6.6 days vs. 1.5 days, p < 0.0005) compared with those who were never thrombocytopenic. For every 10% fall in platelet count from the time of admission, the OR for mortality was 1.4 (95% CI 1.1-1.8) and the length of stay was longer (p < 0.0005). Patients with normal platelet counts at admission who later developed thrombocytopenia had increased mortality (OR 18.6, 95% CI 3.2-107.3) and longer length of stay (p < 0.0005) compared with those who did not develop thrombocytopenia.

CONCLUSION

Thrombocytopenia and falling platelet counts are associated with increased risk of mortality and length of stay in the pediatric intensive care unit.

Platelet function in sepsis

OBJECTIVE

To evaluate platelet function in sepsis.

DATA SOURCES

The MEDLINE database and bibliographies of selected articles.

DATA SYNTHESIS

The common occurrence of thrombocytopenia in critically ill patients has been recognized for many years and is known to be associated with an increased mortality rate. Platelet function can be divided into four areas: activation, adhesion, aggregation, and secretion. Studies have found that activated platelets secrete key components of the coagulation and inflammatory cascades and are involved in the regulation of vascular tone. However, studies on platelet function in sepsis have been scarce, and their data are often conflicting. In sepsis, aggregation of circulating platelets seems to be reduced, yet platelet receptors are present in normal amounts.

CONCLUSIONS

Platelets play a complex role in sepsis; they are able to modulate not only their own function but also that of cells around them. Further study is needed to better define the precise mechanisms and effects of platelet activation in sepsis and to determine the benefits and risks of inhibiting platelet function.

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.

Time course of platelet counts in critically ill patients

BACKGROUND

Although thrombocytopenia in the intensive care unit (ICU) is associated with a poorer outcome, the precise relationship between the time course of platelet counts and the mortality rate has not been well defined.

OBJECTIVE

To describe the time course of the platelet count in relation to the mortality rate in critically ill patients.

DESIGN

Substudy of a prospective, multicenter, observational cohort analysis.

SETTING

Forty ICUs in 16 countries from Europe, America, and Australia.

PATIENTS

Data were collected from all ICU admissions in a 1-month period, excluding patients younger than 12 yrs old and those who stayed in the ICU for <48 hrs after uncomplicated surgery. A total of 1,449 critically ill patients were enrolled, including 257 who stayed in the ICU for >2 wks.

INTERVENTIONS

None.

MEASUREMENTS

Platelet counts were collected daily throughout the ICU stay, together with other measures of organ dysfunction. Thrombocytopenia was defined as a platelet count of <150 x 103/mm3. A relative increase in platelet count was defined as a 25% increase above the admission value, together with an absolute platelet count of > or =150 x 103/mm3.

MAIN RESULTS

For the entire population, the platelet count was lower in the 313 nonsurvivors than in the 1,131 survivors throughout the ICU course. Of the 257 patients who stayed in the ICU for >2 wks, 187 (64%) survived. The platelet count decreased significantly in the first days after admission to reach a nadir on day 4 in both survivors and nonsurvivors. In the survivors, the platelet count returned to the admission value by the end of the first week and continued to rise to become significantly greater than the admission value by day 9. In the nonsurvivors, the platelet count also returned to the admission value after 1 wk, but there was no subsequent increase in platelet count. A total of 138 (54%) patients had thrombocytopenia on day 4, and these patients had a greater mortality rate than the other patients (33% vs. 16%; p <.05). On day 14, 51 (20%) patients had thrombocytopenia, and these patients had a greater mortality rate than the other patients (66% vs. 16%; p <.05). Thrombocytopenia was less common on day 14 than on day 4 (20% vs. 54%; p <.05), but the mortality rate was greater in the thrombocytopenic patients on day 14 than those who were thrombocytopenic on day 4 (66% vs. 33%; p <.05). The ICU mortality rate of nonthrombocytopenic patients on day 14 was also significantly lower in patients with, than without, a relative increase in platelet count on day 14 (11% vs. 30%; p <.05).

CONCLUSION

Platelet count changes in the critically ill have a biphasic pattern that is different in survivors and nonsurvivors. Late thrombocytopenia is more predictive of death than early thrombocytopenia. A relative increase in platelet count after thrombocytopenia was present in survivors but not in nonsurvivors. Although a single measured platelet count is of little value for predicting outcome, changes in platelet count over time are related to patient outcome.