This study focuses on the role of platelet membrane glycoproteins and platelet-leucocyte adhesion in patients with sepsis and multiple organ failure (MOF). Specifically, the study raises the following issues: (1) the influence of sepsis and MOF on platelet activation as assessed by surface expression of platelet membrane glycoproteins GPIIb-IIIa and thrombospondin; and (2) the effect of sepsis and MOF on platelet adhesion to circulating leucocytes. In addition, platelet activation and platelet-leucocyte adhesion are evaluated according to clinical outcome. Forty-five patients with suspected sepsis or MOF were evaluated by intensive care scoring systems (APACHE II and Elebute) to assess severity of disease. Flow cytometric techniques were used to examine platelet membrane expression of various adhesion molecules on circulating platelets and the appearance of platelet specific antigen (CD41) on leucocytes as an index of platelet-leucocyte adhesion. The results were compared with severity of disease and according to outcome in patients. Twenty-eight patients of the total study population were septic and 17 were non-septic. Twenty-two of the 28 septic patients suffered from severe MOF (APACHE II > or = 20) whereas in six septic patients MOF was absent. Eleven of the non-septic group suffered from moderate MOF whereas in six, severe MOF was present. In septic patients fibrinogen receptor activity on platelets was significantly above normal values (P < 0.001). When MOF was present, thrombospondin surface expression on circulating platelets also increased significantly (P < 0.05). Concomitantly, platelet-leucocyte adhesion was increased in sepsis (P < 0.05) and decreased in patients with MOF (P < 0.05). Significant lower levels of circulating platelet-leucocyte aggregates occurred in non-survivors (P < 0.05). We conclude that sepsis is associated with increased surface expression of platelet adhesion molecules and an increased occurrence of circulating platelet-leucocyte aggregates. The decrease in circulating platelet-leucocyte peripheral sequestration. An increased platelet-leucocyte adhesion and sequestration might account for development of MOF in the course of sepsis.

Hemodialysis is associated with simultaneous changes in leukocytes and platelets, but it is unclear whether these alterations affect the interactions between these cell types. To evaluate this process, we examined the appearance of platelet specific antigens (CD41) on leukocytes as an index of platelet-leukocyte aggregation during hemodialysis using three different synthetic membranes. Patients with end-stage renal disease (ESRD) on long-term hemodialysis treatment were enrolled. Flow cytometric techniques and platelet specific monoclonal antibodies (MoAb) that recognize the glycoprotein complex on resting and activated platelets (anti-CD41), the activated GPIIb-IIIa complex receptor (anti-LIBS1), and the p selectin GMP140, that is exposed on platelet plasma membrane after activation and platelet degranulation (anti-CD62), were used. Subjects with ESRD had a lower predialysis platelet surface expression of CD41 and LIBS1 compared to normal controls, but unchanged CD62 expression. In parallel, patients with ESRD manifested a uniformly reduced platelet-leukocyte microaggregates predialysis compared to normal controls. When examined across the dialyzer, however, an increase in platelet-neutrophil and platelet-monocyte microaggregates was observed with all three synthetic membranes at both 15 and 30 minutes after initiation of dialysis. This phenomenon could be duplicated in vitro by physiologic concentrations of the platelet specific agonist ADP, but not by the complement factors C3a or C5a. We conclude that platelet-leukocyte aggregates occur during dialysis likely related to a primary platelet activation mechanism. This phenomenon may serve as a new biocompatibility parameter and may shed light on some of the biologic consequences of hemodialysis.

To date, selective extracorporeal low‐density lipoprotein (LDL) removal can only be performed from plasma; that is, a plasma‐cell separation step using a centrifuge or a plasma membrane separator is necessary initially. This article characterizes a new polyacrylate‐based LDL adsorber directly applicable to whole blood. In vitro single‐pass hemoperfusion tests using pooled donor blood showed quantitative adsorption of atherogenic LDL‐cholesterol (LDL‐C) and complete recovery of protective high‐density lipoprotein C. Fibrinogen, another independent risk factor of atherosclerosis, was also adsorbed to a lesser extent. Single‐pass ex vivo biocompatibility using fresh donor blood on‐line was excellent and resulted in minimal cell loss. Neither signs of hemolysis nor activation of monocytes (interleukin‐l production) were detected. Only slight activation of leukocytes (elastase release) and thrombocytes (platelet factor 4 secretion) as well as of coagulation (thrombin‐antithrombin complex formation) and complement (C3a, C5a generation) was observed. Under the experimental conditions used, the optimal anticoagulation regimen was 0.5 IU heparin plus 0.375 mg citratelml blood. Priming the column with a buffer of pH 7.4 containing heparin, citrate, and Ca2+ is recommended. In conclusion, this new adsorber exhibited selective LDLC adsorption in vitro combined with excellent ex vivo biocompatibility and thus holds great promise for a successful clinical application in a closed‐loop system in patients.

Multiple hemostatic changes occur in sepsis and multiple organ failure (MOF). To evaluate the role of platelets in patients with sepsis and MOF, we examined changes in surface glycoproteins on circulating platelets of 14 patients with suspected sepsis and MOF. The severity of sepsis and MOF was assessed by the Elebute and APACHE II scoring systems, respectively. Using flow cytometric techniques and platelet specific monoclonal antibodies, platelet surface expression of fibrinogen receptor on GPIIb-IIIa, of von Willebrand Factor receptor GPIb, and of granule glycoproteins (thrombospondin (TSP), GMP-140, GP53) was measured. Plasma membrane expression of GPIIb-IIIa and GPIb on circulating platelets was not affected by sepsis of MOF. Septic patients, however, showed a significantly elevated fibrinogen receptor activity (LIBS1 expression) (p < 0.05) that correlated with severity of disease (r = 0.597, p = 0.043). No significant change in surface expression of granule glycoproteins (TSP, GMP-140, GP53) was noted in septic patients. In contrast, degranulation of granule glycoproteins was significantly elevated in MOF (p < 0.05) which well with severity of MOF (GMP-140, r = 0.611, p = 0.013; TSP, r = 0.643, p = 0.026). We speculate that platelets in sepsis circulate in a hyperaggregable but still reversible state that results in increased risk of microthrombotic events. In the course of the disease, irreversible platelet degranulation of adhesion molecules occurs that may play an important role in the development of MOF.