Search

HISTORY AND CLINICAL FINDINGS A 58-year-old man was admitted after he was found to have a huge aneurysm of the thoracic aorta. 38 months previously he had first experienced subacute pain in the right thorax. After this the aneurysm gradually increased in size. On admission a pulsating mass, 20 cm in diameter, was obvious, having broken through the right ventral thoracic wall. It was causing venous inflow congestion in the upper part of the body. The patient's general condition was poor: he had marked orthopnoea. INVESTIGATIONS Serological tests for syphilis gave the following results: VDRL test, 1:32; FTA-ABS test reactive; TPHA test, 1:8000; treponema-specific IgM negative. Computed tomography with contrast-medium injection exactly defined site and extent of the aneurysm. It started at the aortic root and extended to the aortic arch. Third-degree aortic valvar regurgitation was demonstrated on echocardiography. Pulmonary function tests indicated severe restrictive ventilatory abnormality with clearly reduced respiratory reserve. TREATMENT AND COURSE The symptoms improved after 2 weeks on oral medication of captopril (25 mg/d), furosemide (80 mg/d), spironolactone (100 mg/d), codeine phosphate (90 mg/d) and thick paraffin (20 mg/d as needed). The patient declined further treatment. He died 8 weeks later at home.

Background: The access site used for platelet sampling has been suggested to be an important variable for clinical flowcytometric platelet analysis. In this study, we have evaluated the influence of different blood sampling sites (16 G central venous catheter, 20 G radial artery cannula, 16 G peripheral venous cannula and 19 G hypodermic needle) on platelet activation and aggregation. Material and Methods: Blood samples were collected from 17 adult patients undergoing abdominal surgery who did not have any medication known to alter platelet function. All samples were taken and measured by the same investigator after catheter placement and 2 h later. Surface expression of the glycoprotein IIb/IIIa (CD41), the platelet activation marker P-selectin (CD62P), and the percentage of platelet-leukocyte complexes (CD45+/CD41+) were measured by flow cytometry. Results: Regarding the site of blood sampling, there were no significant differences in the expression of CD41, CD62P and plateletleukocyte complexes. Repeated failure to place a central vein catheter or an arterial cannula resulted in increased platelet activation which was not detectable anymore 2 h later. Conclusion: Besides withdrawal by hypodermic needles (blood sample taken without stasis), samples for flowcytometric platelet function tests could also be taken from arterial cannulae, central venous catheters, and peripheral venous cannulae. Repeated failure of central venous or arterial puncture should be avoided since it results in transient platelet activation.

Objective: Exposure of platelets to anaesthetic agents may alter their functional characteristics and in patients undergoing surgery or long-term sedation this may be clinically relevant. We investigated the influence of thiopentone and propofol on the expression of platelet membrane P-selectin, fibrinogen receptor, and leukocyte-platelet aggregates ex vivo. Methods: In patients undergoing surgery blood samples were taken from a peripheral vein cannula before induction of anaesthesia with propofol (3.0 mg kg -1 BW) or thiopentone (7.0 mg kg -1 BW) and five minutes later (n = 11 in each group). Surface expression of the fibrinogen receptor complex (GP Ib/IIIa), P-selectin, and the percentage of leukocyte-platelet aggregates were measured by flow cytometry after stimulation via the ADP or thrombin receptor pathway. Results: There was no significant difference in the expression of gpIIb/IIIa, P-selectin, and percentage of leukocyte-platelet aggregates in the thiopentone and propofol group after induction of anaesthesia. Conclusions: In clinically relevant concentrations thiopentone and propofol did not influence the surface expression density of fibrinogen receptors, P-selectin molecules, and the percentage of leukocyte-platelet aggregates ex vivo.

Severe haemophilia is a serious, haemorrhagic disorder of the plasmatic coagulation system. In this study we investigated, whether 'compensatory' activation of the platelet coagulation system occurs in this situation. Platelet function was investigated with aggregation, adhesion and flow cytometric assays. In addition, we performed clot and platelet plug formation tests and determined endogenous thrombin potentials in patients with severe haemophilia A or B; results were compared to those of healthy controls. Platelet aggregation in response to stimulation with ADP, ristocetin and epinephrine was similar in patients and controls; aggregation in response to collagen was reduced significantly in haemophiliacs. Flow cytometric analysis of P-selectin (CD 62P) and CD 63, of the conformationally changed GP IIb/IIIa with PAC 1 and of thrombospondin bound to CD 36 (GP IV) was performed at baseline and post stimulation. Baseline expression of all markers was similar in haemophiliacs and controls. After stimulation of the platelet thrombin receptors with the thrombin receptor activating peptide (TRAP) 6, the surface expression of all markers increased significantly; again, the expression was similar in haemophiliacs and controls. With thrombelastography and PFA 100 analysis, clot formation under low shear and platelet plug formation under high shear is measured. Both test results revealed a significantly reduced clot and platelet plug formation capacity in severe haemophiliacs. Our results did not reveal signs of enhanced platelet preactivation in haemophiliacs, indicating that baseline platelet reactivity in severe haemophilia remains in a neutral state, despite the severely haemorrhagic condition. As expected, both thrombin and clot formation capacities were impaired significantly in severe haemophilia. The reduced response to collagen-based platelet stimulation tests is indicative of a concomitant platelet function defect. This defect probably contributes to the intensity of bleeding events in patients with severe haemophilia.

Pregnancy (including puerperium) is a period of hypercoagulability and seems to be an independent major risk factor for venous thromboembolism (VTE). However, the basis of the increased risk of VTE in pregnancy and around delivery is unknown. We hypothesized that changes in PRL, which is a prominently increased hormone during pregnancy and lactation, might be involved in the activation of platelets. To investigate platelet functional abnormalities in pregnancy, we assessed the ADP-stimulated and nonstimulated P-selectin expression of platelets in 42 consecutive pregnant women, 22 normo- and hyperprolactinemic patients with pituitary tumors, and controls. In addition, the aggregation of platelets by human PRL in vitro was studied. We found a significant correlation between PRL values and ADP stimulation of platelets in pregnant women (r = 0.56; P < 0.0001) and patients with pituitary tumors (r = 0.57; P = 0.006). Hyperprolactinemic pregnant women or hyperprolactinemic patients with pituitary tumors revealed significantly higher ADP stimulation of platelets (P < 0.0001) than healthy controls or normoprolactinemic patients with pituitary tumors. These results were reconciled by increased in vitro stimulation and aggregation of platelets using human PRL. Our novel findings demonstrate that hyperprolactinemia causes increased platelet aggregation via ADP stimulation both in vitro and in vivo. Moreover, our data indicate that PRL may be a physiological cofactor of the delicate coagulation balance during pregnancy and puerperium that might explain the increased risk of VTE in pregnant women around delivery. Further studies of the interaction between PRL and platelets will clarify the clinical relevance of hyperprolactinemia as a potential risk factor for VTE.

HISTORY AND ADMISSION FINDINGS A 27-year-old woman presented with increased bleeding tendency and known oculocutaneous albinism. In addition to frequent nasal and gingival bleedings she had since childhood spontaneous extensive cutaneous bleedings. In addition she was extreme sensitive to UV light with visual disturbances. Bone-marrow biopsy when aged 9 years had revealed abnormal pigment-storing cells. Physical examination showed a very fair skin and hair, spontaneous nystagmus and extensive rash in the face. INVESTIGATIONS Prothrombin, partial thromboplastin and thrombin times as well as fibrinogen level were normal. On re- admission bleeding time varied greatly, while platelet count was normal. Mean platelet volume was slightly reduced. Von Willebrand antigen, factor VIII:C, factor IX:C, factor XIII and alpha (2)-antiplasmin were all normal. Aggregometry indicated abnormal platelet function; there was reduced platelet aggregation after stimulation with adenosine diphosphate. Flow cytometry of whole blood demonstrated abnormal storage function of thrombocytic delta-granules. The underlying cause of the described symptoms was shown to be a gene defect in typical location on the long arm of chromosome 10. DIAGNOSIS AND TREATMENT The triad of tyrosinase-positive oculocutaneous albinism, abnormal thrombocytic delta-granules and ceroid deposition in the cells of the reticuloendothelial system or the bone-marrow is called Hermansky-Pudlak syndrome (after those who first reported it). There is as yet no causal treatment. But the patient was advised to use a nasal spray of desmopressin for spontaneous or difficult to stop bleedings after minor injuries. Desmopressin i. v. should be given prophylactically before any operation.

OBJECTIVE In a prospective study surface antigens associated with platelet activation, aggregation, and adhesion and the platelet volume were measured to investigate the mechanism of the platelet function defect of cardiopulmonary bypass (CPB). METHODS Blood samples were obtained during cardiac surgery before and after heparinization, as well as during and following extracorporeal circulation. The expression of the platelet surface glycoproteins (GP) IIb-IIIa, Ib, 53, and the granule membrane protein (GMP) 140 were measured using flow cytometry in platelet-rich plasma (PRP) before and after in vitro stimulation with adenosine diphosphate. A full blood count including mean platelet volume (MPV) was taken. RESULTS Heparinization resulted in a significant increase of GP 53 and GMP 140 and a significant decrease of GP Ib expression. During and following CPB, GP IIb-IIIa and Ib were significantly decreased. Similarly, the expression of the activation markers was reduced significantly. The mean platelet volume decreased significantly from 8.6 +/- 0.7 fl at baseline to 7.9 +/- 0.8 fl at the end of the study period. CONCLUSION Our data suggest that heparinization induces platelet activation. We assume that a loss of larger and more activated platelets from the circulation contributes substantially to the platelet function defect of CPB.

Prolactin is a newly recognized platelet coactivator that functions through potentiation of ADP-induced platelet activation. However, the possible association between hyperprolactinemia and venous thromboembolism (VTE) has not been systematically investigated up to now; prolactin signaling mechanisms in platelets still need to be elucidated. In this study, plasma prolactin levels in healthy subjects and patients with VTE were determined, demonstrating that patients with VTE and no other congenital risk factors had significantly increased plasma prolactin levels. Moreover, prolactinoma patients demonstrated a higher incidence of VTE than the general population. To elucidate the molecular mechanisms for the development of venous thrombosis, prolactin receptor signaling during platelet activation was investigated with a focus on ADP-stimulated G-protein-regulated signaling pathways. The short isoform of prolactin receptors was detected on platelets. Signaling through this receptor, although not directly linked to Gq-proteins, substitutes for Gq-protein regulated signaling pathways involved in platelet activation. We identified protein kinase C, a well-established signaling molecule in platelet activation, as a target molecule for prolactin signaling pathways in human platelets. Our findings indicate that hyperprolactinemia may be an important novel risk factor for VTE, suggesting that its thrombogenic effect may be mediated through enhanced platelet reactivity. Revealing the molecular mechanisms of prolactin signaling will allow the design of new antithrombotic therapies.

Recently, elevated levels of the coagulation factors IX and XI as risk factors for venous thrombosis were described by Bertina and Rosendaal (1). Increased levels are associated with a two- to threefold increased risk of venous thrombosis. Reports from several groups indicate that the prevalence of elevated levels in the normal population is about 10% (2). In patients with a first episode of venous thrombosis the prevalence is about 20%. However, the risk of venous thrombosis in connection with elevated F IX and F XI is also age-dependent. Comparable with deficiencies of protein C or protein S, the prevalence is relatively high, which seems to be similar to the prevalence of the well-known APC resistance caused by F V Leiden. Furthermore, a correlation between the levels of coagulation factors and the relative risk of thrombosis has been shown (3). Compared with the risk shown in connection with elevated factor VIII:C, existence of an analogous relation between risk and single factor activity is suggested for the newly described risk factors IX and XI. Data on the association of elevated coagulation factors and arterial occlusions, especially in patients who had strokes, are rare. Only the ARIC study (Arteriosclerosis Risk in Communities) investigated the association between hemostatic variables like F VIII:C, von Willebrand factor and fibrinogen and stroke (4, 5).

Wiskott-Aldrich syndrome (WAS) is an inherited X-linked disorder caused by mutations of the WAS protein (WASP) gene. Within a family of similar proteins, WASP is responsible for signal transduction from the cellular membrane to actin cytoskeleton. Impaired regulation of actin polymerization in hematopoietic progenitor cells due to altered WASP has been shown to cause the pathophysiology of WAS. Clinical features of WAS are severe disease of platelets (small size, thrombocytopenia, reduced function), of lymphocytes (immunodeficiency) and eczema(1,2,3,5,7). X-linked thrombocytopenia is considered to be a mild form of WAS with isolated thrombocytopenia(2). Prognosis depends on bleeding and immunological complications(1). Stem cell transplantation is nowadays the only successful therapy. The development of gene therapy will be a new therapeutic option, depending on future techniques(6,7).

Patients with severe forms of von Willebrand disease (vWD) most frequently require substitution of both factor VIII and von Willebrand factor (vWF). Immunate is a high-purity, double-virus inactivated FVIII/vWF concentrate derived from human plasma. The clinical efficacy of Immunate concerning the management of acute bleeding episodes and surgical prophylaxis in patients with von Willebrand disease (vWD) is being investigated and documented in a prospective, phase III, open-label, single-armed multicenter trial. Data on its pharmacokinetics are collected, and the product's safety with respect to adverse experiences is monitored.

SummaryAprotinin reduces blood loss following cardiopulmonary bypass operations (CPB) by the prevention of hyperfibrinolysis. Its influence on circulating platelets is uncertain. In this prospective trial we investigated activation, adhesion, and aggregation receptors on the platelet surface in 20 patients who underwent elective coronary artery bypass grafting. These patients were randomly assigned to receive either a high dose of aprotinin or placebo. Flow cytometry was performed to determine platelet activation [P-selectin, glycoprotein (GP) 53], adhesive (GP Ib), and aggregatory (GP IIb-IIIa) receptors on circulating platelets, before, during, and after CPB. Aprotinin had neither a significant effect on platelet activation nor on adhesive and aggregatory receptors. Plasma levels of D-dimers were measured before and after CPB to assess fibrinolytic activity. D-dimers following CPB and chest tube drainage were significantly less in the aprotinin group. We conclude that aprotinin reduces blood loss by its effect on fibrinolysis but has no direct influence on platelet function.