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The term hemostasis refers to the critical physiologic response to arterial injury that serves to limit hemorrhage. Thrombosis, a pathologic process, results when the coagulation system is excessively activated in the absence of bleeding. The mechanisms that regulate these processes, as well as the mode of action of pharmacologic agents that attenuate thrombosis, are discussed.
The consequences of acute insults to the hemostatic system, whether congenital or acquired, frequently present a considerable challenge in diagnosis and therapy. Logical and effective management depends upon the proper identification of the hemostatic compartments involved; an appreciation for the considerably complex, delicately modulated interplays of various enzyme/inhibitor systems; and knowledge of the mechanism by which a variety of apparently unrelated disease processes precipitate sometimes catastrophic events--thrombosis/embolism/hemorrhage. We have attempted a logical review of basic mechanisms of hemostasis. The text is obligatorily brief, focusing on key elements of the biochemistry and physiology of the vessel wall, the platelet, and pertinent plasma factors. The section on plasma proteins pays particular attention to biocybernetic principles (positive/negative feedback loops) and to the interrelationship of enzyme systems involved in coagulation, fibrinolysis, kinin generation, and complement activation. No attempt was made to be encyclopedic. In the interest of brevity and clarity, the text has been limited to current concepts, with the reference material selected, whenever possible, in the form of review articles, volumes and monographs. We apologize for omissions. It is our belief that a working knowledge of basic mechanisms provides not only advantages in diagnostic/therapeutic management but also serves as a firm foundation for the development of novel diagnostic and therapeutic modalities.
Abstract. Abnormal hemostasis in dengue hemorrhagic fever includes:- 1. Vasculopathy which occurs during the early febrile to pre-shock and shock phase. The evidences support are: 1.1 Increased anaphylatoxin, released by complement activation causing leakage of intravascular fluid in to serous space. 1.2 Positive tourniquet test, some of which occur preceeding thrombocytopenia in the acute phase of DHF. 1.3 Excessive increased in PGI2 which is the most potent vasodilator and platelet aggregation inhibitor. 2. Platelets: 2.1 Thrombocytopenia due to 2.1.1 The bone marrow hypocellularity with increased in all forms of megakaryocytes but the vacuolated and disintegrated ones. 2.1.2 Destruction by the liver and spleen. 2.1.3 Immune-mediated injury as demonstration of dengue antibody complexes on the platelet surface. 2.1.4 The in vitro spontaneous aggregation to vascular endothelial cell pre-infected by dengue virus inducing platelet aggregation, causing lysis and platelet destruction. 2.2 Dysfunction shown by 2.2.1 Increased release of betathromboglobulin (BTG), PF4 and PGI2. 2.2.2 In vitro hypoaggregation stimulated by ADP and defect in ADP-releasing ability. 3. Coagulopathy including: 3.1 Prothrombin complex deficiency due to liver damage. 3.2 Consumptive coagulopathy due to the activation by mononuclear phagocytes, PF3 released from platelet aggregation. DIC is seen in prolonged shock cases of DSS.
Lipid peroxidation and some parameters of hemostasis were studied during exposure to various hyperoxia schemes combined with heparin therapy before and after treatment in 124 patients aged 16 to 69 with CNS involvement which developed as a result of atherosclerosis and essential hypertension, 60 of whom presented with initial manifestations of cerebral circulation insufficiency (IMCCI), 33 with posthypoxic encephalopathies (PE), and 31 with ischemic stroke (IS). Hyperoxia mechanisms were differently directed in the studied groups of patients, this necessitating a differentiated approach to the choice of schemes of hyperbaric oxygenation. Use of a short course of hyperbaric oxygenation (up to 3 sessions at 1.2 to 1.25 atA) is recommended for patients with IMCCI and PE. For patients with IS in the acute period hyperbaric oxygenation at 1.4 atA is advisable combined with heparin therapy in doses of 150 to 300 U/kg b.w. a day.
OBJECTIVE: The aim of the study was to improve the detection of small hemorrhages with minimal symptoms and of unruptured aneurysms after a subdural and subarachnoid bleeding by the control of the intravascular hemostatic system. DESIGN: Prospective, open study. SETTING: Neurosurgical intensive care unit of a university hospital. PATIENTS: 44 patients undergoing a cranial trepanation. Patients of group 1 (control n = 11) had an intrasellar hypophysoma, patients of group 2 (n = 12) a chronic subdural hematoma without a previous traumatic incident and patients of group 3 (n = 15) a subarachnoid hemorrhage caused by an intracranial aneurysm. INTERVENTIONS: After cranial trepanation changes of plasmatic hemostasis have been assessed by means of immunologically determined parameters of coagulation. The investigation included blood parameters (hemoglobin, hematocrit, thrombocytes), clotting status (prothrombin time, partial thromboplastin time, thrombin time, fibrinogen, plasminogen, antithrombin III [AT III] activity and proteinase inhibitors), as well as immunological methods such as fibrinopeptide A (FPA), thrombin-antithrombin III (TAT), protein C and factor XIII activity (F XIII activity). RESULTS: In comparison to group 1 (control) a significant difference (p < 0.001) was seen in groups 2 and 3 for thrombin-antithrombin III (TAT), fibrinopeptide A (FPA), protein C, and the antithrombin III activity. Intra- and postoperatively increased TAT levels in groups 2 (16.9 ng/ml) and 3 (21.1 ng/ml) and decreased protein C levels (group 2: 61% and group 3: 58%) demonstrated an intravascular thrombin generation. On account of the elevated FPA levels in groups 2 (6.5 ng/ml) and 3 (5.7 ng/ml) and decreased AT III activity in groups 2 (58%) and 3 (62%), this thrombin generation was only incompletely compensated. Caused by proteolytic thrombin effects, another sign for a thrombin-induced turnover of clotting factors is the significant reduction (p < 0.001) of F XIII activity in groups 2 (40%) and 3 (44%). In comparison to group 1 this significantly reduced F XIII activity in groups 2 and 3 was correlated (r = 0.99) to changes in FPA and TAT plasma levels, an indication of latent chronic clotting activity. No significant difference was found concerning total amount of infusion, intra- and postoperative blood loss and blood parameters. Eight patients (group 2: 5 patients, group 3: 3 patients) showed a rebleeding episode without operative interventions. In these patients increased clotting activity (TAT, FPA, protein C) caused by proteolytic thrombin effects was combined with a factor XIII activity smaller than 40%. CONCLUSION: The results of the recent study indicated that immunologically determined TAT, FPA, protein C, factor XIII and AT III activities might serve to improve management in patients with intracranial bleeding events. In view of these parameters the evaluation of risks for a rebleeding is improved. A decrease of the plasma factor XIII activity under 40% associated with a latent clotting activity induced by a thrombin generation caused a higher risk of rebleeding after an initial intracranial bleeding event. The necessity of substituting factor XIII in such cases should be elucidated to minimize risks of rebleeding.
Factor V and VIII activity was measured by a one-stage assay on capillary blood issuing from a skin cut. This activity increases during bleeding. The phenomenon is suppressed by a previous injection of a low dose of heparin. These data give evidence of a very early local formation of thrombin during hemostasis. The study of this activation process in patients with congenital deficiency of blood clotting factor allows to investigate the mechanism of thrombin formation in vivo. This demonstrates the preeminence of the tissue factor pathway and the need of factor VIII for factor X activation in the extrinsic system.
Scientific and Standardization Committee (SSC) of International Thrombosis and Hemostasis has acted its activity since 1955 for establishing international concept on terminology, methodology in the fields of blood platelets, coagulation and fibrinolysis. Among the reports from 15 sub-committee in 1993 meeting, some clinically interesting topics are reported. In von Willebrand factor (vWF) Subcommittee, new classification of von Willebrand disease including new variant of VFW which shows defect on factor VIII binding capacity, is proposed. In Control of Anticoagulation Subcommittee, the necessity of coagulation monitoring during low molecular weight heparin (LMWH) administration was discussed. For prophylaxis use, monitoring is unnecessary except patients having renal failure or high-low body weight. For the treatment of venous thrombosis once or twice monitoring every 10 days would be necessary. In Lupus anticoagulant (LA)/phospholipid dependent antibodies Subcommittee, results of 3rd international survey for LA sent to 38 laboratories in 16 countries including Japan were reported. Most laboratory used APTT and dRVVT simultaneously as screening tests. Sensitivity and specificity of confirmatory test for LA are compared; the best one was Staclot LA and the second was DVVT.
Treatment with recombinant human erythropoietin (rhEPO) for the anemia of end-stage renal disease has been associated with thrombotic complications. To detect prothrombotic changes in autologous blood donors given 500 U/kg rhEPO subcutaneously (twice weekly during a 3-week period), changes in variables of hemostasis and fibrinolysis and in blood rheology before and at the end of treatment were investigated. In 21 patients, platelet count increased from 272 +/- 55 x 10(9)/L to 313 +/- 55 x 10(9)/L (p < 0.05). Although activated partial thromboplastin time and protein C antigen decreased significantly during rhEPO treatment, these changes remained within normal ranges. No changes in the hemostatic variables prothrombin time, fibrinogen, factor V, von Willebrand factor antigen, antithrombin III activity, protein S antigen, and prothrombin fragments F 1 + 2 were found. Measurements of plasminogen activity, alpha 2-antiplasmin activity, tissue plasminogen activator, and plasminogen activator inhibitor-1, representing variables of fibrinolysis, were normal and constant during the study. In 5 patients no changes in red cell deformability and whole blood viscosity, corrected for differences in hematocrit, were observed. Plasma viscosity showed a slight but clinically not relevant increase in 4 out of 5 patients. The absence of evident (pro)thrombotc changes in this study confirms the safety of high-dose rhEPO therapy in autologous blood donors, who donate 2 units (i.e., 2 x 450 ml) of blood.
BACKGROUND: L-asparaginase (L-ase) affects the synthesis of several hemostatic factors, including the naturally occurring clotting inhibitors antithrombin III, protein C and S, and thromboembolic events are a well-recognized complication of the hypercoagulable state resulting from this treatment. Recently, in addition to the widely used E. Coli-derived L-ase, a new L-ase derived from Erwinia Carotovora has been introduced into clinical studies. This formulation seems to have lesser side-effects, but data on its effects on the hemostatic system are very limited. We report here the hemostatic changes observed in 10 adult patients with acute lymphoblastic leukemia (ALL) treated with Erwinia- or with E. Coli-derived L-ase. METHODS AND RESULTS: The decreases (percentages of basal level) of antithrombin III, protein C and plasminogen (functional assays) were similar in both groups of patients (about 50% of the basal value 6 or 8 days after starting L-ase) and so were the number of instances in which the level of these proteins fell below 70% of normal. On the contrary, the fibrinogen level (PT-derived method) was less severely decreased by Erwinia L-ase (34% of basal value for E. Coli L-ase versus 58% for Erwinia L-ase; P = 0.048) and there were more instances in which the fibrinogen level was less than 100 mg/dL than with E. Coli L-ase (40% versus 16%; P = 0.051). Thrombin-AT-III complexes (ELISA) showed similar pattern during both treatments. Two patients treated with Erwinia L-ase had moderate hyperglycemia, requiring insulin treatment but not L-ase discontinuation. No allergic reaction or pancreatitis was observed. A patient in the Erwinia L-ase-treated group developed deep venous thrombosis on day 7 after the start of L-ase and was treated with subcutaneous heparin (12,500 U x 2/day), with prompt improvement. CONCLUSION: This study shows that the two L-ase formulations have similar effects on hemostasis. Patients treated with Erwinia L-ase may develop thrombotic symptoms, as already reported for E. Coli-L-ase.
BACKGROUND: Dermal dendrocytes are a newly-recognized cell type in human skin. They express coagulation Factor XIIIa (FXIIIa), also known as fibrin stabilizing factor, and their number is increased in certain inflammatory dermatoses. Current dogma suggests that these recently described cells may represent a subset of antigen-presenting macrophages. The present study therefore was undertaken to examine further the phenotype and potential function of these novel cells. EXPERIMENTAL DESIGN: Conventional ultrastructure, single and dual label immunofluorescence and immunocytochemistry, confocal laser scanning microscopy, and immunoelectron microscopy were used to define structure and potential heterogeneity among dermal dendrocytes. Human neonatal foreskin organ culture exposed to mast cell secretagogues, inhibitors, and relevant recombinant cytokines (tumor necrosis factors alpha) was employed to gain insight into functional characteristics of FXIIIa expression. RESULTS: We found that dermal dendrocytes are phenotypically unique dermal cells, separate from conventional macrophages, with antigenic heterogeneity of FXIIIa and CD34 expression related to their microanatomical location in the dermis. Moreover, they express specialized membrane-matrix plaques that may stabilize their placement in various dermal strata. Finally, superficial subpopulations of dermal dendrocytes are closely-associated with mast cells and show enhanced FXIIIa expression in response to mast cell degranulation, an event that appears to result from liberation of mast cell tumor necrosis factor in the dendrocyte microenvironment. CONCLUSIONS: These new insights establish dermal dendrocytes as distinctive fixed skin cells with potential functional capacity for mast cell-dependent facilitation of fibrin cross-linking and matrix remodeling. These previously unrecognized phenotypic and functional characteristics of dermal dendrocytes therefore may be relevant to cellular interactions responsible for cutaneous wound healing and hemostasis.
A total of 80 patients aged 34 to 65 years who suffered from stage-II hypertensive disease were followed up. The selective beta-adrenoblocker tenolol was used alone. Platelet hemostasis, cyclic nucleotides, thromboxane-prostacyclin system and blood rheological properties were examined. Tenolol was found to have a pronounced antihypertensive effect in the patients and to be beneficial in correcting impaired blood rheological properties and platelet homeostasis. It is concluded that the baseline blood rheological properties and the status of the hemostatic system largely determine the natural history of hypertension and the efficacy of therapy.
Methods and results from the quality assurance program of the Atherosclerosis Risk in Communities (ARIC) Study regarding hemostasis variables are presented, following up previous reports in this journal on standardized procedures for blood collection and processing (7) and an organized plan for the performance of those procedures (8). Efforts were made to control for and assess all sources of variability, from venipuncture to laboratory analysis, including also local field center processing and sample shipping. The quality control program included (a) a standardized protocol for blood collection and processing; (b) training, certification, and annual recertification of field center personnel for blood collection and processing; (c) monitoring of fasting times, phlebotomy times, processing times, and shipping problems; (d) hemostatic laboratory internal quality control; (e) a replicate blood sample program; (f) an intraindividual variability study; and (g) continual monitoring of quality control and study participants' data. This paper focused on items (c), (d), and (e). Measures of variation, generally standard deviations and coefficients of variation, are estimated for replicate blood sampling and internal quality control data, for activated partial thromboplastin time, fibrinogen, factor VII and VIII activity, von Willebrand factor, antithrombin-III, and protein C. The results demonstrate that it is possible to reliably measure these hemostatic variables in a large multicenter study.
Human and bovine brain tissues were used as a model to study phasic pattern and dynamic properties of lipid and protein components of damaged biological membranes as well as the relationships of this process with initiation of hemostasis external pathway. It was established that thromboplastic reaction is initiated by factor VII contact with the surface of apoprotein III-containing membrane. Enhanced mobility of borderline lipids correlated with thromboplastic activation of the membrane. The study made use of 1H, 31P-NMR and the test system specifically sensitive to apoprotein III.
21 children who died from meningococcemia were studied. Shock disturbances of the microcirculation and thrombocytic part of hemostasis prevailed within first hours of the disease in the form of adrenal hemorrhages and brain edema as immediate cause of death. With an increase of the disease duration, aggregational thrombocytopenia, generalized microthrombosis, coagulopathy, fibrinolysis activation resulted in massive hemorrhages in a number of organs and tissues and manifested in the syndrome of polyorganic failure. No significant differences were found depending upon treatment.
The length of aortic cross clamp time and the difficult control of bleeding sites can represent two major problems during the Ross operation. Dissection of the pulmonary root before aortic cross clamping as well as reconstruction of the right ventricular outflow tract only after completion of the aortic anastomosis and removal of the cross clamp appear to facilitate accurate hemostasis, reducing in addition the time of myocardial ischemia.
A study of 126 patients with stenocardia receiving antianginal treatment was carried out with purpose of evaluating the effect of plasmapheresis on the clinical course of the disease, functional activity of thrombocytes, eicosanoids and lipid metabolism. It was shown that plasmapheresis improves the clinical condition of patients with ischemic heart disease, increases the tolerance to physical loads in patients with stenocardia. The mechanism of action of plasmapheresis is related to improvement of the lipid metabolism, system of eicosanoids, and thrombocytic link of hemostasis.
The effects of capoten on hemostasis were studied in 63 patients with Stages I and II hypertensive disease in relation to the hemodynamic type and severity of the disease. Thrombophilia was revealed just at the onset of the disease mainly due to hemostatic endothelial dysfunction which progresses with the hemodynamic development of hypertensive disease. Capoten optimizes hemostatic parameters by affecting endothelial function, which serves an additional mechanism of the antihypertensive effect of the drug. Supplementary techniques affecting the rheological properties should be used in the treatment of hypertensives with moderate-to-serve courses along with resistive hemodynamics.
Hemostasis was evaluated in cows with experimentally induced endotoxemia and mastitis, caused by intramammary infusion of endotoxin (1 mg) derived from Escherichia coli. Hemostatic tests included prothrombin time; activated partial thromboplastin time; thrombin time; fibrinogen, fibrin(ogen) degradation products, and platelet concentrations; and antithrombin-III and plasminogen activities. Significant alterations were observed in the mean values of most analytes (prothrombin time was increased; thrombin time was increased with subsequent decrease; activated partial thromboplastin time, fibrinogen concentration, plasminogen activity, and platelet concentration were decreased; and antithrombin-III activity and fibrin(ogen) degradation products concentration were unchanged) at 1 or more postchallenge sample collection times (3, 12, or 24 hours) after endotoxin administration, compared with mean values obtained from samples prior to endotoxin administration. These data indicated activation of hemostatic mechanisms, initiated either directly by endotoxin or by inflammatory mediators released or produced in response to endotoxin infusion.