Quantification of the effects of thrombin activatable fibrinolysis inhibitor and alpha2-antiplasmin on fibrinolysis in normal human plasma.

Two major proteins that inhibit fibrinolysis include thrombin activatable fibrinolysis inhibitor (TAFI) and alpha2-antiplasmin. Our goal was to quantify the contribution of TAFI and alpha2-antiplasmin to antifibrinolytic defenses with thrombelastography. Plasma activated with tissue factor/kaolin was subjected to fibrinolysis with tissue-type plasminogen activator (100 U/ml). Prior to activation, TAFI activity was inhibited with either potato carboxypeptidase inhibitor (25 microg/ml) or an anti-TAFI antibody, and alpha2-antiplasmin activity was inhibited with an anti-alpha2-antiplasmin antibody. Data were collected for 30 min, with the time of onset and rate of fibrinolysis determined. Compared with uninhibited samples, TAFI inhibition significantly (P < 0.05) decreased the time of onset of fibrinolysis by 70% and increased the rate of lysis by 70%. There was no difference between potato carboxypeptidase inhibitor and anti-TAFI antibody inhibition. Inhibition of alpha2-antiplasmin resulted in a significantly (P < 0.05) decreased time of onset (85%) and increased the rate of lysis (557%) compared with uninhibited samples. Inhibition of alpha2-antiplasmin activity resulted in a significantly (P < 0.05) greater fibrinolytic response than TAFI inhibition. In conclusion, utilization of standard inhibitors and thrombelastography permitted quantification of the effects of TAFI and alpha2-antiplasmin on fibrinolysis in plasma. Future investigation of diseases involving hypofibrinolysis (e.g. left ventricular assist devices) could be conducted using this assay system.     

Hemostasis and fibrinolysis in severe liver failure and their relation to hemorrhage

In a study of severe, decompensated liver failure, we tried to find a correlation between hemorrhage and parameters of hemostasis and fibrinolysis. Three groups of patients were studied: alcoholic cirrhosis; nonalcoholic cirrhosis, and acute liver failure without known prior liver disease. The two cirrhotic groups did not differ significantly from each other in coagulation or in fibrinolytic parameters, although liver function was more impaired in nonalcoholic cirrhosis. The levels of clotting factors, antithrombin III, prekallikrein, plasminogen and alpha 2-antiplasmin were significantly lower in the third group. Mean values of fibrinolytic activity (fibrin plate method) were slightly reduced as compared to normal in all three groups. Tissue plasminogen activator-related antigen tended to be elevated especially in alcoholic cirrhosis. The free fast-acting plasminogen activator inhibitor showed extremely high and extremely low levels in some patients among all three groups. Nonvariceal, capillary-type bleeding, including mucosal bleeding, hematomas and bleeding from puncture sites correlated with low thrombotest and normotest levels (p less than 0.01), low fibrinogen concentration (p less than 0.05) and with a high quotient of fibrinolytic activity (square root of lysis area) and normotest (p less than 0.001). The ratio between fibrin formation and dissolution appears to be an important parameter of hemorrhagic tendency in liver disease. Variceal bleeding appeared not to be related to impairment of hemostasis or fibrinolysis.     

The pathogenesis of accelerated fibrinolysis in hepatosplenic schistosomiasis.

Seventy patients with different stages of hepatosplenic schistosomiasis and 18 non-bilharzial normal controls were studied. Plasminogen, plasminogen activators (PA), tissue-type plasminogen activator (t-PA), urokinase-type plasminogen activator (u-PA), alpha 2-antiplasmin (alpha 2-AP), plasminogen activator inhibitor (PAI), fibrinogen/fibrin degradation products (FDP) and D-dimer were determined to elucidate the role of plasminogen activators and inhibitors in the pathogenesis of accelerated fibrinolysis in schistosomiasis. There was a progressive increase in the levels of PA, t-PA, u-PA, FDP and D-dimer indicating enhanced fibrinolytic activity with advancing disease. In addition, there was progressive decrease of plasminogen, alpha 2-AP and PAI levels which might be due to decreased hepatic synthesis and/or increased peripheral consumption. These findings suggest that the pathogenesis of accelerated fibrinolysis in schistosomiasis is multifactorial, but may be due to the progressive increase in the levels of plasminogen activators. In addition, the increase of FDP and D-dimer levels are evidence of secondary fibrinolysis following thrombin generation.     

Differential binding of plasminogen to crosslinked and noncrosslinked fibrins: its significance in hemostatic defect in factor XIII deficiency

In spontaneous fibrinolysis of an alpha 2-plasmin inhibitor-deficient plasma clot or tissue-type plasminogen activator-induced fibrinolysis in a purified system without alpha 2-plasmin inhibitor, the lysis was faster when factor XIII-mediated crosslinking of fibrin to fibrin did not occur. During the initial period, the binding of plasminogen to fibrin steadily increased with incubation time. The initial level and subsequent increase of the binding, which may be critical for the subsequent development of fibrinolysis, were more remarkable when fibrin was not crosslinked. The amount of glu- or lys-plasminogen bound to noncrosslinked fibrin was around 4 or 1.5 times larger than the amount of the respective plasminogen bound to crosslinked fibrin. Plasmin was also found to be bound to noncrosslinked fibrin twice as much as the amount bound to crosslinked fibrin. Structural changes induced by crosslinking of fibrin alpha-chain may reduce either the affinity or the number of available complementary sites to lysine binding sites of plasmin(ogen), thereby decreasing the binding of plasmin(ogen) to fibrin. These results suggest that an increased affinity of noncrosslinked fibrin for plasmin(ogen) is contributory to the accelerated fibrinolysis observed in factor XIII deficiency, in addition to an absence of crosslinking of alpha 2-plasmin inhibitor to fibrin.     

Thrombin-activatable fibrinolysis inhibitor deficiency in cirrhosis is not associated with increased plasma fibrinolysis.

BACKGROUND AND AIMS: The bleeding tendency of patients suffering from cirrhosis is in part ascribed to accelerated fibrinolysis. In this study, the role of the recently discovered inhibitor of fibrinolysis, thrombin-activatable fibrinolysis inhibitor (TAFI) in cirrhosis was examined. METHODS: In 64 patients with cirrhosis of varying severity, TAFI antigen levels were measured by enzyme-linked immunosorbent assay and compared with TAFI levels in control subjects. Furthermore, a plasma-based fibrinolysis assay was performed in the presence and absence of a specific inhibitor of activated TAFI. RESULTS: TAFI levels were decreased in cirrhosis. Mean TAFI levels were 66% in Child's A, 55% in Child's B, 47% in Child's C cirrhosis, and 26% in acute liver failure. Decreased TAFI antigen levels were highly correlated with antithrombin and alpha(2)-antiplasmin activity levels. Clot lysis times and clot lysis ratio (defined as ratio between clot lysis time in the absence and presence of a specific inhibitor of activated TAFI) of cirrhotics were not significantly different from healthy controls. CONCLUSIONS: Despite decreased levels of TAFI and other components of the fibrinolytic system, no evidence of increased plasma fibrinolytic potential in cirrhosis is observed using the plasma-based assay of this study. The reduction of antifibrinolytic factors in cirrhosis is compensated by the concomitant reduction in profibrinolytics.     

Fibrinolysis during liver transplantation in humans: role of tissue- type plasminogen activator

Human liver transplantation is frequently associated with a coagulopathy and bleeding diathesis developing during the anhepatic phase of surgery. The hemostatic defect has been attributed in part to accelerated fibrinolysis. In this study we evaluated changes in specific blood fibrinolytic parameters occurring in eight adult patients undergoing first-time orthotopic liver transplantation. Five of the eight patients experienced moderate to severe systemic fibrinolysis as reflected by alpha 2-antiplasmin consumption and fibrinogen degradation with the concomitant appearance of fibrin(ogen) degradation products. In association with these changes, an increase in tissue-type plasminogen activator (t-PA) activity and t-PA antigen levels was also observed. Fibrinolysis was most pronounced during the anhepatic phase of surgery and decreased after revascularization of the grafted liver. Three additional patients who underwent the same procedure manifested much less evidence of systemic fibrinolytic activation and had minimal elevation of t-PA antigen levels or activity. Urokinase-type plasminogen activator levels, although elevated in three patients, were disassociated from increased t-PA levels and concomitant systemic fibrinolysis. The operative course of those patients developing t-PA-associated fibrinolysis was characterized by shock, acidosis, generalized bleeding, and a need for substantially greater blood product support during surgery. These findings suggest that the observed fibrinolytic defect is related to increased circulating plasma levels of t-PA, presumably resulting from a combination of increased intravascular release and decreased hepatic clearance of t-PA. These observations may have implications for intraoperative therapy for the transplant-related coagulopathy and its associated bleeding.     

Synergistic fibrinolysis: combined effects of plasminogen activators and an antibody that inhibits alpha 2-antiplasmin.

To improve the efficacy of plasminogen activators, we produced a monoclonal antibody (RWR) that inhibits human alpha 2-antiplasmin (alpha 2AP). In addition to inhibiting alpha 2AP in plasma, RWR binds to and inhibits fibrin cross-linked alpha 2AP and reproduces the "spontaneous" clot lysis that is the hallmark of human alpha 2AP deficiency. By inhibiting the inactivation of plasmin by alpha 2AP, RWR interacts synergistically with plasminogen activators to increase the potency (for 50% clot lysis) of urokinase by 80-fold, tissue plasminogen activator by 27-fold, and streptokinase by 20-fold. Yet, for a given amount of fibrinolysis, the combination of RWR and lower doses of plasminogen activator leads to less fibrinogen consumption than is obtained with higher, equipotent doses of plasminogen activator alone. These results suggest a strategy for increasing the efficacy of plasminogen activators. More generally, this approach to amplifying enzymatic activity by immunoneutralizing an inhibitor may be useful in other biologic processes that are rigidly governed by inhibitors.     

Effective lysis of model thrombi by a t-PA mutant (A473S) that is resistant to alpha2-antiplasmin

This study used two mutants of tissue-type plasminogen activator (t-PA) with resistance to inhibitors of fibrinolysis to define the contribution of plasminogen activator inhibitor (PAI)-1 and alpha2-antiplasmin (alpha2-AP) to the control of fibrin lysis. Wild-type t-PA was compared with KHRR296-299AAAA, which is resistant to PAI-1, and with A473S, which is resistant to alpha2-AP. We examined these forms of t-PA in model systems that are physiologically relevant. Neutralization of alpha2-AP was essential for lysis of plasma clots, irrespective of their platelet content, by either wild-type t-PA or KHRR296-299AAAA. In marked contrast, A473S lysed plasma clots without neutralization of alpha2-AP. Model thrombi, with structures similar to in vivo thrombi, were lysed slowly by wild-type t-PA; the rate and extent of lysis were enhanced by the addition of antibodies to alpha2-AP or PAI-1. A473S was more effective than wild-type t-PA without the addition of antibodies by virtue of its resistance to alpha2-AP. This resistance was remarkable, in that no complex formed between A473S t-PA and alpha2-AP, even after extended incubation, when 50% of wild-type t-PA could be converted to complex. Comparison of A473S and KHRR296-299AAAA mutants showed their similar effectiveness in lysis of platelet-rich model thrombi. Thus, PAI-1 and alpha2-AP contribute approximately equally to the inhibition of thrombus lysis. This study underlines the functional significance of alpha2-AP as a direct inhibitor of t-PA and further explains the basis of the accepted role of alpha2-AP as a regulator of fibrin persistence and thrombus resistance to lysis.     

Excessive fibrinolysis in suspected amyloidosis: demonstration of plasmin-alpha 2-plasmin inhibitor complex and von Willebrand factor fragment in plasma

We performed a hemostatic evaluation in detail in a patient with suspected amyloidosis who was suffering from several bleeding episodes. He had a shortened euglobulin clot lysis time, decreased alpha 2-plasmin inhibitor (alpha 2-PI), decreased plasminogen, elevated tissue-type plasminogen activator (t-PA), elevated plasmin-alpha 2-PI complex, and decreased ratio of ristocetin cofactor to von Willebrand factor (vWF) antigen. Fibrinogen and fibrin/fibrinogen degradation products levels fluctuated, with abnormal values on several occasions. On crossed immunoelectrophoresis, plasmin-alpha 2-PI complex and vWF fragment were demonstrated in the patient plasma. These abnormal findings and bleeding symptoms improved following the administration of tranexamic acid. Discontinuation of tranexamic acid resulted in deterioration of these parameters. These observations indicate that pathologic fibrinolysis (continuous intravascular plasmin generation) characterized by the consumption of alpha 2-PI and plasminogen, formation of plasmin-alpha 2-PI complex, and fragmentation of vWF contributed to the bleeding in this patient. It is important to recognize excessive fibrinolysis as the underlying cause of bleeding in these patients, since specific treatment with antifibrinolytic agents is effective in controlling the bleeding.     

LACK OF EVIDENCE FOR ABNORMAL FIBRINOLYSIS IN CHRONIC LOW BACK PAIN

It has been reported that plasma fibrinolytic activity is abnormalin some patients with chronic low back pain. In an attempt toconfirm this finding we studied 22 patients with chronic mechanicallow back pain and compared them with 18 healthy controls whodenied symptoms of back pain. Factors known to interfere withplasma fibrinolysis such as age, weight, seasonal and diurnalvariation, exercise, smoking and drugs were controlled as faras possible. Plasma fibrinogen was significantly higher (2.8versus 2.3 g/l, P<0.005) in patients than in controls, butthere were no significant differences in the median plasma concentrationsof euglobulin clot lysis time, fibrin plate lysis area, plasminogen,-2-antiplasmin, tissue plasminogen activator activity, and antigen,tissue plasminogen activator inhibition and plasminogen activatorinhibitor-1 antigen level. The results fail to confirm abnormalitiesof plasma fibrinolytic activity in a group of unselected casesof chronic low back pain. KEY WORDS: Impaired fibrinolysis, Backache     

Severity of coronary artery disease and basal fibrinolysis

Basal venous blood levels of several components of the fibrinolytic enzyme system (plasminogen activator, plasminogen, fibrin degradation products, alpha 2-antiplasmin, and alpha 2-macroglobulin) were measured in 100 white men with angiographically defined coronary artery disease. The tests of fibrinolysis were not related to the severity of coronary artery disease, as indicated either by the number of vessels involved or by a coronary score system. Fibrinogen levels, however, did show a modest association with the extent of coronary atheroma (r = 0.21, p less than 0.05). Triglyceride levels were associated with the inhibitors of fibrinolysis: positively with alpha 2-antiplasmin (r = 0.31, p less than 0.005) and negatively with alpha 2-macroglobulin (r = -0.25, p less than 0.05). The alpha 2-antiplasmin levels were significantly elevated in patients with hypertriglyceridaemia. Neither smoking nor beta-blockade had any effect on the tests of fibrinolysis. This study adds support to the association of plasma fibrinogen with ischaemic heart disease.     

The primary plasminogen-activator inhibitors in endothelial cells, platelets, serum, and plasma are immunologically related.

Monospecific antiserum to an unusually stable Mr 50,000 plasminogen-activator inhibitor (PAI) purified from cultured bovine aortic endothelial cells was employed in conjunction with reverse fibrin autography to determine whether human platelets, serum, and plasma contain immunologically related inhibitors. Reverse fibrin autography revealed the presence of a Mr 50,000 inhibitor in the platelet and serum samples but not in normal plasma. However, a Mr 50,000 inhibitor was detected in plasma obtained from individuals with increased PAI activity. In each case, treatment of the sample with the anti-inhibitor serum removed the Mr 50,000 inhibitor. The inhibitor present in each sample neutralized exogenously added tissue-type plasminogen activator in a rapid manner. Inhibition was associated with the formation of a NaDodSO4-resistant enzyme-inhibitor complex of Mr 120,000. Again, treatment of the samples with the anti-inhibitor serum removed both the inhibitory activity and the component in these samples that binds to tissue-type plasminogen activator. Thus, the rapidly acting PAI present in human platelets, serum, and patient plasma is immunologically related to the PAI synthesized by cultured bovine aortic endothelial cells. This molecule may be the physiologically relevant inhibitor of plasminogen activator in the vascular system and, as such, may serve an important role in regulating the initiation of vascular fibrinolysis.     

Inhibition of clot-bound alpha 2-antiplasmin enhances in vivo thrombolysis.

Recent experiments in vitro have shown that inhibition of human alpha 2-antiplasmin by a monoclonal antibody (MAb RWR) markedly enhances clot lysis by plasminogen activators. To extend these studies in vivo, we tested whether inhibition of clot or fibrin-bound alpha 2-antiplasmin by MAb RWR could enhance the lysis of a human clot by tissue-type plasminogen activator (t-PA) in a rabbit jugular vein thrombosis model. Compared with a saline placebo or a control antibody, MAb RWR significantly increased thrombolysis by endogenous plasminogen activator in rabbits to which no t-PA was administered (p less than 0.05). In rabbits that received t-PA, the combination of MAb RWR and t-PA caused significantly greater thrombolysis than equivalent doses of t-PA alone (p less than 0.05). However, compared with equipotent doses of t-PA alone, the combination of MAb RWR and t-PA did not increase the nonspecific consumption of fibrinogen. These experiments suggest that the combination of an alpha 2-antiplasmin inhibitor and a plasminogen activator could be a more potent thrombolytic strategy.     

Plasma inhibitor of glomerular fibrinolysis in the hemolytic-uremic syndrome

To detect an inhibitor of glomerular fibrinolysis, dilutions of human plasma were incubated on microscope slides with two frozen sections of normal human kidney. The slides were studied by the fibrin slide technique. The lysis inhibitory titer was defined as the highest dilution completely inhibiting glomerular fibrinolysis. Of 27 children without renal disease, none had a lysis inhibitory titer greater than 1:2. Defining an elevated lysis inhibitory titer as 1:8 or greater, we found an elevated lysis inhibitory titer in plasma from all 17 children with hemolytic-uremic syndrome. No correlation was found between the lysis inhibitory titer and the hematocrit, white blood cell or platelet counts, serum creatinine level, or levels of the antiplasmins alpha 1-antitrypsin, alpha 2-macroglobulin, C1-esterase inhibitor, or alpha 2-antiplasmin. The inhibitor was found to have a molecular weight of less than 12,000. A close correlation was discovered between the duration of lysis inhibitory titer elevation and the clinical course; removal of the inhibitor from the plasma by peritoneal dialysis was associated with improvement in renal function. Results suggest that the inhibitor may play an important role in the pathogenesis and persistence of glomerular fibrin deposition.     

Progress of fibrinolysis during tumor necrosis factor infusions in humans. Concomitant increase in tissue-type plasminogen activator, plasminogen activator inhibitor type-1, and fibrin(ogen) degradation products.

Several investigators have reported that tumor necrosis factor (TNF) can alter the production of plasminogen activator type-1 (PAI-1) and plasminogen activators (PAs) by endothelial cells in vitro. We have examined the in vivo effects of recombinant human TNF administration on fibrinolysis as assessed by parameters in plasma during a 24-hour period of continuous TNF infusion to 17 cancer patients with active disease. The plasma levels of PAI activity increased sevenfold after 3 and 24 hours of TNF infusion. This was the result of an increase of PAI-1 antigen; PAI-2 antigen was not detectable. Plasma concentrations of tissue-type PA (t-PA) antigen increased twofold to fivefold after 3 and 24 hours of TNF infusion, whereas urokinase-type PA antigen levels in plasma remained unaltered. After 3 hours of TNF infusion the plasma levels of alpha 2-antiplasmin were slightly decreased, 5% on average, suggesting that fibrinolysis continued. After 24 hours of TNF infusion a highly significant increase in fibrin- plus fibrinogen-degradation products, and separately of fibrin degradation products and fibrinogen degradation products, was found. This indicates that fibrinolysis persisted, at least partly, in the presence of high levels of PAI activity. Whereas PAI-1 production increased, t-PA production by human endothelial cells in vitro remains unaltered or even decreases on TNF addition. It has been shown previously that TNF infusion in our patients results in thrombin and fibrin generation. Therefore, it is possible that thrombin, not TNF, is the actual stimulus for t-PA production in our patients. We speculate that fibrin is formed during TNF infusions and that plasmin is generated by t-PA action immediately on the initial formation of (soluble) fibrin molecules. Such a process may explain the generation of degradation products of both fibrin and fibrinogen during infusion of TNF in patients.     

Decreased contact factor mediated fibrinolysis in cirrhosis

Summary. We studied extrinsic and intrinsic fibrinolysis in 20 patients with cirrhosis (nine mild/moderate, group 1:11 severe, group 2) and 19 normal controls to define the role of intrinsic (contact factor mediated) fibrinolysis in cirrhosis.
Global plasma fibrinolytic activity (fibrin plate lysis) was similar in all groups. Dextran sulphate activated contact factor mediated fibrinolysis was decreased in group 2 (median 95.2%) compared with group 1 (121.0%) and controls (131.7%). Tissue plasminogen activator antigen (t-PA Ag) levels were increased in group 2 (28.2 ng/ml) compared both with group 1(8.5 ng/ml) and controls (5.9 ng/ml). Plasma t-PA activity was raised in group 2 (5.50 IU/ml) and group 1 (5.25 IU/ml) versus controls (0.82 IU/ml). Plasminogen activator inhibitor-1 (PAI-1 Ag) levels were raised in group 2 (28.0 IU/ml) versus controls (8.5 IU/ml) but PA1 activity was similar in all groups. Factor XII activity was decreased in group 2 (48.76 u/dl), but not group 1. versus controls (89.1 u/dl). Prekallikrein activity was decreased both in group 2 (27.27 u/dl) and group 1 (33.01 u/dl) versus controls (108.59 u/dl) and was lower in group 2 than group 1. C1-esterase inhibitor chromogenic activity was decreased in group 1 (102.30 u/dl) and group 2 (58.76 u/dl) versus controls (116.24 u/dl).
The normal global fibrinolytic activity despite increased t-PA activity may be due to a concomitant increase in PAI. The decreased intrinsic fibrinolysis in severe cirrhosis, unaccompanied by a rise in C1-esterase inhibitor, may be explained by the decreased factor XII and prekallikrein activity. These changes are probably due to reduced liver cell mass.     

Hemostasis associated with abnormalities of fibrinolysis

Hemostatic plugs consist of platelet aggregates and fibrin mesh containing blood cells and plasma components. Hemostatic efficiency depends on the rate of formation of hemostatic plugs as well as the structural integrity and stability of the formed hemostatic plugs. Fibrin elements are major constituents contributing to the structural integrity and stability, but they are subject to fibrinolytic activity occurring spontaneously after fibrin formation. Fibrinolysis is usually suppressed by endogenous inhibitors. Increase of a profibrinolytic component or deficiency of an inhibitor would result in an accelerated fibrinolysis, causing a premature lysis of hemostatic plugs before restoration of injured vessels, leading to a hemorrhagic tendency. Such a state can be seen typically in patients with congenital deficiency of alpha 2-plasmin inhibitor or a hereditary increase of plasminogen activator, and it is also seen in acquired situations such as amyloidosis, liver cirrhosis, disseminated intravascular coagulation (particularly in patients with acute promyelocytic leukemia) and thrombolytic therapy. The hemorrhagic tendency can be well controlled by an administration of an antifibrinolytic agent: epsilon-aminocaproic acid or tranexamic acid. In contrast to an accelerated fibrinolysis causing a hemorrhagic tendency, retarded fibrinolysis may predispose an individual to a thrombotic tendency. Retarded fibrinolysis may be due to either an increase in plasminogen activator inhibitors or decrease of plasminogen activators. Quantitative or qualitative deficiency of plasminogen may also lead to a thrombotic tendency.     

Profound imbalance of pro-fibrinolytic and anti-fibrinolytic factors (tissue plasminogen activator and plasminogen activator inhibitor type 1) and severe bleeding diathesis in a patient with cirrhosis: correction by liver transplantation.

A 49-year-old male with alcoholic cirrhosis suffered several spontaneous, life-threatening, deep muscle bleeding episodes. Laboratory evaluation indicated excessive fibrinolysis with low plasminogen, low alpha2-antiplasmin, undetectable plasminogen activator inhibitor type 1 (PAI-1) activity, high tissue plasminogen activator (t-PA) activity and high t-PA antigen. Treatment with oral anti-fibrinolytic agents prevented further bleeding episodes. Decompensated cirrhosis eventually necessitated orthotopic liver transplantation. Post-operatively, the patient did not require oral anti-fibrinolytic agents, and there were no significant bleeding events. Circulating PAI-1 activity, t-PA activity and antigen normalized by 3 months post transplant. In short, the profound bleeding diathesis, as well as the imbalance in t-PA and PAI-1 levels, corrected after liver transplantation. Recognition of such patients is important, because the bleeding diathesis is an indication rather than a contraindication for orthotopic liver transplantation.     

Hydroxyethyl starch enhances fibrinolysis in human plasma by diminishing alpha2-antiplasmin-plasmin interactions.

Hydroxyethyl starch (HES) solutions are effective volume expanders but are also associated with poorly understood coagulopathy. Enhanced fibrinolysis following dilution with HES has been demonstrated. This investigation sought to identify the interactions of HES with critical fibrinolytic/antifibrinolytic enzymes. Normal plasma or plasmas deficient in factor XIII, thrombin activatable fibrinolysis inhibitor or alpha2-antiplasmin were either not diluted or were diluted 20% with 0.9% NaCl, 5% human albumin, high-molecular-weight HES (HES 450) or low-molecular-weight HES (HES 130). Plasma was activated with celite and exposed to 75 IU/ml tissue-type plasminogen activator. Coagulation growth/disintegration kinetics were determined with thrombelastography. Compared with undiluted plasma, diluted plasma had a significant decrease in the clot lysis time and the time to maximum rate of lysis in all plasma types except in alpha2-antiplasmin-deficient plasma. The hierarchy of the decrease in clot lysis time and time to maximum rate of lysis was HES 450 = HES 130 > 5% human albumin = 0.9% NaCl. In conclusion, HES dilution enhances fibrinolysis by diminishing alpha2-antiplasmin-plasmin interactions. Further laboratory and clinical investigation is warranted to better define the mechanisms by which HES enhances clot disintegration and to find new therapeutic roles for HES to either prevent or treat thrombosis.     

Plasma alpha 2-antiplasmin activity. Role in the evaluation and management of fibrinolytic states and other bleeding disorders

To determine the clinical significance of acquired alpha 2-antiplasmin deficiency in patients with bleeding disorders, I reviewed the results of assays performed on 184 patients over a 4-year period. Thirty-two evaluable patients had alpha 2-antiplasmin activity levels of less than 50% of normal (defined as severe deficiency), and 35 patients had levels between 50% and 75% of normal (mild deficiency). Records of these patients and of 32 patients who had normal levels were reviewed. Most patients with severe alpha 2-antiplasmin deficiency had either liver disease or disseminated intravascular coagulation and/or fibrinolysis, or both. There was a high incidence of severe alpha 2-antiplasmin deficiency among patients with acute promyelocytic leukemia. Five patients with pathologic bleeding had no identifiable coagulation abnormalities other than alpha 2-antiplasmin deficiency. The group with severe alpha 2-antiplasmin deficiency had a significantly higher incidence of life-threatening or fatal bleeding and the most striking laboratory evidence of hyperfibrinolysis. Using the presence of severe alpha 2-antiplasmin deficiency as an indication for therapy, epsilon-aminocaproic acid treatment was associated with cessation of life-threatening bleeding in 8 of 11 patients.