Fibrin degradation products in pre-eclamptic toxaemia and eclampsia

Biosensing of D-dimer, making the transition from the central hospital laboratory to bedside determination

Since the disclosure of the fibrinogen degradation mechanism, around half a century ago, a significant number of papers have been published related to the clinical relevance of D-dimer, a molecule immune to additional enzymatic decomposition by plasmin. Due to the obliquity of regulating blood coagulation in pathological events, the number of diseases and conditions associated with abnormal levels of D-dimer includes deep vein thrombosis, pulmonary embolism, sepsis, myocardial infarction, disseminated intravascular coagulation, among many others. D-dimer not only is an important player in medical diagnosis but also its role as a prognosis biomarker is being revealed. However, the number of analytical alternative methods has not accompanied this trend, even though novel simple point-of-care devices would certainly boost the relevance of D-dimer in emergency medicine. Some reasons for that could be related to the fact that D-dimer is a challenging analyte present in complex samples like blood. In this manuscript, subsequent to a fibrinogen degradation process introduction, it is provided a historical overview of the early D-dimer assays, followed by an extended focus on innovative solutions, with a spotlight on the electrochemical bioanalytical devices. The discussion is accompanied with a critical analysis and concluding thoughts concerning future perspectives.

Intravascular coagulation in gestational hypertension and pre-eclampsia: the value of haematological screening tests

Routine investigations designed to detect excessive intravascular coagulation in patients with gestational hypertension and pre-eclampsia have been analysed in 936 cases. Reticulocyte counts did not differ significantly from those in normal controls and abnormal red cell morphology was detected in only two patients. Fibrinogen degradation products and thrombocytopenia were found in about 10% of all hypertensive women and macrothrombocytosis in 32%. Neither reticulocyte counts nor the scanning of stained blood films for evidence of microangiopathic haemolysis have a place in the routine investigation of pre-eclampsia and it is doubtful whether any of the other screening tests can influence the management of patients with uncomplicated gestational hypertension. In fully developed pre-eclampsia, macrothrombocytosis is found in about 50% of patients, fibrinogen degradation products and thrombocytopenia in about 15%. All three parameters reflect the degree of clinical severity of the disease.

Laboratory findings in hypertensive disorders of pregnancy

This study sought to determine whether a normal platelet count is a reliable predictor of the absence of other coagulation abnormalities in patients with a hypertensive disorder of pregnancy. A retrospective review of laboratory data obtained from 80 patients with hypertensive disorders of pregnancy was carried out. Results of complete blood cell count, prothrombin time (PT), partial thromboplastin time (PTT), D-dimer, fibrin split products, and fibrinogen, bilirubin, and liver enzyme levels were reviewed. Minor abnormalities of PT, PTT, and fibrinogen level were frequent, even in the presence of a normal platelet count. These were found mostly in patients with severe pre-eclampsia. A baseline complete blood cell count including platelet count is probably sufficient in patients with a hypertensive disorder of pregnancy. Fibrinogen level and PT and PTT determinations are recommended in patients who have severe preeclampsia and for whom operative delivery or regional anesthesia is planned. This will detect minor abnormalities in a few patients despite a normal platelet count. This information may help prevent bleeding complications.

Inhibition of the tissue factor-factor VII complex: involvement of factor Xa and lipoproteins

Inhibition of the procoagulant activity of a tissue factor-Factor VII (TF-FVII) complex by Al(OH)3-adsorbed plasma (AP) was found to require the presence of Factor Xa (FXa). Inhibitory activity seems to be generated through the interaction of FXa with a component in AP rather than with the TF-FVII complex. Quantitation of inhibitor activity was carried out using an amidolytic assay for TF-FVII activity. Incubation of AP with various antisera demonstrated that the inhibition was mainly associated with the presence of apolipoprotein B (apo B) rather than alpha 2-macroglobulin or antithrombin III. Purified lipoprotein-rich fractions prepared from AP, using density gradient ultracentrifugation, all contained some inhibitory activity. Incubation with anti-apo B greatly reduced the inhibitor in the very low density lipoprotein (VLDL)- and low density lipoprotein (LDL)-rich fractions but had essentially no effect on inhibition by the high density lipoprotein (HDL) fraction, which was rich in apo A. The inhibitory activity of AP was 60% that of normal plasma and this correlated well with the relative apo A and apo B concentrations. It is proposed that inhibition requires the interaction of FXa with plasma lipoproteins or associated components and that the product of this interaction is then able to bind to and inhibit the TF-FVII complex.

Bilateral retinal detachment in association with preeclampsia

Bilateral, serous, non-rhegmatogenous retinal detachment is a rare complication of preeclampsia. Duke-Elder and Dobree (1967) stated than Van Graefe reported the first case in 1855. Since then 24 further cases have been reported--Wagener (1933), Wahrsinger (1943), Singh (1953), Bosco (1961), Gitter (1968), Klein (1968), Kenny (1972), Mabie (1980) and Oliver (1980). The incidence over the past 40 years appears to be decreasing and probably reflects the lower incidence of severe preeclampsia as a result of better antenatal care. These detachments are bilateral, serous and non-rhegmatogenous i.e. atraumatic. They often only involve the posterior pole. Bosco (1961) arrived at an incidence of 1 in 18,524 pregnancies. Previous case reports have suggested a higher incidence in primigravidas and all previous cases have occurred antenatally. In all but 1 previous case (Mabie, 1980), the detachment occurred concomitantly with hypertensive retinopathy. We report a multigravida with preeclampsia who, in the absence of any hypertensive retinopathy, developed bilateral, bullous retinal detachments in the puerperium.

Coagulation problems in human pregnancy

Coagulation problems in pregnancy are primarily associated with overactivity of the intrinsic clotting system. This accounts for the increased incidence of thrombo-embolism during pregnancy. Where specific obstetric complications cause clotting problems the common underlying feature is usually placental pathology as in abruptio placentae, pre-eclampsia or hydatidiform mole. Abnormal activation of the clotting system is an early, and occasionally the first detectable feature of pre-eclampsia, but there is no evidence that this is a primary change. Therefore the role of anticoagulant treatment in the management of pre-eclampsia remains questionable. A new test for estimating factor VIII consumption is proving to be a sensitive index of early activation of the clotting system and can be used for the diagnosis of early pre-eclampsia.

Early platelet consumption in pre-eclampsia

One hundred and thirty-one women with chronic hypertension were studied serially during pregnancy to determine the sequence of events in the development of superimposed pre-eclampsia and to discover the time of onset. Twenty-seven women developed a sustained rise in plasma urate concentrations, which began at about 28 weeks' gestation and which is characteristic of pre-eclampsia. The mean platelet count was already significantly reduced and continued to fall until delivery, which was on average at 36 weeks' gestation. A comparable but smaller decrease in platelet count was seen in 55 women who had borderline but consistent increases in plasma urate concentrations. In 49 women whose plasma urate concentrations remained steady the platelet count did not change significantly before delivery. The reduced platelet count in women who develop pre-eclampsia suggests that increased platelet consumption is an early feature of the disorder.

Studies on toxemia of pregnancy with special reference to blood pressure. I. Incidence and some characteristic features of the mothers and infants

An investigation was made of 150 women who were diagnosed at the Department of Obstetrics and Gynaecology, University Hospital, Uppsala in 1964-68 as having toxaemia of pregnancy. Eleven had eclampsia and the remainder pre-eclampsia. Toxaemia occurred in 0.88% (average) of all parturients during the study period. Some characteristics of the mothers and their infants are reported. Thus, there were more instrumental deliveries in the toxaemia group than in the non-toxaemic patients delivered in the clinic. The maternal weight at delivery was also greater in the toxaemia group. The frequency of complications among the infants was higher in the group with toxaemia. There were more stillbirths, lower birth weights and more congenital malformations. With regard to blood pressure, almost identical pressures were noted in the eclamptic and pre-eclamptic groups, with one exception. The maximum blood pressure recorded during delivery was higher in the eclamptic than in the pre-eclamptic group (198/127 and 175/117).

Components of the haemostatic mechanism in twin pregnancy

Components of the haemostatic mechanism were measured at intervals throughout pregnancy in 11 patients with twins and compared with a group of 21 patients with singleton pregnancies. Mean plasma fibrinogen levels were consistently (but not significantly) elevated in the mothers of twins while other parameters showed no differences.

Coagulation and fibrinolysis in molar pregnancy

Coagulation and fibrinolysis tests were performed in 14 patients with hydatidiform mole before any significant therapy was given and again, after evacuation of the mole, in eight instances. The results were compared with those found in a group of ten volunteers with normal pregnancies. The most frequent abnormalities in the problem cases were a shortening of the partial thromboplastin time and a prolongation of the thrombin time. From a total of seven cases with complete hematologic profiles before and shortly after evacuation of the mole, first showed important drops in platelets and fibrinogen. The most altered profiles occurred after expulsion of the mole in cases with important previous uterine activity. The findings suggested a latent state of hypercoagulability with higher turn over rate of fibrinogen and increased levels of fibrinogen-fibrin degradation products, that may exist even before the mechanism of expulsion begins. It was concluded that the alterations in coagulation and fibrinolysis seen in molar pregnancies most likely have a multifactorial pathogenesis, but the initiating causes must depend on several events taking place in the trophoblast itself and their consequences upon a very distorted intervillous blood circulation.

Arterial blood gases in pre-eclampsia

Arterial blood gases, physiological dead space and percentage pulmonary venous admixture (physiological shunt) were measured in 31 patients with proteinuric pre-eclampsia. There was no difference in pulmonary function in 22 patients with moderate pre-eclampsia when compared with normal pregnancy, but in 9 patients with severe pre-eclampsia, there was a significant increase in alveolar-to-arterial PO2 difference and physiological shunt, indicating a degree of pulmonary ventilation/perfusion imbalance. There was no accompanying hypoxaemia, suggesting that the impairment was of no clinical importance.

Coagulation and fibrinolysis in intact hydatidiform molar pregnancy

Tests of coagulation, fibrinolysis, and platelet function were performed in 17 patients with intact molar pregnancies. Women with intact molar pregnancies had higher fibrinogen factor VIII, and fibrinogen degradation products, concentrations and lower prothrombin, factor X, plasminogen, and plasminogen activator concentrations than controls with normal pregnancies. They also had reduced platelet counts and thromboelastographic values, which indicated hypocoagulability. These results suggest that intravascular coagulation occurs in intact hydatidiform molar pregnancies.

Sequential studies on components of the haemostatic mechanism in pregnancy with particular reference to the development of pre-eclampsia

Components of the haemostatic mechanism were studied at intervals in 60 primigravidae over the course of pregnancy and the puerperium; 12 of these developed pre-eclampsia. During pregnancy there was a fall in fibrinolytic activity and fibrinolytic capacity and a rise in fibrinogen, FR-antigen, alpha 1-antitrypsin and alpha 2-macroglobulin. The women who subsequently developed pre-eclampsia could not be identified on the basis of these measurements. Following delivery there was a more rapid return of fibrinolytic activity and capacity towards normal in the women who had not had pre-eclampsia. The urinary FR-antigen level was higher in the women with pre-eclampsia.

Hepatic fibrinogen deposits in pre-eclampsia. Immunofluorescent evidence

To investigate if fibrin (or fibrinogen), immunoglobulins and complement were present in the liver of patients with toxemia of pregnancy, we performed immunofluorescence studies on needle biopsies of pre-eclamptic women. Fibrin (or fibrinogen) outlining the hepatic sinusoids was found in all 12 cases; in two of them there were also large nodular deposits of fibrin (or fibrinogen) and to a lesser extent of IgG, IgM and C3 in areas of necrosis. Immunofluorescence study of 13 control liver biopsies, six from pregnant women, was negative. Our findings suggest that the factors involved in glomerular and hepatic injury are similar. To explain the predominant involvement of liver and kidney, we propose that in these organs, the vasospasm characteristic of toxemia is more severe; this enhanced severity, in the presence of a systemic yet mild blood hypercoagulability, would create adequate local conditions for the precipitation of fibrin-fibrinogen.

Use of coagulation tests to predict the clinical progress of pre-eclampsia

The clinical manifestations of severe pre-eclampsia are normally separated from those of mild pre-eclampsia and normal pregnancy on arbitrary grounds. A clinical index, based on the increase in diastolic blood-pressure and the presence of proteinuria, was developed to reflect the spectrum of disease from mild to severe pre-eclampsia. This was related to a coagulation index based on the platelet-count, plasma-factor-VIII, and serum-fibrinolytic-degradation-products. The two indices were shown to be strongly correlated. All cases of perinatal death associated with pre-eclampsia had coagulation indices in the most severely abnormal range. These results suggest that intravascular coagulation is a highly characteristic feature of pre-eclampsia and that the coagulation index may be of value in monitoring the progress of the disease.

A serial study of coagulation factors XII, XI and X in plasma in normal pregnancy and in pregnancy complicated by pre-eclampsia

A serial study of coagulation factors XII, XI and X in plasma has been carried out on 60 primigravidae, prospectively comparing those who remained normal with those who developed pre-eclampsia. In the normal group of 48 patients, the levels of all factors rose as pregnancy advanced, a secondary increase in factors XI and X occurring in the puerperium. Cord levels of all three factors were depressed. In the pre-eclampsia group of 12 patients, factor XII was significantly higher than in the normal group throughout the study, while factors XI and X were slightly lower. Observed changes failed to support the idea of a strong primary role for the coagulation mechanism in the pathogenesis of pre-eclampsia.

Coagulation changes in eclampsia: their frequency and pathogenesis

The maternal coagulation mechanism has been investigated in an effort to identify its role, if any, in the pathogenesis of eclampsia. Thrombocytopenia was identified in 28 of 95 cases (29 per cent), a prolonged thrombin time in 19 of 38 (50 per cent), abnormally elevated serum fibrinogen-fibrin degradation products in two of 65 (3 per cent), and circulating fibrin monomer in one out of 20 (5 per cent). Overt hemolysis was rare (2 per cent). Thus the pattern as well as the degree of change in the maternal coagulation mechanism differed remarkably from that typical of severe abruptio placentae and of prolonged retention of a dead fetus, the classic obstetric models of fast and slow disseminated intravascular coagulation. It is concluded that the coagulation changes when present in eclampsia are effect rather than cause. Moreover, the changes may evolve primarily from platelet adherence at sites of vascular endothelial damage as the consequence of segmental vasospasm and vasodilatation rather than be triggered by the escape of thromboplastin from the placenta into the maternal circulation.

Abnormal coagulation and fibrinolysis in eclampsia. A clinical and laboratory correlation study

This study evaluated the existence of abnormally increased coagulation and fibrinolysis in 33 severely toxemic and eclamptic women by means of a combined hemotologic profile with clinical and morphologic correlations. The dominant findings were: different degrees of thrombocytopenia, abnormal levels of blood fibrinogen, prolonged thrombin time, and positive protamine sulfate test. Altered activated partial thromboplastin time and positive ethanol gelation test were slightly less frequent, and only few cases showed prolonged prothrombin time or early lysis of euglobulins. These abnormalities seemed to be more numerous and more pronounced in the worst cases of the series and their severity seemed to be associated with the age of the patient and the presence of previous underlying disease. These variously handicapped pregnant women exhibited worse hematologic hematologic abnormalities, and provided most of the fatal cases in the series. Finally, the main findings were discussed and commented upon.

Circulating levels of fibrin/fibrinogen degradation fragment E measured by radioimmunoassay in pre-eclampsia

Levels of fibrin/fibrinogen degradation products have been measured by a sensitive and specific radioimmunoassay in pregnancies associated with pre-eclampsia or essential hypertension. The incidence of elevated levels was low (2-4%) in mild and moderate cases, and rather higher (30%) in severe cases. In no patients were the levels consistently elevated prior to the onset of clinical signs.

Conditions for collection of serum samples for the measurement of fibrin(ogen) degradation products by radioimmunoassay of fragment E

A number of conditions have been assessed for the collection of serum samples for the measurement of fibrin(ogen) degradation products using a radioimmunoassay for degradation fragment E, which permits precise quantitation of differences. Blood should be collected using minimal venous occlusion into glass tubes containing 10 mg/ml of epsilon amino caproic acid and allowed to clot at 4 to 20 degrees C for at least 4 hours before centrifugation. The serum may be stored at 4 or -20 degrees C. Samples from patients receiving anticoagulant therapy should be treated with 10 IU of thrombin per ml.

The histology of eclamptic lesions

A brief description is given of the main lesion found in eclampsia. Emphasis is placed on the marked difference between the type of lesion found in the kidney and those found in other organs. It is suggested that they may be explained on the basis of increased coagulability of the blood, hypertension and possibly increased permeability of blood vessels. Hypertension may damage vessels and determine the sites of thrombus deposition. Increased permeabilithe mesangium of the glomerulus.

Circulating levels of fibrin/fibrinogen degradation fragment E in normal pregnancy, and in association with intrauterine growth retardation and perinatal asphyxia

Levels of fibrin/fibrinogen degradation products have been measured by aspecific and sensitive radioimmunoassay for degradation fragment E (FgE) in pregnant patients. Maternal FgE levels rose from the 16th week reaching a plateau at the 36th week in normal pregnancy. There was no correlation between maternal FgE levels and maternal age, parity or the occurrence of perinatal asphyxia. A minority of patients (5 per cent) with evidence of intrauterine growth retardation showed prolonged elevation of FgE levels.

Failure of heparin therapy to affect the clinical course of severe pre-eclampsia

In view of the association between pre-eclampsia and disseminated intravascular coagulation, three patients presenting with severe pre-eclampsia before the 28th week of pregnancy were treated with heparin. In all three patients, there was deterioration of hypertension and proteinuria that necessitated the withdrawal of treatment after five to six days. During treatment, serum and urinary fibrinolytic degradation products (FDPs) continued to rise or remained unaltered, plasminogen levels showed a steady fall, and the platelet count remained at a reduced level. These data suggest that heparin was an ineffective form of treatment and did not prevent the intravascular fibrin deposition associated with severe pre-eclampsia.

Treatment of pre-eclampsia and eclampsia as a hypoperfusion syndrome

A therapeutical program in pre-eclampsia and eclampsia is presented. The results in 10 patients suggest that the same basic program as is used in the hypoperfusion syndrome can be used in pre-eclampsia and eclampsia: Chlorpromazin to combat vasoconstriction and dilate the vascular bed. Plasma expanders, plasma, albumin and glucose with electrolytes to fill up the dilated vascular bed and restore the tissue perfusion. Buffers to combat acidosis, oxygen to combat hypoxemia, hypertonic Mannitol to mobilize edema. Furosemide to force diuresis.

Blood coagulation profile in Indian patients with pre-eclampsia and eclampsia

Twelve Indian patients with pre-eclampsia, 15 with eclampsia and 15 with normal pregnancy in the third trimester were investigated. A systemic bleeding diathesis was encountered in two patients with eclampsia and in none with pre-eclampsia; two patients with pre-eclampsia, however, had excessive uterine haemorrhage. Coagulation studies showed statistically significant prolongation of thrombin time, elevation of serum fibrinogen degradation products (FDP) and hypofibrinogenaemia in patients with pre-eclampsia as well as eclampsia. In patients with eclampsia, significant thrombocytopenia also occurred. Euglobulin lysis time showed no significant change in patients with pre-eclampsia and eclampsia. There was no significant difference in the coagulation profile between patients with eclampsia and pre-eclampsia, except for more hypofibrinogenaemia in the former. The laboratory findings suggest the occurrence of intravascular coagulation in patients with pre-eclampsia and eclampsia.

Assessment of coagulation and fibrinolysis in pre-eclampsia

A method is described for distinguishing coagulation from fibrinolysis by three estimates of fibrinogen. This "fibrinogen series" together with plasma antithrombin and urinary urokinase have been compared in pregnant patients with venous thrombosis and pre-eclampsia. Evidence is presented for active coagulation during deterioration of the pre-eclampsia state and for enhanced fibrinolysis during improvement.

Coagulation and fibrinolytic systems in pre-eclampsia and eclampsia

The coagulation and fibrinolytic mechanisms were investigated in a group of patients with severe pre-eclampsia and eclampsia and the findings were compared with those of healthy women in late pregnancy. In patients with pre-eclampsia the following significant differences were found: (1) greater depression of plasma fibrinolytic activity (euglobulin lysis time) than in normal pregnancy, (2) a higher level of inhibitor to urokinaseinduced lysis, (3) increased levels of serum fibrin degradation products, and (4) reduced platelet counts.In patients with eclampsia a progressive increase of the level of serum fibrin degradation products was found over the three days following eclamptic seizures. No such increase occurred after grand mal seizures in late pregnancy. The findings in this study support the view that intravascular clotting is taking place in pre-eclampsia and that this disturbance of the balance between coagulation and fibrinolysis may be localized to certain areas of the vascular compartment, particularly the placental and renal circulations. Fibrin deposition in the maternal vessels supplying the placenta would impair the placental blood flow, which may explain the placental insufficiency which occurs in pre-eclampsia. Likewise fibrin deposition in the renal vasculature will result in glomerular damage and proteinuria. Hypertension may be related to the renal ischaemic changes or a compensatory response to the presence of fibrin deposition in the vascular compartment. This evidence of intravascular fibrin deposition raises the question of the possible therapeutic value of antithrombotic agents to inhibit the clotting process. On a theoretical basis such treatment might be expected to improve blood flow to the placenta and thereby fetal growth.