Postoperative antithrombin-3 concentration

Pathophysiology and diagnosis of deep venous thrombosis

Lower-limb deep venous thrombosis (DVT) affects between 1% to 2% of hospitalized patients. These thrombi disrupt the vascular integrity of the lower limbs and are the source of emboli that kill approximately 200,000 patients each year in the United States. The causes of thrombosis include vessel wall damage, stasis or low flow, and hypercoagulability. These factors favor clot formation by disrupting the balance of the opposing coagulative and fibrinolytic systems. The symptoms and signs of venous thrombosis are caused by obstruction to venous outflow, vascular inflammation, or pulmonary embolization. About 70% of patients referred for clinically suspected venous thrombosis, however, do not have the diagnosis confirmed by objective testing. Among the 30% who have venous thrombosis, about 85% have proximal vein thrombosis, and the remainder have thrombosis confined to the calf. Physicians cannot rely on signs and symptoms to make the diagnosis of DVT and must depend on imaging studies to guide treatment. Patients with proximal vein thrombosis who are inadequately treated have a 47% frequency of recurrent venous thromboembolism over 3 months. In contrast, clinically detectable recurrence occurs in less than 2% of patients with proximal vein thrombosis if an adequate anticoagulant response is achieved. Of the diagnostic procedures for DVT, venography is the only invasive test of proven value, and ultrasonographic (US) studies are the most commonly used noninvasive modaity. Other procedures are occasionally used to diagnose DVT, including impedance plethysmography, computed tomography, and magnetic resonance imaging. US examinations are noninvasive, they are rapidly obtained, and they can be performed serially. In symptomatic patients, venous US is sensitive and specific for proximal DVT; however, US is insensitive to calf vein thrombosis and to asymptomatic DVT occurring after surgery. Patients with symptoms of recurrent DVT also can present a difficult diagnostic problem. Only about 20% to 30% of these individuals actually have the disease; the rest have symptoms arising from chronic venous insufficiency or from any of the causes of lower extremity pain. After an acute episode, up to 50% of patients have compression ultrasound abnormalities for 6 months that are indistinguishable from the original findings of DVT. Hence, there are a significant number of patients and clinical circumstances in which the diagnosis of DVT is difficult. 99mTc-radiolabeled peptides that target the molecular biology of thrombosis should aid in the management of the disease, particularly in asymptomatic patients at high risk, in patients with recurrent symptoms, in patients with active DVT in the calf and/or pelvis, and in patients with intermediate- or low-probability lung scans.

The effect of operation and subcutaneous heparin on plasma levels of antithrombin-III

Plasma antithrombin III (AT-III) levels were measured in 61 patients undergoing general surgery. The patients were randomly allocated to a test or a control group. The test group received 5000iu of subcutaneous heparin two hours before operation and then twelve hourly for seven days. The control group received subcutaneous saline. Plasma levels of AT-III and of heparin were estimated before operation, at two, four and six hours after heparin injection on the day of operation and thereafter before the morning injection on the first, third and sixth postoperative days. Antithrombin III decreased progressively during and after operation in both groups. The decrease was greater in the test group at six hours after the first injection. These findings support the hypothesis that AT-III is consumed during coagulation and its utilization is increased in the presence of heparin.

Detection of antithrombin III microheterogeneity

Antithrombin III microheterogeneity was investigated by isoelectric focusing and immunofixation in healthy individuals and in patients with clinical conditions in which antithrombin III is known to vary (liver disease, nephrotic syndrome, after surgery and anticoagulant therapy). In normal plasma microheterogeneity was present with ten bands of varying intensity being visible in a pI range from 5.0-5.7. One variant was observed which was not associated with a clinical disorder. Low concentrations of antithrombin III were detected in some patients with liver disease, nephrotic syndrome and those on anticoagulant therapy and these demonstrated a decrease of intensity in all bands. Alterations in microheterogeneity were seen in patients tested after surgery and those with nephrotic syndrome. This indicates that changes in the subpopulations of antithrombin III can occur and may be relevant to clinical abnormalities.

Fluorogenic substrate assay of antithrombin III: a clinical study

The fluorogenic substrate assay of antithrombin III (AT III) was compared with a thrombin inhibition (two-stage) clotting test and a radial immunodiffusion assay. Normal ranges based on a population of 25 individuals were 88-121% (fluorogenic substrate), 72-111% (clotting) and 22.5-35.3 mg/dl (RID). A clinical comparison of the methods showed a linear relationship between the fluorogenic substrate and immunologic methods (r = 0.69, p less than 0.005), as well as between the fluorogenic substrate and clotting methods (r = 0.75, p less than 0.005). The fluorogenic substrate assay reflected the highest incidence of low AT III levels in all three clinical groups included (36 patients with arteriosclerosis, 18 with fractures and 37 with thrombosis/embolism).

A comparison of antithrombin III procedures

Antithrombin III (AT III) is the most potent physiologic inactivator of thrombin and other serine proteases in the blood clotting mechanism. Hereditary deficiency of this protein is associated with recurrent deep-vein thrombosis that begins in late adolescence. Untreated, this disease may lead to early death from recurrent and massive pulmonary emboli. Attempts to identify groups of patients who are the most likely to develop thromboembolic disease because of an acquired deficiency of AT III have been frustrated by the lack of standardization of the assays and the inability to compare results of the different AT III assays. The functional assays and immunoelectrophoretic determinations do not measure the same component. In order to compare the ability of current AT III procedures to determine levels of AT III in various disease states, we used immunoelectrophoretic, chromogenic, and clottable assays to measure the AT III of patients with congenital AT III deficiency and of patients with possible acquired AT III deficiency.

Relation between postoperative antithrombin III concentrations and site of operation

Antithrombin III concentrations were measured in 305 patients before and at intervals after operation for up to 12 days. The blood concentrations fell significantly after both major and minor surgery, but there was no relation between the expected degree of surgical trauma or the amount of blood transfused and the fall in concentration of antithrombin III. Some surgical procedures such as cholecystectomy, laparotomy, hernia repair, highly selective vagotomy, and transurethral resection of the prostate were associated with a greater depletion of antithrombin III than were other common operations and it is suggested that there are factors related to the actual site of the operation which affect the concentration of circulating antithrombin III in the postsurgical period.

Coagulation changes in elective surgery and trauma

Although antithrombin-3 (AT-3), a naturally-occurring inhibitor of thrombin, has been associated with a variety of thrombotic disorders, it has been studied in surgery and trauma. Three groups of patients were studied: Group I (20 patients) who underwent elective surgery; Group II (ten patients) who sustained moderate trauma: Group III (ten patients) who sustained severe trauma. Hypercoagulability panels were run preoperatively, intraoperatively, and postoperatively. Nine units of banked blood were also tested. The coagulation pattern changed during the stress, becoming hypercoagulable in proportion to the stress endured by the patient. In the severe trauma group, AT-3 fell significantly (p less than or equal to 0.002) in all patients, indicating extreme hypercoagulability. Three of these patients sustained thrombosis and loss of the involved extremity. The banked blood was found to be hypercoagulable. It appears that patients who sustain severe trauma, have multiple transfusions, and major operative procedures are at increased risk of developing postoperative thrombotic complications, including loss of limb.

Comparison of three methods for the estimation of plasma antithrombin

Plasma antithrombin levels were measured by clotting, immunological, and amidolytic methods on two groups of subjects: 20 normal individuals and nine patients studied serially post-operatively (hip replacement). The postoperative patients were observed for the emergence of deep-vein thrombosis using 125I-fibrinogen uptake measurements (FUT). The three methods gave similar ranges for the normal subjects, were reproducible (cv less than 5%), and detected early postoperative reduction of antithrombin levels. All three methods failed to show any significant differences in preoperative antithrombin levels between the positive and negative FUT groups. Correlation studies were performed on the pooled data from the normal and postoperative group (range 60-130% of normal; 100 samples). The best correlation (r = 0.75; P less than 0.01) was achieved with the chromogenic kit assay method versus the Mancini immunoassay technique. The thrombin agarose (total antithrombin) gel diffusion technique correlated less well with the chromogenic (r = 0.65; P less than 0.01) and Mancini immunoassay (r = 0.45; P less than 0.01) methods. It is concluded that the chromogenic kit method gives a rapid, reproducible, and specific measurement of antithrombin III. The thrombin agarose diffusion method, though not specific for antithrombin III, is a cheap and simple method to perform. The potential of the three methods for detecting the prethrombotic stage and early thrombosis is discussed.

Thrombosis and intravascular coagulation

Stress, including trauma and sepsis, is associated with a state of hypercoagulability. In these circumstances the patient is at risk of generalized or local thrombotic complications. New laboratory investigative procedures facilitate diagnosis and permit improved assessment of therapy, which at present remains of unproven efficacy both in the general and local situation.

A five year experience of the use of factor IX type DE(I) concentrate for the treatment of Christmas disease of Oxford

A survey is presented of the use of the Oxford type DE(I) II-IX-X concentrate in the treatment of Christmas disease in Oxford from January 1970 to September 1974. 72 different patients were treated with a total of 2436 bottles of this concentrate from 143 different batches (each bottle containing 800-1000 units of factor IX). Although most doses were given for the treatment of minor haemorrhages into joints and muscles, 717 bottles of concentrate were used to treat 11 patients who underwent 14 major surgical operations. No episode of intravascular clotting or pulmonary embolism was seen in any patient receiving the concentrate. A detailed study of the plasma levels of factor V, VIII, total progressive antithrombin, platelets and fibrinogen degradation products was carried out before and after transfusion of type DE(I) concentrate in 14 patients. No significant alteration in those factors was found after the transfusion.