Extrinsic Pathway Inhibitor in Elective Surgery: A Comparison with other Coagulation Inhibitors

Impact of Adrenal Function on Hemostasis/Endothelial Function in Patients Undergoing Surgery

Context

Glucocorticoids regulate hemostatic and endothelial function, and they are critical for adaptive functions during surgery. No data regarding the impact of adrenal function on hemostasis and endothelial function in the perioperative setting are available.

Objective

We assessed the association of adrenal response to adrenocorticotropic hormone (ACTH) and markers of endothelial/hemostatic function in surgical patients.

Methods

This prospective observational study, conducted at a tertiary care hospital, included 60 patients (35 male/25 female) undergoing abdominal surgery. Adrenal function was evaluated by low-dose ACTH stimulation test on the day before, during, and the day after surgery. According to their stimulated cortisol level (cutoff ≥ 500 nmol/L), patients were classified as having normal hypothalamic-pituitary-adrenal (HPA)-axis function (nHPA) or deficient HPA-axis function (dHPA). Parameters of endothelial function (soluble vascular cell adhesion molecule-1, thrombomodulin) and hemostasis (fibrinogen, von Willebrand factor antigen, factor VIII [FVIII]) were measured during surgery.

Results

Twenty-one patients had dHPA and 39 had nHPA. Compared with nHPA, patients with dHPA had significantly lower peak cortisol before (median 568 vs 425 nmol/L, P < 0.001) and during (693 vs 544 nmol/L, P < 0.001) surgery and lower postoperative hemoglobin levels (116 g/L vs 105 g/L, P = 0.049). FVIII was significantly reduced in patients with dHPA in uni- and multivariable analyses; other factors displayed no significant differences. Coagulation factors/endothelial markers changed progressively in relation to stimulated cortisol levels and showed a turning point at cortisol levels between 500 and 600 nmol/L.

Conclusions

Patients with dHPA undergoing abdominal surgery demonstrate impaired hemostasis which can translate into excessive blood loss.

Tissue factor pathway inhibitor: structure, biology and involvement in disease

Tissue factor (TF)-initiated coagulation plays a significant role in the pathophysiology of many diseases, including cancer and inflammation. Tissue factor pathway inhibitor (TFPI) is a plasma Kunitz-type serine protease inhibitor, which modulates initiations of coagulation induced by TF. In a factor (F) Xa-dependent feedback system, TFPI binds directly and inhibits the TF-FVII/FVIIa complex. Normally, TFPI exists in plasma both as a full-length molecule and as variably carboxy-terminal truncated forms. TFPI also circulates in complex with plasma lipoproteins. The levels and the dual inhibitor effect of TFPI on FXa and TF-FVII/FVIIa complex offers insight into the mechanisms of various pathological conditions triggered by TF. The use of selective pharmacological inhibitors has become an indispensable tool in experimental haemostasis and thrombosis research. In vivo administration of recombinant TFPI (rTFPI) in an experimental animal model prevents thrombosis (and re-thrombosis after thrombolysis), reduces mortality from E. coli-induced-septic shock, prevents fibrin deposition on subendothelial human matrix and protects against disseminated intravascular coagulation (DIC). Thus, TFPI may play an important role in modulating TF-induced thrombogenesis and it may also provide a unique therapeutic approach for prophylaxis and/or treatment of various diseases. In this review, we consider structural and biochemical aspects of the TFPI molecule and detail its inhibitory mechanisms and therapeutic implications in various disease conditions.

Coagulation in Sepsis

Activation of the coagulation cascade during invasive infection can result in purpura fulminans, with rapid progression of tissue ischemia, or may manifest as abnormal clotting indices alone. Although severe derangements in coagulation are associated with organ dysfunction and increased mortality, the contribution of coagulopathy to the pathophysiology of sepsis remains incompletely understood. Over the past decade, investigators have evaluated several therapeutic anticoagulant strategies in sepsis, and manipulation of the coagulation system has emerged as a key concept in the current management of this disease. Clinical observations during treatment of septic patients with the endogenous anticoagulant activated protein C have stimulated additional study of interactions between endothelial injury, coagulation, and inflammation. This review describes clotting abnormalities during sepsis and discusses the clinical experience with therapeutic strategies intended to oppose excessive coagulation.

Influence of total intravenous and inhalational anaesthesia on haemostasis during tympanoplasty

BACKGROUND

Surgical trauma leads to systemic changes in haemostasis. Haematological changes activated by surgery may become so prominent that changes caused by anaesthesia might be hidden or underestimated. Therefore, we have undertaken a prospective study to compare the behaviour of selected factors involved in the coagulation and fibrinolytic systems.

METHODS

Forty healthy adult patients scheduled for otological surgery were enrolled in the study. Upon receiving informed consent, they were randomly assigned to receive either inhalational (IA) or total intravenous anaesthesia (TIVA). Platelet function (PFA100TM), disseminated intravascular coagulopathy (DIC) panel, and generalized d-dimer (GFC) were studied during certain periods of anaesthesia to identify the changes in haemostasis.

RESULTS

Statistically, no significant change in DIC parameters were encountered between the two groups. No statistical difference was found between the two groups in the measured coagulation parameters, but statistically GFC showed slight activation in the 1st hour of surgical intervention.

CONCLUSION

Presuming a minimal traumatic effect of surgical procedure on the determined variables, we conclude that different anaesthetic techniques have a negligible effect on platelet activation and fibrinolysis. The clinical relevance of coagulation activation and fibrinolysis during different anaesthetic techniques remains to be investigated.

Heparin cofactor II deficiency

OBJECTIVES

To review of the state of the art relating to congenital heparin cofactor II deficiency as a potential risk factor for thrombosis, as reflected by the medical literature and the consensus opinion of recognized experts in the field, and to make recommendations for the use of laboratory assays for assessing this thrombotic risk in individual patients.

DATA SOURCES

Review of the medical literature, primarily from the last 10 years.

DATA EXTRACTION AND SYNTHESIS

After an initial assessment of the literature, including review of clinical study design and laboratory methods, a draft manuscript was prepared and circulated to participants in the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia. Recommendations were accepted if a consensus of experts attending the conference was reached. The results of the discussion were used to revise the manuscript into its final form.

CONCLUSIONS

Consensus was reached that there is insufficient evidence to recommend testing for heparin cofactor II deficiency in patients with thromboembolic disease.

Bioequivalence of subcutaneous and intravenous body-weight-independent high-dose low-molecular-weight heparin Certoparin on anti-Xa, Heptest, and tissue factor pathway inhibitor activity in volunteers

The objective of the study was to demonstrate the bioequivalence of subcutaneously (s.c.) and intravenously (i.v.) administered fixed, high-dose low-molecular-weight heparin (LMWH) on anti-activated factor X activity (anti-FXa). Secondary objectives were the analysis of the pharmacodynamic effects on Heptest, thrombin inhibition, tissue factor pathway inhibitor (TFPI), and the urinary excretion of LMWH in the randomized cross-over study following i.v. and s.c. application of 8000 anti-FXa units LMWH Certoparin in 18 healthy subjects. The bioequivalence following s.c. administration was demonstrated from the antilog of the point estimator for the application differences (s.c. minus i.v.) by an area under the activity-time curve (0-24 h) of 101% (range, 93-110%). LMWH was bioequivalent also on Heptest and TFPI, and was 50% on thrombin inhibition. The urinary excretion of biologically active material was 4.1 and 3.6% following i.v. and s.c. administration, respectively. Differences in the pharmacodynamic parameters of the assays indicate specific biological actions of high and low molecular sacharide chains of the LMWH.

A comparative study of functional assays for tissue factor pathway inhibitor using normal plasma and clinical samples

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type inhibitor that regulates the initiation of tissue factor-mediated coagulation. Recent reports in the literature have described variable results using different methodologies for TFPI measurement. In this study, we used one clotting and two amidolytic methodologies to assess TFPI functional levels. The study groups included normal healthy donors as well as patients with acute hepatitis, diabetes, coronary artery bypass graft operations, deep vein thrombosis, and prior to and during heparin therapy. The aims were to compare the results obtained in normal plasma using different assay systems, to compare TFPI levels in a range of clinical samples, including those previously not determined using a clotting methodology, and to report TFPI levels in patient groups previously not investigated. The results clearly demonstrate poor correlation between functional TFPI values using the different methodologies, highlighting the requirement for standardization.

Hemostatic abnormalities in patients with thrombotic complications on maintenance hemodialysis

Before hemodialysis (HD), plasma levels of tissue factor (TF), free-TF pathway inhibitor (TFPI) and thrombomodulin (TM) were significantly higher in patients with HD than in healthy volunteers. Plasma levels of (T-F) TFPI and plasmin plasmin inhibitor complex (PPIC) were significantly higher in patients with HD than in healthy volunteers. During HD, plasma levels of TF and (T-F) TFPI were not significantly increased, but plasma levels of total TFPI and free TFPI at 1 hour after and at the end of HD were significantly increased, compared with levels before start of HD. Plasma level of PPIC 1 hour after start of HD was significantly higher than before start of HD, and plasma levels of thrombin antithrombin complex (TAT), PPIC, D-dimer, TM, and protein C (PC) at the end of HD were significantly higher than before start of HD. In patients with thrombosis complications, plasma TF levels were significantly higher than in patients without thrombotic complications during HD. Plasma levels of PC were significantly lower in patients with thrombotic complications than in patients without thrombotic complications. There was no significant difference between both groups during HD in hemostatic parameters, with the exception of TF and PC. Hemostatic abnormalities existed in patients with HD; especially, increased TF and decreased PC might cause thrombotic complications.

Increased truncated form of plasma tissue factor pathway inhibitor levels in patients with disseminated intravascular coagulation

To evaluate that the relationship between the truncated form of tissue factor pathway inhibitor (TFPI) and the stage of disseminated intravascular coagulation (DIC), we measured the plasma levels of tissue factor (TF) antigen and the intact and truncated forms of TFPI antigens in 41 patients with DIC, 12 with pre-DIC, and 20 with non-DIC. The plasma TF and total TFPI antigen levels were significantly higher in patients with DIC than in non-DIC patients. Plasma levels of intact TFPI antigen in the pre-DIC groups were significantly lower than in the non-DIC and DIC groups. The truncated form of TFPI antigen levels in DIC patients were significantly increased compared with those in non-DIC and pre-DIC patients. The fact that the intact form of TFPI was decreased in pre-DIC patients compared with that in non-DIC patients, suggests that it is consumed in the pre-DIC state and that hypercoagulability occurs in pre-DIC patients. The increased level of the truncated form of TFPI in DIC patients may be attributed to proteolysis of the intact form of TFPI in these patients. The increased level of the truncated form of TFPI may be a useful index for the diagnosis of DIC.

Neuroendocrine stress hormones do not recreate the postoperative hypercoagulable state

Surgery causes changes in hemostasis, leading to a hypercoagulable state that has been linked to both arterial and venous thrombotic complications. The etiology of this state is unknown, but many investigators have hypothesized that perioperative neuroendocrine changes are responsible. We have previously demonstrated minimal increases in hemostatic function with a stress hormone infusion. This study was undertaken to further examine the relationship between neuroendocrine hormones and hemostatic function. Seventeen healthy volunteers were administered a stress hormone cocktail i.v. (epinephrine, cortisol, glucagon, angiotensin II, and vasopressin) for 24 h in a blind, placebo-controlled, cross-over design in our clinical research center. Venous blood samples were obtained for measurement of hemostatic function before the infusion and at 2, 8, and 24 h. There were no demonstrable increases in any measure of hypercoagulability. Alternatively, there was an increase in tissue plasminogen activator and protein C activity. These changes are consistent with an inhibition of coagulation and improved fibrinolysis. These data suggest that this combination of neuroendocrine hormones is not responsible for the postoperative hypercoagulable state.

IMPLICATIONS

Infusion of five stress hormones (epinephrine, cortisol, glucagon, vasopressin, and angiotensin II) to normal volunteers does not cause increases in procoagulant proteins and platelet reactivity or decreases in fibrinolytic proteins. Alternatively, these five hormones caused increased levels of fibrinolytic proteins (tissue plasminogen activator) and endogenous anticoagulants (protein C antigen and activity).

An enzyme linked immunosorption assay for tissue factor pathway inhibitor

An assay for the quantification of full-length and carboxy-terminus truncated tissue factor pathway inhibitor (TFPI) has been developed. The assay is a classical two-antibody sandwich assay with a monoclonal capture antibody directed against the third Kunitz-type domain of human TFPI and a polyclonal rabbit peroxidase-labelled anti-human TFPI detecting antibody. The assay is sensitive to full-length and carboxy-terminus truncated TFPI with intact third Kunitz-type domain, but not to two-domain TFPI. TFPI associated with lipoproteins is not or only sparsely detected and TFPI in complex with factor Xa only partially measured. The assays gives linear reference curves in the dose range of 5 to 100 ng/ml in a double logarithmic plot. The normal range assessed from analyses on citrated plasma from 81 normal human donors is 7.8 to 26.0 ng/ml (average +/- 2 SD, log-normal distribution). There is no statistically significant difference between TFPI levels measured in 10 fasting and 10 non-fasting individuals. The reproducibility of the assay is about 5.6-5.9% (relative standard error) and the within-days and between-day reproducibilities are 4.7-5.1% and 5.9-8.5%, respectively. The assay is in very good agreement with a commercial ELISA assay recently marketed. A robust, reproducible and convenient ELISA assay for the determination of full-length and three-domain TFPI has been developed.

Hamster antithrombin III: purification, characterization and acute phase response

Antithrombin III was purified to homogeneity from hamster plasma by affinity chromatography on heparin-agrose, ion-exchange chromatography on Mono Q and size-exclusion chromatography on TSK G3000SWG column with 50% yield. The molecular mass of hamster antithrombin III was estimated at 62.5 kDa and the absorption coefficient (A280 nm 1%, 1 cm) at 6.48 (in 0.1 M sodium phosphate pH 7.0). Several isoforms of the inhibitor were detected with the pI in range of 4.95-5.25. The protein contains all residues characteristic for complex-type carbohydrate chains. The N-terminal amino acid sequence shows 84% of identity to mouse and 76% to human analogue. The hamster antithrombin III gives low immunological cross-reactivity with antibodies to human antithrombin III. Initiation of the acute phase response only slightly affected the plasma concentration of inhibitor (+/- 10% within 72-h period). The kinetic data suggest high efficiency in bovine and human thrombin inhibition. In summary, the study shows only similarities between hamster and other mammal antithrombins.

Plasma tissue factor and tissue factor pathway inhibitor levels in patients with disseminated intravascular coagulation

We measured the plasma levels of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) in patients with disseminated intravascular coagulation (DIC) to examine the relationship between TFPI and vascular endothelial cell injury. Plasma TF (273 +/- 90 pg/ml) and TFPI (252 +/- 125 ng/ml) levels were significantly increased in patients with DIC compared with non-DIC patients. Plasma TF antigen level was significantly increased in pre-DIC patients (285 +/- 85 pg/ml), while the plasma TFPI level (152 +/- 54 ng/ml) was not markedly increased in such a state. The plasma TF/TFPI ratio was high in the pre-DIC patients (2.10 +/- 0.90), and low in the DIC patients (1.40 +/- 0.87) and healthy volunteers (0.84 +/- 0.26). There was no significant difference between the DIC patients with a good outcome and those with a poor outcome in terms of plasma TF levels, although the plasma TFPI level in the DIC patients with a good outcome (289 +/- 133 ng/ml) was significantly higher than that in those with a poor outcome (187 +/- 75 ng/ml). During the clinical course of DIC, plasma TF antigen was increased first, and an increase of the plasma TFPI level followed the increase in plasma TF level. These findings suggest that plasma TFPI is released from vascular endothelial cells and it may reflect vascular endothelial cell injury. It is conceivable that TF and TFPI may play an important role in the onset of DIC.

The potential risks, complications, and prevention of deep vein thrombosis in oral and maxillofacial surgery patients

PURPOSE

Deep vein thrombosis is a complication in surgical patients with a potential for disastrous results. This article discusses the pathogenesis, prevention, and treatment of this condition.

CONCLUSION

Surgeons should be acutely aware of the potential development of deep vein thrombosis and should take prophylactic measures to prevent this problem as part of their surgical routine.

Plasma concentration of tissue factor and factor VII in patients after abdominal surgery

Tissue injury following trauma and surgery may induce alterations in blood coagulation and fibrinolysis. Hypercoagulable state after surgery can be associated with the risk of postoperative thromboembolic complications. The contact of coagulation factors with TF after injury of vessel wall and organ tissues may contribute to the development of thrombosis after surgery (1). TF, the cell surface receptor and cofactor of factor VII/VIIa is normally not expressed by cells within the vasculature. Only monocytes and endothelial cells can be stimulated to express TF transiently by a variety of inflammatory and immunological reactions (for review see 2,3). Also surgical treatment was reported to induce TF synthesis in monocytes (4,5,6). TF is present in many extravascular tissues as vascular adventitia, organ capsules, epidermis, colonic mucosal epithelium, liver stroma, pancreas stroma and also on tumor cells (7-12). In this study, we investigated, whether we can detect the release of TF from the traumatized tissues and from activated monocytes into the circulation following abdominal surgery. To test the dependence of the extension of tissue injury during surgery we segregated the patients into group A with major abdominal operations and group B consisting of patients with appendectomy and cholecystectomy. No relationship could be established between changes of TF and postoperative thromboembolic complications.

Postoperative hypercoagulability and deep-vein thrombosis after laparoscopic cholecystectomy

Patients who undergo laparoscopic cholecystectomy (LC) are operated on under general anesthesia, in a reverse Trendelenburg position, with 12-15-mmHg pneumoperitoneum. All of these factors can induce venous stasis of the legs, which may lead to postoperative deep-vein thrombosis (DVT). The objectives of this study were to assess the degree of hypercoagulability and to determine the rate of postoperative DVT in a group of 100 patients in whom LC was completed. Whole-blood thrombelastography (TEG) and plasma-activated partial thromboplastin time (PTT) determination were carried out preoperatively and on the 1st postoperative day. All patients received pre-, intra-, and postoperative graduated compression stockings and sequential pneumatic compression devices until fully ambulatory. Twenty-six percent of the patients with a risk score > 4, or a post-operative TEG index > +5.0, received subcutaneous heparin (5,000 units b.i.d.), beginning in the postoperative period and continuing for 4 weeks as an outpatient. A complete venous duplex scan of both legs was performed on the 7th postoperative day, at the time of their office visit. Our results revealed significant postoperative hypercoagulability for the TEG index (P < 0.005) and for PTT (P < 0.05). One patient had an asymptomatic DVT (1%), and no side effects from the mechanical or pharmacological prophylaxis occurred in this series. These data suggest that the low incidence of thrombosis in the face of theoretical and laboratory evidence of postoperative hypercoagulability may reflect an effective prophylactic regime.(ABSTRACT TRUNCATED AT 250 WORDS)

The current status of coagulation

In 1964, the events of haemostasis were organized into the intrinsic and extrinsic pathways by the cascade/waterfall hypothesis, with primary physiological importance being given to the intrinsic pathway. Recent experimental evidence, as well as information about the clinical course of patients with various coagulation factor deficiencies, indicates a more prominent role for tissue factor. Rediscovery of the plasma protease inhibitor, tissue factor pathway inhibitor, and new information about the activation of factor XI have supported a revised theory of coagulation.

Prevention of postoperative venous thromboembolism following laparoscopic cholecystectomy

Advantages of laparoscopic cholecystectomy are less patient discomfort and shorter hospital stay than with the traditional open approach. Nevertheless, this operation is performed under general anesthesia, using muscle relaxants and pneumoperitoneum, with most patients in the reverse Trendelenburg position. It has been shown that this procedure is associated with significant hypercoagulability and dilation of the veins of the leg. We review the role of these factors as potential risk factors for the development of postoperative venous thromboembolism and also report the rate of thromboembolic complications following laparoscopic cholecystectomy. Based on the available evidence, it is concluded that laparoscopic cholecystectomy, despite being a "minimally invasive procedure," may be associated with a definite risk of developing postoperative venous thromboembolism that could extend beyond hospital discharge. Accordingly, thrombosis prophylaxis should be considered for these patients.

Coagulation inhibition and activation in pancreatic cancer. Changes during progress of disease

BACKGROUND

To elucidate the disturbed hemostatic balance in patients with pancreatic cancer, the levels of plasma coagulation inhibition and coagulation activation were determined.

METHODS

Twenty-one patients with adenocarcinoma of the pancreas were followed from time of diagnosis until death, using plasma analyses of coagulation inhibitors and a molecular marker of coagulation activation (thrombin-antithrombin complex, TAT).

RESULTS

TAT was increased significantly at the time of diagnosis of pancreatic cancer compared with age-adjusted healthy control subjects (mean, 6.2 +/- 4.6 micrograms/l [standard deviation] versus 2.0 +/- 0.7 micrograms/l). It increased with disease progression (mean in the terminal phase, 14.1 micrograms/l; P < 0.05). Plasma levels of tissue factor pathway inhibitor (TFPI) also were increased significantly at the time of diagnosis compared with the control group (mean, 176 +/- 80% versus 127 +/- 29%; P < 0.05). The TFPI decreased to normal levels (121 +/- 40%) after surgical removal of the pancreatic tumor (n = 4) or relief of the cholestasis using a bypass procedure (n = 6). The TFPI levels increased significantly as the malignant disease progressed (from 1-3 months postoperatively to the terminal phase of disease; mean, 114 +/- 52% versus 154 +/- 60%). There was a significant positive correlation between TFPI levels and bilirubin levels; the correlation coefficient at diagnosis was 0.70 (P < 0.001). The levels of the coagulation inhibitors antithrombin, heparin cofactor II, protein C, and free protein S decreased significantly with disease progression compared with the normal values found at diagnosis.

CONCLUSIONS

The mechanism for TFPI increase in cancer is not known. It may be related to the preoperative cholestasis seen in this study, but the increased degree of coagulation activation also may contribute.

Procoagulant activity in bronchoalveolar fluids: no relationship with tissue factor pathway inhibitor activity

Abnormalities in local coagulation may explain alveolar fibrin deposition which often accompanies human lung injuries. The purpose of this study was to investigate the generation of procoagulant activity (PCA) and tissue factor pathway inhibitor (TFPI) in selected bronchoalveolar lavage fluids (BAL) from controls (n = 7) and from patients with interstitial lung diseases (n = 9), Pneumocystis carinii (PCP) pneumonia (n = 11) and bacterial pneumonia (n = 8). As compared with controls a significant increase of PCA was observed in the three groups with lung diseases. PCA in BAL from patients with untreated interstitial lung diseases (PC Units mean of 162 +/- 48) was significantly higher than PCA of treated patients (PC Units 36 +/- 10; p less than 0.05). Increases of PCA paralleled protein levels in BAL and the protein/albumin ratios were comparable in the four groups. TFPI was significantly increased in PCP (p less than 0.02) and bacterial pneumonia (p less than 0.03), but only marginally increased in interstitial lung diseases when compared with controls. No correlation was found between TFPI and PCA in any of the four groups. These data indicate that increased procoagulant activity observed in various lung diseases is not counterbalanced by TFPI.

Regional fibrinolysis following total hip replacement

The local effect of operative trauma on the fibrinolytic system was studied in ten patients undergoing total hip replacement. Catheters were inserted in the femoral veins on both sides and blood was sampled from these catheters perioperatively. The following fibrinolytic variables were analysed in plasma and related to the different steps of surgery: tissue plasminogen activator (t-PA) activity, t-PA antigen and plasminogen activator inhibitor (PAI-1) activity. During surgery PAI-1 activity and t-PA antigen in the operated limb were significantly increased compared with preoperative values. There was a significant difference in PAI-1 activity and t-PA antigen between the operated and the non-operated limbs during surgery and within one hour postoperatively. During fixation of the femoral implant there was a significant difference between the operated and the non-operated limbs in t-PA activity. Thus the regional fibrinolytic response to trauma was dissociated from the response in the non-operated limb. The clinical relevance of the observed alterations in regional fibrinolysis, as related to thrombogenic mechanisms after hip surgery, remains to be elucidated.

Generation of procoagulant (thromboplastin) and plasminogen activator activities in peripheral blood monocytes after total hip replacement surgery. Effects of high doses of corticosteroids

Development of thromboplastin (tpl) and plasminogen activator (PA) activity in monocytes and the effects of high doses of corticosteroids (HCD) on these activities were studied in patients undergoing a standardized surgical trauma. Twelve patients who received uncemented total hip prostheses were divided into a nonsteroid group (n = 6) and a steroid group (n = 6). We found no significant differences between the two patient groups regarding tpl or PA activities of peripheral blood mononuclear cells (PBM) isolated during the postoperative phase. However, in the nonsteroid group there was a tendency for increased expression of procoagulant activity and decreased fibrinolytic activity on the 1st postoperative day, favoring the formation of fibrin in the monocyte microenvironment. Further, PBM isolated on the 1st and 2nd day after surgery were significantly less capable of generating tpl activity on endotoxin stimulation than cells isolated preoperatively. This was not the case in the steroid group. These patients had also a tendency for decreased fibrinolysis at the end of the 1st postoperative week, indicating increased imbalance towards a more thrombotic stage after surgery.

Deep vein thrombosis: effect of graduated compression stockings on distension of the deep veins of the calf

The mechanisms by which graduated compression stockings prevent deep vein thrombosis are not completely understood. Recent work has suggested that venous distension plays a role in initiating the process. Our previous work has shown that the deep veins of the lower limb distend in patients undergoing surgical procedures. We have investigated 40 patients receiving surgical treatment on the abdomen or neck. A medial gastrocnemius vein was studied using ultrasound imaging during the operations. In half the patients a graduated compression anti-embolism stocking was applied to the limb under study at the start of the operation, immediately after initial measurements of vein diameter. The median vein diameter in both groups was the same at the start of the operative procedures (control, 2.6 mm, interquartile range 2.1-3.3 mm; stocking, 2.6 mm, interquartile range 2.1-3.7 mm). After application of a stocking the median diameter in this group fell to 1.6 mm (interquartile range 1.3-2.8 mm) and then decreased slightly at the end of the operation. In the control group the vein diameter increased to 2.9 mm (interquartile range 2.3-4.0 mm) during the operative procedure.