Changes in Endothelial-Related Goagulation Proteins in Response to Venous Occlusion

Endothelial Dysfunction Syndromes after Allogeneic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the only therapy with a curative potential for a variety of malignant and non-malignant diseases. The major limitation of the procedure is the significant morbidity and mortality mainly associated with the development of graft versus host disease (GVHD) as well as with a series of complications related to endothelial injury, such as sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD), transplant-associated thrombotic microangiopathy (TA-TMA), etc. Endothelial cells (ECs) are key players in the maintenance of vascular homeostasis and during allo-HSCT are confronted by multiple challenges, such as the toxicity from conditioning, the administration of calcineurin inhibitors, the immunosuppression associated infections, and the donor alloreactivity against host tissues. The early diagnosis of endothelial dysfunction syndromes is of paramount importance for the development of effective prophylactic and therapeutic strategies. There is an urgent need for the better understanding of the pathogenetic mechanisms as well as for the identification of novel biomarkers for the early diagnosis of endothelial damage. This review summarizes the current knowledge on the biology of the endothelial dysfunction syndromes after allo-HSCT, along with the respective therapeutic approaches, and discusses the strengths and weaknesses of possible biomarkers of endothelial damage and dysfunction.

Impaired fibrinolytic activity is present in children with dyslipidemias

Dyslipidemias are major risk factors for atherosclerosis and cardiovascular disease. Abnormalities of fibrinolytic and coagulation components are considered useful predictors of cardiovascular morbidity and mortality in adults. This study examined whether fibrinolytic and coagulation components are abnormal in children with dyslipidemia. Thirty-six children with asymptomatic dyslipidemia, and 26 control subjects underwent venous occlusion stress testing with collection of preocclusion and postocclusion blood samples. All samples were assayed for tissue plasminogen activator, plasminogen, plasminogen activator inhibitor-1, alpha(2)-antiplasmin, alpha(2)-macroglobulin, D-dimer, fibrinogen, and von Willebrand factor. Children with dyslipidemia had significantly decreased levels of tissue plasminogen activator in both preocclusion and postocclusion samples compared with control subjects, reflecting decreased fibrinolytic activity. Children with dyslipidemia also had significantly increased levels of plasminogen, alpha(2)-macroglobulin, and fibrinogen in preocclusion and postocclusion samples compared with control subjects. In conclusion, decreased fibrinolytic activity is present in asymptomatic children with dyslipidemias, potentially reflecting endothelial dysfunction and increased risk of cardiovascular disease in early adult life. Further studies are required to determine the usefulness of this marker in predicting disease progression or response to therapy.

Changes in Clotting and Fibrinolytic Parameters Produced by Venous Stasis

Vascular endothelial cells have thrombosis- prevention properties through the release of some fibri nolytic factors. This capacity of endothelium was studied using the venous occlusion test (VOT) and measuring proteins released during stasis. Blood samples were col lected before and after 10 and 20 min VOT in tubes con taining sodium citrate at pH 7.0 or 4.3. A significant shortening of the euglobulin clot lysis time (ECLT) was obtained 10 and 20 min after VOT in plasma collected in citrate pH 7.0 or 4.3. No statistical difference was noted between results obtained 10 and 20 minutes after VOT. The shortening was related to the increase of tissue plas minogen activator (t-PA) released during VOT. No differ ence was detected in the concentration of tissue plasmin ogen activator inhibitor 1 (PAI-1), but PAI-1 activity mea sured in plasma from blood collected in citrate pH 7.0 decreased progressively from 10.8 ± 9.2 arbitrary units (AU)/ml to 3.76 ± 4.5 AU/ml and 0.8 ± 1.02 AU/ml (p < 0.001) after 10 and 20 min, respectively, of stasis. When the PAI-1 activity was determined in blood collected in citrate pH 4.3 for preventing in vitro complexing of PAI-1 and t-PA, results were different: PAI-1 activity decreased from a basal value of 29.2 ± 15.3 AU/ml to 24.9 ± 12.2 ( p = NS) and 18.7 ± 11.5; p < 0.02) 10 and 20 min after VOT. As result of fibrinolytic activation, other factors were modified: increase of plasminogen activators, de crease of plasminogen, and increase of D-dimer. Fibrin ogen, fibronectin, protein C, protein S, von Willebrand factor, and tissue factor pathway inhibitor concentration remained unchanged after VOT. According to our find ings, VOT can be performed with a stasis of 10 min. Good responders are related to the endothelial capacity for re leasing t-PA and urokinase-type PA (u-PA) and defined as those with an ECLT of <60 min after 10 min VOT when blood was collected in sodium citrate pH 7.0.

Changes in circulatory indices of thrombosis and fibrinolysis during total knee arthroplasty performed under tourniquet

Deep vein thrombosis may begin during surgery with the tourniquet inflated. Arterial levels of fibrinopeptide A, thrombin-antithrombin complexes, D-dimer, tissue plasminogen activator (t-PA) activity, and t-PA antigen were measured before surgery, during surgery with the tourniquet inflated, and following deflation of the tourniquet in 12 patients undergoing total knee arthroplasty. Minimal increases in fibrinopeptide A, thrombin-antithrombin complexes, and D-dimer were noted during surgery with the tourniquet inflated, but significant increases occurred immediately following deflation of the tourniquet. In 10 patients, intravenous heparin administration significantly suppressed the rise in fibrinopeptide A, but did not significantly alter the increases in either thrombin-antithrombin complexes, D-dimer, t-PA antigen, or t-PA activity. This study provides further evidence that deep vein thrombosis begins during surgery.

Factors affecting deep vein thrombosis rate following total knee arthroplasty under epidural anesthesia

A retrospective review was performed of 448 consecutive patients undergoing primary, unilateral, bicondylar, and cemented total knee arthroplasty under epidural anesthesia by three surgeons to determine factors contributing to deep vein thrombosis rate. All had venography on the fourth or fifth postoperative day and received aspirin and elastic stockings as their only thromboprophylaxis. The overall deep vein thrombosis rate was 41% (2% had proximal clots). The rate of deep vein thrombosis was not related to obesity, history of heart disease, hypertension, prior malignancy, smoking, diagnosis of osteoarthritis, duration of surgery, type of local anesthetic used, or the use of postoperative epidural analgesia. The rate of deep vein thrombosis varied significantly between surgeons: one surgeon had an overall deep vein thrombosis rate of 58% (proximal thrombi, 4%) whereas the other two surgeons had a deep vein thrombosis rate of 35% (proximal clot thrombi, 1%). A number of possible mechanisms to explain the variation in deep vein thrombosis rates between surgeons are provided.