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Protein C: a new plasma protein related to postoperative hypercoagulability.

Protein C is a vitamin-K dependent plasma protein, whose activation is catalyzed by alpha-thrombin. Unlike vitamin-K dependent coagulation factors, activated Protein C is an anticoagulant enzyme. Purpose of the present study was to evaluate the pathophysiology of Protein C in patients undergoing minor and major elective surgery. A third group of patients were operated for cancer of the gastrointestinal tract. Protein C levels have significantly decreased in all patients in third postoperative day, while this decrease occurred since the first postoperative day in the case of cancer patients. This suggests that Protein C is consumed after surgery in its anticoagulant and profibrinolytic activity. The acquired Protein C deficiency may be related to postoperative hypercoagulability and increased risk of deep vein thrombosis.

Adolescent↗

[Thrombocyte proteins].

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Adenosine Triphosphatases↗

Surreptitious bleeding in surgery: a major challenge in coagulation.

Apart from inadequate surgical haemostasis, postoperative bleeding can be related to acquired disorders of platelet number, platelet function or coagulation proteins (e.g. Vitamin K deficiency, DIC or liver injury). We highlight our experience with three patients who suffered life-threatening bleeding in the postoperative setting. The three patients - a 47-year-old man and 70- and 74-year-old women -- all had negative histories for excessive bleeding with prior surgeries, and all had normal preoperative PT and aPTT tests. Surgeries were resection of ischaemic bowel, cholecystectomy and coronary artery bypass grafting. All patients experienced unexpected bleeding within the first few postoperative days requiring multiple red cell transfusions and surgical re-explorations. Evaluations within the first 4--7 days after surgery revealed that these three patients had developed prolonged aPTT due to demonstrable factor VIII antibodies initially at low titre. One patient was treated with high doses human factor VIII, corticosteroids, intravenous gammaglobulin and plasma exchanges. The inhibitor was no longer demonstrable after 6 weeks of such therapy, and he has remained in remission without therapy. The second patient was initially treated with high-dose human factor VIII infusions. Five months later, prednisone and 6-mercaptopurine were begun for worsening inhibitor titre and diffuse purpura and subcutaneous haematomas. The factor inhibitor remitted, but the patient died from liver failure related to post-transfusion hepatitis. The third patient was initially managed with high-dose human factor VIII. Two months later, worsening inhibitor titre and tongue haematoma was treated with activated prothrombin complex, corticosteroids and cyclophosphamide. Eight years later, she is on no therapy, demonstrates a mild bleeding tendency and has a stable low-titre inhibitor. There have been a few case reports of inhibitors to coagulation factors including factor VIII becoming manifest in the postoperative setting but surgery has not been widely recognized as an underlying cause for acquired haemophilia. This paper speculates on pathogenesis and reviews treatment options. This syndrome is remarkable for its abrupt onset in the first few postoperative days and for its substantial morbidity. The problem is potentially reversible with immunosuppressive therapy. Clinicians should be aware of this syndrome, considering acquired haemophilia in patients with unexpected postoperative bleeding.

Adult↗

Approach to the bleeding patient.

A broad, open, inquisitive, and semiskeptical mind must be used when approaching the bleeding patient. As in most endeavors in medicine, the history and physical examination provide an important baseline. Key laboratory tests must be quickly ordered and interpreted. Using this data base, one can quickly determine whether the hemorrhagic disorder is congenital or acquired, severe or mild, and progressive or stable. Hemostasis may fail owing to deficiencies of platelets, the plasma coagulation protein system, or endothelial disturbances. A precise diagnosis and appreciation of the tempo of the disorder will guide specific therapy.

Blood Coagulation Factors↗

The hypercoagulable states.

Patients are considered to have hypercoagulable states if they have laboratory abnormalities or clinical conditions that are associated with an increased risk of thrombosis (prethrombotic states) or if they have recurrent thrombosis without recognizable predisposing factors (thrombosis-prone). The number of specific primary hypercoagulable states that are recognized is growing. These disorders are generally inherited abnormalities of coagulation in which a physiologic anticoagulant mechanism is defective: for example, antithrombin III deficiency, protein C and protein S deficiency, abnormalities of the fibrinolytic system, and dysfibrinogenemias. Secondary hypercoagulable states are generally acquired disorders in patients with underlying systemic diseases or clinical conditions known to be associated with an increased risk of thrombosis: for example, malignancy, pregnancy, use of oral contraceptives, myeloproliferative disorders, hyperlipidemia, diabetes mellitus, and abnormalities of blood vessels and rheology. The complex pathophysiologic features of these secondary hypercoagulable states are discussed, and a framework is provided for the laboratory investigation and systematic clinical approach to the patient.

Antithrombin III Deficiency↗

[Venous sinus thrombosis in puerperium].

UNLABELLED: BACKGROUND, PATIENT RESPECTIVELY AND METHODS: Based on a case-report we demonstrate which symptoms are indicative of a cerebral sinus-venous thrombosis, how it can develop, and which diagnostic and therapeutic methods are available. RESULTS: Cerebral sinus-venous thrombosis in puerperium can be hidden behind unspecific symptoms like strong headache, nausea, vomiting. Literature reorts varying mortality between 5 and 30%. CONCLUSIONS: The obstetrician has to be attentive whenever these symptoms appear for the course and prognosis decisively depend on a quick diagnosis by means of computertomography and angiography. DISCUSSION: Blood coagulation disorders such as lack of Antithrombin III, protein C, or protein S, have been identified as a particularly important origin of the cerebral sinus-venous thrombosis. It is subject to discussion whether the patient should be advised against any further pregnancy. From a medical point of view, a subsequent pregnancy seems acceptable because the risk of another thrombosis, which is a rare event anyway, can be significantly reduced by providing anticoagulation substances.

Adult↗

[Cerebral sinus thrombosis and ulcerative colitis: two cases].

Inflammatory bowel diseases (IBD)--ulcerative colitis and Crohn's disease--are associated with increased risk for thrombotic complications both in the arterial and venous system. Cerebral sinus thrombosis is a rare but potentially fatal consequence of these diseases. Modern imaging methods made this uncommon complication of IBD more frequently recognized. The link between IBDs and thrombosis has been extensively studied. Inherited coagulation disorders (APC resistance, antithrombin III and protein-S deficiency), acquired diseases (antiphospholipid syndrome), and the frequent use of corticosteroids were suspected. Two cases of ulcerative colitis associated with cerebral sinus thrombosis successfully treated are reported. The connection between IBD and thrombotic complications and the therapeutic risks are discussed as well.

Adult↗

Protein S deficiency: imaging findings.

Protein S deficiency is an autosomal-dominant inherited disorder of coagulation associated with spontaneous and recurrent venous thrombosis. Approximately 5% of patients with deep venous thrombosis of the lower extremities who are less than 45 years old have a deficiency of protein S. Patients frequently have spontaneous and recurrent deep venous thrombosis and pulmonary embolism during young adulthood. Thrombosis occurs less commonly in the splanchnic and cerebral veins. Arterial thrombosis is rare but is seen in the cerebral circulation. Radiologists should include protein S deficiency in the differential diagnosis of unexplained thrombosis in young patients. This pictorial essay illustrates the range of imaging findings encountered in patients with this disorder.

Adult↗

Modified ultrafiltration attenuates dilutional coagulopathy in pediatric open heart operations.

BACKGROUND: Extreme hemodilution caused by relatively large prime volumes required for cardiopulmonary bypass in infants causes a dilutional coagulopathy, characterized by low concentrations of fibrinogen and other circulating coagulation factors. Modified ultrafiltration results in hemoconcentration and is associated with decreases in postoperative bleeding and transfusion requirements in children. This study was undertaken to quantify the effect of modified ultrafiltration on concentrations of fibrinogen, plasma proteins, and platelets in infants and small children. METHODS: Twenty patients less than 15 kg were studied. Cardiopulmonary bypass circuits were primed with crystalloid solutions. Red blood cells were added during cardiopulmonary bypass for hematocrits less than 15%. Colloid solutions were not administered. Concentrations of fibrinogen, plasma proteins, and platelets, and hematocrit were measured before cardiopulmonary bypass, before modified ultrafiltration, and after modified ultrafiltration. RESULTS: Modified ultrafiltration was associated with significant (p < 0.001) increases in hematocrit (19% +/- 6% to 31% +/- 9%), fibrinogen (65 +/- 29 to 101 +/- 45 mg/dL), and total plasma proteins (2.7 +/- 0.3 to 4.9 +/- 0.7 g/dL), but no change (p = 0.129) in platelet count. CONCLUSIONS: We conclude that modified ultrafiltration significantly attenuates the dilutional coagulopathy associated with cardiopulmonary bypass in infants.

Blood Coagulation Disorders↗

[Acquired protein S deficiency in HIV infections].

A prospective study of protein S was carried out in 17 consecutive HIV-infected patients. One subject was excluded because of severe chronic liver disease. Of the 16 evaluable patients (10 men, 6 women), 3 had AIDS, 7 ARC, 4 lymphadenopathy and 2 were asymptomatic. Total protein S and C4bBP (bound protein) were normal in all of them. In contrast, all but one subject had a free protein S deficiency: 35.5% (range: 0-68) for the whole group; 12.4% (range: 0-29) for the women: 50.9% (range: 27-68) for the men. From these results, we concluded that: a) free protein S deficiency is common in HIV-infected patients, b) this deficiency is more pronounced in female than male subjects, and c) this deficit is not linked to elevated C4bBP levels. The mechanism and the clinical consequences of this deficiency are discussed.

Adult↗

Vascular thrombohemorrhagic disorders: hereditary and acquired.

This review has summarized the more important diseases that may be accompanied by or lead to a disorder of hemostasis or thrombosis via alterations of the vasculature. It is to be stressed that the vascular component of hemostasis is often overlooked by clinicians caring for patients with disorders of hemostasis and thrombosis. It should be appreciated that the vasculature is intricately related to the coagulation protein system and to platelets when involved in thrombohemorrhagic diatheses. Although many vascular disorders may lead to hemorrhage or thrombosis, it must be appreciated that often it is impossible to discern between a primary vascular defect/damage and a defect that has been induced by platelet activation/dysfunction or procoagulant abnormalities.

Amyloidosis↗

Disseminated intravascular coagulopathy in a patient undergoing total hip arthroplasty for carcinoma. A case report.

A 78-year-old man was treated by total hip arthroplasty (THA) for metastatic carcinoma of the proximal femur. After operation, disseminated intravascular coagulopathy (DIC) developed. DIC is a known complication of malignancy but is reported infrequently as a complication of THA. Its occurrence in this patient may have been triggered by the release of coagulant proteins from surgical manipulation of the tumor. The disorder was characterized clinically by profuse uncontrollable hemorrhage from the surgical wound. Laboratory abnormalities indicated a consumptive coagulopathy. Guidelines for the diagnosis and management of a patient with DIC are available. Orthopedic surgeons should be alerted to the potential of this serious complication in patients treated by THA for metastatic bone abscess of the hip.

Aged↗

Protein C activators from snake venoms and their diagnostic use.

Proteinases converting the zymogen protein C (PC) of vertebrates into activated PC have been detected in several snake venoms. Most PC activators have been purified from venom of snake species belonging to the genera of the Agkistrodon complex. Unlike the physiological, thrombin-catalyzed PC activation reaction which requires thrombomodulin as a cofactor, most snake venom activators directly convert the zymogen PC into the catalytically active form which can easily be determined by means of coagulation or chromogenic substrate techniques. Due to this feature, the fast-acting PC activator Protac from Agkistrodon contortrix contortrix (southern copperhead snake) venom has found a broad application in diagnostic practice for the determination of disorders in the PC pathway. Recently, screening assays for the PC pathway have been introduced, based on the observation that the PC pathway is probably the most important physiological barrier against thrombosis.

Agkistrodon↗

Coagulation and inflammation.

The protein C anticoagulant pathway is critical for controlling microvascular thrombosis and is initiated when thrombin binds to thrombomodulin (TM) on the surface of the endothelium. Protein C activation is augmented by an endothelial cell protein C receptor (EPCR). EPCR is shed from the vasculature by inflammatory mediators and thrombin. EPCR binds to activated neutrophils in a process that involves proteinase 3 and Mac-1 and appears to inhibit leukocyte extravasation. EPCR can undergo translocation from the plasma membrane to the nucleus where it re-directs gene expression. During translocation, EPCR can carry activated protein C (APC) to the nucleus, possibly accounting for the ability of APC to modulate inflammatory mediator responses in the endothelium. TNF-alpha and other inflammatory mediators can down-regulate EPCR and TM. Inhibition of protein C pathway function increases cytokine elaboration, endothelial cell injury and leukocyte extravasation in response to endotoxin and infusion of APC reverses these processes. In vitro, APC has been reported to inhibit TNF-alpha elaboration from monocytes and to block leukocyte adhesion to selectins. Since thrombin can elicit many inflammatory responses in microvascular endothelium, loss of control of microvascular thrombin generation due to impaired protein C pathway function probably contributes to microvascular dysfunction in sepsis.

Animals↗