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===Disorders of Haemostasis===

===Disorders of Haemostasis===

Patients with defective primary haemostasis typically present with pinpoint (petechial) haemorrhages affecting the skin and mucous membrane bevause plateles fail to deal even tiny capillary defects. Petechiae often merge into small, flat bruises called ecchymoses. Ocular haemorrhage (conjunctival, scleral, iridial and retinal petechiae, and hyphaema) is common. Intact secondary haemostasis often prevents major haemorrhage. Disorders of primary haemostasis typically prevents with multiple minor bleeds and prolonged bleeding.

Abnormalities can develop in any of the components of haemostasis. Disorders of primary haemostasis include vessel defects (i.e. vasculitis), thrombocytopenia (due to decreased production or increased destruction) and abnormalities in platelet function (e.g. congenital defects, disseminated intravascular coagulation). These lead to the occurence of multiple minor bleeds and prolonged bleeding. For example, petechial or ecchymotic haemorrhages may be seen on the skin and mucous membranes, or ocular bleeds may arise. Generally, intact secondary haemostasis prevents major haemorrhage in disorders of primary haemostasis .

Disordered secondary haemostasis typically causes haemorrhage into joints and body cavities. Haemothroax, haemoperitoneu, or haemoarthrosis may cause dyspnoea, abdominomegaly or joint swelling and lameness. Although subcutaneous and intramuscular haemorrhages occur, intact primary haemostasis prevents minor capillary bleeding (petechiae and ecchymoses). Disorders of secondary haemostasis typically present with large bleeds and "rebleeding".

When secondary haemostasis is abnormal, larger bleeds are frequently seen. Haemothroax, haemoperitoneum, or haemoarthrosis may occur, in addition to subcutaneous and intramuscular haemorrhages. Petechia and ecchymoses are not usually apparent, as intact primary haemostasis prevents minor capillary bleeding.  

 

patients with abnormalities of either primary or secondary haemostasis may show external haemorrhage such as epistxis, haematemesis, melaena and haematuria.. Sever blood loss may cause hypovolaemia and/or anaemia. Small volumes of blood within a sensitive location (for example, the brain, eyes. spinal cord or pericardial sac) can cause dramatic clinical signs. Many patients with haemostatic defects, however, can appear to be stable or clinically normal.

disroders of fibrinolysis may result in thrombus formation and loss of blood supply. The fomation of thrombi is promoted by: local endothelial injury (vascular damage), circulatory stasis and changed in anticoagulants or procoagulants, e.g. decreased ATIII. The most common mechanisms for AT deficiency are glomerular disease (AT is similar in size to albumin and is thus lost via the urine in glomerular diseasesP and accelarated consumption which occurs with disseminated intravascular coagulation or sepsis.

disroders of fibrinolysis may result in thrombus formation and loss of blood supply. The fomation of thrombi is promoted by: local endothelial injury (vascular damage), circulatory stasis and changed in anticoagulants or procoagulants, e.g. decreased ATIII. The most common mechanisms for AT deficiency are glomerular disease (AT is similar in size to albumin and is thus lost via the urine in glomerular diseasesP and accelarated consumption which occurs with disseminated intravascular coagulation or sepsis.