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Disorders of Haemostasis

Abnormal bleeding can arise from disorders of:
(1) the initiation of haemostasis, involving the vascular endothelium and platelets, and manifest as purpura and haemorrhage from or into superficial surfaces;
(2) the consolidation of haemostasis, involving the coagulation and fibrinolytic pathways, and slowing clinically as uncontrolled haemorrhages from or into deeper tissues.
Disorders of the initiation of haemostasis result from:
1) abnormalities of the endothelium;
2) abnormalities of platelet function;
3) thrombocytopenia.
Damage to endothelium is a common cause of purpura and haemorrhage in the tropics.
Infections are important, leading to haemorrhage through either direct toxicity to the endothelium (the haemorrhagic fevers), or to an immune damage during convalescence from several of the common childhood diseases, or to late immune damage as in Henoch-Schönlein purpura.
The viral haemorrhagic fevers include dengue, yellow fever, Lassa fever, Rift Valley, Ebola haemorrhagic fevers.
In immunocompromised individuals herpes-viruses (simplex and varicella) and arboviruses (O`nyong-nyong, African chikungunya) can cause haemorrhages which are sometimes fatal.
Dengue is the most common of the haemorrhagic fevers.
Purpura resulting from disordered platelet function (thrombopathy) can complicate the course of some of the:
 haemorrhagic fevers (Lassa, dengue, Ebola)
 alcoholism,
 hepatic cirrhosis,
 uraemia,
 paraproteinaemias,
 leukaemias
 myeloproliferative disorders,
 can also result from ingestion of non-steroidal anti-inflammatory agents (aspirin, indomethacin) and other drugs.
The bleeding tendency of patients with uraemia can be corrected temporarily by cryoprecipitate.

Thrombocytopenia:
An abnormally low platelet count may result from defective production, destruction or consumption in the peripheral blood, splenic pooling, or a combination of these mechanisms.
Many of the common causes in the tropics have been discussed already:
 viral,
 bacterial and protozoal infections,
 AIDS,
 hypersplenism,
 megaloblastosis,
 alcoholism,
 over dosage with pyrimethamine and trimethoprim,
 benzene exposure Onyalai (blood blister);
These have been described in Africa south of the equator.
Recently, auto antibodies to glycoprotein II b / III a - of platelets have been demonstrated in 12 out of 14 patients with onyalai.
• acute appearance of haemorrhagic bullae in the mucous membranes of the mouth, tongue and palate;
• Epistaxis is often present and may be severe;
• Blood loss can lead to haemorrhagic shock;
• Profound thrombocytopenia;
• Hyperplasia of the erythron and megakaryocytes;
• Platelets are morphologically normal.

Treatment and Prognosis:
Mortality in the acute phase used to be about 10%: patients dying of haemorrhagic shock or from cerebral haemorrhage.
• transfusion of whole blood for haemorrhage shock;
• supportive measures reduce mortality (oral hygiene);
• intravenous immunoglobulin or vincristine.

Coagulation Disorders:
The disorders of blood coagulation may be acquired or congenital.

Hypoprothrombinaemias:
Vitamin K deficiency is (haemorrhagic disease of the newborn). The premature is with – low levels of vitamin K.
Classical haemorrhagic disease of the newborn (HDN) is the result of Vitamin K deficiency:
• bleeding into skin, gastrointestinal tract;
• possible intracranial haemorrhage of late HDN due to Vitamin K deficiency;
• the diagnosis is confirmed by a prolonged PT;
• Vitamin K intravenously for treatment;
• co-trimoxazole, chloramphenicol.

Hepatic disease:
• bleeding in liver disease is multifactorial;
• a mild disorder of haemostasis;
• a fibrinogenaemia;
• fibrinogen and reduced platelet function;
• treatment by transfusion of cryosupernate or fresh frozen plasma.

Disseminated intravascular coagulation:
• damage to the endothelium with activation of the intrinsic pathway of the coagulation cascade;
• the release of thromboplastin-like materials from tissues;
• the injection of procoagulants of various snake venoms;
• obstetric disorders can trigger severe DIC (haemorrhage, endothelial damage, activated plasmin);
• In sub acute and chronic DIC red cells are ruptured by being forced through fibrin networks in small blood vessels;
• the obstruction of small blood vessels can cause ischemia, tissue necrosis, and renal failure;
• minor abnormalities of clotting tests;
• reduced platelet count;
• intravascular haemolysis;
• small fragmented red cells with bizarre shapes in the peripheral blood;
• thrombocytopenia, raised plasma FDPs.

Treatment:
• antibiotics and snake envenomation;
• transfusions;
• concentrated red cells plus saline;
• saline and colloids.

African snakes:
Echis carinatus (particularly prevalent in West Africa during the early rains)
• the venom contains an activator of thrombin;
• the blood is incoagulable, which is diagnostic of severe E. carinatus envenomation;
• death follows intracranial haemorrhage;
• haemorrhagic shock and renal failure;
• therapy is with an antivenom which must be known to be effective in the locality because antigenic specificity of venoms varies.

Naja nigricollis: (The spitting cobra is common throughout sub-Saharan Africa, except in the central African forest and the temperate south.)
• spontaneous haemorrhages may be fatal;
• raised FDP`s;
• a failure of clot retraction.

Bitis arietans: (The puff adder is found throughout sub-Saharan Africa except in dense forest).
• effects on the heart, nervous system, the kidney;
• spontaneous haemorrhages;
• endothelial damage;
• thrombocytopenia;
• complications of microangiopathic haemolytic anaemia;
• specific polyvalent antivenom treatment.

Dispholidus typus: (The green African tree-snake or boom slang is widespread in wooded areas of sub-Saharan Africa, except in the dense central African forest.)
• Only those who handle snakes are liable to be bitten;
• The course may be complicated by microangiopathic haemolysis and renal failure;
• Mortality without treatment is high, but antivenoms are effective.

Congenital Disorders:
• The prevalence of haemophilia A is about 10/100,000, of von Willebrand`s disease is greater, and of haemophilia B is about 0,1/100000 population;
• Cerebral haemorrhages can result from the raised intracranial pressure of persistent coughing;
• Plasma products (mind HIV) – contaminated cryoprecipitate;
• Cryosupernate;
• desmopressin for Willebrand`s disease;
• blood and blood products – use appropriately.

Vocabulary:
Prevalence [`prevǐlǐns] – поширення
Puff adder [`pǎf `ædə] – гадюка, вуж
Superficial surfaces [sјυpə`fǐ∫ǐəl] – зовнішні поверхні
Cryoprecipitate [krǐəprǐsǐpǐ`teǐt] – поява спаду температури
proliferative [prə`lǐfərətǐv] – поширюваний
Benzene exposure [`benzǐn ǐks`pəυзə] – піддавання впливу бензолу
splenic pooling [`splǐnǐk`pυlǐŋ] – дослідження селезінки
Blood blister [`blǎd`blǐstə] – кров'яний пухир
bullae [`bјυlə] – пухирці
Congenital [kən`dзǐnǐtl] – вроджений
Mucous [`mјυkəυəs] – слизовий
Intrinsic [ǐn`trǐnzǐk] – внутрішній
cryosupernate [krǐəυ`sјυpəneǐt] – поява температури
Obstetric [əb`stetrǐk] – акушерський
Clotting tests [`klotǐŋ`tests] – тести на згустки крові
Bizarre shapes [bǐ`zα:`∫eǐps] – дивні форми
Venom [`vǐnəm] – яд
Clot retraction [`klot rǐ`træk∫n] – витягування згустку

Questions:
1. What disorders of haemostasis do you know?
2. What is notable about the viral haemorrhagic fevers in the tropics?
3. What can be laboratory findings in case of thrombocytopenia?
4. Can we treat thrombocytopenia in the tropics?
5. How can we diagnose the hepatic disease and disseminated intravascular coagulation in the tropics?
6. Are there any congenital disorders in the tropics?

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