Thromboembolismand Shock 血管栓塞和休克

Transcription

1 Thromboembolismand Shock 血管栓塞和休克

2 Major Hemodynamic Disorders Edema Hypermia and Congestion 充血 Haemorrhage Hemostasis 止血 and Blood Coagulation 血液凝固 Thrombosis 血栓形成 Embolism 栓塞 Infarction 梗死 Disseminated Intravascular Coagulation (DIC) Shock

3 Hemostasis-1 Definition: Hemostasis 止血 is the maintainence of the clot-free state of blood & the prevention of blood loss via the formation of hemostatic plug. Hemostasis depends on three general components: a) Vascular wall b) Platelets c) Coagulation 血液凝固

4 Hemostasis-2 Whenever a vessel is ruptured or severed 切断, hemostasis is achieved by several mechanisms: A. Vascular spasm B. Formation of platelet plug C. Formation blood clot as a result of blood coagulation 凝结 D. Eventual growth of fibrous tissue in to the blood clot to close the hole in the vessel permanently.

5 Thrombosis Definition: Thrombosis 血栓形成 is defined as the formation of a solid or semisolid mass from the constituents of the blood within the vascular system during life. Pathogenesis: There are three factors that predispose 使易于 to thrombus formation. A: Endothelial injury B: Stasis or turbulence of blood flow C: Blood hypercoagulability

6 A: Endothelial injury It is the most important factor in thrombus formation and by itself can lead to thrombosis. Endothelial injury is particularly important in thrombus formation in the heart & arterial circulation.

7 B: Turbulence or Stasis (Alterations in normal blood flow) Under physiologic conditions normal blood flow is laminar 流线的, that is, the cellular elements flow centrally in the vessel lumen separated from endothelium by slowing moving clear zone of plasma. Stasis & turbulence therefore: a. Disrupt the laminar flow and bring platelets in to contact with the endothelium b. Prevent dilution of activated clotting factors c. Retard or make a time lag in the inflow of clotting factor inhibitors and permit the build up of thrombi.

8 C: Hypercoagulablity Definition: Hypercoagulability is any alteration of the coagulation pathway that predisposes to thrombosis. Hypercoagulability is a less common cause of thrombosis, it can be divided into: 1. Primary (Genetic) 2. Secondary (Acquired)

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10 Embolism-1 Definition:- An embolus 栓子 is a detached intravascular solid, liquid or gaseous 气态的 mass that is carried by blood to sites distant from its point of origin. After traveling via the blood, the embolus can obstruct a vessel.

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12 Causes of embolism: An embolus can arise from: Embolism-2 Thrombus (99% of emboli arise from a thrombus. Such an embolus is called thromboembolus) Platelets aggregates Fragment of material from ulcerating atheromatous 动脉粥样化 plaque Fragment of a tumour Fat globules 小珠 Bubbles of air Amniotic 羊膜 fluid Infected foreign material Bits of bone marro

13 Embolism-3 a) Pulmonary thromboembolism (PTE) PTE is refers to the impaction of an embolus in the pulumonary arteries & their branches. Such an embolus is derived from a thrombus in the systemic veins or the right side of the heart. b) Systemic thromboembolism Systemic emboli arise from the left side of the heart or from thrombi & atheromatous debris in large arteries. And they impact in the systemic arteries.

14 Disseminated Intravascular Coagulation (DIC) Definition: -DIC is an acute, or chronic thrombohemorrhagic disorder occurring as a result of progressive activation of coagulation pathway beyond physiologic set point secondary to a variety of diseases resulting in failure of all components of hemostasis. Hence the other term for DIC is consumption coagoulopathy.

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18 Shock Definition: Shock is a state in which there is failure of the circulatory system to maintain adequate cellular perfusion resulting in widespread reduction in delivery of oxygen & other nutrients to tissues. In shock, the mean arterial pressure is less than 60 mmhg or the systolic blood pressure is less than 90 mmhg.

19 Classification of shock Shock can be divided into: A. Hypovolemic 血容量减少 shock B. Cardiogenic shock C. Distributive 分配性 shock

20 A. Hypovolemic shock Definition: This is shock caused by reduced blood volume. Reduction in circulating blood volume results in the reduction of the preload which leads to inadequate left ventricular filling, reflected as decreased left & right ventricular end diastolic volume and pressure. The reduced preload culminates in decreased cardiac out put which leads to widespread tissue perfusion (shock).

21 B. Cardiogenic shock Definition: This is shock that results from severe depression of cardiac performance. It primarily results from pump failure [myocardial failure].

22 C. Distributive shock Definition: Distributive shock refers to a group of shock subtypes caused by profound peripheral vasodilatation despite normal or high cardiac output.

23 Septic shock Definition: This is a kind of shock caused by systemic microbial infection, most commonly by gram negative infection (endotoxic shock) but can also occur with gram positive or fungal infections.

24 Clinical course of shock Patient with shock may manifest as having a weak and rapid pulse, cool, clammy 冷湿, cyanotic skin. In septic shock, the skin will initially be warm & flushed because of peripheral vasodilation. The patient may present with confusion, restlessnes, decreased urine output, coma, and death.