Embolism, Infarction, Shock final 2024.PDF

Embolism, infarction, shock Three common circulatory disorders: ⚫ ⚫ ⚫ Embolism Infarction Shock Learning outcomes ⚫ To describe the process of embolism and its clinical implications ⚫ To explain the pathogenesis of Infarction and its consequences ⚫ To understand the concept of shock and its ma...

Embolism, infarction, shock Three common circulatory disorders: ⚫ ⚫ ⚫ Embolism Infarction Shock Learning outcomes ⚫ To describe the process of embolism and its clinical implications ⚫ To explain the pathogenesis of Infarction and its consequences ⚫ To understand the concept of shock and its main causes Embolism, infarction, shock ⚫ ⚫ ⚫ Embolism Infarction Shock Embolism An embolus is a mass of material in the vascular system able to become lodged within a vessel and block its lumen The most common is pulmonary embolism from deep leg vein thrombosis ⚫ Most of the emboli are from dislodged thrombus, hence the term thromboembolism ⚫ The outcome depends on where the emboli originate and where they lodge Sources of emboli ⚫ Pieces of thrombus, mixed thrombus and blood clot ⚫ Infected lesions within the blood stream ⚫ Gas bubbles e.g. air, N2 (divers transferred too rapidly from high to low pressure environments) ⚫ Fat, bone marrow (in bone fractures) ⚫ Tumour cells ⚫ Others: amniotic fluid (during labour) Pulmonary embolism Most pulmonary emboli (60% to 80%) are small and clinically silent ~95% of cases from leg deep vein thrombosis Can cause sudden death, right heart failure, cardiovascular collapse If the blockage is in a middle size vessel, it can cause pulmonary haemorrhage Multiple emboli over time may cause pulmonary hypertension Embolism Large embolus derived from a lower extremity deep venous thrombosis and impacted in a pulmonary artery branch Systemic arterial emboli ⚫ ⚫ ⚫ ⚫ Emboli arise in the arterial circulation ~80% from intracardiac mural thrombi ~10-15% of unknown origin Can travel to a wide variety of sites The site of lodge depends on the source and the relevant amount of blood flow that downstream tissues receive In general, arterial emboli cause tissue infarction Systemic arterial emboli Atheroma Plague thrombus Atrial thrombus Valve vegetation brain kidney intestine Originate from the left heart or major arteries LV Infarct thrombus Lower limbs Other organs: spleen Infarction or gangrene is the usual consequence Embolism, infarction, shock ⚫ ⚫ ⚫ Embolism Infarction Shock Infarction An infarct is an area of ischemic necrosis caused by occlusion of either the arterial supply or the venous drainage in a particular tissue Tissue infarction is a common and very important cause of clinical illness and death The death of tissue from other causes, such as toxins or trauma, is not infarction but simply necrosis Infarction ⚫ Nearly 99% of all infarcts result from thrombotic or embolic events, and almost all result from arterial occlusion ⚫ Other causes: − − − − vasospasm, haemorrhage into atheromatous plaque vessel compression (by tumour) traumatic rupture Shape of infarcts Shape reflects the territory of occluded blood supply Wedge-shaped: in lung, Triangular: in kidney Scarred: in spleen Classification of infarcts Classification: Based on their colour (reflecting the amount of haemorrhage) and the presence or absence of microbial infection White (anaemic): in solid organs with end arterial circulation (such as heart, spleen, and kidney) Red (haemorrhagic) Septic: infected infarct Bland: uninfected infarct Development of infarction Major factors that influence the outcome of an infarction: The nature of the vascular supply The availability of alternative blood supply The rate of which an occlusion develops Slow occlusion provides time for alternative perfusion pathways Vulnerability to hypoxia Neurons and myocardial cells are vulnerable The oxygen content of the blood Evolution of myocardial infarct Infarcted area varies in appearance depending on the time after infarction Normal 24 h Pallor visible inflammation at edge days to wks Macrophage infiltration +fibrosis months Fibrous scar In lecture case study and discussion True or false? On gross examination of the heart at autopsy, a myocardial infarct can usually be recognised approximately 2 hours after coronary artery occlusion. In lecture case study and discussion True or false? In a typical acute myocardial infarct, leukocytic infiltration is most prominent 2 to 4 days after the occlusion of a coronary artery. Embolism, infarction, shock ⚫ ⚫ ⚫ Embolism Infarction Shock Shock ⚫ A final common pathway for several lethal clinical events best described as inadequate tissue perfusion ⚫ Characterised by systemic hypotension due to ⚫ ⚫ reduced cardiac output reduced effective circulating blood volume Causes of shock ⚫ Cardiogenic shock: results from low cardiac output due to heart failure Causes of shock Hypovolaemic shock: results from low cardiac output due to the loss of blood or plasma volume Causes of shock Septic shock: results from vasodilatation and peripheral pooling of blood as part of a systemic immune reaction to bacterial or fungal infection Causes of shock Symptoms of shock First aid of shock In class MCQ test A thrombus which has broken loose, moving with blood flow is called: a) an embolism b) a thrombosis c) an occlusion d) a clot e) an infarction In class MCQ test How many litres of blood does the healthy 70 kg adult male's body contain? a) b) c) d) e) 3 litres 5 litres 8 litres 10 litres 12 litres

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