Haemostasis, Thrombosis & Embolism Lecture Notes PDF

Haemostasis Definition: A physiological response to vessel injury. Haemostasis -...

Haemostasis Definition: A physiological response to vessel injury. Haemostasis - The process by which bleeding is arrested. Thrombosis and Embolism Apply pressure ? Hemostasis has three major steps: Ischaemia and infarction 1. Vasoconstriction Istop blood fibrinogen 2. Activation of platelets adhere and aggregate Converted Tanvier Omar from flowing Division of Anatomical Pathology Faculty of Health Sciences outof the Vessel until - plug at the injury site temporary block 3. Activation of the coagulation cascade fibrin - prin Room 3L27, 3rd floor thrombus formation closure of site of injury Wits University naemostasis [email protected] occurs These processes seal the defect until tissues are repaired. ① ③ Lecture objectives: HAEMOSTASIS – pathogenesis The contact of blood with tissues activates To identify the factors controlling haemostasis To define the terms thrombosis and clotting coagulation cascade. To outline Virchow's triad 13 coagulation factors fibrinogen, a soluble plasma To define terms relating to the concept of embolism protein, is cleaved into fibrin, a non-soluble plasma protein. To differentiate the various types of emboli and their The fibrin proteins stick together forming a thrombus. relationship to ischaemia and infarction. To explain the pathophysiology of hypoxia O Fibrinolytic system: plasminogen plasmin lysis of (physiological To outline causes of ischaemia and effects on organs fibrin clot. Explore examples of infarcts in different organs thrombus is dissolved ② ④  Thrombosis: Definition of terms Blood CLOTS –In a test-tube –In blood vessels after death Blood COAGULATES in the LIVING BODY to form a THROMBUS Therefore: A thrombus is a solid or semi-solid mass formed from the constituents of blood within the vascular system DURING LIFE post mortem, blood may separate out into an upper pale part and a lower dark red part. The yellow, pale portion is often referred to as “chicken fat” clot. ~carse,granular inegar smothje , , Thrombus in the Vessel Thrombosis-anactive process in the living o a femoral vein wall Blood clot Virchow's triad: Three factors that contribute to thrombosis 0 Trauma, T inflammation, atheroma a Plaquesinves ~ um Platelets adhere to wall endothelial injury dehydrat mobile -less M blood viscosity ↓ Stasis, obstruction un Dehydration, post-surgery Stasis ? ↳ tumor blood vessels constricting num Cexternal (planes)  Types of thrombi Types of thrombi 1. Venous Thrombi: ~ nothing wrong with veins. 2. Arterial thrombi: Damage to wall e.g. atheroma, Phlebo-thrombosis – vein not inflamed. inflammation. Disturbance to flow – stasis, e.g. Cause: Stasis – heart failure, shock, bed rest, post partum, - post surgery, dilatation aneurysm, tumour. um Usually, involves deep calf veins of vessel 3. Cardiac thrombi: Atria – mitral stenosis - stasis, Clinically – pain, on pressure and dorsiflexion, oedema ↓ ventricles – myocardial infarct, myocarditis, aneurysm with rein turbulent Thrombo-phlebitis –thrombosis at: - something wrong flow 4. Capillary Thrombi: -Site of inflammation, e.g. drip site, with damage to vessel ↓ wall. Site of local infection e.g. appendicitis. predisposed disseminated intravascular coagulopathy (DIC) to thrombus Veins in the muscles of the lower limb NORMAL HEALTHY AORTA ABDOMINAL AORTA BELOW THE RENAL ARTERIES - SEVERE endothelial FROM A 20 YEAR OLD MALE COMPLICATED ATHEROMA injury · e Endothelial injury Macroscopic appearance Low-power microscopy  obstruction , narrowing , turbwent flow. clot breaks Cardiac thrombus Arterial thrombus ↓ Clot developes Y v off and empolises O arterial thrombus in Coronam artery https://slideplayer.com/slide/5018472/ https://www.uaz.edu.mx/histo/pathology/ed/ch_7/c7_19.jp g Myocardial infarct https://www.123rf.com/photo_104097826_acute-myocardial-infarction- histology-of-heart-tissue-light-micrograph-area-of-infarct-is-paler- than.html O https://emedicine.medscape.com/article/1960472-overview Fate of a thrombus THROMBO-EMBOLIC DISEASE thrombus ① Dissolution: Clot W dissolves; lumen returns to Definition of terms:- normal Embolus – a mass of undissolved material ② Propagation: Along length of vessel transported from one part of the vascular tree ③ Recanalization: Capillaries invade thrombus – to another. re-establish blood flow; may result in multiple In most cases this consists of thrombotic small lumina doesn't recanalize material (most cases : thrombic emboli ~ ⑪ Organisation: Scar tissue; lumen obliterated ⑤ Embolization: To a distant site  Venous thrombo-embolic disease OTHER TYPES OF EMBOLI Extremely common cause of morbidity/mortality Arterial thrombo-emboli -usually put Atheromatous - thrombotic material admixed with Post-operative, bed-ridden, aged patients ~ on anticoagulants atheromatous debris Air/gas “economy class air travel” ~ predisposes to thrombic emboli – Abortions – Head & neck surgery Deep vein thrombosis in lower limbs embolises to: – Sudden decompression – diving/anaesthetics -Pulmonary trunk = saddle embolus usually fatal Amniotic fluid embolus – post delivery - Segment of lung sub-pleural infarct Fat emboli – extensive trauma to skeleton These thrombo-emboli do not travel through the lung – Tumours they never affect the systemic (lt. side) of the circulation Foreign bodies /Parasites Thrombosus in (4) L systemic Arterial and cardiac Emboli G Pulmonary emboli https://www.slideshare.net/csbrprasad/5-embolism thrombus Otarombus  Definition of terms: Hypoxia ISCHAEMIA thrembic embolism eg : 4 types : ~ Generalised - cardiac failure – affects the whole body Localised - affect only part of the body 1. Ischaemic hypoxia: Inadequate blood supply - Complete -high altitude - Partial 2. Hypoxic hypoxia: O2 in blood respiratory failure Causes: ↓ pulmonary oedema : In most cases due to failure of the arterial 3. Anaemic hypoxia: Too little Haemoglobin to carry O2 blood supply – thrombo-embolus, atheroma, spasm, external pressure Call prevent flow of plood) 4. Toxic or histotoxic hypoxia: caused by cell injury blocking the uptake of O2 e.g. Cyanide :May also result from venous obstruction e.g. in poisoning the gut – volvulus, strangulated hernia. num ↓ bowel twists C obstructs blood flow) : Ischaemia and Infarction colaterals ? Ischaemia: Factors affecting the extent/severity of ischaemia: Definition of terms: Blood supply: Double blood supply liver/lungs braineasible me to Ischaemia is a condition of inadequate blood - ischaemia than Collateral blood supply brain, lower limbs supply to an area of the body. conective End arteries heart/kidney/spleen/distal cerebral arteries nothing Tissue ① –Partial to pickup ! Rate of onset: too rapid to allow collateral to develop – poor the stack ① –Complete localised areaHissue of ischaemic necrosis i.e. = infarction infarcts) Degree of vascular occlusion: partial vs. complete Ischaemia hypoxia - too little O2 Nature of tissue e.g. brain vs. connective tissue anoxia ( no O2) cells will die. reduced nutrition to cells Anaemia poorer outcome accumulation of waste Respiratory compromise poorer outcome Lunable to oxygenate blood w ~ hypoxia : O2 sats below go % ⑳  Splenic Infarction: CLASSIFICATION OF INFARCTS 1. Colour: ① -Pale (anaemic) kidney /spleen Recent subcapular infarct Start off by being haemorrhagic briefly, but rapidly become pale due to the density of the tissue which swells after infarction, pushing out the blood within the infarcted area ②-Haemorrhagic lung/gut Start off and remain haemorrhagic as the tissues are less dense Healed infarct consisting of dense scar tissue 2. Presence or absence of Infection –Bland = non-septic Cogut –Septic = are initially infected or become so early in their development infarct. LUNG: Pleural surface of lung showing the presence of a Myocardial infarct recent haemorrhagic infarct Wedge shaped, hemorrhagic https://emedicine.medscape.com/article/1960472-overview https://www.123rf.com/photo_104097826_acute-myocardial-infarction- histology-of-heart-tissue-light-micrograph-area-of-infarct-is-paler-than.html Thank You [email protected] O