overview of coagulation

1. Blood coagulation, Embolism, Ischaemia
and Infarction
DR. OSITA EDE
CONSULTANT ORTHOPAEDIC SURGEON
NATIONAL ORTHOPAEDIC HOSPITAL
ENUGU

2. Outline
Overview of the coagulation system
Thrombosis
Embolism
Ischaemia/Infarction

3. Overview of the coagulation system
 Coagulation is the formation of a blood clot at sites of vascular injury.
 Fine interplay between coagulation and fibrinolytic system to maintain blood in a fluid state in a
normal vessel and form clots only at sites of vascular injury.
 The vessels, platelets, coagulation factors, and fibrinolytic systems work together to maintain
hemostasis.

4.  Vascular Constriction
 Platelet adhesion and activation
 Platelet aggregation
 Formation of fibrin monomers
 Cross-linking of fibrin monomers to polymers
 Activation of fibrinolytic system

6.  Thrombosis:
 Formation of a solid mass from the constituents of free-flowing blood within the vasculature of a
living person.
 Risk factors for thrombosis: Virchow’s triad

7.  Endothelial injury
 Major cause of arterial thrombosis(white thrombus), causes
flow turbulence
 Arterial plaque rupture
 Cigarette smoking
 Toxins
 Sepsis
 Stasis
 Major cause of venous thrombosis(red thrombus), causes flow
slowing
 Aneurysms
 Myocardial infarction
 Atrial fibrillation
 Valvular stenosis
 Varicosities
 Immobilisation

8.  Hypercoagulability
 Associated with venous thrombosis
 Congenital (rare) : factor v Leiden mutation. Protein c and s def, antithrombin def
 Acquired(common): cancer, DIC, OC use, snake venom, polycythemia, SSDx, Nephrotic syndrome

9.  Thrombus outcomes:
 Propagate
 Dissolve (fibrinolysis)
 Organize and recanalize
 Embolize

10.  Embolism:
 A free-flowing intravascular mass carried to a distant site from its origin with the potential of causing
distal vascular occlusion.
 Types: thrombo-embolus (most common), air, fat, amniotic fluid, foreign body
 Pulmonary embolus: embolus from DVT(the most common form of thromboembolism)
 Systemic embolus: embolus from an arterial thrombus(intramural cardiac thrombi)
 Air embolism – decompression sickness
 Fat embolism – multiple long bone fractures

11.  PE:
 Incidence 2-4/1000
 60-80% are silent
 Sudden heart failure (Cor pulmonale) if >60% pulmonary luminal obstruction
 Pulmonary haemorrhage, rupture of obstructed medium-sized arteries
 Pulmonary infarction, obstruction of small end-arterioles
 Pulmonary hypertension with right ventricular failure

12.  Ischaemia & Infarction:
Ischaemia is the restriction in blood supply to an area causing tissue hypoxia and reversible cellular
damage.
Necrosis is microscopic cellular death from prolonged ischaemia.
Infarction is macroscopic tissue death from prolonged ischaemia.
An infarct is an area of ischemic necrosis caused by occlusion of either the arterial supply or the venous
drainage.
Ischemia comprises not only insufficiency of oxygen, but also reduced availability of nutrients and
inadequate removal of metabolic wastes

13.  Signs and symptoms of ischaemia:
 The six Ps:
 -paraesthesia
 -pain
 -pallor
 -poikilothermia
 -pulselessness
 -paralysis

14.  Causes of ischaemia/infarction:
 Vascular occlusion: thrombus, embolus, atheroma
 Vascular injury: laceration, spasm, external compression(compartment syndrome)
 Vascular pedicle torsion (testicular, bowel)

15.  Classification of infarcts: based on the gross appearance of the infarcted tissue
 Red: venous occlusions, loose spongy tissue, dual circulations, reestablishment of flow to infarcted
tissue
 White: end-arterial occlusion

16.  Factors affecting the development of infarcts:
 -tissue blood supply(end or collateral supply?)
 -vascular occlusion rate
 -tissue vulnerability to hypoxia

17. Thank you