6. Thrombosis, embolism and shock Flashcards
Thrombosis
The formation of a solid or semi-solid mass from the
constituents of the blood while moving within the vascular system during life.
Locations where thrombi may form
Lumen of the heart
Arteries
Veins
Capillaries
Capillaries (thrombi)
Disseminated intravascular coagulation:
Involves both thrombus formation and
haemorrhage!
Triggers include infections, septicaemia,
malaria, neoplasms and liver disease.
Capillaries may be occluded by minute
thrombi causing scattered ischaemic
lesions.
Factors that promote thrombosis
Virchow’s triad:
- Abnormalities of the vessel wall
- Abnormalities of blood flow
- Abnormalities of the blood’s constituents
Abnormalities of the vessel wall
Arteries = Atheroma, Inflammation
Heart = Myocardial infarction, Rheumatic endocarditis
Veins = Trauma, Inflammation
Chemicals - sclerosants
(irritant substances injected to obliterate
varicose veins)
glucose
(atheroma in diabetes mellitus)
Capillaries = InflammationAbnormalities of blood flow
Arteries = Turbulence, aneurysms, plaques, spasm
Heart = Atrial fibrillation, Aneurysms
Veins = Local problem
compression
inactivity
(postoperative bed rest; economy class
syndrome)
General problem heart failure circulatory shock
Abnormalities of the blood constituents (1)
Increased viscosity:
Polycythaemia = Dehydration, Chronic hypoxia,
Polycythaemia rubra vera
Hyperproteinaemia = Multiple myeloma (Tumour of
plasma cells in bone marrow with
accumulation of immunoglobulins
in plasma)
Abnormalities of the blood constituents (2)
Abnormalties of clotting:
Pregnancy = (prevents bleeding when placenta detaches)
Some (older) contraceptive pills
Following trauma (liver produces more clotting factors)
Thrombocythaemia
Tumours
Inherited
Fate of thrombi
Resolution = Fibrinolysis. Very common fate.
Organisation = Incorporation into a scar (mural nodule or
web) by macrophages and fibroblasts.
Vessel lumen remains narrowed or
occluded.
Intimal cell proliferation, capillary invasion
and recanalisation. Vessel again becomes
patent.
Detachment = Thromboembolism
Embolism
The transport of abnormal material (solid, liquid, gas)
by the blood stream and its impacting in a blood vessel.
Types of emboli (1)
Thrombi
Fat
Gas = Infusions, Vascular surgery
Caisson disease - On ascending from the depths
too rapidly, bubbles of N2 form in the blood stream
and on entering the bones and joints cause the pain
known as “the bends.”
Types of emboli (2)
Tumour material = When tumour penetrates blood vessel
parts may break away to form
metastases.
Infective agents = Includes fragments of vegetations
growing on heart valves in infective
endocarditis.
Atheroma = Fragments of atheromatous plaque may
break off
Amniotic fluid = uterus may force amniotic fluid and
squames from infant into uterine veins of
mother.
Foreign bodies = intravenous drug abuse, iatrogenic
Shock
Shock is a physiological state characterized by a significant, systemic reduction in tissue perfusion, resulting in decreased tissue oxygen delivery and insufficient removal of cellular metabolic products, resulting in tissue injury
not the same as emotional shock
Hypovolaemic shock
haemorrhage – internal or external
severe burns
Cardiogenic shock
large acute myocardial infarction
other acute cardiac disease
