F. Path Week 6: Fluid and Vascular Disturbances

haemorrhage

Escape of blood from circulation due to failure of haemostasis.

types of haemorrhage

External (outside the body) and internal (into tissues or cavities).

haemarthrosis

Bleeding into a joint.

petechiae

Small pinpoint haemorrhages in skin or mucous membranes.

haematoma

Localised swelling of blood in tissue.

haematemesis

Vomiting of blood, typically from the upper gastrointestinal tract.

goals and phases of haemostasis

Prevents blood loss from damaged vessels. Phases: Vasoconstriction, Coagulation (formation of fibrin clot via thrombin activation), Fibrinolysis and recanalisation (plasmin dissolves clot, vessels restore flow), Clot retraction and organisation.

Intrinsic pathway

Activated by contact with surface agents (e.g. collagen).

Extrinsic pathway

Coagulation pathway activated by tissue factor (e.g. trauma).

Where intrinsic and extrinsic pathways converge

At activation of Factor X (start of the common pathway).

Thrombin

Enzyme that converts fibrinogen to fibrin.

main goal of the clotting cascade

To form fibrin and stabilise a blood clot.

effects and risks of haemorrhage

Hypovolaemia, low blood pressure, reduced oxygen to brain/heart; Small cerebral bleeds can be fatal; severity depends on volume and rate of loss.

deficient factor in Haemophilia A

Factor VIII.

thrombocytopenic purpura

Purpura caused by reduced platelet count.

non-thrombocytopenic purpura

Purpura due to defective blood vessels despite normal platelet count.

thrombasthenic purpura

Purpura due to abnormal platelet function despite normal count.

primary vs secondary shock

Primary: Neurovascular response with no fluid loss. Secondary: Involves fluid imbalance and loss (e.g. haemorrhage, burns).

causes of hypovolaemic shock

Loss of blood, plasma, or fluids (e.g. burns, diarrhoea, haemorrhage).

causes of cardiogenic shock

Heart or lung failure (e.g. myocardial infarction).

cause of septic shock

Septicaemia and bacterial endotoxins (especially Gram-negative).

condition with reduced renal perfusion and altered fluid balance

Secondary shock.

thrombosis

Formation of a solid or semi-solid mass (thrombus) from blood constituents in vessels during life.

embolism

Lodgement of abnormal material (embolus) transported by the bloodstream into a vessel downstream.

infarction

Tissue death (anoxic necrosis) due to acute interruption of blood supply; the area is an infarct.

sequence from thrombosis to infarction

Thrombus forms → dislodges → becomes thromboembolus → blocks smaller vessel → causes infarct.

Virchow's triad components

Vessel wall damage, Abnormal blood flow (stasis or turbulence), Altered blood constituents (e.g. increased clotting factors).

example of vessel wall damage causing thrombosis

Atherosclerosis damaging the intima.

stasis of blood

Complete stoppage or slowing of blood flow.

what are blood composition changes which increase thrombosis risk

Hypercoagulability or increased clotting factors

Atherosclerosis

A condition caused by lipid deposition in the arterial intima.

Pale (white) thrombi

Thrombi composed of platelets and fibrin, typically found in fast-flowing arterial blood.

Dark red (red) thrombi

Thrombi composed of fibrin, red blood cells, and white blood cells, typically found in static venous blood.

Mixed (laminated) thrombi

Thrombi with Lines of Zahn — alternating layers of platelets/fibrin and red/white blood cells.

Mural thrombus

A thrombus attached to one side of the vessel wall without completely obstructing the lumen.

Occlusive thrombus

A thrombus that completely blocks the vessel lumen.

Coralline thrombus

An irregular, branching thrombus that may become occlusive.

Propagating thrombus

A thrombus that extends into adjacent vessel branches.

Ball thrombus

A free-floating, spherical thrombus often found in the heart.

Septic thrombus

A thrombus associated with infection.

Vegetations (in thrombosis)

Thrombi on heart valves, commonly seen in infective endocarditis.

Thromboembolism

A clot fragment that detaches and blocks a vessel elsewhere.

Fat embolism

Commonly caused by fracture of long bones (e.g. femur).

Atherosclerotic embolism

Embolism involving lipids from ruptured plaques.

Air embolism

Caused by IV lines, childbirth, or open-heart surgery.

Nitrogen embolism

Caused by rapid ascent in divers — Caisson disease (the bends).

Foreign body embolism

Caused by materials like needle fragments, splinters, talc, catheter tips, and bone cement.

Tumour embolism

Tumour cells entering blood vessels and spreading via circulation.

Amniotic fluid embolism

Caused by amniotic fluid entering maternal bloodstream during childbirth.

Complications of amniotic fluid embolism

Disseminated Intravascular Coagulation (DIC) and acute alveolar wall damage.

Talc embolism

Caused by the use of contaminated needles by IV drug users.

Pulmonary embolus

Caused by a venous thrombus dislodging from a deep leg vein.

Arterial embolus

Caused by a thrombus dislodging from a coronary artery.

Saddle embolus

A large embolus that straddles the bifurcation of the pulmonary trunk.

Phlebolith

A calcified thrombus in a vein ("vein stone").

Recanalisation

Formation of new vascular channels through an organised thrombus to restore blood flow.

Gangrene in thrombosis

Caused by persistent vascular obstruction leading to tissue death and secondary infection.