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W's MoD > Lect 14 - Ischaemia, Infarction & Shock > Flashcards

Lect 14 - Ischaemia, Infarction & Shock Flashcards

1
Q

What is hypoxia?

A

Any state of reduced tissue oxygen availability

this can be generalised - whole body e.g. altitude, anaemia

or regional - specific tissues affected

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2
Q

what is Ischaemia

A

Pathological reduction in blood flow to tissues

Usually as a result of obstruction to arterial flow

commonly as a result of thrombosis / embolism

Ischaemia results in tissue hypoxia

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3
Q

what is infarction

A

Ischaemic necrosis caused by occlusion of the arterial supply or venous drainage

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4
Q

Give some causes of infarction that are not caused by blood clots

A 
Vasospam
Atheroma expansion
Extrinsic compression (e.g. tumour)
Twisting of vessel roots (e.g. volvulus)
Rupture of vascular supply (e.g. AAA)
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5
Q

what are the types of infaction?

A 
Red infarction (haemorrhagic)
White infarction (anaemic)
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6
Q

what shape are infarcts?

A

Most infarcts are wedge-shaped

Obstruction usually occurs at an upstream point, everything downstream is affected.

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7
Q

what would you expect to see histologically in infarction?

A

Coagulative necrosis (Colliquative) in the brain

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8
Q

what 4 factors influence the degree of ischaemic damage

A

Nature of the blood supply

Rate of occlusion

Tissue vulnerability to hypoxia

Blood oxygen content

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9
Q

give examples of areas which are less prone to ischaemic damage due to nature of blood supply

A

Lungs (pulmonary and bronchial arteries)
Liver (hepatic artery and portal vein)
Hand (radial and ulnar artery)

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10
Q

why does a quick rate of occlusion make ischaemic damage worse?

A

doesn’t allow time for the development of alternative (collateral) perfusion pathways

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11
Q

what tissues are the most vulnerable to lack of oxygen?

A

The brain

(irreversible cell damage in 3 to 4 minutes)

The heart

(Mycocyte death in 20 to 30 minutes)

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12
Q

what is the leading cause of death in men and women in the West

A

Ischaemic heart disease

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13
Q

give 2 causes of ischaemic stroke

A

Thrombosis secondary to atherosclerosis

Embolism (e.g. mural thrombus)

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14
Q

give 2 Causes of a haemorrhagic stroke

A

Intracerebral haemorrhage (hypertensive)

Ruptured aneurysm in the circle of Willis (subarachnoid

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15
Q

What disease presents with abdominal pain and is caused by the same pathological process as Ischaemic heart disease

A

Ischaemic bowel disease

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16
Q

what does limb ischaemia lead to?

A

Gangrene

17
Q

what types of Gangrene are there?

A

Dry gangrene (Ischaemic coagulative necrosis only)

Wet gangrene (Superimposed infection)

Gas gangrene (Superimposed infection with gas producing organism)

18
Q

define gangrene

A

Infarction of entire portion of limb (or organ)

19
Q

define shock

A

A physiological state characterised by a significant reduction of systemic tissue perfusion (severe hypotension) resulting in decreased oxygen delivery to the tissues.

20
Q

what does shock lead to?

A

cellular hypoxia and derangement of critical biochemical processes at first cellular and eventually systemic levels.

21
Q 
give some Cellular effects 
of shock (5)
A 
Membrane ion pump dysfunction
Intracellular swelling
Leakage of intracellular contents into the extracellular space
Inadequate regulation of intracellular pH
Anerobic respiration ( makes lactic acid)
22
Q

give some Systemic effects of shock (4)

A

acidaemia
vascular leakage
Stimulation of inflammatory and anti-inflammatory cascades
End-organ damage

23
Q

after shock becomes irreversible, what sequence of events leads to death?

A

Cell death
End-organ damage
Multi-organ failure
Death

24
Q

what is Hypovolaemic shock?

A

Intra-vascular fluid loss.

less preload therefore less cardiac output.

25
Q

what Causes hypovolaemic shock

A

Haemorrhage, Diarrhoea, vomiting, heat stroke, burns

26
Q

what is Cardiogenic shock

A

Cardiac pump failure

27
Q

what are the Categories of cardiogenic shock

A

Myopathic (heart muscle failure)

Arrythmia-related (abnormal electrical activity)

Mechanical

Extra-cardiac (obstruction to blood outflow)

28
Q

what are the casues of myopathic cardiogenic shock

A

Myocardial infarction
Right ventricular infarction
Stunned myocardium (following prolonged ischemia)

29
Q

what arrhythmias cause cardiogenic shock

A

Atrial and ventricular arrhythmias (fibrillation / flutter )

also Ventricular tachycardia, bradyarrhythmias, and complete heart block

30
Q

give some causes of Extra-cardiac cardiogenic shock

A

Anything that impairs cardiac filling or ejection of blood from heart

Massive pulmonary embolism
tension pneumothorax
Severe constrictive pericarditis
pericardial tamponade

31
Q

what is Distributive shock?

A

severe vasodilation that massively lowers systemic vascular resistance.

32
Q

what sub types of Distributive shock are there?

A

SEPTIC SHOCK
ANAPHYLACTIC SHOCK
NEUROGENIC SHOCK
TOXIC SHOCK SYNDROME

33
Q

what is Septic Shock?

A

Severe, over-whelming systemic infections.

Cytokines and mediators casue the VASODILATION

DIC can also cause Ischaemia

34
Q

what is Anaphylactic shock

A

Severe type I hypersensitivity reaction:

Massive mast cell degranulation casues Vasodilation and also respiratory distress. Patients undergo Circulatory collapse.

35
Q

what is Neurogenic shock?

A

Spinal injury / anesthetic accidents

Loss of sympathetic vascular tone leads to Vasodilation

36
Q

what is Toxic shock syndrome?

A

S. aureus /S. pyogenes produce exotoxins known as “superantigens” that Do not require processing by antigen-presenting cells.

this casues Non-specific binding of class II MHC to T cell receptors - Widespread release of massive amounts of cytokines

37
Q

are there combined types of shock?

A

Yes. like septic shock with a Primary distributive component/Hypovolemic component/ Cardiogenic component

the infection can lead to symptoms which then compound the shock (like diarrhoea)

38
Q

what is the mortality of Cardiogenic shock?

A

60 – 90% mortality

W's MoD (18 decks)

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