14 Ischaemia infarction and shock Flashcards Preview

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Flashcards in 14 Ischaemia infarction and shock Deck (18)
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1
Q

Differentiate between hypoxia and ischaemia.

A

Hypoxia: any state of reduced tissue oxygen availability.
Ischaemia: pathological reduction in blood flow to tissues.

2
Q

Why is reperfusion of non-infarcted but ischaemic tissues sometimes bad?

A

May cause repercussion injury. Inflammatory cells generate reactive oxygen species causing further cell damage.

3
Q

What causes infarction?

A

Thrombosis, embolus.
Vasospasm, extrinsic compression, vessel root twisting, vascular supply rupture.
Venous occlusion.

4
Q

Differentiate between red and white infarction.

A

Red: dual blood supply (lungs).
White: single blood supply (heart).

5
Q

What shape are infarcts?

A

Wedge shaped.

6
Q

What are the histological features of infarction?

A

Coagulative necrosis.

If brain = colliquative.

7
Q

What factors influence the degree of ischaemic damage?

A

Nature of blood supply.
Rate of occlusion - collaterals.
Tissue vulnerability to hypoxia (brain:4mins, heart:30mins).
Blood oxygen content.

8
Q

Which organs are particularly vulnerable to ischaemic damage?

A

Single supply: kidney, spleen, testis.

9
Q

What causes gas gangrene?

A

A gas producing organism e.g. clostridium perfringens.

10
Q

What are the cellular effects of shock?

A
Membrane ion pump dysfunction.
Intracellular swelling.
Intracellular content leakage.
pH dysregulation.
Lactic acid production.
11
Q

What are the systemic effects of shock?

A

Serum pH changes.
Vascular leakage.
Stimulation of inflammatory cascades.
End-organ damage.

12
Q

What are the classifications of shock?

A

Hypovolaemic.
Cardiogenic.
Distributive: anaphylactic, septic, TSS, neurogenic.

13
Q

What are the causes of hypovolaemic shock?

A

Haemorrhage.

Non-hemorrhagic: D+V, heat stroke, burns, third spacing (acute loss of fluid into internal body cavities).

14
Q

What are the categories of cardiogenic shock?

A

Myopathic (heart muscle failure).
Arrhythmia-related.
Mechanical (valvular/septal defects).
Extra-cardiac (obstruction to blood outflow).

15
Q

What are the causes of extra-cardiac cardiogenic shock?

A

Massive PE.
Tension pneumothorax.
Severe constrictive pericarditis.
Pericardial tamponade.

16
Q

How does septic shock occur?

A

Increased cytokines/mediators cause vasodilation.

DIC causes ischaemia.

17
Q

How does neurogenic shock occur?

A

Spinal injury/ anaesthetic accidents causing loss of sympathetic vascular tone and systemic vasodilation.

18
Q

What is toxic shock syndrome?

A
S. aureus / S. pyogenies produce exotoxins which do not require processing by antigen presenting cells. 
Non specific binding of class II MHC to T cell receptors. 
20% T cells activated with massive cytokine release.