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Pathology > Disturbances in circulation > Flashcards

Disturbances in circulation Flashcards

1
Q

Describe some aspects of haemorrhage…

A

Bleeding from a damaged vessel

  • Often caused by trauma
  • Vascular disease may predispose to
  • Local high blood pressure may predispose to
  • A diffuse haemorrhage may occur in coagulation disorders
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2
Q

What is diapedesis?

A

Loss of individual RBCs between endothelial cells

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3
Q

What is a haematoma?

A

A local accumulation of blood that is usually clotted

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4
Q

What is petechiae?

A

Pin-point haemorrhages

- usually capillary bleeds

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5
Q

What is ecchymoses?

A

Paint brush “splashed” haemorrhages over skin or mucous membranes

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6
Q

What are some local effects of haemorrhage?

A

The effect depends on location

  • Space-occupying lesions
  • Small haemorrhages
  • Larger haematomas
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7
Q

What are the systemic affects of haemorrhage?

A

Depends on the severity and speed of onset

  • Repeated minor blood loss may lead to iron deficiency
    e. g. GIT ulcers
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8
Q

When is hypovolaemic shock likely?

A

When there is acute blood less of 30% or more

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9
Q

What happens if there is slower loss of 30% of total blood volume?

A

Compensation may be enough

- The body has its own compensatory mechanisms that come into play

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10
Q

Describe the three compensatory mechanisms…

A

Redistribution is a Rapid Response occurs within minutes

Restoring blood fluid volume is a medium term mechanism that occurs within hours

Replacing RBCs is a longer term mechanism that occurs within 5-14 days

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11
Q

Describe the Blood redistribution compensatory mechanism…

A

Some arterioles constrict to divert blood to vital organs

- Spleen contracts at the same time

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12
Q

Describe the Restoration of blood volume compensatory mechanism…

A

Extravascular fluid moves into the vascular system

  • this helps to maintain blood pressure
  • Causes Haemodilution

Takes 48 hours
- then you can estimate the blood loss by PCV

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13
Q

What level of PCV would you expect in a dog that has just lost 20% of its circulating blood volume?

A

Normal

- it has lost RBCs and fluid in the same ratio

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14
Q

What level of PCV would you expect in a dog that has lost 20% of its circulating blood volume 24 hours ago?

A

Low

  • due to haemodilution
  • the extravascular fluid has moved into the vascular system and diluted the blood
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15
Q

Describe the replacement of lost erythrocytes compensatory mechanism…

A

This is a bone marrow response

  • Makes as many RBCs as it can
  • Indicated by reticulocytes which are immature form of RBCs
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16
Q

What are haemorrhagic diatheses?

A

Haemorrhagic tendencies associated with:

  • disorders of the blood clotting mechanism
  • Vascular disease
17
Q

What is purpura haemorrhagica? Describe it…

A

Horse vascular disease

  • Haemorrhage and oedema
  • Due to allergic reactions causing damage to arteriole epithelium
  • Often due to previous strangles infection
18
Q

Describe Vitamin C deficiency…

A

Vitamin C is a cofactor in collagen

  • Results in weakness of connective tissues
  • Haemorrhage from multiple vessels
  • Delayed wound healing
  • Tends to only be seen in species that can’t synthesise their own vitamin C e.g. guinea pigs
19
Q

What is shock?

A

Failure of the circulatory system to adequately perfuse vital organs
- disparity between circulating blood volume and the size of the vascular space

20
Q

What are the three categories of shock?

A
  • Hypovolaemic
  • Cardiogenic
  • Vasculogenic (septic)
21
Q

What is hypovolaemic shock…

A
  • Decreased blood volume
  • Loss of fluid by vascular compartment
    e. g. sweating, diuresis
22
Q

What is vasculogenic/ septic shock?

A

Septicaemia with gram -ve bacteria (endotoxaemia)
- Systemic vasodilation

Widespread endothelial cell damage

23
Q

What is cardiogenic shock?

A

Decreased cardiac output

  • acute severe myocardial failure
  • improper diastolic filling
  • improper systolic emptying

Blood sits stagnant and doesn’t circulate properly

24
Q

What is irreversible shock?

A

When the body’s compensatory mechanisms are insufficient to sustain the patient

  • inadequate tissue perfusion
  • causes ischaemic injury to cells
25
Q

What are the consequences of inadequate tissue perfusion?

A

Endothelial cells cause leaky vessels

  • Vascular fluid lost
  • RBCs sludge due to lack of vascular fluid
  • Kidney and liver cell necrosis
  • Heart arrythmias
  • Brain damage/ loss of consciousness
26
Q

What are the consequences of inadequate tissue perfusion?

A

Anaerobic metabolism
- build up of metabolites
- these metabolites exacerbate perpetuating failing C.O and worsen perfusion
= irreversible shock

27
Q

What is Oedema?

A

Excessive accumulation of tissue fluid

28
Q

How does oedema form?

A

When too much fluid forms

  • Increased hydrostatic pressure
  • Decreased colloid osmotic pressure
  • Increased vascular permeability

OR

Not enough fluid is removed
- Impaired lymphatic drainage

29
Q

What normally occurs in a blood vessel in terms of fluid regulation?

A

It is a balance between hydrostatic and osmotic pressures in blood vessels (starling’s law)
- some fluid moves out of vessels at the arterial end but is balanced by lymphatic drainage plus resorption (COP) of fluid at the venous end

30
Q

Describe increased hydrostatic pressure…

A

Increased pressure in the capillaries
- determined by venous pressure

Local i.e. finger obstruction

OR

Systemic i.e. heart failure

31
Q

Decreased COP…

A 
Due to decreased production of albumin
- decreased AA supply 
- severe chronic liver disease
OR
Increased loss of albumin
- haemorrhage
- inflammation
- kidney
- burns

Albumin in the most important osmotically active substance in the blood
- Little protein but there is plenty of it

ALWAYS SYSTEMIC

32
Q

Impaired lymphatic drainage…

A

Causes LOCALISED oedema
- a.k.a lymphoedema

Can be external or internal obstruction

33
Q

Increased vascular permeability…

A

Usually local
Most often results from inflammation
Increased endothelial leakiness
Loss of fluid, cells, protein into the tissues
- this results in a high protein fluid called exudate

34
Q

What is transudate?

A

Fluid

  • Low protein
  • Doesn’t clot
  • Few cells present
  • Low specific gravity
  • Clear/ straw coloured
35
Q

What is exudate?

A

Fluid

  • High total protein
  • Clots
  • High cellularity
  • High specific gravity
  • Turbid
36
Q

Describe the gross appearance of oedema in an animal

A
  • Body cavities contain free fluid
  • Solid tissues are wet, heavy and enlarged
  • Sub cut tissues
    • distension
    • swelling
    • gravity dependent
    • incised tissue may pour fluid

Pathology (12 decks)

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