CV compensation 2

Question 1

What does hypovolaemia mean

Answer 1

Decreased volume of circulating blood

Question 2

What does hypovolaemia result in?

Answer 2

1. If drops enough = hypovolemic shock
2. Acute drop in mean arterial pressure. = reduced preload = reduced CO = reduced BP = reduced perfusion (blood flow to organs) = tissue hypoxia (too low oxygen)
3. leads to organ dysfunction which leads to organ failure

Question 3

What 3 things cause hypovolaemic shock?

Answer 3

1. Heamorrhage
2. Severe dehydration
3. Sequestration of blood (trapped somewhere and can’t circulate e.g. horse and colic)

Question 4

What parts of the body detect hypovolaemia? and how do these signal to the CV centre?
what deos it then initiate

Answer 4

1. arterial baroreceptors = drop in pressure
2. atrial volume receptors = drop in blood volume
3. Signal = reduced rate of AP to CV centre
4. initiates the baroreflex: sympathetic nervous system, inc HR, inc contractility, inc CO, inc SV, non essential tissues = vasoconstriction, vasodilation to heart, skeletal, brain

Question 5

What effect does hypovolaemia have on the spleen

Answer 5

1. splenic contraction

2. spleen full of blood vessels = holds lot of blood in so contracts and inc blood volume

Question 6

Why does starling’s law of capillaries help to inc blood volume if hypovolaemic?

Answer 6

1. vasoconstriciton to most organs = those caps not much blood flows through = lower hydrostatic pressure in these capillary beds = absorption of ISF in these cap beds = inc blood volume a little

Question 7

If hypovolaemia persists what system kicks in?

Answer 7

renin–angiotensin–aldosterone system RAAS

Question 8

Describe and explain the features of forward heart failure

Answer 8

1. systolic failure - reduced CO therefore reduced mean arterial pressure
2. clinical signs = those of reduced perfusion:
   a) pale mucous membrane as tissues not enough blood flow
   b) prolonged capillary refill time (longer than 2 seconds)
   c) lethargic and unwilling to exercise
   d) collapse if made to exercise
   e) may be able to feel reduced pulse as systolic pressure reduced
   d) cold extremities

Question 9

What disease starts as a result of forward heart failure?

What can you see on a ultrasound

Answer 9

Dilated cardio myopathy DCM.

1. reduced ventricular wall thickness: reduced SV
2. Hardly any contraction

Question 10

If you have a diastolic issue that results in a lack of filling, what type of heart failure and what would this look like on an ultrasound

Answer 10

1. Forward heart failure: can’t full

2. RV squashed flat = never particularly full

Question 11

Describe adn explain the features of backwards heart failure

Answer 11

1. Blood “backs up” in the venous circulation causing increased atrial pressure
2. commonly referred to as congestive heart failure
3. Heart can’t cope with preload so pressure builds up in A, V and capillaries = oedema and effusions

Question 12

What is an effusion

Answer 12

Collection of free fluid in a body cavity = aecities

Question 13

If left sided backwards heart failure where would oedema be?

Answer 13

LUNGS: pulmonary oedema

Question 14

what disease results as a result of left sided backwards heart failure?

Answer 14

Degenerative valve disease: AV valves damaged = don’t close = on radiograph huge LA enlargement. Lot of fuzziness in lungs = oedema, trachea pushed up

Question 15

What si forward heart failure also known as

Answer 15

SYSTOLIC

Question 16

When does forward heart failure occur?

Answer 16

1. any heart disease where cardiac output is reduced, usually due to reduced SV e.g. is muscle wall of heart is thinned adn stretched, V unable to contract effectively, hence SV decreases/

Question 17

What type of heart failure is as a result of mitral valve disease? what happens

Answer 17

Backwards heart failure (congestive heart failure).- presents with left sided congestive heart failure.

2. Mitral valve incompetent and allows blood to flow back into LA during V systole.
3. Inc LA pressure, reduced pulmonary venous drainage into A, inc pulmonary venous pressure

Question 18

What does left sided CHF lead to? (backwards)

Answer 18

1. pulmonary oedema, causing inc resp rate: TACHYPNOAE and sometimes resp difficulty DYSPNOAE and audible crackles on auscultation of the lungs.

Question 19

What deos right sided CHF lead to (backwards)

Answer 19

1. increased systemic venous pressure causes visible distension of the jugular vein and liver enlargement (Hepatomegaly) and spleen (Splenomegaly)
2. hence fluid leakage often leads to effusions - abdomical effusion = ascities
   3.may cause subcutaneous oedema
   4.

Question 20

Why will forwards failure usually lead to backwards?

Answer 20

1. reduced ventricular emptying results in increasing atrial pressure which increases venous pressure

Question 21

Why will backwards failure lead to forwards?

Answer 21

If regurgitation of blood from ventricle to atrium is significant enough to reduce stroke volume and hence cardiac output

Question 22

What is the endogenous compensation for heart disease?

Answer 22

1. How the body compensates for the early stages of heart failure
2. deos this to maintain CO and BP in early stages
3. this only works for a while as the system the body sues aren’t designed for long term activation = very quickly decompensate