Physiology and Treatment of Shock Flashcards Preview

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Flashcards in Physiology and Treatment of Shock Deck (27)
1

How is "shock" defined?

Inadequate perfusion to sustain normal organ function

2

What are the 5 main categories of Shock?

Hypovolaemic - loss of circulating volume
Cardiogenic - inefficient pump
Obstructive - physical blockage to heart filling/outflow
Distributive - circuit too big (vasodilation)
Cytotoxic - reduced oxygen delivery/ uptake

3

Loss of what components can cause hypovolaemic shock?

blood
interstitial fluid
RARE = pure water deficit

4

Why should we be aware of young patients who may go into hypovolaemic shock?

They compensate incredibly well before crashing
- BP can be maintained for longer than in older patients

5

How do our bodies attempt to compensate in hypovolaemic shock?

- Baroreceptor reflex => detects less stretch and inhibits parasympathetic outflow => HR increases

- Sympathetic neurohormonal => releases vasoconstrcitors => redirects blood away from peripheries to the heart

- Capillaries absorb interstital fluid

- Hypothalamo-Pituitary Response => vasoconstriction and ADH secretion to retain Na and water

6

When do our bodies begin to decompensate?

When circulating vasodilators increase

7

How can the heart increase its cardiac output?

- Increase rate
- Increase Stroke Vol. (children cant do this)
- Increase both

8

How do we attempt to increase cardiac output in a patient who is hypovolaemic?

Fluid challenge
- Frank Starling curve shows this will have large effect on stroke volume and increase BP

9

Why should excess fluid be carefully monitored in patients with heart failure?

Can result in pulmonary congestion
- if the heart cant pump as well, it increases its end diastolic volume to increase the stroke volume
- this causes back pressure => pulmonary congestion

10

What are the principles of prescribing fluids to patients in shock?

1. Fluids are a drug => do you know what's in it? Dose?

2. Consider individual patient (e.g. small/elderly dont need 3 litres maintenance saline)

3. Consider the fluid AND electrolyte requirements

4. Consider the difference between resuscitation and
maintenance
(i.e. dont give 500ml fluid challenge as maintenance)

11

What is the most common cause of cardiogenic shock?

- acute MI
but may also follow acute valve dysfunction (e.g. if papillary muscles are ruptured during MI)

12

WHat are the clinical signs of cardiogenic shock?

Poor forward flow
=> Hypotension/shock
=> fatigue
=> syncope

Backpressure
=> Pulmonary oedema
=> elevated JVP
=> hepatic congestion

13

If the main issue of cardiogenic shock is an inefficient pump, how can this be treated pharmacologically?

- drugs given to improve contractility of pump i.e. INOTROPES

=> β and dopaminergic stimulation
– Dobutamine, adrenaline
– Dopamine, Dopexamine

14

What can be inserted to help treat cardiogenic shock?

- Intra aortic balloon pump

- Inflates during ventricular diastole (allows coronary arteries to perfuse heart better)
- Deflation during ventricular systole (reduced afterload => reduces pressure that heart needs to pump against)

15

Causes of obstructive shock usually cause a problem with the heart filling rather than emptying. Give examples of this and how we treat it

– Pulmonary embolism – Anticoag. +/- thrombolysis
– Cardiac tamponade – Pericardial drainage
– Tension pneumothorax – Decompression/ chest drainage

16

How can a PE be identified on an ECHO?

– Dilated RV - not much movement
– Bowing of interventicular septum into LV
– RV apex is moving lots

17

What are the 3 main subtypes of distributove shock and how do they make the circuit "too big"?

Septic – Bacterial toxins mediate vasodilation
Anaphylactic – Mast cell release of histamine = vasodilation
Neurogenic – Loss of thoracic sympathetic outflow following spinal injury = unopposed vasodilatation from parasympathetics

18

What treatments should be given early in septic shock?

Early use of antibiotics and vasopressors

19

What treatment is given in anaphylactic shock and why?

Adrenaline
- Acts as both a vasoconstrictor and a mast cell stabiliser

20

What test can be done to check if a patient is in anaphylactic shock?

Serum mast cell tryptase levels
(Tryptase is released from mast cells when they degranulate)

21

Why do patients in neurogenic shock normally experience BRADYcardia?

Occurs due to unopposed vagal tone

- if thoracic sympathetic outflow is compromised, this will not oppose parasympathetics

=> bradycardia

22

What should clinicians be aware of if they think a patient is in neurogenic shock?

- dont perform any examinations/procedures which increase vagal tone (e.g. PR exam, suction)
- this could exacerbate bradycardia, making patient less likely to survive

23

HOw is neurogenic shock normally treated?

Dopamine and vasopressors (to squeeze dilated vessels)

24

What are the 8 reversible causes of cardiac arrest?

4Hs
Hypovolaemia
Hypoxia
Hypothermia
Hypo/Hyper- kalaemia (OR other metabolic causes)

4Ts
Thrombosis
Tamponade
Tension Pneumothorax
Toxins

25

What is the importance of allowing the chest to recoil during CPR?

decreases the intra-thoracic pressure
=> allows more venous return to the heart

26

What Cardiac Arrest Rhythms are Shockable?

Ventricular Fibrillation (VF)
Pulseless Ventricular Tachycardia (pVT)

27

What cardiac arrest rhythms are NON-shockable?

Pulseless Electrical Activity
Asystole