Week 5: CTB Flashcards
1
Q
Define Shock
A
- Any circumstance where circulatory insufficiency results in inadequate perfusion and so insufficient oxygen delivery to the tissues of the body.
- OXYGEN DEMAND outstrips the oxygen SUPPLY
2
Q
List the categories of shock
A
- Hypovolaemic
- Cardiogenic
- Distributive
- Obstructive
3
Q
Define Hypovolaemic Shock
A
- Loss of blood/fluid from circulatory system
- E.g. Haemorrhage - Common cause of hypovolaemia
- Trauma e.g. Extrinsic bleed / Intrinsic body compartments - abdominal cavity, pelvic, long bones, chest
- Non-trauma - AAA, thoracic aneurysm
4
Q
Give a non-traumatic cause of Hypovolaemic shock
A
- AAA / Thoracic aneurysm
- Spontaneous bleeding into GI tract
- Diarrhoea and vomiting
- Diabetic ketoacidosis - Via osmotic diuresis
- Burns
5
Q
Give examples of Non-traumatic Haemorrhagic Hypovolaemic shock
A
- AAA/Thoracic aneurysm
- Spontaneous bleeds e.g. due to alcoholism / Anticoagulant drugs
6
Q
Define Cardiogenic Shock
A
- Failure of the pump in the circulatory system - Specifically Ventricular dysfunction
- 2 causes: Affecting heart itself / Systemic
- Heart: MI, Myocarditis, Valvular heart disease, Cardiomyopathy,
- Systemic: Overdose, Sepsis, Pancreatitis
7
Q
What are examples of Causes of Cardiogenic shock
A
- STEMI
- Ventricular Tachycardia
- Overdose
8
Q
Define Distributive shock
A
- Category of shock defining no fluid/blood loss but have excessive vasodilation + subsequent maldistribution of blood within circulatory system
- Septic shock - Dysregulated host response to infection, inflammatory, excessive vasodilation
- Neurogenic shock - Secondary to spinal cord injury, interruption to ANS outflow, inability to raise BP/HR
- Anaphylactic shock - Excessive vasodilation due to Systemic IgE mediated hypersensitivity reaction
9
Q
Define Obstructive shock
A
- Physical obstruction to blood flow through blood vessels
- Due to problem within blood vessels/external pressure
- e.g. Pulmonary embolism, Tension Pneumothorax, Cardiac Tamponade (can be cardiogenic), SVC (more common due to lymphatic/lung malignancy) / IVC obstruction
10
Q
Compare normal short-term and long-term physiological control of blood pressure - Humoral control
A
- Humoral control - RAAS system
- BP falls, Na+ falls
- Renin produced by Kidneys/ Juxtoglomerular cells in Afferent arteriole
- Renin –> Angiotensinogen from liver to Angiotensin I
- ACE –> Angiotensin I to Angiotensin II
- Brain effects - Thirst centre, and ADH (Hypothalamus) - More aquaporins
- Adrenal cortex - Aldosterone - Increase Na+ reabsorption, water follows
- Arteries - Vasoconstriction
11
Q
Compare normal short-term and long-term physiological control of blood pressure - Neural Control
A
- Neural control - Baroreceptors primarily in aortic arch and carotid sinus
- Reduced arterial pressure
- Decreased baroreceptor firing
- Increased sympathetic activity and reduced vagal activity in medulla
- Increased CO and CVR
12
Q
What does Starling’s Law state?
A
- End Diastolic Left Ventricular blood volume determines the myocardial muscle fibre length and thus contractility to a point
- So Increasing preload/filling of heart –> Increases contractility
13
Q
What is preload
A
- End diastolic left ventricular volume
- Determined by amount of blood returned to heart from venous system
14
Q
What are the factors affecting Stroke volume?
A
- Preload
- Pump (contractility)
- Afterload (SVR)
15
Q
What is a normal MAP?
A
> 65 mm Hg
