Shock Flashcards
What is the definition of blood pressure?
The pressure exerted on vessel walls by the blood
How is blood pressure generated?
By the ventricles ejecting blood into the arteries
What vessels are used to measure B.P.
Large systemic arteries such as the brachial
What is the main characteristic of B.P.?
It is pulsatile
What 3 main factors affect B.P?
- Blood Volume
- Vascular Resistance
- Venous Return
Blood volume of an adult?
Approximately 5litres
What are Baroreceptors?
Pressure/Stretch Receptors
Where are the main baroreceptor bodies?
- Aortic Arch
2. Carotid Arteries
Where is the B.P. Control centre?
Brainstem (medulla oblongata)
What are the two main ‘effectors’ for a change in B.P.
- Heart
2. Vasculature
What are the 3 other B.P. Inputs?
- Cerebral cortex
- Limbic System
- Hypothalamus
What nerve is innervated to control heart rate and what nervous system is used?
Vagus nerve via parasympathetic inputs
What nerves increase heart rate and contractility? What Nervous system is used?
Cardiac accelerator nerves via the sympathetic nervous system
What nerves constrict blood vessels and what nervous system is used?
Vasomotor nerves via the sympathetic nervous system
What are the 4 main inputs to the CV control centre?
- Higher brain centres
- Propriceptors
- Baroreceptors
- Chemoreceptors
What do chemoreceptors monitor?
Gas levels in blood and CSF
What 3 main things do chemoreceptors monitor for?
- Oxygen
- Carbon Dioxide
- pH
What do changes in blood composition trigger?
Homeostatic responses
What would an increase in CO2 and a decrease in O2 and pH result in?
Increased RR –> Increased minute ventilation to ‘blow off’ excess CO2 to reduce blood pH
What are the 5 main hormonal influences on B.P?
- Sympathetic nervous system
- ADH
- ANP
- RAA system
- Erythropoietin
What effect does SNS innervation have on homeostatic mechanisms
- Increases CO
2. Peripheral vasoconstriction
How does ADH attempt to conserve blood pressure?
Leads to vasocontriction –> less fluid output
How does ANP attempt to influence BP?
Vasodilation –> salt and water loss in urine
How does the RAA system attempt to conserve BP?
Aldosterone promotes water and sodium reabsorption in the kidneys which leads to an increase in vascular volume
Vasoconstriction
What does Erythropoietin do to conserve BP long term?
- increases RBC production
- increases blood viscocity
What reflex is used short term to correct BP?
Barorecpetor reflex
What manages BP long term?
Endocrine response
In blood vessels what exerts pressure inwards?
Plasma proteins
What process occurs at the arterial end of blood vessels?
Filtration
What process occurs at the venous end of blood vessels?
Reabsorption
In the first stages of Haemorrhage what does the body do to compensate?
Increases reabsorption to increase plasma volume
What maladaptive response develops when tissues become hypoxic? What is the effect of this?
Capiliary permeability increases. This leads to loss of plasma volume which leads to decrease BP as colloid osmotic pressure decreases
What is the definition of CV shock?
The failure of the CV system to meet the needs of tissues metabolic needs
What can tissue hypoxia lead to the damage of?
Cells, Tissues, Organs and Organ systems
What is the severity of shock dependent on?
The extent and duration of shock
What are are the 4 types of shock?
- Cardiogenic
- Distributive
- Hypovolaemic
- Obstructive
Name 3 causes of Distributive shock?
- Neurogenic (such as spinal injury)
- Septic shock
- Anaphylaxis
How does spinal injury cause shock?
It leads to a lack of vascular tone and reduced sympathetic innervation which causes a drop in BP and a loss of CO
What ‘type’ of allergic reaction leads to anaphylaxis?
Type I
Which immune cells degranulate releasing chemical mediators to cause the symptoms?
Mast cells
What in the body causes septic shock?
Bacteria releasing toxins that cause a widespread systemic inflammatory response.
Name some of the symptoms potentially seen in septic shock. (6)
- Reduced BP
- Loss of GCS
- Increased HR
- Urinary Retention
- Acidosis
- Peripheral vasoconstriction (Central Vasodilation?)
What does endothelial damage in septic shock lead to? (3)
- Vasodilation
- Complement activation
- Procoagulation (in small vessels)
What are some of the symptoms seen due to the release of chemical mediators in anaphylaxis? (7)
- Rhinitis
- Bronchospasm
- Urticaria
- Hypotension
- Tachycardia
- GI symptoms
- Coagulopathy
Name a cause of cardiogenic shock and the result
aMI - reduced myocardial perfusion
Name a cause of obstructive shock and the result
Pericarditis/Tamponade - Affects pumping and filling of heart (output)
Name a cause of hypovolaemic shock and the result
Haemorrhage/Burns - Loss of vascular volume
Name a cause of distributive shock and the result
Anaphylaxis/Septic shock - Excessive vasodilation and possible arryhthmia (action of inflammatory mediators)
Where is renin produced?
Kidneys
Where is angiotensinogen converted to angiotensin I?
bloodstream
Where is angiotensin I converted to angiotensin II?
lungs
What catalyses the conversion of angiotensin I>II?
ACE (angiotensin converting enzyme)
What does angiotensin II stimulate to produce aldosterone?
The adrenal cortex
What does aldosterone do in the kidneys?
Increase H20 and Na+ reabsorption
