Physiology of Shock Flashcards
What are the 5 main types of shock.
Hypovolaemic Cytotoxic Cardiogenic Obstructive Distributive
What is the basis behind Hypovolaemic Shock?
There isn’t enough circulating volume to meet metabollic demands.
Why does a reduction in circulating volume result in shock?
Reduced cardiac output and preload
How is hypovolaemic shock usually brought about?
Loss of blood interstitial flood or rarely pure water
Bleeding Sweating Vomiting
What are some of the best ways to monitor and grade someones hypovolaemic shock?
Measure there BP and Urinary output
How are young people affected by hypovolaemic shock?
Young people compensate really well up to certain level at which they rapidly degenerate.
List 4 compensatory mechanisms in action during hypovolaemic shock?
Baroreceptors
Sympathetic Neurohormonal
Capillary Absorption
Hypothalmo-pituitary-adrenal responce
How do Baroreceptors work to restore Cardiac Output in hypovolaemic shock?
Afferent impulses sent to CV complex in medulla are reduced.
Reduction in parasympathetic (Vagus)
Increase in Sympathetic
Where are the two main groups of Baroreceptors located and to which nerves are they linked?
Carotid Sinus CNIX Glossopharyngeal
Aortic Arch CNX Vagus
What is Chronotropy?
Heart Rate
What is Ionotropy?
Force of Contraction
What are Chronotropy and Ionotropy controlled by?
Sympathetic nerves
What hormones are released as a result of increased sympathetic activity in response to fluid loss?
Adrenaline
Angiotensin
Norad
Vasopressin
What is the function of the vasoconstriction in regards to fluid loss?
Reducing fluid levels in peripheral tissues.
What other process helps drive the response in hypovolaemic shock?
Lactic Acidosis - Enhances response
How does Capillary Absorption help negate hypovolaemic shock?
Reduced Capillary Hydrostatic pressure
Increased Inwards net filtration
Increased Volume of blood
Where is Renin released from?
JGA
Juxto Glomerular Apparatus
What detects reduced Blood pressure with the kidney s?
Intrarenal baroreceptors
What is the function of Renin?
Converts Angiotensin to Angiotensin I
What converts Aniotensin I to II?
ACE
What are the two functions of ACE?
Vasoconstriction
Release of Aldosterone from Adrenal glands
What does Aldosterone do?
Increased Reabsorption of Na+ and water in the kidneys.
Activation of Renin Angiotensin system in hypovolaemic shock does what?
Increased blood volume - Aldosterone
Increased SV - Increased Vascular resistance in peripheral tissues
What two things dictate Cardiac Output?
Heart Rate
Stroke Volume
How can stroke volume be increased?
Increased Blood volume
Decreased Vascular resistance
What is the basic principle behind the frank starling curve?
The greater the End Diastolic Volume the greater the ventricular ejection.
End Diastolic Volume
Pre Load
How much blood has filled the ventricle by the end of diastole.
Why does someone with heart failure often present with signs of pulmonary congestion?
Reduction in Inotropy - Reduced stroke volume
Increased EDV to maintain the stroke volume
Backlog into pulmonary vessels
Addition of ionotropes does what to the frank starling curve?
Curve is shifted up
What is the basic principle behind cariogenic shock?
Heart does not pump properly.
What are the most common causes of cariogenic shock?
Acute MI
Also acute valve dysfunction
What are some clinical signs of poor forward flow due to cardiogenic shock?
Hypotension
Fatigue
Syncope
What are some clinical signs of back pressure flow due to cardiogenic shock?
Pulmonary oedema
Elevated JVP
Hepatic congestion
What drugs are inotropic?
Beta agonist
Dopaminergic stimulation
Give a list of drugs which are ionotropes?
Dobutamine Adrenaline Dopamine Dopexamine Milrinone Levosimendan
When is an intra aortic balloon pump used?
Cardiogenic shock
How does intra aortic balloon pump work?
Inflates in diastole
Deflates during during systole
Increases the volume of blood in the heart and reduces after load.
What is the basis behind obstructive shock?
Something in the way a physical obstruction of the heart and great vessels.
List three causes of obstructive shock.
PE
Cardiac tamponade
Tension Pneumothorax
How is a PE treated?
Antiocoagulation +/- thrombosis
How is cardiac tamponade treated?
Pericardial drainage
How is tension pneumothorax treated?
Decompression and chest drainage
What is the basic principle behind distributive shock?
The system is too big.
List the three common causes of distributive shock?
Septic
Anaphylactic
Neurogenic
What is the cause is septic shock?
Bacterial endotoxin
What is the cause of Anaphylactic shock?
Mast cell degranulation
What is the cause of neurogenic shock?
Thoracic sympathetic innovation is lost
If an increase in lactate levels are detected what can this indicate?
Hypo-perfusion before hypotension occurs in septic shock.
List two key dictators of survival in septic shock
Every hour delay in abx increases mortality by 7.5%
Early Vasopressor increases perfusion and minimises excessive fluid volume.
Why does uncontrolled histamine release result in shock?
Histamine causes vasodilation and increased outward net filtration.
Net result is blood volume is decreased.
What is the first line drug used to treat acute anaphylactic shock?
Adrenaline - Vasoconstrictor and mast cell stabiliser
What biochemical is used to confirm diagnosis of anaphylactic shock?
Serum tryptase
What is a common cause of neuronal shock?
Spinal chord trauma
Why does hypotension follow spinal chord trauma?
Inappropriate vagal tone as unopposed parasympathetic output.
Loss of sympathetic tone within blood vessels.
What is the mainstay of treatment for neuronal shock?
Dopamin
Vasopressers
