Session 11.2 Flashcards
What is haemodynamic shock?
- acute condition of inadequate blood flow throughout the body
- a catastrophic fall in arterial BP = circulatory shock
- can be due to fall in CO or TRP
How can a fall in CO occur?
- mechanical shock: ventricle cant fill properly
- cardiogenic shock: pump failure
- hypovolaemic shock: reduced blood volume leads to poor venous return
What is cardiogenic Shock and what are the causes?
Acute failure to maintain CO (pump failure)
Central venous pressure may be normal or raised and get a dramatic drop in arterial BP. Tissues are poorly perfused.
Causes
- damage to LV following MI
- arrythmias
- Heart failure
What’s cardiac tamponade and how does it link to mechanical shock?
Mechanical = ventricle cant fill properly
Cardiac tamponade
- blood or fluid build up in pericardial space
- restricts filling of heart = limits EDV
High central venous pressure and low arterial Blood pressure.
How can mechanical shock result from a pulmonary embolism?
- pulmonary artery pressure is high
- RV cannot empty
- central venous pressure is high
- reduced return of blood to left heart = limited filling
- left atrial pressure is low
- arterial BP is low
- shock
How may an embolus reach the lungs?
- usually a DVT
- portion of thrombus breaks off
- travels in venous system to right side of heart
- pumped via pulmonary artery to lungs
- effect depends on size of thrombus
What’s hypovolaemic shock?
Reduced blood volume, most commonly due to haemorrhage
Severity of shock is related to amount and speed of blood lost
What’s hypervolemic shock?
There is a greater net movement of interstitial fluid into vessels from tissues.
Increased peripheral resistance reduces capillary hydrostatic pressure.
What are the symptoms of hypovolemic shock and what are the problems?
Symptoms
Tachycardia
Weak pulse
Cold, clammy hands
Risks
- danger of decompensation
- tissue damage due to hypoxia
- TPR falls
- BP falls
- multi system failure
What’s distributive shock?
Abnormal distribution of blood flow in the smallest blood vessels = inadequate supply to tissues
Peripheral vasodilation = decreased TPR
So, blood volume constant but volume of the circulation has increased
E.g toxic and anaphylactic shock
What is toxic/septic shock and how is it caused?
Persistent hypotension requiring treatment
Endotoxins released by circulating bacteria
- causes profound vasodilation
- dramatic fall in TPR
- fall in arterial bp
How will a patient present with septic shock?
Tachycardia
Warm
Red extremities in later stages of sepsis
Vasoconstriction = Localised hypoperfusion
What’s anaphylactic shock?
Severe allergic reaction
Release of histamine from mast cells = powerful vasodilator effect = fall in TPR
Dramatic drop in arterial pressure = increased sympathetic response but cant overcome vasodilation
Impaired perfusion of organs
Mediators also cause bronchoconstriction and laryngeal oedema = difficulty breathing
What are the symptoms of anaphylactic shock?
- difficulty breathing
- collapsed
- tachycardia
- red, warm extremities
