CVS Shock Flashcards
What do organic nitrates do when used for angina?
Release NO which VENOdilates so reduces pre-load of the heart
What is cardiac arrest?
There is unresponsiveness associated with a lack of pulse. Heart has either stopped or ceased to pump effectively
What is pulseless electrical activity?
A type of cardiac arrest where there is a dissociation between electrical and mechanical activity of the heart
(can happen in severe hypoxia)
What is shock?
An acute condition of inadequate blood flow throughout the body. It is caused by a catastrophic fall in arterial BP
What is the equation for mean arterial blood pressure and how does this relate to the cause of shock?
Mean arterial BP = CO x TPR
Therefore shock can be caused by:
- fall in CO
- fall in TPR beyond the capacity of the heart to cope
What types of shock cause a fall in cardiac output?
- Cardiogenic shock (pump failure)
- Mechanical shock (obstruction preventing filling)
- Hypovolaemic shock (poor venous return)
What are the potential causes of cardiogenic shock?
- damage to LV following MI
- acute worsening of heart failure
- serious arrhythmias eg severe bradycardia or ventricular tachycardia
What would happen to central venous pressure and arterial BP in cardiogenic shock?
CVP increase
Mean arterial BP decrease
What is the equation for cardiac output?
CO = SV x HR
What is the cause of mechanical shock?
Cardiac tamponade - restricts filling so limits end diastolic volume
Massive pulmonary embolism - RV cannot empty
What would happen to central venous pressure and arterial BP in mechanical shock?
CVP high - may see distension of neck due to high JVP
Low arterial BP
What are the causes of hypovolaemic shock?
Heamorrhage
- less than 20% loss unlikely to cause shock
- 20-30% mild shock
- over 30% serious shock
(also severe burns or diarrhoea)
What factors is the severity of hypovolaemic shock related to?
AMOUNT and SPEED of blood loss
What happens to central venous pressure and mean arterial blood pressure in hypovolaemic shock?
CVP falls
Arterial BP falls
What are the symptoms of hypovolaemic shock?
Huge sympathetic drive results in:
- tachycardia
- weak pulse
- pale skin
- cold, clammy extremities
What is decompensation wrt hypovolaemic shock?
Peripheral vasoconstriction impairs tissue perfusion
There is tissue damage due to hypoxia –> releases vasodilator mediators –> TPR falls –> BP falls dramatically leading to multi system failure
What types of shock cause a fall in TPR?
- Toxic shock
2. Anaphylactic shock
What is toxic shock?
Also known as septicaemia
Circulating bacteria release endotoxins which cause profound vasodilation and leaky capillaries
What happens to arterial pressure and heart rate during toxic shock?
Arterial pressure falls
Heart rate increase
What are the symptoms of toxic shock?
- tachycardia
- warm red extremities
What causes anaphylactic shock?
A severe allergic reaction. Releases histamine from mast cells which have a powerful vasodilator affect.
Mediators can also cause bronchoconstriction and laryngeal oedema - difficulty breathing
What are the symptoms of anaphylactic shock?
Tachycardia
Difficulty breathing
Red warm extremities
How is anaphylactic shock acutely treated?
Adrenaline (EpiPen)
- vasoconstricts via a1
