Flashcards in CVS Session 12- Shock Deck (23)
What is shock?
An acute circulatory failure with inadequate or inappropriate tissue perfusion due to inadequate flow and therefore a lack of oxygen.
What is the main characteristic of shock?
A dramatic fall in arterial blood pressure.
What is cardiogenic shock?
Shock due to pump failure. This means that the ventricles can't empty properly.
When does cardiogenic shock occur? (3)
-following an MI
-due to a serious arrythmia
What happens in cardiogenic shock? (3)
-the central venous pressure may be normal or raised
-the heart fills but is unable to pump effectively
-arterial BP dramatically falls
What is mechanical shock?
Shock due to obstruction, meaning that the heart cannot be filled adequately.
What are the two main causes of mechanical shock?
What happens due to cardiac tamponade? (2)
There is a high CVP because the heart cannot fill properly, therefore blood backs up into the venous system.
There is a low arterial BP as there is little blood in the heart to pump out.
What happens due to pulmonary embolism? (4)
The pulmonary artery pressure increases due to occlusion
The RV can't empty due to the occlusion, therefore blood backs up and causes high CVP.
There is reduced blood return to the L heart as filling is limited.
L atrial pressure is low and therefore arterial pressure is low.
What is Hypovolaemic shock?
Shock due to reduced blood volume and therefore poor venous return.
What is the most common cause of Hypovolaemic shock?
What is the severity of shock related to? (2)
The amount and speed of blood loss
What happens in Hypovolaemic shock due to haemorrhage? (4)
Haemorrhage causes a fall in venous pressure
Cardiac output falls as less blood in means less out.
Arterial a blood pressure falls.
This is detected by the baroreceptors, which cause a sympathetic response.
What is internal transfusion and when is it seen? What is it the result of?
It is the net movement of fluid into the capillaries due to an increase TPR that means that hydrostatic pressure inside the capillaries is reduced.
This causes increase blood volume.
It is seen in Hypovolaemic shock as a result of sympathetic stimulation.
What are the signs and symptoms of Hypovolaemic shock? (4) what are they due to?
Cold, clammy extremities
Due to sympathetic compensatory mechanism
What is decompensation? When is it seen?
It is peripheral vasoconstriction as a result of sympathetic compensation.
It is seen in Hypovolaemic shock.
The vasoconstriction causes tissue damage, meaning chemical mediators are released and cause vasodilation. This causes TPR to fall and arterial pressure to fall dramatically.
What is toxic shock?
Endotoxins are released by bacteria and cause vasodilation
This causes decreased TPR and consequent low arterial BP.
The low arterial BP is detected by baroreceptors and sympathetic stimulation therefore occurs.
What are the signs and symptoms of toxic shock? (2)
Warm, red extremities.
What is anaphylactic shock?
Shock due to an allergic reaction.
What happens in anaphylactic shock? (3)
Histamine is released by mast cells and causes vasodilation.
This lowers TPR and BP as a result.
There is a sympathetic response which causes increased CO, but this can't overcome the vasodilation.
What are the signs and symptoms of anaphylactic shock? (4)
Difficulty breathing (as mediators cause bronchoconstriction)
Red, warm extremities
What is the treatment for anaphylactic shock?