CVS Shock Flashcards
How does shock come about?
Dramatic fall in arterial blood pressure due to either:
Fall in cardiac output
Fall in total peripheral resistance
Give 3 types of shock due to a fall in cardiac output.
Hypovolaemic shock - fall in blood volume.
Cardiogenic shock - pump failure.
Mechanical shock - filling failure.
What volume of blood must be lost for hypovolaemic shock to occur?
What causes hypovolaemic shock and how?
Haemorrhage leads to reduced blood volume.
Venous pressure falls
Arterial pressure falls
What is the compensatory response to hypolvolaemia?
Baroreceptors in carotid sinus/arch of aorta detect fall in arterial blood pressure.
This results in sympathetic activation resulting in peripheral vasoconstriction and positive inotropy and chronotropic to increase cardiac output.
Venoconstriction results in reduction of capillary hydrostatic pressure allowing a net movement of water into capillaries.
How does a patient with hypovolaemic shock present?
Fast heart rate
Pale, cold, clammy hands
Weak pulse
Describe decompensation in hypovolaemic shock.
Peripheral vasoconstriction results in hypoxia in peripheral tissues.
vasodilator metabolites result in a reduced total peripheral resistance resulting in a fall in blood pressure.
Vital organs cannot be perfumed leading to system failure.
What can hypovolaemic shock result from?
Haemorrhage
Severe burns
Severe diarrhoea
Describe the changes in cardiogenic shock.
Heart cannot pump effectively.
Venous pressure is normal so end diastolic volume is normal however this is not pumped.
Dramatic fall in arterial blood pressure.
What can cardiogenic shock be due to?
Myocardial infarction.
Serious arrhythmia
Heart failure
What can cardiogenic shock result in?
Coronary arteries poorly perfused, exacerbating problem.
Kidneys poorly perfused, less urine production.
Describe what can cause mechanical shock.
Cardiac tamponade
Pulmonary embolism
How does cardiac tamponade lead to mechanical shock?
Fluid accumulates in pericardial space.
Inelastic fibrous pericardium does not allow for expansion.
Heart is compressed so end diastolic volume is reduced.
Thus, venous pressure increases and arterial pressure falls.
There is a low stroke volume.
How does pulmonary embolism result in mechanical shock?
Embolus occluded pulmonary artery.
This increases pulmonary artery pressure.
RV cannot empty.
Central venous pressure increases.
Less venous return to left atrium.
Limits filling of left heart, reducing stroke volume.
Arterial pressure is low.
What is distributive normovolaemic shock. Give two types.
Due to a fall in TPR.
Blood volume is normal but volume of circulation increases.
Septic shock
Anaphylactic shock
Describe anaphylactic shock.
Severe allergic reaction.
Mast cells release powerful vasodilator histamine.
Causes profound peripheral vasodilation.
TPr falls and so arterial pressure falls.
Baroreceptors in carotid sinus and arch of aorta detect fall but cannot compensate with SNS.
Mediators also cause bronchoconstriction and laryngeal oedema.
How does a patient with anaphylactic shock present?
Difficulty breathing
Red, warm, clammy hands.
Tachycardia.
Collapse
Describe septic shock.
Endotoxins cause peripheral vasodilation reducing TPR. Arterial blood pressure falls. Impaired perfusion. Leaky capillaries reduces blood volume. SNS is overridden by vasodilation.
How does a septic shock patient present?
Tachycardia
Red, warm, clammy extremities.
How do you treat hypovolaemic shock
Infuse colloid intravenous fluid. This raises arterial blood pressure.
How do you treat cardiogenic shock
Positive ionotropic medication.
Anti arrhythmic agents.
How do you treat cardiac tamponade.
Pericardiocentesis to drain fluid from pericardial space
How do you treat pulmonary embolism?
Heparin
Thrombolytic drugs
How do you treat anaphylactic shock
Adrenaline to act on alpha1 for vasoconstriction.
