Shock -- Session 12 Flashcards
What is cardiogenic shock?
When does it occur?
Inability of heart to eject enough blood
MI, serious arrhythmias, acute worsening on heart failure
What is mechanical shock?
When does it occur?
Due to:
- Restriction on heart filling e.g. Cardiac tamponade
- Obstruction to blood flow thorough lungs e.g. Pulmonary embolism
What happens in cardiogenic shock?
Heart fills, but can’t pump effectively
Drop in arterial BP
Tissues are poorly perfused
What happens in cardiac tamponade?
Blood in pericardial space, restricts heart filling, lowers end diastolic vol
Have high CVP and low arterial BP
What happens in a pulmonary embolism?
embolus occludes large pulmonary artery, RV cant empty, incerase pulmonary artery pressure, limits left heart filling, low left arterial pressure, low arterial blood pressure –> shock
Causes chest pain and dyspnoea
What causes hypovolaemic shock?
Reduced blood volume
Usually due to haemorrhage
20-30% loss = some signs of shock
30-40% loss = substantial mean BP decrease, serious shock response
– severe burns
– sever diarrhoea, vomiting and loss of Na+
What is the severity of hypovolaemic shock related to?
amount and speed of blood loss
What are the effects of hypovolaemic shock?
What is the compensatory response of the body?
Venous pressure falls causing cardiac output to fall. Arterial pressure falls, detected by baroreceptors which causes:
- increased sympathetic stimulation
- tachycardia
- increase force of contraction
- peripheral vasoconstriction
- venoconstriction
Describe internal transfusion and why it is present in hypovolaemic shock
Increased peripheral resistance decreases the capillary hydrostatic pressure.
Fluid moves into capillaries from tissue
What are the clinical signs of hypovolaemic shock?
Tachycardia
Weak pulse
pale skin
cold and clammy extremities
What are the overall effects of peripheral vasoconstriction?
Impairs tissue perfusion
- hypoxia causes tissue damage
- vasodilators released
- TPR falls
- BP falls
- vital organs aren’t perfused
- multi-system failure
What is distributive shock also known as?
What is distributive shock?
When does it occur?
Normovolaemic shock
Due to uncontrolled falls in peripheral resistance.
There is increased peripheral vasodilation decreasing TPR
(Blood vol is constant, but the volume of the circulation has increased)
Toxic and anaphylactic shock
Describe what happens in toxic shock
Endotoxins are released by circulating bacteria
- cause vasodilation, decreased TPR, decreased arterial pressure, impaired perfusion of vital organs, capillaries become leaky reducing blood volume
- decreased arterial pressure increases sympathetic output, increasing HR and stroke volume
What are the clinical signs of toxic shock?
Tachycardia
Warm, red extremities
What are the clinical signs of anaphylactic shock?
– difficulty breathing – bronchoconstriction and laryngeal oedema
– collapsed
– rapid heart rate
– red, warm extremities
What happens in tissues in an anaphylactic shock?
Release of histamine from mast cells as well as leukotrienes and bradykinin
Causes fall in TPR due to vasodilator effects
Fall in arterial pressure, increasing sympathetic response to increase CO
Vital organ perfusion is prevented
Bronchoconstriction and laryngeal oedema occur
What is the treatment for anaphylactic shock?
What does it do?
Adrenaline
Causes vasoconstriction via actin present at alpha one receptor in blood vessels
Causes and increase in TPR, increasing arterial pressure
How can you treat cardiogenic shock?
Getting fluids into the patient
What is the pulmonary arterial occlusion pressure?
How is it measured?
Catheter which is entered into femoral vein and travels up to heart to measure pressure in pulmonary artery. A pressure transducer on the end of the catheter is wedged into a small pulmonary artery to measure pressure in the left atrium.
How would you treat septic shock?
Fluids and antibiotics
How would you treat hypovolaemic shock?
Infuse 500ml of fluids then measure to see if BP and HR have stabilised. If not, measure central venous pressure by JVP to see if they have fluid overload.
What are some chemical mediators released in anaphylaxis?
Histamine
Leukotrienes
Bradykinin
Define general shock
Acute circulatory failure as a result of inadequate or inappropriately distributed tissue perfusion, resulting in generalised lack of O2
