Session 5-Haemodynamic Shock Flashcards
What are the equations for mean arterial blood pressure?
MABP = CO x TPR
MABP = SV x HR x TPR
MABP = diastolic pressure + 1/3 pulse pressure
What is haemodynamic shock?
Acute condition of inadequate blood flow throughout the body
True or false: shock can be due to fall in CO or fall in TPR beyond capacity of the heart to cope
TRUE
How can shock lead to excessive vasodilation?
Fall in peripheral resistance
What is cardiogenic shock?
Acute failure of the heart to maintain CO - pump failure
What are the potential causes of cardiogenic shock? (3)
1) following MI
2) serious arrhythmias
3) acute worsening of heart failure
True or false: central venous pressure may be normal or raised in cardiogenic shock
TRUE
Which tissues may be poorly perfused in cardiogenic shock?
Coronary arteries
Kidneys
What can poor perfusion of kidneys lead to?
Reduced urine production (oliguria)
What is the definition of cardiac arrest?
Unresponsiveness associated with lack of pulse
True or false: asystole is loss of electrical and mechanical activity
TRUE
What is the most common form of cardiac arrest?
Ventricular fibrillation
What are the two types of mechanical shock?
Cardiac tamponade
Pulmonary embolism
Which side of the heart does cardiac tamponade affect?
BOTH
True or false: cardiac tamponade leads to low central venous pressure but high arterial blood pressure
FALSE - high venous and low arterial
Complete the sentences:
Pulmonary embolus occluded a large pulmonary artery, leading to _____ pulmonary artery pressure. The right ventricle cannot empty so central venous pressure is _____ and there is __________ return of blood to left heart. Left atrial pressure is _____, arterial blood pressure is ______ and this leads to shock, chest pain and dyspnoea.
High High Reduced Low Low
How might an embolus reach the lungs?
Due to deep vein thrombosis, portion breaks off, travels in venous system to right side of the heart and is pumped out via pulmonary artery to lungs.
What is hypovolaemic shock?
Reduced blood volume, most commonly due to haemorrhage
What % of blood loss results in a serious shock response?
30-40%
What is the severity of shock related to?
Amount and speed of blood loss
What is the compensatory response for hypovolaemic shock? (5)
1) Increased sympathetic stimulation
2) Tachycardia
3) Increased force of contraction
4) Peripheral vasoconstriction
5) Venoconstriction
In hypovolaemic shock, what dos increased peripheral resistance do to capillary hydrostatic pressure?
Reduces it
What are the symptoms of hypovolaemic shock?
Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities
True or false: hypovolaemic shock can also result from burns and diarrhoea or vomiting (loss of Na+)
TRUE
How can hypovolaemic shock lead to decompensation (organ failure)?
Peripheral vasoconstriction impairs tissue perfusion -
1) tissue damage due to hypoxia
2) release of vasodilators
3) TPR falls
4) BP falls
5) vital organs no longer perfused
6) multi system failure
How many days does it take for blood fluid volume to be restored if there has been 20% blood volume loss?
About 3 days if salt and water intake are adequate
What is distributive shock?
Low resistance shock (normovolaemic) due to profound peripheral vasodilation (decreased TPR)
What are the two types of distributive shock?
Toxic (septic) shock
Anaphylactic shock
What are the consequences of toxic/septic shock? (5)
1) vasodilation -> fall in TPR
2) fall in arterial pressure
3) impaired perfusion of vital organs
4) leaky capillaries
5) increased coagulation
What are the symptoms of septic/toxic shock? (2)
1) tachycardia
2) warm, red extremities initially
What causes anaphylactic shock?
Severe allergic reaction
What is released from mast cells during anaphylactic shock and what does this cause?
Histamine
Vasodilator effect, fall in TPR
Drop in arterial pressure
Impaired perfusion of vital organs
Bronchoconstriction and laryngeal oedema - difficulty breathing
What are the symptoms of anaphylactic shock? (4)
1) Difficulty breathing
2) Collapsed
3) Rapid heart rate
4) Red, warm extremities
What is given to patients suffering from anaphylactic shock?
Adrenaline -> vasoconstriction via action of alpha1-adrenoceptors
How can anaphylactic and septic shock lead to multi-organ failure?
Distributive shock -> decreased TPR -> decreased BP -> decreased tissue perfusion
OR
Distributive shock -> decreased cardiac output due to leaky capillaries -> decreased blood pressure -> decreased tissue perfusion
How can haemorrhage or severe burns lead to multi-organ failure?
Hypovolaemic shock -> decreased cardiac output -> decreased blood pressure -> decreased tissue perfusion
How can MI or heart failures cause multi-organ failure?
Cardiogenic shock -> decreased cardiac output -> decreased blood pressure -> decreased tissue perfusion
How can cardiac tamponade or pulmonary embolism lead to multi-organ failure?
Mechanical shock -> decreased cardiac output -> decreased blood pressure -> decreased tissue perfusion
