Haemodynamic Shock Flashcards
Mean Arterial pressure = ? OR ?
Stroke Volume x Heart rate x Total Peripheral Pressure
Cardiac Output x Total Peripheral resistance
What is haemodynamic shock?
Inadequate blood flow around the blood, fall in arterial blood pressure leading to shock.
Fall in cardiac output or fall in total peripheral resistance
What does a fall in cardiac output lead to?
Pump cannot fill
Pump failure
Loss of blood volume
What does a fall in peripheral resistance lead to?
Excessive vasodilation
Lack of tissue perfusion
What is cardiogeneic shock?
Where the ventricle cannot empty properly - pump failure
What are some causes of cardiogenic shock?
Following a myocardial infarction (damage to left ventricle)
Serious arrhythmia (pumping top slowly)
Worsening heart failure
What happens to venous and arterial pressure in cardiogenic shock?
Venous pressure normal or raised
Drop in arterial BP
What can cardiogenic shock lead to?
Poorly perfused tissues - especially kidneys
Oliguira - reduced urine output
What is the difference between Asystole and Pulseless Electrical Activity?
Aystole - loss of electrical and mechanical activity
PEA - no pulse but some electrical activity
What can be done in the case of cardiac arrest?
Basic Life Support
Defibrillation - depolarises cells and puts them in refractory period to allow co-ordinated electrical activity.
Adrenaline - enhances myocardial function
What is mechanical shock (cardiac tamponade)?
Blood or fluid filling up the pericardial space which restricts filling of heart.
What impact does mechanical shock have in arterial and venous pressure?
High venous pressure
Low Arterial pressure
How would a pulmonary embolism cause mechanical shock?
Embolus occludes pulmonary artery Right ventricle cannot empty Central venous pressure rises Reduced return of blood to left heart Limits filling of left heart Left atrial pressure low Arterial BP low Shock
What is hypovolemic shock?
Reduced blood volume commonly due to a haemorrhage.
How much blood % can you lose before you go into shock?
20%
Explain how the sympathetic nervous system can cause a compensatory responses following hypovolaemic shock due to a haemorrhage.
Haemorrhage Venous pressure falls Cardiac output falls Arterial output falls This is detracted by the baroreceptors
Leads to increased sympathetic stimulation
Tachycardia
Increased force of constriction
Vasoconstriction
Apart from activating the symmetric system, what other systems does the body use to bring up blood volume following a haemorrhage?
Normally the body there is a net movement of fluid out to the tissues due to interstitial oncotic pressure and hydrostatic pressure.
After a haemorrhage, increased peripheral resistance (as less dilated) reduces capillary hydrostatic pressure and there is a net movement of fluid into the capillaries.
What are some signs of hypovolaemic shock?
Tachycardia
Weak pulse
Pale skin
Cold, clammy extremities
In hypovolaemic shock, lack of tissue perfusion can lead to the release of vasodilators. How does this worsen the situation?
Total peripheral resistance falls
BP falls
Vital organs cannot be perfused
Organ failure
What is distributive shock?
Low resistance shock.
Due to profound peripheral vasodilation.
How can a inflammatory response in relation to sepsis lead to septic shock?
Inflammatory shock leads to vasodilation
Dramatic fall in total peripheral resistance
Fall in arterial pressure
Impaired tissue perfusion
Leaky capillaries due to fluid exudate also reduces blood volume
How does anaphylaxis causes an anaphylactic shock?
Severe allergic reaction
Release of histamine - vasodilation - fall in total peripheral resistance
Drop in arterial pressure
Sympathetic response activated but not enough to overcome vasodilation
Impaired perfusion
What are effects of anaphylaxis (minus anaphylaxis shock) can be fatal to the patient?
Brochoconstriction
Laryngeal oedema
What treatment is given to someone to anaphylactic shock?
Adrenaline - vasoconstriction via action at the alpha adrenoceptors
Apart from a haemorrhage, what is another traumatic cause of hypovolaemic shock?
Severe burns
