Haemodynamic Shock Flashcards
What is the term Haemodynamic Shock used to describe?
Acute circulatory failure with either inadequate or inappropriately distributed tissue perfusion, resulting in generalised lack of oxygen supply to cells
What are 2 types of causes of haemodynamic shock
- Fall in Cardiac Output
- Fall in Total Peripheral Resistance beyond capacity of heart to cope
Describe 3 causes of a fall in Cardiac Output that can lead to Haemodynamic Shock
Cardiogenic shock;
- Inability of heart to eject enough blood
Hypovolaemic shock;
- Due to loss of circulating fluid volume
Mechanical shock;
- Due to a restriction of the filling of the heart
- Obstructed blood flow through the lungs
Suggest 1 cause of Cardiogenic and Hypovolaemic Shock.
Suggest 2 for Mechanical Shock
Cardiogenic shock;
- MI (Also, arrhythmia, worsening of heart failure)
Hypovolaemic shock;
- Haemorrhage
Mechanical shock;
- Pulmonary embolism
- Cardiac tamponade
Describe 1 cause of a fall in TPR, leading to Haemodynamic Shock
Distributive/ normovolaemic shock
- Due to excessive vasodilation
Suggest 2 causes of Distributive/ Normovolaemic shock
- Sepsis
- Anaphylaxis
In Cardiogenic shock, the heart fills but fails to pump effectively.
Describe the;
- Central Venous Pressure
- Arterial BP
- Tissue perfusion
CVP: May be normal or raised
Arterial BP: Large decrease
Tissues: Poorly perfused (If in kidneys-> Reduced urine-Oliguria)
Cardiac arrest is defined as “Unresponsiveness association with lack of pulse”
What are 3 forms of Cardiac Arrest?
- Asystole
- Pulseless Electrical Activity (PEA)
- Ventricular fibrillation (most common, often after MI)
What are 3 ways of treating a Cardiac Arrest?
- Basic life support (chest compression, external ventilation)
- Advanced life support (Defibrillation depolarises all cells, putting them in refractory period)
- Adrenaline
What is Cardiac Tamponade?
How are the Central Venous Pressure and Arterial Blood Pressure affected?
Blood/ fluid build up in pericardial space to the point where filling of the heart is affected
CVP: High
ABP: Low
Pulmonary Embolisms can present with Chest Pain and Dyspnoea, and can lead to Mechanical Shock.
Describe the;
- Pulmonary Artery Pressure
- Central Venous Pressure
- Left Atrial Pressure
- Arterial Blood Pressure
Pulmonary Artery: High
CVP: High
Left Atrial: Low
Arterial: Low
What percentage of blood must be lost for there to be a substantial decrease in mean Arterial Blood Pressure, with serious shock response
30% - 40%
20% - 30% blood loss shows some signs of shock response
A fall in arterial pressure is detected by baroreceptors. This leads to a COMPENSATORY RESPONSE
List 4 features of this compensatory response
Increased sympathetic stimulation;
- Tachycardia
- Increased force of contraction
- Peripheral vasoconstriction
- Venoconstriction
Normally, there is a small net movement of fluid out of capillaries and into tissues.
Explain how this is affected by Hypovolaemic Shock?
This is reversed
- Increased TPR reduces the capillary hydrostatic pressure (less blood downstream of site of vasoconstriction)
- Therfore, there is a net movement of fluid into capillaries
What are 5 features of Hypovolaemic shock
- Tachycardia
- Weak pulse
- Pale skin
- Cold, clammy extremities
- Low Central Venous Pressure
Other than haemorrhage, name 2 causes of Hypovolaemic shock
- Severe burns
- Severe diarrhoea/ vomiting and Na+ loss
How can Hypovolaemic Shock lead to Decompensation
- Peripheral vasoconstriction leads to tissue damage to hypoxia
- Release of chemical mediators causing vasodilation
- Dramatic fall in blood pressure
- Vital organs can’t be perfused-> Multi-system failure
Distributive/ normovolaemic shock involves a normal blood volume, but a large drop in total peripheral resistance.
What are 2 causes?
- Toxic/ septic shock
- Anaphylactic shock
How do Bacteria cause septic/ toxic shock?
- Release endotoxins, cause excessive inflammatory response, producing cytokines
- Endotoxins and cytokines cause vasodilation, so fall in arterial pressure-> Impaired vital organ perfusion
- Capillaries become leaky
- Increased coagulation and hypo-perfusion (later stages)
In Septic shock, why do we get Tachycardia?
- Low arterial pressure detected by baroreceptors, so increased sympathetic output
- Vasoconstrictor effect< Vasodilator effect
- HR and SV increased (Increased CO)
How does a Septic Shock patient present? In 3 ways
- Tachycardia
- Initially, warm red extremities (due to vasodilation)
- In later stages, localised hypo-perfusion
Anaphylactic shock is due to a severe allergic reaction (anaphylaxis).
This involves the release of histamine from mast cells (and other mediators). What 4 effects does this have?
- Vasodilation-> Fall in TPR
- Increased sympathetic response, but can’t overcome vasodilation
- Mediators also cause bronchoconstriction
- Impaired vital organ perfusion
How does a patient in anaphylactic shock present? In 4 ways
How do you treat?
- Difficulty breathing
- Collapsed
- Tachycardia
- Red, warm extremities (vasodilation)
Adrenaline (causes vasoconstriction through Alpha 1 receptors)
