Haemodynamic Shock Flashcards
What is haemodynamic shock?
Acute condition of inadequate blood flow throughout the body
*a catastrophic fall in arterial blood pressure leads to circulatory shock
What types of shocks are there due to fall in cardiac output?
Cardiogenic shock (pump failure)-V dont empty properly
Mechanical shock (obstructive)- v cannot fill properly
Hypovolaemic shock -reduced blood volume leads to poir venous return
What is cardiogenic shock?
Acute failure of the heart to maintain cardiac output - pump failure
Similar to heart failure but different in that is it an acute condition
What are the potential causes of cardiogenic shock?
- MI causing damage to left ventricle, part of myocardial has died therefore cannot pump enough blood to maintain BP
- serious arrhythmias-heartmight be pumping too slowly (bradycardia) or too fast (tachycardia) which might mean the ventricle isn’t able to fill
- acute worsening of heart failure
What issues does cardiogenic shock produce?
Raised CVP
Dramatic drop in arterial BP
Poorly perfused tissues (if the coronary arteries are affected it can exacerbate the problem, if the kidneys are poorly perfused it may result in poor urine production- oliguria)
What is cardiac arrest?
Unresponsiveness associated with lack of pulse
Heart has stopped or ceased to pump effectively
Asystole, pulseness electircal activity (no pulse but there is still electively activity- appears normal on ECG), ventricular fibrillation (can cause asystole)
How do you treat cardiac arrest?
Basic life support- chest compression and external ventilation
Advances life support- defibrillation- puts all cells in refractory period allowing the pacemaker cells to start setting the pace again
Adrenaline- enhances myocardial function,increase peripheral resistance (acts on a1 receptors)
What is mechanical shock?
When the ventricle cannot fill properly
Ie Cardiac tamponade
-blood or fluid builds up in pericardial space, restricts filling of the heart- limits end diastolic volume
What does mechanical shock cause?
High central venous pressure (blood returns to heart but cant get in )
Low arterial blood pressure (very little cardiac output due to low stroke volume)
During mechanical shock the heart will continue to beat and will attempt to increase the cardiac output. If stroke volume is being limited how can the heart do this?
Increase heart rate
How can a massive pulmonary embolism cause mechanical shock?
- Embolus occludes large pulmonary artery
- Pulmonary artery pressure rises
- Relight ventricle cannot empty
- Central venous pressure rises
- Reduced return of blood to left heart
- Limits filling of the left side of the heart
- Left atrial pressure is low
- Arterial pressure is low
- Shock
What are the other side effects of PE aside from mechanical shock?
Chest pain, dyspnoea
What is hypovolaemic shock?
Haemodynamic shock due to Reduced blood volume
(Most commonly due to haemorrhage, but can also be caused by severe burns, severe diarrhoea or vomiting and loss of Na+)
Severity of shock is related to amount and speed of blood loss
How does the body attempt to counteract hypovolaemic shock caused by a haemorrhage. How it is detected in the first place?
Haemorrhage Venous pressure falls (fall in stroke volume) Cardiac output falls Arterial reassure falls Detected by baroreceptors
Increased sympathetic stimulation
Cause; tachycardia, increased inotropy, peripheral vasoconstriction (NA acting on A1 receptors), venoconstriction
How does internal transfusion occur during hypovolaemic shock?
Increased peripheral resistance reduced the capillary hydrostatic pressure causing net movement of fluid into capillaries
How will a patient present with hypovolaemic shock?
Tachycardia
Weak pulse (due to poor perfusion)
Pale skin (due to poor perfusion)
Cold and clammy extremities (due to sympathetic stimulation)
What is a danger of hypovolaemic shock? How does it occur?and what further complication does it cause?
Decompensation
Caused by Peripheral vasoconstriction which impairs tissue perfusion which can lead to:
- tissue damage due to hypoxia
- release of chemical mediators (vasodilator)
- TPR falls
- BP falling dramatically
- vital organs no longer being perfused
- multi-system failure
*give fluid and electrolytes in order to maintain blood plasma volume
What is the type of shock that refers to the shock that occurs when there is low TPR?
Distributive shock (low resistance shock/ normovolaemic)
What are the two types of distributive shock?
Toxic/septic
Anaphylactic
How is septic/toxic shock caused?
Endotoxins released by circulation bacteria
Triggered inflammatory response
Causes profound vasodilation
Dramatic fall in TPR
Fall in arterial pressure
Impaired perfusion of vital organs
(Capillaries become leaky-reduced blood volume)
Increased coagulation and localised hypo-prefusion
What is septic shock?
Persisting hypotension requiring treatment to maintain blood pressure despite fluid resuscitation
How does the body deal with septic shock?
Decreased arterial pressure is detected by baroreceptors and this increases sympathetic output. However, Vasoconstrictor effect overridden by mediators of vasodilation (endotoxins)
Body will increase heart rate and stroke volume too
How would a patient with septic shock present?
Tachycardia
Warm, red extremities intimately but in the later stages of sepsis there is vasoconstriction which causes localised hypo-perfusion
What is anaphylactic shock?
Server allergic reaction (anaphylaxis)
How does anaphylactic shock occur?
- Histamine released from mast cells (and other mediators )
- Causes vasodilation = fall in TPR
- Dramatic drop in arterial pressure
- Increase sympathetic response to increase CO but vasodilation cannot be overcome
- Impaired perfusion of vital organs
- Mediators also cause bronchoconstriction ad laryngeal oedema = difficulty breathing
How would a patient with anaphylactic shock present?
Difficulty breathing
Collapsed
Rapid heart rate
Red, warm extremities
How is anaphylactic shock treated?
Give adrenaline which causes vasoconstriction via action at A1 adrenoreceptors =increases HR
