19 Haemodynamic Shock Flashcards
Define haemodynamic shock.
Acute condition of inadequate blood flow (catastrophic fall in arterial blood pressure)
What are the 3 equations used to work out Mean Arterial Blood Pressure?
=
In general terms, what causes shock?
Fall in CO or TPR beyond capacity of heart to cope
What is cardiogenic shock?
Heart unable to pump enough blood to meet body’s needs
Pump failure- ventricle cannot empty properly
What are the potential causes of Cardiogenic shock?
- Myocardial infarction (LV damage) 2. Serious arrhythmias 3. Acute, worsening heart failure
What occurs within the heart and body as a result of cardiogenic shock?
Central Venous Pressure:
Arterial BP:
Urine:
Central Venous Pressure= normal/raised,
Arterial BP= drops
Oliguria (reduced urine production)-kidney’s= poorly perfused
What is a ‘Cardiac Arrest’?
Unresponsiveness associated with lack of pulse- heart stopped and ceased to pump effectively
What is ‘asystole’?
Complete loss of electrical and mechanical activity
What are the common causes of cardiac arrest?
Ventricular fibrillation
MI
Electrolyte imbalance
Arrythmias
How do we respond to a patient who has gone into cardiac arrest?
- BASIC LIFE SUPPORT: chest compression + external ventilation
- ADVANCED LIFE SUPPORT: defibrillation, electric current (depolarises cells- puts them in refractory period allowing coordinated electrical activity to restart)
- ADRENALINE: enhance myocardial function, increase peripheral resistance
What are the two main types of mechanical shock?
1) Cardiac tamponade
(accumulation of fluid in the pericardial space)
2) Pulmonary embolism
What is cardiac tamponade?
Blood/fluid build up in pericardial space- restricts heart filling- limits EDV
What happens to the central venous pressure and arterial blood pressure is cardiac tamponade occurs?
High CVP and Low arterial BP
How does a pulmonary embolus develop to ‘shock’?
Large pulmonary artery occluded
Pulmonary artery at high pressure
Right ventricle cannot empty
CVP is high
Reduced return of blood to left heart-limits filling
Left arterial pressure is low- arterial pressure is low
What symptoms might a person with a pulmonary embolus experience?
- Chest Pain 2. Dyspnoea (difficult breathing)
What % blood loss is required to cause ‘hypovolaemic shock’?
20-30%= some signs of shock 30-40%=serious shock response
What may cause hypovolaemic shock?
1, Haemorrhage 2, Severe burns 3, Severe diarrhoea/vomiting
If cardiac output and arterial pressure fall, what is the body’s compensatory response?
Pressure fall detected by BARORECEPTORS
Increased SYMPATHETIC stimulation
- TACHYCARDIA + increased FORCE of contraction
- Peripheral vasoconstriction + venoconstriction
If a patient has hypovolaemic shock what symptoms will they have?
Tachycardia
Weak pulse
Pale skin
Cold+clammy extremities
Low CVP
What is there a danger of if someone develops hypovolaemic shock?
DECOMPENSATION= peripheral vasoconstriction impairs tissue perfusion- tissue damage due to hypoxia- chemical mediators(VASODILATORS) released- TPR falls-blood pressure drops dramatically- vital organs no longer perfused.
If the body loses about 20% of blood volume, how does the body restore original body volume? How long does it take?
1)Renin-angiotensin-aldosterone system 2)ADH - takes about 3 days
What is distributive shock?
Low resistance shock- profound peripheral vasodilation- TPR drops (i.e. circulation volume increased, blood volume= constant)
What are the 2 main causes of DISTRIBUTIVE SHOCK?
1) Toxic (septic) shock 2) Anaphylactic shock
How could sepsis lead septic shock?
Endotoxins- released by circulating bacteria- profound circulatory inflammatory response- profound vasodilation- fall in TPR- impaired perfusion- +capillaries=leaky
