Week 4: Shock Flashcards
What is shock?
Shock is a syndrome characterised by decreased tissue perfusion and impaired cellular metabolism
Cell demand for oxygen exceeds supply
What conditions are required for tissue oxygenation and perfusion?
Ability of lungs to oxygenate blood
Ability of heart to pump blood to tissues
Adequate haemoglobin and blood volume
Effective vasculature
What is stroke volume?
Amount of blood pumped into the aorta with each contraction of the left ventricle
What is cardiac output?
Amount of blood pumped per minute into the aorta by the left ventricle
CO = SV X HR
What is mean arterial pressure?
Is a product of CO and systemic vascular resistance
DP + (SP –DP)/3
What are the consequences of shock?
Tissue hypoperfusion Activation of the sympathetic nervous system Activation of neurohormonal responses Systemic Inflammatory response Multi organ dysfunction
What are the classifications of shock?
Hypovolaemic Cardiogenic Circulatory or distributive Anaphylactic Neurogenic Septic
What are the classifications for hypovolaemic shock?
Absolute fluid loss
Haemorrhage
Gastrointestinal losses -vomiting and/or diarrhoea
Water loss e.g. diabetes insipidus
Relative fluid loss
Fluid volume moves out of the intravascular space into the extravascular spaces (e.g. burns fluid leaks into the interstitial space)
Include pathophysiology and S + S hypovolaemic shock
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What is cardiogenic shock?
Results from either diastolic or systolic dysfunction and there is reduced cardiac output
What is systolic dysfunction?
Inability of the heart to pump blood forward
What is the main cause of systolic dysfunction?
Myocardial infarction
Include pathophysiology and S + S cardiogenic shock
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What are the types of distributive shock?
Anaphylactic
Neurogenic
Septic
What is the pathophysiology of distributive shock?
Massive peripheral vasodilation –> reduced preload –> reduced SV –> reduced CO
What is neurogenic shock?
Can occur within 30 minutes of spinal cord injury above T5
Loss of sympathetic tone causes unopposed parasympathetic tone (results in vasodilation)