SHOCK Flashcards
What is shock defined as?
Shock is defined as a clinical state of under delivery of O2 and essential nutrients to the cells and tissues in the body. Inadequate supply/utilisation of this leads to anaerobic glycolysis the activation of complex cellular and immune mediated pathways and cellular damage
What are the factors affecting tissue oxygen delivery? (4 things)
1) the ability of lungs to take up oxygen
2) the oxygen carrying capacity of blood
3) Haemoglobin concentration
4) Blood flow
What is the definition of cardiac output?
Volume of blood injected by each ventricle per minute therefore cardiac output equates to volume of blood injected with each beat multiplied by heart rate
What is the cardiac output equation?
Cardiac output = stroke volume x heart rate
What can cardiac output be affected by?
Preload/myocardial contractility/afterload/heart rate/systemic blood pressure
What is preload?
The volume of blood in the ventricle at the end of diastole
Starlings law
The greater the preload the greater the consequent stroke volume
What inotropes both positive and negative?
Positive inotropes produce greater contraction for a given length. for example adrenaline noradrenaline dopamine which are naturally produced
Negative inotropes reduce contractility for example antiarrhythmics and anaesthetic agents
What is afterload?
This is the resistance faced by ventricular myocardium during contraction
What happens during diastole as heart rate increases?
Ventricular filling is shortened meaning a smaller Stroke volume and a fall in cardiac output
Describe the important facts of tissue oxygen consumption
3
1) tissues only use 20 to 25% of oxygen available
2) For resting healthy male the total consumption of oxygen per minute is between 100 and 160 mils per minute per metre squared
3Normally increased oxygen demands is increased by the increased delivery of oxygen usually from arise in cardiac output
4) VO2 or total consumption of oxygen per minute decreases because delivery of oxygen DO2 is falling
What are the causes of shock in trauma? (5)
Hypervolaemic/cardiogenic/neurogenic/septicaemic/anaphylactic
Three pathophysiological entities which will result in shock are?
Reduced Venus return
Impaired cardiac function
Reduced vascular tone
Hypovolaemic shock
Reduced Venus return
Causes haemorrhage burns and crush injury
Cardiogenic shock
Impaired cardiac function
Causes - cardiac contusion/Tamponade/ischaemic heart disease/antiarrhythmic drugs/underlying cardiomyopathy