Shock Flashcards
Define shock and how quickly can it kill someone ?
- Shock is inadequate organ perfusion leading to inadequate oxygen delivery to tissues and eventually organ failure due to circulatory failure i.e. problem with the heart, blood vessels or flow of blood
- Can lead to death in seconds to hours
SBP <90
MAP <50-60
What is MAP and how can it be calculated ?
Mean arterial pressure - is defined as the average pressure in a patient’s arteries during one cardiac cycle
MAP = CO x TPR
MAP = (2 x DBP) + SBP all divided by 3
can be rewrote as 2DBP/3 + SBP/3
What is someones MAP a good measure of and what level or MAP would indicate shock?
MAP is a good measure of tissue organ perfusion i.e. the oxygen reaching the organs
For normal tissue perfusion you need a MAP of 50-60mmHg (note if someone has atherosclerosis then this would need to be higher to adequately perfuse there tissues)
So MAP <50-60 would indicate shock
What does the inadequate tissue organ perfusion in stroke lead to ?
- Metabolic Acidosis (pH < 7.35) due to ATP hydrolysis and lactic acid formation (due to anaerobic metabolism) further worsening global enzyme function and cellular performance
- Thrombus formation can occur at a capillary level resulting in patchy tissue injury, or in large vessels, leading to infarction.
- Eventual cellular necrosis results in mortality
In survivors, a degree of tissue injury may be irreversible, contributing to chronic morbidity
What are the 3 main immediate signs of tissue hypoperfusion (shock)?
- Skin: mottling
- Brain: confusion, agitation, reduced GCS (<15)
- Kidneys: oliguria (<0.5ml/kg/h)
What 2 things can shock essentially result from ?
Think back to the MAP = CO x TPR (SVR)
CO = HR x SV
So shock can essentially result from inadequate CO or a loss of systemic vascular resistance (TPR), or both
After seeing the immediate signs of tissue hypoperfusion (shock) what test is then diagnostic that someone is in shock?
Measure someones arterial blood gases:
- see a metabolic acidosis
- lactate levels >2mmol/L
What are the 2 main types of shock which primarily result in inadequate cardiac output?
- Hypovolaemic shock
- Cardiogenic shock (has a subtype known as obstructive shock)
What are the main types of shock which result in peripheral circulatory failure (decreased SVR)
- Septic shock
- Anaphylactic shock
- Neurogenic shock
These are all grouped as disruptive shock
Define stroke volume
The amount of blood pumped by the left ventricle of the heart in one contraction.
Describe the mechanism behind cardiogenic shock
- There is sustained decreased cardiac contractility
- This results in reduced force of cardiac contraction and ==> decreased stroke volume
- This reduced SV results in decreased CO and ==> decreased MAP (below 50-60 resulting in inadequate tissue organ perfusion and ==> shock)
How do the body try to compensate for the decreased CO in cardiogenic shock and what sign does this result in ?
MAP = CO x TPR
The body tries to compensate by increasing TPR this results in COOL, CLAMY peripheries
List the main causes of cardiogenic shock
- ACS - e.g. MI
- Arrhythmias
- Aortic dissection
- Acute valve failure
Obstruction shock (subtype of cardiogenic):
- PE
- Tension penumothorax
- Cardiac tamponade
Along with the 3 general signs of shock what would make you think cardiogenic shock ?
- Cool, clamy peripheries
- Tachycardia
- Normal temp
- Hypoxia
- Hypotension
What is the treatment of cardiogenic shock ?
Careful fluid management
Ionotropes e.g. dobutamine or vassopressors e.g. noradrenaline for increasing BP
What key sign would make you think of obstructive shock (subtype of cardiogenic)?
Evidence of raised Jugular Venous Pressure (JVP) and Distended Neck Veins may
Note the rest of its symptoms are the same as cardiogenic shock
Define what cardiac tamponade is
This is where percardial fluid collects resulting in
What is the classical traid of cardiac tamponade ?
Classical features - Beck’s triad:
- Hypotension
- Raised JVP
- Muffled heart sounds
What are the additional features of cardiac tamponade other than becks triad ?
- Dyspnoea
- Tachycardia
- An absent Y descent on the JVP - this is due to the limited right ventricular filling
- Pulsus paradoxus - an abnormally large drop in BP during inspiration
- Kussmaul’s sign (raised JVP on inspiration)
- ECG: electrical alternans
What is the management of cardiac tamponade ?
Urgent pericardiocentesis
What is the treatment of obstructive shock ?
Describe frank-starling mechanism
The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume)
Describe the mechanism of hypovolaemic shock
- Reduced blood volume
- Lower venous return to the heart (ventricular filling = end-diastolic volume)
- Reduced force of cardiac contraction and Cardiac Output (Frank-Starling law)
- Therefore reduced BP (MAP) due to reduced CO which results in inadequate tissue perfusion (shock)
What are the causes of hypovolaemic shock ?
- Bleeding - trauma, ruptured aortic aneurysm, GI bleed
- Fluid loss - vomiting, burns, heat exhaustion, pancreatitis
What are the main signs/symptoms of hypovolaemic shock along with the 3 initial signs of shock ?
- Tachyponea
- Tachycardia
- BP decreased but may be compensated for by SVR in smaller haemorrhage
- Cool clamy peripheries - due to increased SVR
What is the treatment of hypovolaemic shock?
What are the 3 classifications of hypovolaemic haemorrhagic shock?
Note - BP normal until > 30% of blood lost
What types of shock are strongly suggested by a patient presenting with the immediate signs of shock plus cold and clamy peripheries ?
Cardiogenic (including obstructive) and hypovolaemic shock is suggested
Describe the mechanism behind distributive shock
- Reduced Systemic Vascular Resistance due to Vasodilatation with WARM, RED PERIPHERIES
- Reduced Mean Arterial Pressure (MAP = CO x TPR (SVR))
- Compensatory increase in Cardiac Output
There is pooling of blood in the tissues due to the vasodilation ==> warm, red peripheries
What is the key feature which suggests septic shock ?
Warm and well perfused, with bounding pulse
Note the other causes of distributive shock also cause this its just sepsis is so much more common
What are the main subtypes of distributive shock and which is the most common ?
- Septic - the most common
- Anaphylactic
- Neurogenic
What are the causes of neurogenic shock ?
- Spinal cord injury
- Epidural or spinal anaesthesia
What are the causes of septic shock
Infection
what are the causes of anaphlatic shock
- Drugs e.g. penicillin and contrast media in radiology
- Latex
- Stings e.g. bees, eggs, fish, peanuts, strawberries
It is an IgE mediated hypersensitivity reaction caused by mast cell (essentially a basophil) degranulation
What signs and symptoms along with the 3 immediate shock signs and patient having an acidosis suggest septic shock?
- Warm and vasodilated
- Bounding pulse
- Increased temp >38
- Cardiac output initially increased
- tachycardia and tachyponea
- hypotension
What features would make you think anaphylactic shock ?
- Normal temp
- Tachycardia and tachyponea
- Hypotension
- Urticarial rash
- Itching, oedema, erythema
- Diarrhoea and vomiting
- Sweating
- Wheeze, laryngeal obstruction, cyanosis
What is the 1st line treatment in anphylactic shock ?
Give adrenaline
What is the management of sepsis ?
BUFALO
- B take bloods,
- Measure urine output
- Give fluids
- Give antibiotics
- Measure lactate
- Give oxygen
What is the treatment of distributive shock ?
Describe the initial approach to the management of shock
ABCDE
In the treatment of shock when someone is hypotensive what is the rate at which they would be fluid challenged ?
Fluid challenge ¼ or ½ L in less than half an hour
