Circulatory Shock Flashcards
Clinical shock
Acute circulatory failure with inadequate or inappropriately distributed tissue perfusion resulting in cellular hypoxia and end organ damage
What are the main mediators of vasodilation
Nitric oxide
Prostacyclin
How does vasodilation regulate blood flow
Enhances blood flow to certain areas
Decr systemic vascular resistance
What hormones cause vasoconstriction
Noradrenaline - a2
Angiotensin
Vasopressin
Is vasoconstriction controlled by the sympathetic or parasympathetic nervous system
Sympathetic
Which receptors does noradrenaline work on to cause vasoconstriction
Alpha 2
What are the 3 causes of shock
Decr cardiac output
Reduced systemic vascular resistance
Incr afterload
How is shock a vicious cycle
Inadequate blood flow -> heart and circ system failure -> further cardiac output decr -> worsening shock and perfusion
Why is shock very difficult to reverse once initiated
Involves lots of positive feedback mechanisms
How does hypoxia cause cell death
Cells switch to anaerobic metabolism -> lactic acid made -> cell function ceases + swells -> ICF membrane permeability -> electrolytes + fluids enter + leave -> Na/K+ pump impaired -> cells swell -> mitochondria damage -> cell death
4 stages of shock
Initial
Compensatory
Progressive
Refractory
Which stage of shock is irreversible
Refractory
What causes a patient to go from compensatory to progressive stage shock
Body can’t compensate anymore
Features of initial stage shock
Body switches to anaerobic metabolism
Incr lactic acid
Subtle clinical sign changes
Features of compensatory stage shock
Sympathetic stimulation
Incr catecholamine release
Incr cardiac contractility
Vasoconstriction
Aldosterone release
Decr urine output
Incr heart rate
Incr glucose level
Features of progressive stage shock
Electrolyte imbalance
Metabolic acidosis
Respiratory acidosis
Peripheral oedema
Irregular tachyarrhythmia
Hypotension
Pallor
Cool clammy skin
Altered level of consciousness
Features of refractory stage shock
Irreversible cellular and end organ damage
Impending death
4 types of shock
Obstructive
Distributive
Cardiogenic
Hypovolaemic
Obstructive shock
Physical obstruction to vessels entering or leaving heart reduces flow to heart, decreasing preload and cardiac output
What causes obstructive shock
Physical obstruction to large vessels entering or leaving heart
What type of shock can a pulmonary embolism cause
Obstructive
What type of shock can a tension haemothorax cause
Obstructive
How does a pulmonary embolism cause shock
Clot blocks artery in lungs increasing heart afterload
How does tension haemothorax cause shock
Obstructs venous return to heart impairing left ventricular filling
What type of shock does cardiac tamponade cause
Obstructive
How does cardiac tamponade cause shock
Increases intra pericardial pressure, restricting cardiac filling and decr cardiac output
Distributive shock
Excessive vasodilation impairs blood flow distribution
Characteristic signs of distributive shock
Drop in peripheral vascular resistance
Hypotension
What type of shock is septic shock a form of
Distributive
Septic shock
Life threatening organ dysfunction due to dysregulated host response to infection
Signs of septic shock
Altered mental status
Systolic BP <100mmHg
RR >22 breaths/min
Signs of infection
How does septic shock cause hypotension
Bacteria in blood release chemicals causing uncontrolled hypotension
What type of shock is anaphylactic shock a form of
Distributive
What causes anaphylactic shock
Pathological allergy response
How does anaphylactic shock cause uncontrolled hypotension
Exposure to antigen -> IgE mediates mast cell degranulation -> histamines released -> vasodilation + capillary leaking -> decr peripheral vascular resistance -> hypotension
Neurogenic shock
Sudden loss of vasomotor tone throughout body due to loss of sympathetic input
What causes neurogenic shock
Loss of sympathetic input leaving unopposed parasympathetic activity
Cardiogenic shock
Failure of heart to pump blood due to ventricular dysfunction
What is the most common cause of Cardiogenic shock
Acute myocardial infarction
What type of shock can acute myocardial infarction cause
Cardiogenic
Hypovolaemic shock
Reduced circulating volume causes reduced venous return and preload
Hypovolaemia causes
Haemorrhage
GI losses
Surgery
Burns
How can GI system issues cause hypovolaemia
Diarrhoea and vomiting cause dehydration
How can surgery lead to hypovolaemia
Internal structures exposed to air and heat
What types of shock can burns lead to
Distributive and hypovolaemic
How can burns lead to hypovolaemia
Fluid shift into Extravascular space due to inflam response
Loss of fluid due to loss of skin barrier
Why is bleeding into the skull not likely to cause Hypovolaemic shock
Patient would die from coning before Anouilh blood was lost to go into shock
Haemorrhage signs and symptoms (inc internal)
Confusion
Anxiety
Clammy skin
Cold
Low BP
Hugh heart rate
Slow capillary refill
Greyish pallor
Bruising
Bleeding
Melaena
What happens to arterial pressure and cardiac output during haemorrhage
Decr
How many classes of Haemorrhagic shock are there
4
How much blood loss is needed for class 4 Haemorrhagic shock
2 lites
How much blood loss is class 1 Haemorrhagic shock
<750 ml
How much blood loss for class 2 Haemorrhagic shock
750ml - 1.5 litres
How much blood loss for class 3 Haemorrhagic shock
1.5 - 2 litres
Acute compensatory mechanisms for Haemorrhagic shock
Constriction of small arterioles
Constriction of veins and venous reservoirs
Increased heart rate and contractility
Noradrenaline and adrenaline from adrenal medulla
How is Haemorrhagic shock detected by body
Decreased arterial pressure detected by baroreceptors
Long term compensatory mechanisms for Haemorrhagic shock
RAAS system activation
Vasopressin release
Albumin and other plasma protein synthesis stimulation in liver
Incr fluid absorption from GI tract
Incr erythropoietin release
How is shock treated
A - E
Treat underlying cause
Supportive management
