Shcok Flashcards
CO = [] X []?
BP = [] x []?
CO = HR X SV
BP = CO x Systemic vascular resistance
What are the overall physiological consequences of shock ? [3]
- Increased afterload
- Reduced systemic vascular resistance (Failure to maintain peripheral vasoconstriction)
-
Decreased CO
i) reduced preload
ii) reduced contactility
Vasoconstriction is predominately activated by which molecule on which receptors? [2]
Name two alternative compounds that can cause vasoconstriction [2]
Vasoconstriction is predominately activated by which molecule on which receptors? [2]
Noradrenaline on alpha 2 recptors
Name two alternative compounds that can cause vasoconstriction [2]
Angiotensin
Vasopressin
Vasodilation is mediated by the activation of which two compounds? [1]
Explain their basic mechanism [1]
Nitric oxide and prostacyclin [1]
MoA: Through cGMP and cAMP respectively, secondary messengers cause decrease in calcium and smooth muscle relaxation
How does obstructive shock ?
What are the 4 classifications of shock? [4]
Obstructive shock
Distributive shock
Cardiogenic shock
Hypovolaemic shock
Name and describe the 4 stages of shock
Describe how shock is a positive feedback cycle
- Increased circ. shock with worsening perfusion
- Causes inadequate blood flow to tissues: deterioation of end organ tissue function
- Causes heart and circ system failure to start
- Further reduction in CO
- Repeat 1 f
Explain three examples that could cause obstructive shock xx [2]
PE
Tension pneuomothorax air gets trapped in pleural space: compresses against vena cava and heart: stops blood flow into right side of heart: reduced preload: reduced CO
Cardiac tamponade :accumulation of pericardial fluid: causes increas in intrapericardial pressure which reduceds cardiac filling
Describe the effects to cells of hypoxia and hypoperfusion
- Cells switch from aerobic to anaerobic metabolism
- Lactic acid production
- Cell function ceases & swells
- Membrane becomes more permeable
- Electrolytes & fluids seep in and out of cell
- Na+/K+ pump impaired
- Cells swell causing mitochondria damage
- Cell death
What are the signs of shock?
- Pulse is weak and rapid
- Pulse pressure reduced - mean arterial pressure (MAP) may be maintained - NOTE; ARTERIAL BP is NOT A GOOD INDICATOR OF SHOCK since it will be maintained until a very large amount of blood loss
- Reduced urine output
- Reduced pH
- Confusion, weakness, collapse and coma
Describe how disitributive shock works xx
Results from excessive vasodilation and the impaired distribution of blood flow
Characterized by a significant drop in peripheral vascular resistance and, as a result, hypotension
Explain 3 examples of distributive shock x
Sepsis: dysregulated host response to infection where bacteria in blood release chemicals causing uncontrolled hypotension
Anaphylactic shock: allergic response to antigen: IgE mediated mass degranulation releasing histamines: vasodilation and capillary leaking
Neurogenic shock: Sudden loss of vasomotor tone throughout the body. Occurs due to loss of sympathetic input due to spinal injury above T6 / Spinal anaesthesia with high block / brain damage in brainstem
Explain the mechanism of septic shock xx
Pathogens have unique cell wall molecules called pathogen associated molecular patterns (PAMPS) that bind to pattern recognition receptors (TLRs) on immune cells
Causes pro-inflam cytokines: activates the adaptive immune, which causes direct and indirect host injury
Causes release of NO: vasodilation and drop in BP
Cytokine release causes the endothelial lining of blood vessels to become more permeable. This causes fluid to leak out of the blood and in to the extracellular space leading to oedem, a reduction in intravascular volume, and therefore amount of oxygen reaching tissues
Activation of the coagulation system leads to deposition of fibrin throughout the circulation further compromising organ and tissue perfusion. It also leads to consumption of platelets and clotting factorsas they are being used up to form the clots within the circulatory system.
What is cardiogenic shock?
Name 4 causes of cardiogenic shock xx [4]
Failure of the heart to pump blood
Occurs as a result of ventricular dysfunction (esp. LV)
Causes:
* Acute myocardial infarction leading to ventricular dysfunction
* Arrhythmias
* Valvular rupture
* Decompensated heart failure
What is hypovolaemic shock?
Reduced circulating volume leads to reduced venous return and therefore preload
Explain 4 causes of hypovolaemic shock xx
- Haemorrhage
- GI losses: severe diarrhoea and vomiting
- Surgery: exposure of internal structures to heat
- Burns: fluid shift into extravasuclar space due to inflam response
Explain the compensatory mechanisms for haemorrhagic shock [3]
Baroreceptors detect drop in arterial pressure
Activates sympathetic stimulation:
- Constriction of small arterioles increasing total peripheral resistance thereby maintaining BP
- Veins and venous reservoirs constrict, maintaining venous return
- Increased heart rate and contractility to maintain cardiac output
CNS ischaemia results in increased noradrenaline and adrenaline secretion from adrenal medulla
How does RAAS system work to compensate shock? [3]
- Water retention and salt reabsorption
- Vasomotor centre in the medulla signals to the hypothalamus to release vasopressin (ADH)
- Urine flow and sodium excretion decrease
Describe the 4 classes of haemorrhagic stroke
Name 3 long term compensatory mechanisms of shock [3]
- There is (by an unknown mechanism) stimulation of albumin and other plasma protein synthesis in the liver.
- Increased fluid absorption from GI tract
- Fibroblasts surrounding the kidney tubules are sensitive to hypoxia and release increased amounts of erythropoietin: Red cell production
Anaphylactiv shock is which type of hypersensitivity? [1]
Type 1
Explain the MoA of anaphylactic shock
pathological allergic response:
- an antigen (usually inhaled or swallowed) reacts with IgE on mast cells & basophils; This is called Type 1 hypersensitivity.
- The cells degranulate and release inflammatory mediators including histamine.
- Histamine reacts on capillaries and arterioles to cause endothelial cells to lose their tight junctions and separate. This allows water to leak out into tissues.
- Causing swelling and vasodilation leading to uncontrolled hypotension and anaphylactic shock
MI would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
MI would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
MI would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
MI would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
PE would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
PE would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
Neurogenic shock would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
Neurogenic shock would cause which of the following type of shock?
Hypovolaemic shock
Obstructive shock
Distributive shock
Cardiogenic shock
Which immunoglobin is associated with anaphylactic shock?
IgD
IgM
IgE
IgG
IgA
Which immunoglobin is associated with anaphylactic shock?
IgD
IgM
IgE
IgG
IgA
Explain which of HR or BP falls first in major haemorrhage stroke :)
Cardiac output can accommodate c. 10% blood loss before change in CO
Between 10-20% fall in blood loss, arterial pressure compensates by vasoconstriction
SO you see a raise in HR to compensate fall in SV BEFORE you see a fall in BP
Whats the A-E of shock management?
Airway: probs ok unless they have analphylaxis
Breathing: usually ok, may have compensatory increase in RR to compensate hypoxia in tissues. OR might have tension pneumothorax. Later stages: hypoxic
Circulation: give IV access: increase fluids to increase BP
Disability: Low: cant respond bc of lack of 02
Exposure: look at skin – rash / burns / pale
