Shock Flashcards
what is tissue hypoperfusion?
oxygen supply does not meet metabolic demands
what is cellular dysfunction?
often leads to multiple organ failure if prolonged
what is cardiac output loss?
fundamental cause of shock
what is shock?
a life-threatening condition characterised by inadequate tissue perfusion, leading to cellular hypoxia and metabolic dysfunction
what does shock include?
tissue hypoperfusion
cellular dysfunction
cardiac output loss
multiple factors involved (especially in late-stage shock)
severity and rate determine progression
causes of impaired oxygen delivery:
decreased cardiac output
decreased haemoglobin saturation or conc
increased afterload (elevated diastolic pressure limiting ejection)
causes of decreased cardiac output?
decreased stroke volume, heart rate, preload or contractility
key determinants of oxygen delivery?
- DO₂ = CO × CaO₂ (Cardiac Output × Oxygen Content)
- CO = SV × HR (Stroke Volume × Heart Rate)
- CaO₂ = (Hb × 1.39) × SaO₂ (Hemoglobin Concentration × Oxygen
Saturation)
describe oxygen utilisation and energy production when in shock?
decreased oxygen –> anaerobic metabolism –> (2 ATP/glucose) lactic acidosis & ATP depletion
what does a reperfusion injury include?
oxygen reintroduction –> reactive oxygen species –> DNA and protein damage
what does cellular dysfunction and death include?
Na+ & Ca+ accumulation –> cellular swelling and ischemia
inflammation: capillary permeability increases, leukocyte activation, mitochondrial dysfunction
what is hypovolemic shock?
inadequate circulating volume
cause of hypovolemic shock?
fluid loss (trauma, internal bleeding, burns) –> decreased preload –> decreased cardiac output –> shock
what is cardiogenic shock?
heart pump failure
what is the cause of cardiogenic shock?
arrhythmia, myocardial infarction (MI), congestive heart failure (CHF)
what is distributive shock?
relative hypovolemia (vasodilation & TPR)
three types of distributive shock?
septic shock
anaphylactic shock
neurogenic shock
what is septic shock?
where bacterial toxins –> systemic vasodilation –> total peripheral resistance (TPR)
what is anaphylactic shock?
histamine release –> vasodilation –> decreased total peripheral resistance
what is neurogenic shock?
loss of autonomic nervous control –> vasodilation –> decreased TPR
what is obstructive shock?
blood flow obstruction
what is the cause of obstructive shock?
physical obstruction –> decreased cardiac output –> circulatory arrest
examples of obstructive shock?
constrictive pericarditis, pneumthorax
clinical signs and symptoms of the early stage of shock?
panting
rapid heart rate
bounding pulses
bright red mucous membranes (lips, gums, tongue)
clinical signs and symptoms of the later stage of shock?
pale skin and mucous membranes
drop in body temp
cold extremities
slow resp rate
dull and depressed appearance
unconsciousness
weak or absent pulse
compensatory responses in shock for the CV system?
increased heart rate (tachycardia)
vasoconstriction
increased myocardial contraction - redistribution of blood flow
compensatory responses in shock for the resp system?
increased resp rate (tachypnea)
hyperventilation
bronchodilation
compensatory responses in shock for the endocrine system?
activation of the sympathetic nervous system - release of epinephrine + norepinephrine
renin-angiotensin-aldosterone system (RAAS) activation
cortisol release
antidiuretic hormone (ADH) secretion
what are the 4 cv responses in shock?
baroreceptor-mediated reflex
peripheral vasoconstriction
auto-transfusion of interstitial fluid
long-term volume restoration
what does baroreceptor-mediated reflex result in?
increased heart rate (tachycardia)
enhanced myocardial contractility
what is the baroreceptor-mediated reflex?
decreased arterial blood pressure –> decreased stimulation of baroreceptors in carotid sinuses + aortic arch
triggers decreased vagal tone and increased sympathetic outflow
what is peripheral vasoconstriction?
generalised arteriolar and venoconstriction via sympathetic activation
most pronounced in cutaneous, skeletal muscle and splanchnic vascular beds
renal vasoconstriction in prolonged/severe hemorrhage –> decreased renal perfusion
cerebral + coronary circulations spared (minimal vasoconstriction)
preserves perfusion to the brain and heart at the expense of other organs
what is auto-transfusion of interstitial fluid?
arterial hypotension, arteriolar constriction and reduced venous pressure and lower capillary hydrostatic pressure
what does auto-transfusion of interstitial fluid promote?
promotes reabsorption of interstitial fluid into capillaries
what does auto-transfusion of interstitial fluid help with?
helps to temporarily restore circulating volume
dilates plasma proteins and decreases colloid osmotic pressure
what does long term volume restoration require?
water and electrolyte retention (via ADH & RAAS)
synthesis of albumin and plasma proteins (by liver)
stimulation of erythropoiesis (in bone marrow) to restore RBC mass
goal of cv response to shock?
maintain perfusion of vital organs (brain and heart) while restoring intravascular volume and pressure
what are the 3 respiratory response in shock?
chemoreceptor activation
respiratory compensation
cardiovascular impact
what does chemoreceptor activation lead to?
stimulation of peripheral chemoreceptors
carotid bodies, aortic bodies and cardiac chemoreceptors
sensitive to decrease in pO2, increase in pCO2 and decrease in pH
MABP?
mean arterial blood pressure
what is chemoreceptor activation?
mean arterial blood pressure does not directly activate baroreceptor reflex for resp control
instead low BP –> decreased tissue perfusion –> hypoxia & lactacidosis
what does resp compensation help with?
helps improve oxygen uptake and reduce CO2 (corrects acidosis)
what is resp compensation?
chemoreceptor activation –> resp stimulation
increased resp rate (tachypnea)
resp alkalosis may result transiently from hyperventilation
what is the cardiovascular impact for resp response in shock?
enhanced resp activity supports
venous return via thoracic pump mechanism
sympathetic vasoconstriction
what is sympathetic vasoconstriction?
it amplifies vasoconstriction initiated by baroreceptors and maintains blood pressure and organ perfusion
what is the integrated goal of the resp response in shock?
maintain oxygenation, support circulation and mitigate acidosis during shock
what are the 4 endocrine compensatory response in shock?
sympatho-adrenal axis activation
vasopressin (ADH) secretion
renin-angiotensin-aldosterone system (RAAS)
erythropoietin (EPO) release
effects of sympatho-adrenal axis activation?
increased heart rate + myocardial contractility
arteriolar vasoconstriction –> maintains blood pressure
mobilisation of glucose + fatty acids for energy
what is sympatho-adrenal axis activation?
decreased blood pressure + tissue perfusion –> triggers sympathetic nervous system (SNS)
Catecholamine release from adrenal medulla
catecholamine release from adrenal medulla includes?
adrenaline (epinephrine) - exclusively from adrenal medulla
noradrenaline (norepinephrine) - from adrenal medulla + sympathetic nerve endings
what are the functions vasopressin?
potent vasoconstrictor
enhances renal water reabsorption –> conserves circulating volume
mediated via the hypothalamic -pituitary-adrenal (HPA) axis
describe vasopressin (ADH) secretion:
secreted by the posterior pituitary in response to a decrease in blood volume/pressure and increased plasma osmolarity
