shock Flashcards
what is the definition of shock?
“…….a life-threatening, generalized form of acute circulatory failure associated with inadequate oxygen utilization by the cells.”
what are the multiple causes for shock?
Insufficient O2 and nutrient supply
Hypoxia
Cellular dysfunction
Trauma
Heatstroke
Blood loss
Allergic reaction
Severe infection
what are the 4 classifications of shock
hypovolaemic
cardiogenic
distributive
obstructive
what are the stages of shock
initial stage
compensation/ nonprogressive
progressive shock
refractory shock
what happens in the inital stage of shock?
No outward clinical signs to observe or document
Cells are being starved of O2
Reduced production of ATP for energy
Switch to anaerobic metabolism – lactic acid produced
what happens in the compensation, non progressive stage of shock
Initial detection of reduced perfusion
Activation of compensatory (homeostatic) mechanisms
Cardiovascular compensation
Renal compensation
Endocrine compensation
Outward clinical signs
Respiratory
Cardiovascular
Renal
Skin
what are the clinical cardiovascular observations for shock?
NO CHANGE IN BLOOD PRESSURE
(Remember it is being compensated)
Effects of activated sympathetic Nervous system
Increased Heart Rate (Tachycardia)
Pale, cool clammy skin (Vasoconstriction)
Decreased pulse pressure (Weak pulse)
what does the autonomic (sympathetic) regulation do of GFR? and when?
Occurs during compensation phase
Overrides renal autoregulation
Maintains blood flow to heart, brain, muscles at expense of GFR
Sympathetic response - release of adrenaline from adrenal medulla
Causes greater constriction of afferent arteriole than efferent arteriole so
Glomerular hydrostatic pressure reduced
GFR reduced
what are the clinical signs of compensatory shock?
Cardiovascular
Tachycardia
NO CHANGE IN BP
Renal
Oliguria
Skin
Cool
Pale
Clammy
Respiratory
Increased Respiratory Rate
what is the effect of shock on gas exchange?
Efficient Gas exchange requires sufficient ventilation (V) AND perfusion (Q)
Shock reduces perfusion – high V/Q ratio
what happens in progressive (non-compensated) shock
Compensatory mechanisms begin to fail
Perfusion begins to fall
Metabolic acidosis present
Oxygen deprivation in the brain – confusion
Multiple Organ Failure – organ damage
can shock be reveresed?
no
what is hypovolemic shock
Reduction in Circulatory volume (hence ↓ Cardiac Output)
Blood Loss
Trauma
Oesophageal varices
Lower GI bleed
PR bleed (rectal bleeding)
Aortic aneurysm
Dehydration
what is the pathophysiology of hypovolemeic shock?
hypovolemia
decrease in venous return
decrease in preload
reduce cardiac output
hypotension
perfusion failure and tissue hypoxia
organ dysfunction
multiorgan failure
what is cardiogenic shock and what are the causes?
Failure of heart as a pump
Loss of cardiac output (Heart rate & Contractility)
Causes
Major myocardial infarction
Severe left ventricular failure – Ischaemic heart disease
Difficult to treat
Efforts to restore perfusion often make situation worse
