Hypovolemic Shock

¯ circulating blood volume due to either hemorrhage or fluid depletion (dehydration, vomiting, diarrhea)

-most common in clinic

ncompensatory mechanisms try to maintain Blood Pressure (BP)
n
  • baroreflexes (­ Heart rate (beats/min), ­ stroke volume (litres/min), ­ SVR and vascular tone)
n
    • neurally mediated
n
  • humoral effects (e.g. vasopressin, aldosterone) restore blood volume
n
  • catecholamines (­ HR, ­ stroke volume, ­ SVR and vascular tone)
    Mild
    Moderate
    Severe
    (<20% loss)
    (20-40% loss)
    (>40% loss)
    Cool extremities
    Same, plus:
    Same, plus:
    ­ Capillary refill time
         Tachycardia (­ HR)
         Hemodynamic instability
    Diaphoresis (sweating)
         Tachypnea (­ RR)
         Marked tachycardia
    Collapsed veins
         Oliguria (¯ urine output)
         Hypotension
    Anxiety
         Orthostatic hypotension
             (¯ BP while upright)
         Mental status changes
n¯ blood pressure results from ¯ preload
n
  • inadequate ventricular filling
n
  • ¯ stroke volume ® ¯ cardiac output
n¯ hydrostatic pressure within capillaries
n
  • ¯ tissue perfusion
n
    • worsened by arteriolar vasoconstriction attempting to preserve BP
n
  • fluid moves from extracellular space to blood
n
    • loss of skin turgor
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