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Cloned from: SHOCK pathology



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Etiologic Factors of SHOCK
  1. Inadequate Blood Volume
  2. Incr size of vascular system d/t vasodilation with unchanged blood volume
  3. Decr CO d/t myocardial failure
  4. Obstruction of blood flow
Major causes:
  • Hypovolemic Shock
  • Hemorrhage
  • Trauma
  • Surgery
  • Burns
  • Fluid loss (vom/dia - esp in children)
Major Causes
  • Vasogenic/Distributive Shock
  • neurogenic shock (syncope/SC injury)
  • Anaphylaxis (ex PCN shock)
  • Septic shock (severe bact infection)
  • not due to any blood or fluid loss; just not enough circulating volume because blood is in "peripheral pooling"
Major Causes
  • Cardiogenic Shock
Blood pumped out of heart decreases
  • Myocardial Infarction
  • Congestive heart failure
  • Arrhythmias
Major Causes
  • Obstructive shock
Blood in major arteries is blocked
  • Pulmonary embolism (saddle emb)
  • Cardiac tamponade
  • Cardiac tumor
  • Tension pneumothorax
Types of Hypovolemic Shock
  • hemorrhagic
  • traumatic
  • burn
  • surgical
Hypovolemic shock Signs and Symptoms
  • Hypotension
  • rapid thready pulse
  • cold clammy skin
  • tachycardia
  • tachypnia (rapid breathing)
Hypovolemic shock: pathophysiology
Inadequate perfusion of tissues inc anaerobic glycolysisInc lactic acid → Decr peripheral vascular response to catecholamines
Hypovolemic shock: Severity
Less severe: compensatory mechs
Severe, persists: Progresses, leads to refractory shock and death
Very severe: death
Hypovolemic shock: Compensatory mechanisms
to maintain CO and Bp:
  • Baroreceptor reflexes
  • sympathetic stimulation/rel of catecholamines
  • activation of RAAS
Hypovolemic shock: use of compensatory mechanisms for -
  • low blood pressure
Low BP→ stim baroreceptor impulses→ inc vasomotor dischg from brainvasoconstriction (exc brain/heart)
results in cold, clammy skin
Hypovolemic shock: use of compensatory mechanisms for -
  • Hypovolemia
Hypovolemia→ incr angiotensin, catecholamines, erythropoietin, vasopressin, ACTH, aldosterone → Na + H2O retention
Hypovolemic shock: use of compensatory mechanisms for -
  • Low BP
Low BP→ stimulates chemoreceptors → tachypnia, tachycardia


Low BPrenal shutdown prerenal azotemia → ARF (Acute renal failure)
Refractory shock
If causes of hypovolemic shock aren't corrected, it passes into refractory shock, which is irreversible.

It is a severe stage showing no response to treatment.
Characteristics of Refractory shock
Cerebral ischemia→ decr vasomotor/cardiac discharge → dec BP → Inc shock!


Myocardial ischemia→ dec BP→inc shock


Endothelial damage→ inc cytokines→ ARDS (acute resp distress syndrome)
Vasogenic/distributive shock
Assoc with systemic vasodilation ("peripeheral pooling")→ sudden increases in vasc bed capacitance leads to hypotension, hypoperfusion, cellular anoxia.


There is an acute disparity between the volume of blood and capacity of vascular system
Types of Vasogenic shock
Neurogenic (SC injury, anesthesia, syncope d/t loss of vascular tone bc of increase in ANS activity), Anaphylactic, Septic
Characteristics of Vasogenic shock
Skin is initially warm due to vasodilation (instead of cold and clammy like hypovolemic shock)
Course of events: allergy→ histamine→ vasodilation→ decr BP
Peripheral pooling in vasogenic shock

*no hemorrhage or fluid loss* d/t acute disparity between volume of blood and capacity of vascular system
  • vasc system capacity is increased due to vasodilation and pooling of blood
  • vasodilation is d/t release of vasoactive substances (cytokines) following tissue destruction, allergic rxn, bacterial infection
Cardiogenic Shock
Decr CO leads to decr tissue perfusion
Causes: MI, cardiomyopathy
S/S: hypovolemic shock + passive venous congestion in lungs/other organs

MI with cardiogenic shock→ 60-90% mortality
Obstructive shock: causes
  • pulmonary embolism
  • cardiac tamponade
  • cardiac tumor
  • tension pneumothorax - result of mediastinal shift which pushes on surrounding BV's and tension pneumo
MCC of death in ICUs
  • vasodilation/peripheral pooling
  • myocardial depression
Sepsis syndrome/septic shock
leading cause of death in ICU
- major risk factors: catheters (esp intravascular), invasive procedures, prosthetic devices and immunosuppressive and cytotoxic drugs
Sepsis
*from spread of severe bacterial infection
*d/t LPS on bacteria causing pathologic changes after lysis
SIRS & MODS
SIRS: systemic inflammatory response syndrome: and exaggerated inflamm reaction, hypermetabolic state.  Often progresses to MODS (multiple organ dysfunction syndrome).
-sirs results from systemic release of cytokines d/t LPS from bacteria
"sepsis syndrome"
Sepsis with decreased perfusion, peripheral vasodilation, hypoxemia, inc lactate, dec urine, dec mental status
Sepsis: characteristics
Tachycardia, tachypnia, temp up or down, WBC count up or down; hypothermia/leukopenia gives a poor prognosis
Hemodynamic disturbances in shock
vasoactive substance release
loss of norm vascular autoregulation → hyperdynamic circulatory state/peripheral pooling→ (distributive shock)


septic shock presents with warm extremities


Myocardial depression leads to biventricular dilation with abnormal ventricular function
Waterhouse-Friderichsen syndrome
meningococcal septicemia→  severe septic shock→ circulatory collapse, adrenal hemorrhage, cyanosis, etc
Morphology of shock:
Hypoxic cellular injury → changes in all tissues/organs
Heart: focal/widespread myocardial necrosis
Brain: ischemic encephalopathy
Lungs: diffuse alveolar damage
GIT: patchy mucosal hemorrhages/necroses
Liver: fatty change, central hemorrhagic necrosis
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