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Pathyophysiology and Classification of Shock

Pathyophysiology and Classification of Shock. KENNEY WEINMEISTER M.D. Definition. Shock is a physiologic state characterized by a significant, systemic reduction in tissue perfusion, thereby resulting in decreased tissue oxygen delivery. Stages of Shock. Early, Preshock, Warm shock

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Pathyophysiology and Classification of Shock

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  1. Pathyophysiology and Classification of Shock KENNEY WEINMEISTER M.D.

  2. Definition • Shock is a physiologic state characterized by a significant, systemic reduction in tissue perfusion, thereby resulting in decreased tissue oxygen delivery.

  3. Stages of Shock • Early, Preshock, Warm shock • Compensation by body’s homeostatic mechanisms • Tachycardia, Peripheral vasodilatation and modest decrement in systemic BP

  4. Stages of Shock • Shock • Homeostatic mechanisms are overwhelmed • Signs and symptoms of organ dysfunction • Tachycardia, tachypnea, metabolic acidosis, oliguria, and cool and clammy skin • 20 to 25% fall in effective blood volume • Fall in CI to < 2.5L/min/M2 • Activation of mediators of sepsis

  5. Stages of Shock • End Organ Dysfunction • Pathophysiology • AG II & NE cause increased Ca+2 in cytosol • Ca + calmodulin = P+myosin • P+myosin + actin = Myosin ATPase • Myosin ATPase = muscle contraction

  6. Pathophysiology of End Organ Shock • Activation of ATP sensitive potassium channels • Activation causes hyperpolarization • Closure of Ca channels • Activated by decrease in cellular ATP and increases in cellular H+ and lactate • Natriuretic peptide and nitric oxide

  7. Pathophysiology of End Organ Shock • Increased production on Nitric Oxide • activation of myosin light-chain phosphatase • leads to dephosphoralation of myosin • Vasopressin deficiency • potentiates vasoconstrictor effects of NE • directly inactivates Katp channels • blunts increase in cGMP • decreases synthesis of NO synthase

  8. Pathophysiology of End Organ Shock • Vascular smooth muscle tone is lost • Resistant vasodilatation • End organ dysfunction and death

  9. Classification of Shock • Hypovolemic shock • Cardiogenic shock • Distributive shock

  10. Hypovolemic Shock • Results from decreased preload • Hemorrhagic • Trauma, GIB, Ruptured aneurysm • Volume loss • Third spacing, GI losses, burns, insensible losses

  11. Cardiogenic Shock • Pump failure • Cardiomyopathies • Ischemic right and left ventricle, • Dilated • Stunned myocardium

  12. Cardiogenic Shock continued • Arrhythmia's • Bradyarrhythmias • Tachyarrhythmias • Mechanical • Valvular; MR, AI, AS • VSD • Atrial myxoma

  13. Cardiogenic Shock continued • Obstructive • Massive PE • Tension pneumothorax • Constrictive pericarditis • Tamponade • Severe pulmonary hypertension

  14. Distributive Shock • Vasodilatory shock resulting in severe decrease in SVR • Septic shock • Activation of systemic inflammatory response • Toxic shock syndrome • Anaphylaxis • Drug or toxins

  15. Distributive Shock continued • Addisonian crisis • Myxedema coma • Neurogenic shock

  16. Evaluation • H & P • Labs • CXR • EKG

  17. Treatment • Goal is early intervention to prevent irreversible organ damage • Recognize early shock • Diagnose and correct the underlying cause • Early goal directed therapy in sepsis • In hospital mortality 46.5% vs 30.5% for treatment group • NEJM, vol 345,No 19 Nov 8 2001

  18. Treatment • Fluid resuscitation • CVP 8-12 • Vasopressors • Norepinephrin infuse mcg/min (4mcg/min) • Dopamine infuse mcg/kg/min • Epinephrine infuse mcg/min (range 1-10 mcg) • Vasopressin infuse units/min (range 0.01 to 0.1 units/minute)

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