Pathyophysiology and Classification of Shock KENNEY WEINMEISTER M.D.

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

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

Stages of Shock w Shock w Homeostatic mechanisms are overwhelmed w 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

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

Pathophysiology of End Organ Shock w 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

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

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

Classification of Shock w Hypovolemic shock w Cardiogenic shock w Distributive shock

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

Cardiogenic Shock w Pump failure w Cardiomyopathies Ischemic right and left ventricle, Dilated Stunned myocardium

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

Cardiogenic Shock continued w Obstructive Massive PE Tension pneumothorax Constrictive pericarditis Tamponade Severe pulmonary hypertension

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

Distributive Shock continued w Addisonian crisis w Myxedema coma w Neurogenic shock

Evaluation w H & P w Labs w CXR w EKG

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

Treatment w Fluid resuscitation CVP 8-12 w 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)