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Shock_and_Hypoperfusion

Shock_and_Hypoperfusion - Shock and Hypoperfusion Vic V...

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Shock and Hypoperfusion Vic V. Vernenkar, D.O. Dept. of Surgery St. Barnabas Hospital
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Introduction and History Ambroise Pare first described symptoms in 1575 French surgeon LeDran 1743 used term “Shock” WW I reduction of O2 to tissues, lactic acidosis (Mcleod) Renal failure Korean War 1970 Swan Ganz catheter and numbers
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Basic Mechanisms Oxygen supply meets demand=aerobic metabolism, glucose metabolized Usually only 25% oxygen in capillaries utilized by tissues for aerobic metab. Tissues can up this to 50-60% when stressed, up to a point, then… Some glucose used anerobic metab.
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Basic Mechanisms Problem with anerobic metab is less energy yield, lactate produced. Lactic acidosis ensues, as cant be cleared as fast as CO2 from tissues. LA impairs at cell level then organ level Impaired organ means poor cellular perfusion….. Shock is a self perpetuating condition.
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Oxygen Delivery Amount of oxygen that a given volume of blood carried multiplied by the speed at which it is carried to the cell. Content of arterial O2 is CaO2 CaO2=1.34 x Hb x SaO2 +(.003xPaO2) Delivery:DO2= CO x CaO2 CO= SV x HR SV is a consequence of preload, afterload, and contractility.
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Cardiac Output Number of beats per minute multiplied by amount of blood per beat. A decrease in one necessitates an increase in the other. Tachycardia earliest and most effective Drops out at over 150 beats per minute Diastolic filling drops off with tachycardia
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Preload Described by Starling in 1915. The stretch on myocardial fibers. Clinically its LVEDV. An increase of LVEDV produces increased CO up to a point, then falls off. This is the flat part of the “curve” At this point failure and pulm edema
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Starling Curve
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Pulmonary Artery Catheter Estimates LVEDV. Catheter passed thru right heart, wedged in the pulm artery. You are now measuring a column of blood all the way to left ventricle in diastole. LVED pressure is a proxy for preload. Many things can affect this measurement of preload.
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Swan Ganz
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Circulation
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Swan Tracings
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Afterload Resistance against which the heart muscle contracts. Physiologically equal to ventricular wall tension during systole. SVR: systemic vascular resistance Clinically SVR measures afterload.
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