Physiologic determinants of cardiac output

Published on 13/02/2015 by admin

Filed under Anesthesiology

Last modified 13/02/2015

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Physiologic determinants of cardiac output

Amorn Vijitpavan, MD

Cardiac output (CO) is the quantity of blood that the heart pumps per minute. CO in a normal 70-kg individual with a heart rate (HR) of 70 to 80 beats/min is 5 to 6 L/min, but it decreases by approximately 25% when the individual is resting in the supine position and may increase approximately eightfold with exertion. The cardiac index (CI) normalizes a person’s CO for body surface area (BSA):

< ?xml:namespace prefix = "mml" />CI (L·min1·m2)=CO/BSA

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A normal CI varies between 2.5 and 3.5·L·min-1·m-2. The two major determinants of CO are stroke volume (SV) and HR:

CO (L/min)=SV×HR

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Stroke volume

The SV is the amount of blood ejected by the ventricle with each contraction. A normal SV is 70 to 80 mL. Determinants of SV include preload, afterload, and contractility.