1 CONCEPTS OF NORMAL HEMODYNAMICS AND SHOCK At the end of this self study the participant will: 1. Define the terms: stroke volume, cardiac output, preload, afterload, contractility, 2. Describe the difference between early and late cardiac compensation 3. Differentiate between three types of shock: a. Hypovolemic b. Cardiogenic c. Septic
CONCEPTS OF NORMAL HEMODYNAMICS AND SHOCK. At the end of this self study the participant will: Define the terms: stroke volume, cardiac output, preload, afterload, contractility, Describe the difference between early and late cardiac compensation Differentiate between three types of shock: - PowerPoint PPT Presentation
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CONCEPTS OF NORMAL HEMODYNAMICS AND SHOCKAt the end of this self study the participant will:
2. Describe the difference between early and late cardiac compensation
3. Differentiate between three types of shock:a. Hypovolemicb. Cardiogenicc. Septic
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Normal Hemodynamics
Blood PressureRegulated by cardiac output
and resistanceNot an indicator of blood
flowPressure of force that blood
exerts against walls of blood vessels
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Stroke Volume (SV)Amount of blood ejected from the left ventricle
with each heart beat
Components of SV Preload Contractility
Afterload
Normal Hemodynamics
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Normal Hemodynamics
Preload Amount of stretch experienced by the ventricle during
diastole Directly related to the volume of blood filling the
chamberAfterload
Force within the vessels which oppose the ventricleA function of vessel constriction of the pulmonary artery
(RV) and the aorta (LV)
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ContractilityForce of recoil from
the myocardium in systole
Starling’s Law states that the greater the stretch, the more forceful the contraction
Normal Hemodynamics
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Cardiac Output (CO)
Amount of blood ejected from the left ventricle within one minute
Equal to heart rate times stroke volume
HR X SV = CO
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Hemodynamic Compensation
Ability of the body to alter components of hemodynamic regulation to maintain homeostasis in periods of low blood flow
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Early Compensation
Preload increases to improve contractility (increased CO)
Heart rate increase to improve CO (sympathetic stimulation)
Afterload (resistance) constriction of the vessels to improve BP and blood flow
Autoregulation of individual organs
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Late CompensationThere is inadequate preload to offset changes in contractility
Declining SV is no longer offset by increase in HR
BP continues to fall and vessels are unable to vasoconstrict any further
Autoregulatory mechanisms fail
Shock symptoms
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Shock
Shock is a progressive, widespread reduction in tissue perfusion that results from a decrease in effective circulating blood volume.
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Initial Stages of Shock
No signs or symptoms may be present Decreased cellular perfusion is present Decreased cardiac output has started
Reduced blood flow secondary to reduced intercellular volume
Peripheral vasoconstriction
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Compensation Begins Body attempts to maintain hemodynamic stability -
homeostatic mechanisms activated
Increased total peripheral vascular resistance (PVR) and heart rate/ contractility results in increased cardiac output, BP, tissue perfusion
Increased Renal blood flow leads to vasoconstriction and H2O retention
Peripheral vasoconstriction increases central volume and vital organ blood supply
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Progressive Stage of Shock Compensatory mechanisms begin to fail
Blood vessels vasodilate reducing total peripheral resistance and BP
Perfusion now very poor leading to anaerobic metabolism and acidosis ACID signals the beginning of vasodilatation
Poor blood flow and agglutination - microclots - DIC
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Refractory Stage of Shock
No response to any form of therapy; Death is likely to occur Loss of autoregulation in micro-circulation Capillary permeability changes and fluid shifts
into interstitial space Venous return and cardiac output almost
negligible Reduced cardiac output leads to severely
impaired tissue perfusion
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Types of Shock Hypovolemic Shock
PRELOAD failure due to loss of circulating volume / intravascular volume
Cardiogenic Shock Primary failure of CONTRACTILITY due to
ischemic insult Septic Shock
Primary failure of AFTERLOAD
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Hypovolemic Shock
Assessment findings / Signs and Symptoms Skin pale and cool Distant heart sounds Low BP Low CO and CVP Clear breath sounds