TAILIEUCHUNG - mosby paramedic (36)

9/11/20121Chapter Objectives.• Define shock• Outline factors necessary to achieve adequate .tissue oxygenation• Describe how the diameter of resistance .vessels influences © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Objectives.• Calculate mean arterial pressure when given a .blood pressure• Outline changes in the microcirculation during .the progression of Objectives.• List the causes of hypovolemic, cardiogenic, .neurogenic, anaphylactic, and septic shock• Describe pathophysiology as a basis for signs .and symptoms associated with the .progression through the stages of .• Defined by Gross in 1850.– “Rude unhinging of the machinery of life”• Robert M. Hardaway, professor of surgery at .Texas Tech University School of Medicine in El .Paso, Texas.– I believe that the best definition of shock is .inadequate capillary perfusion. As a corollary of this .broad definition, almost anyone who dies, except one .who is instantly destroyed, must go through a stage of .shock—a momentary pause in the act of © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning .• Shock is not single event.– Does not have one specific cause and treatment.• Complex group of physiological abnormalities.• Many complexities involved in shock, not adequately .defined by pulse rate, blood pressure, cardiac function7Shock.• Causes.– Healthy patient (adult).•.•.•.•.•.•.•.•.•.•Coronary . cord .• Causes.– Unhealthy patient (adult).•.•.•.•.•.•.•.•Congestive heart © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning .• Causes.– Pediatric.•.•.•.•.•.• wall cord disease10Shock.• Cannot be reduced to loss of circulating blood .or loss of pressure in vascular system.– May affect entire body.• May occur at tissue or cellular level, even with normal .hemodynamics– Understanding of cellular physiology is needed to .recognize subtle aspects of shock.• Will aid in properly assessing severity of various stages .of shock11Tissue Oxygenation.• Perfusion.– Adequate oxygenation of tissue cells.– To achieve adequate oxygenation, three distinct .components of cardiovascular system must work .properly.• Heart.• Vasculature.• Lungs– Hypoperfusion.• Decrease in cellular oxygenation can occur.• Occurs when heart, vasculature, or lungs © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning .• Cardiac cycle.– Pumping action produces pressure changes that circulate .blood through body• Cardiac output.– Crucial determinant of organ perfusion.– Depends on.• Strength of contraction.• Rate of contraction.• Amount of venous return available to ventricle (preload)– Formula to determine cardiac output.• Cardiac output (CO) = Heart rate (HR) × Stroke volume (SV).13Preload, Afterload, and MAP .• Preload.– Amount of venous return to ventricle.– Ventricular volume at end of diastole.– It is "load" that must be given to left ventricle .prior to contraction14Preload, Afterload, and MAP .• Afterload.– Total resistance against which blood must be .pumped.– It is "load" that must be given to heart to .overcome resistance to ventricular ejection • Total peripheral vascular resistance.– Determined by volume of blood in vascular system .and by diameter of vessel walls 15Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company5.

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