Lecture Mosby's paramedic textbook (4th ed) - Chapter 36: Shock

9/11/2012 1 Chapter 36 Shock 2 Learning Objectives • Define shock. • Outline factors necessary to achieve adequate tissue oxygenation. • Describe how the diameter of resistance vessels influences preload. 3 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 1 9/11/2012 Learning Objectives • Calculate mean arterial pressure when given a blood pressure. • Outline changes in the microcirculation during the progression of shock. 4 Learning 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 shock. 5 Shock • 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 death 6 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 2 9/11/2012 Shock • 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 function 7 Shock • Causes – Healthy patient (adult) • Coronary syndromes • Respiratory arrest • Anaphylaxis • Drowning • Traumatic hemorrhage • Spinal cord injury • Electrocution • Hypothermia • Toxic exposures • Pulmonary embolus 8 Shock • Causes – Unhealthy patient (adult) • Congestive heart failure • Renal failure • Uncontrolled hypertension • Uncontrolled diabetes • Obesity • Electrolyte imbalance • Drug toxicity • Stroke 9 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 3 9/11/2012 Shock • Causes – Pediatric • Trauma • Chest wall injury • Fluid loss • Spinal cord injury • Anaphylaxis • Heart disease 10 Shock • 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 shock 11 Tissue 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 malfunction 12 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 4 9/11/2012 Heart • 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) 13 Preload, 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 contraction 14 Preload, 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 15 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 5 ... - tailieumienphi.vn