Chapter 13 Shock Defining Shock Shock is best

Chapter 13: Shock

Defining Shock • Shock is best defined as inadequate tissue perfusion • Can result from a variety of disease states and injuries • Can affect the entire organism or it can occur at a tissue or cellular level • Shock is not adequately defined by: • • • Pulse rate Blood pressure Cardiac function Hypovolemia Loss of systemic vascular resistance

Components of the Circulatory System • The pump (heart) • The fluid (blood) • The container (blood vessels) Any problem with the components can lead to inadequate perfusion.

Cardiac Output • Amount of blood separately pumped by each ventricle per minute, usually expressed in liters per minute • Determined by multiplying the heart rate by the volume of blood ejected by each ventricle during each beat (stroke volume) • Crucial determinant of organ perfusion • Depends on: • Strength of contraction • Rate of contraction • Amount of venous return available to the ventricle (preload)

Baroreceptor Reflexes • Help maintain BP by two negative feedback mechanisms: • By lowering BP in response to increased arterial pressure • By increasing BP in response to decreased arterial pressure

Chemoreceptor Reflexes • Low arterial pressure may stimulate peripheral chemoreceptor cells that lie within the carotid and aortic bodies • When oxygen or p. H decreases, these cells stimulate vasomotor center of medulla

Compensatory Mechanisms • CNS Ischemic Response • Hormonal Mechanisms • • Adrenal-medullary mechanism Renin-angiotensin-aldosterone mechanism Vasopressin mechanism Atrial natriuretic factor • Reabsorption of tissue fluids • Splenic discharge of blood

Role of Adrenal Medulla in Regulating BP Figure 7 -8 A

Renin-angiotensin-aldosterone Mechanism in BP Figure 7 -8 B

Vasopressin (ADH) Mechanism in Regulating BP Figure 7 -8 C

The Body as a Container • The healthy body may be viewed as a smooth‑flowing delivery system inside a container • Container must be filled to achieve adequate preload and tissue oxygenation

The Body As a Container • The external size of the container of any particular human body is relatively constant • Volume of the container is directly related to the diameter of the resistance vessels • Any change in vessel diameter changes the volume of the fluid the container holds, thereby affecting preload Figure 19 -1

Blood Volume • Average adult male has a blood volume of 7% of total body weight • Average adult female has a blood volume of 6. 5% of body weight • Volume increases significantly during pregnancy • Normal adult blood volume is 4. 5‑ 5 L • Remains fairly constant in the healthy body

Plasma • Approximately 92% water • The liquid portion of blood • Circulates salts, minerals, sugars, fats, and proteins throughout the body • Contains 3 major proteins: • Albumin • Globulins (alpha, beta, and gamma) • Fibrinogen

Capillary-Cellular Relationship in Shock • Stage 1: Vasoconstriction • Stage 2: Capillary and Venule Opening • Stage 3: Disseminated Intravascular Coagulation • Stage 4: Multiple Organ Failure

Capillary-Cellular Relationship in Shock

Classifications of Shock • Hypovolemic shock • Distributive shock • Neurogenic shock • Anaphylactic shock • Septic shock • Cardiogenic shock

Compensated Shock • Characterized by signs and symptoms of early shock • Arterial blood pressure is normal or high • Treatment at this stage will typically result in recovery

Compensated Shock

Uncompensated Shock • Characterized by signs and symptoms of late shock • Arterial blood pressure is abnormally low • Treatment at this stage will sometimes result in recovery

Uncompensated Shock

Irreversible Shock • Characterized by signs and symptoms of late shock • Arterial blood pressure is abnormally low • Even aggressive treatment at this stage does not result in recovery

Irreversible Shock