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 Figure 7-18 A

Chemoreceptor Reflexes Low arterial pressure may stimulate peripheral chemoreceptor cells that lie within the carotid and aortic bodies When oxygen or pH decreases, these cells stimulate vasomotor center of medulla Figure 7-18 B

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 Figure 7-8 A

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

Vasopressin (ADH) Mechanism in Regulating BP Figure 7-8 C 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 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 Figure 19-2

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 Figure 19-3

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 Figure 19-4

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 Figure 19-5