Shock Chapter 13:. Defining Shock Shock is best defined as inadequate tissue perfusion Can result...
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Transcript of Shock Chapter 13:. Defining Shock Shock is best defined as inadequate tissue perfusion Can result...
Shock
Chapter 13:
Defining ShockDefining 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 SystemComponents 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 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 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 ReflexesChemoreceptor 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
Compensatory MechanismsCompensatory 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
Figure 7-8 A
Role of Adrenal Medulla in Regulating BPRole of Adrenal Medulla in Regulating BP
Figure 7-8 B
Renin-angiotensin-aldosterone Mechanism in BPRenin-angiotensin-aldosterone Mechanism in BP
Figure 7-8 C
Vasopressin (ADH) Mechanism in Regulating BPVasopressin (ADH) Mechanism in Regulating BP
The Body as a ContainerThe 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
Figure 19-1
The Body As a ContainerThe 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
Blood VolumeBlood 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
PlasmaPlasma
• 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 ShockCapillary-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 ShockCapillary-Cellular Relationship in Shock
Classifications of ShockClassifications of Shock
• Hypovolemic shock
• Distributive shock• Neurogenic shock• Anaphylactic shock• Septic shock
• Cardiogenic shock
Compensated ShockCompensated 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 ShockCompensated Shock
Uncompensated ShockUncompensated 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 ShockUncompensated Shock
Irreversible ShockIrreversible 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 ShockIrreversible Shock