Shock & Exercise - Quiz 11 Flashcards
What is Circlatory Shock?
Not enough blood flow in the body to where tissues are damange d/t lack of oxygen & nutrient delivery - gets worse once it begins
What is the “Last-Ditch Stand”
When the brain lacks O2 & increased CO2, it activates extreme stimulation of SNS as last effort to keep the MAP from falling too low
What Causes Shock?
- Shock is from inadequate Cardiac Output
- Cardiac Abrnomalities effecting pump
- Factors decreasing venous return
How can you have Circulatory Shock even with Normal Cardiac Output?
Excessive Metabolic Rate
&
Abnormal Tissue Perfusion
How much blood can be loss before going into Hemorrhagic/Hypovolemic shock?
> 10% will causes decreases in Cardiac Output & MAP
40-45% Total blood Loss = Cardiac Output & Map of Zero
What happens during the Sympathetic Reflex to shock?
- Arterioles constrict = Increased PVR
- Veins constrict = adequate venous return
- Increased HR
How is blood flow to the Brain & Heart affected by the Sympathetic Reflex during shock?
No Constriction in Brain or Heart
Autoregulation maintains Blood flow as long as MAP > 70 mmHg
What are the Compensatory Mechanisms in Hemorrhage?
- Baroreceptors
- Chemoreceptors
- Cerebral Ischemic Response
- Endogenous Vasoconstrictors
- Reabsorption of Tissue Fluids
- Salt and Water Conservation
How do Baroreceptors work?
Located in Carotid Sinus & Aortic Arch
Senses pressure changes and alters CNS, HR & Contractility accordingly.
How do the Peripheral Chemoreceptors respond to Severe Hypotension?
Decreased organ blood flow leads to acidosis activating the chemoreceptors.
Further increases SNS response & respiration to increase BP
How does the Reabsorption of Tissue Fluids happen in shock?
Hypotension & Vasoconstriction causes a drop in Hydrostatic Pressure and net fluid reabsorption from interstitium into capillaries up to 1L/hr
Can cause Hemodilution = ↓Hct
How does the Kidney come into play during Shock?
- Kidneys release more
- Angiotensin II - Vasoconstriction
- Aldersterone - Salt & Water Reabsorption to increase blood volume
- Stimulates Vasopressin Release
- Important for long-term recovery
What is Circulatory Decompensation or Progressive Shock?
When the body’s compensation mechanisms is not enough to maintain a sufficent MAP to perfuse organs and leads to irreversible shock where everything fails.
What is Cardiogenic Shock?
Poor blood flow to the heart from hypotension causes myocardial hypoxia & acidosis, which depress its function & cause arrythmias
What is Symptathetic Escape?
Buildup of tissue metabolic vasodilators impairs sympathetic vasoconstriction causing more hypotension & hypoperfusion
How does progressive shock affect the brain?
Cerebral Ischemia/Hypoxia
Loss of Sympathetic outflow = more vasodilation, hypotension, and poor cerebral perfusion
What are the Rheological (flow) effects of Progressive Shock?
Increased blood viscosity, reducing perfusion
&
Intravascular Coagulation
What are the Stages of Shock?
-
Non-Progressive/Compensated
- Body can compensate to full recovery
-
Progressive
- W/o therapy, shock gets worse til death
-
Irreversible
- Nothing you can do, patient will die
What are treatments for Hypotension?
Give Blood
Epi/Norepi
Head Down Position
Oxygen
Glucocorticoids
In shock, where is Vasoconstriction most prominent?
Skin, Skeletal Muscle, and Splanchnic Vascular Beds
Blood flow is preferentially redistributed to which body organs in shock states?
Brain and Heart
What are the Decompensatory Mechanisms?
Cardiac & CNS Depression
Acidosis
Vasomotor Failure
Abnormal Clotting
Reticulo-Endothelial System
Cellular Deterioration
Low Flow States
What are the Positive Feedback Decompensatory Mechanisms?
↓CO & Contractility
↓MAP & O2 Transport
Vasodilation
Tissue Hypoxia
What happens on the Cellular Level that leads to Irreversible Shock?
Depletion of high-energy phosphates
What is the normal Rate of Blood flow through muscles?
3-4 mL/min/100g of muscle
What is the Rate of Blood Flow through muscles during Excercise for a nonathlete and an athelete?
Non Athelete: 4-5x normal blood flow
Athelete: 6-7x normal blood flow
(50-80 mL/min/100g of muscle)
What causes Low Blood flow to muscles during muscle contraction?
Muscle contraction compresses blood vessels
Can stop blood flow, but also rapidly weakens contraction
What is the status of some Muscle Capillaries at rest vs. during exercise?
At Rest: Some Capillaries have no flow
During Exercise: All capillaries open, increases surface area 2-3x & enhances o2 diffusion
What causes the tremendous amount of blood flow to the muscles during exercise?
- Vasodilation d/t release of
- Adenosine (ATP)
- Lactic Acid
- Potassium
- Blood flow can increase 20x
What factors helps oxygen unloading from Hgb to muscle tissues during excercise?
Right OxyHgb shift
Acidosis
Increased Temperature
What factor Greatly enhances blood flow to the muscle?
Decreased Oxygen in Muscle
How does Epi and Norepi play a role in Blood Flow to the Muscles?
- Epinephrine
- Alpha: Vasoconscriction in Non-Active Muscles, Renal & Splanchnic vessels
- Beta-2: Mild Vasodilation
- Norepinephrine
- Alpha: Vasoconstriction in Non-Active Muscles, Renal & Splancnic vessels
How much is Oxygen Consumption increased during Exercise?
60x
How is the Heart affected during exercise?
↑Sympathetic & ↓Parasympathetic
↑Cardiac Output: ↑HR, ↑Inotropy, ↑CVP, ↑Lusitropy
↓SVR
How does the change in Cardiac Output correlate to Heart Rate during exercise?
Stroke Volume only increases 10-35% durign exercise
Cardiac Output needs increase via Increase in Heart Rate durign exercise to keep up with oxygen demand
How does the Heart maintain its stroke volume at the high Heart Rates of exercise?
- Abdominothoracic & Skeletal muscles increase venous return to maintain CVP & Preload
- Venous Constriction/Decreased Venous Compliance
- Increased Atrial Inotropy for atrial filling
- Increased Ventricle Inotropy to squeeze out more blood
- Enhanced Ventricle Relaxation for better filling
What factors enhance Venous Return during Exercise?
- Sympathetically-mediated constriction of Capicitance Vessels
- ↓SVR in Muscles
- Contracting Muscles help pump venous blood back to heart
- Deeper & Faster breathing decreases intrathoracic pressure to enhance cardiac blood flow
How is the Mean Arterial Pressure affected by Exercise?
Increase in Cardiac Output is more than the decrease in SVR
MAP increases even though SVR decreases
What is the importance of an Increased MAP during Exercise?
Increased Pressure stretches vessel walls to increase blood flow up to 20x
&
Increased pressure also increases Perfusion Pressure