Physiology 24: Circulatory Shock And Its Treatment

Front 1

What is cardiogenic shock?

Back 1

inability of the heart to pump blood to maintain BP

Front 2

2 major factors leading to cardiac shock

Back 2

decreased pumping ability + decreased venous return to heart

Front 3

2 ways circulatory shock can occur without low cardiac output?

Back 3

high metabolic rate (normal output is inadequate) + poor tissue perfusion (inadequate supply to some tissue)

Front 4

End result of circulatory shock?

Back 4

tissue deterioration from lack of nutrients; vicious cycle as heart also deteriorates leading to a weaker heart and more shock

Front 5

3 stages of shock

Back 5

non-progressive (physiologic compensation occurs), progressive (body cannot compensate, but therapy can), irreversible (even therapy cannot save them)

Front 6

How does hemorrhage lead to shock?

Back 6

hypovolemia decreases cardiac filling pressure

Front 7

What % of blood can be removed from circulation before BP starts dropping?

Back 7

10%, body can compensate for this with sympathetics (vasoconstriction and HR)

Front 8

What % of blood can be removed from circulation before complete cardiac output failure?

Back 8

45%, output is 0

Front 9

After about 30% of body blood volume is lost, the BP plateaus for a bit. Why?

Back 9

last ditch effort of all remaining sympathetic stimulation to try and save the body by increasing BP before 40% volume is lost and cardiac output falls to irreversible 0

Front 10

Sympathetic stimulation during hypovolemic shock has a greater effect on maintaining (cardiac output or arterial pressure)?

Back 10

arterial pressure; the vasoconstriction of the sympathetics increases resistance (which has no bearing on the cardiac output). remember: BP= (CO x HR) (resistance).

Front 11

Why are coronary and cerebral arteries immune to effects of mild BP changes?

Back 11

auto-regulation keep them steady; generic sympathetics are not very selective for coronary and cerebral vessels, these vessels control their own vasomotor activity with local dilators and constrictors

Front 12

Arterial pressure below ____ leads to progressive hemorrhagic shock.

Back 12

45

Front 13

Major mechanisms the body uses to attempt to compensate from hemorrhagic shock

Back 13

baroreceptor reflex, ischemic responses, renin, ADH, adrenal medulla, increased reabsorption of water in GI tract

Front 14

Major cause of cardiac depression in progressive shock?

Back 14

release of toxins during ischemia

Front 15

What happens to right atrial pressure as shock progresses?

Back 15

increases; cardiac output falls

Front 16

What is "sludged" blood?

Back 16

blockage of small arteries during shock due to slow blood flow in these vessels; lactic acid (due to high metabolic rate during shock) coagulates blood also

Front 17

What happens to capillary permeability during shock?

Back 17

increases due to hypoxia and metabolic waste

Front 18

Endotoxin has what effect on the heart?

Back 18

cardiac depression

Front 19

4 major cellular functions that are decreased during shock ( due to hypoxia, ischemia)?

Back 19

Na/K pump, liver mitochondrial activity, lysosomal breakage releases hydrolases, low metabolism at the end of shock

Front 20

What is the pattern of tissue necrosis in shock?

Back 20

patchy due to irregular tissue perfusion in varying organs at various locations;

Front 21

More nutritional deficiencies during shock occur at the (arterial or venous) ends of capillaries?

Back 21

venous

Front 22

What would we expect to see on an ABG of a patient in shock?

Back 22

metabolic acidosis; high CO2, high bicarbonate to compensate

Front 23

What type of feedback is seen with shock?

Back 23

positive; the cycle gets worse and worse

Front 24

In irreversible shock, what major compounds are depleted?

Back 24

high energy phosphate reserves (ATP, ADP, AMP, adenosine). even if we had oxygen and energy, we don't have phosphates to activate anymore. new adenosine is made slowly (2% of total physiologic amount/hour)

Front 25

2 major conditions that show hypovolemic shock (due to plasma loss)

Back 25

intestinal obstruction (distended GI tract can block venous return = distended capillaries = fluid leaves the vascular compartment) and severe burns

Front 26

What is the clinical difference between hemorrhagic shock and hypovolemic shock due to plasma loss?

Back 26

hemorrhagic shock is loss of whole blood. hypovolemic shock due to plasma loss is just fluid loss, but the solutes stay in the fluid and viscosity and concentrations of solutes increase. patients with hypovolemic shock die to plasma loss will have slower blood flow and more clotting issues

Front 27

What is neurogenic shock?

Back 27

loss of inherent vasomotor responses; must give sympathetic hormones to save patient

Front 28

3 major causes of neurogenic shock?

Back 28

deep general anesthesia, spinal anesthesia, brain damage (basal regions)

Front 29

What occurs in anaphylactic shock?

Back 29

major release of histamine (vasodilator) from basophils and mast cells during a severe allergic reaction leads to a severe drop in BP; treat with epi pen to bring back BP

Front 30

Most frequent cause of shock related hospital deaths

Back 30

cardiac, then septic

Front 31

5 major features of septic shock

Back 31

high fever, vasodilation, high cardiac output, blood sludging, DIC (uses up clotting factors so hemorrhage can also occur to make it worse)

Front 32

Hemorrhagic shock is best treated with ...

Back 32

whole blood transfusion

Front 33

Hypovolemic shock due to low plasma is treated with ...

Back 33

fluid therapy to replace plasma volume, possible electrolytes also

Front 34

Fun Fact: In hemorrhagic shock, treatment with plasma will not restore the patient's hematocrit

Back 34

duh. this is done in emergency situations where whole blood is not available. the body can deal with a 50% drop in hematocrit fine

Front 35

What can be used as a plasma substitute?

Back 35

dextran solution

Front 36

Why is dextran used in solution to treat hypovolemic shock?

Back 36

it is large enough to exert a large colloid pressure in the vascular compartment and not be filtered out. good to keep the vascular volume up

Front 37

Sympathetic agents are most useful in treating which types of shock?

Back 37

neurogenic and anaphylactic

Front 38

How can the patient be arranged to help avoid shock?

Back 38

head 6 inches below the feet

Front 39

Hormones that can be used to treat shock?

Back 39

catechoamines, cortisol (increase heart strength, stabilize lysosomes), renin, ADH

Front 40

What is cardiac arrest?

Back 40

all blood flow stops; heart can be shocked, resuscitation can be implemented, anesthesia is stopped

Front 41

Why does cardiac arrest hurt the brain?

Back 41

small clots form in the arteries, leading to ischemia. NOT DUE TO HYPOXIA, treatment with anticoagulant agents delay brain damage in cardiac arrest, even though hypoxia is still occurring