shock

Question 1

define shock

Answer 1

failure of the circulatory system to adequately perfuse vital organs

Question 2

describe what happens to tissues during shock

Answer 2

tissue perfusion and oxygen delivery are insufficient to meet the basal metabolic demands of tissues

Question 3

what is characterized by shock?

Answer 3

low blood flow that is usually accompanied by low blood pressure (hypotension)

Question 4

what is compensated shock?

Answer 4

compensatory mechanism that may maintain viability of vital organs and sustain the life of the patient

Question 5

what is uncompensated shock?

Answer 5

ensues where progressive circulatory collapse leads to increasingly severe disruption of critical cellular metabolic pathways and death

Question 6

what is the primary goal of therapy for shock?

Answer 6

rapid restoration of systemic blood flow by replacement of intravascular fluid and the use of drugs that increase vascular tone and support cardiac function

Question 7

how is shock initiated?

Answer 7

anything that severely and usually relatively suddenly decreases cardiac output, blood volume, and/or peripheral vascular resistance

Question 8

what is the cause of cardiogenic shock?

Answer 8

by insults that negatively affect cardiac output (inhibit the heart’s ability to pump blood)

Question 9

what is the the formula for anything affecting heart rate or contractility can decrease cardiac output or cardiogenic shock?

Answer 9

Cardiac output = heart rate x stroke volume

Question 10

what might occur with myocardial degeneration?

Answer 10

vitamin E/selenium deficiency in pigs (mulberry heart disease), monensin toxicity in horses, or myocardial infarcts (which occur much more commonly in humans than in domestic animals), can cause heart failure and cardiogenic shock

Question 11

what are infarcts

Answer 11

areas where the blood supply has been compromised

Question 12

how does cardiac tamponade cause acute heart failure resulting cardiogenic shock?

Answer 12

fluid (usually blood) accumulates rapidly in the pericardial space and impinges on the ability of the cardiac ventricles to dilate and fill with blood

Question 13

what is an example of electrolyte imbalances that negatively affect heart rate leading to heart failure and cardiogenic shock?

Answer 13

hyperkalemia in uremic animals

Question 14

what is hypovolemic shock caused by?

Answer 14

sudden severe loss of blood volume

Question 15

what are the causes of hypovolemic shock?

Answer 15

• acute hemorrhage involving loss of greater than 1/4 to 1/3 of total blood volume. The blood may be lost externally or into internal spaces such as the peritoneal cavity or the alimentary tract.
• loss of fluid (intravascular and extravascular), which may occur with water deprivation, vomiting, diarrhea, etc.
• increased vascular permeability leading to loss of intravascular fluid, proteins, and sometimes blood cells

Question 16

what injures the vessels when there is increased vascular permeability? specific examples?

Answer 16

infections, toxicities, and immune reactions that injure vessels

Specific examples include equine viral arteritis, African swine fever, hog cholera, and the hemorrhagic fevers (e.g., simian hemorrhagic fever, Ebola virus infection)

Question 17

what causes distributive (or vasogenic) shock?

Answer 17

sudden severe decrease in peripheral vascular resistance that causes extensive pooling of blood within the venous system and subsequent decreased venous return to the heart.

Question 18

what is the cause of septic shock?

Answer 18

bacterial infection (localized or systemic) in which large quantities of endotoxin are released into circulation

Question 19

what are endotoxins?

Answer 19

complex components of the cell wall of gram-negative bacteria and then can really do a number on the body, and especially on the vasculature

Question 20

why are endotoxins sometimes called lipopolysaccharide?

Answer 20

most toxic part of the complex is this type of molecule

Question 21

what is the pathogenesis of endotoxic/septic shock?

Answer 21

Endotoxin binds to serum protein → resulting complex binds to macrophage/monocyte → TNFα secreted into circulation → marked capillary dilation → severe pooling of venocapillary blood → decreased cardiac venous return and cardiovascular collapse

Question 22

what is the pathogenesis of anaphylactic shock?

Answer 22

Exposure to allergens → activation of mast cells or other effector cells → massive release of histamine and other chemical mediators
→ marked venocapillary dilation

Question 23

what is anaphylactic shock?

Answer 23

systemic manifestation of an acute hypersensitivity (allergic) response

Question 24

how does the idiosyncratic reaction of anaphylactic shock occur?

Answer 24

predisposed individuals upon exposure to certain antigens (substances, usually proteins, to which the individual is allergic) such as insect stings, foods, medicines, etc.

Question 25

upon exposure to allergens, histamine and other chemicals are released from what cells?

Answer 25

mast

Question 26

what is the result of histamine binding to receptors?

Answer 26

vasodilation and increased vascular permeability with loss of intravascular fluid

Question 27

how can neurogenic shock happen?

Answer 27

severe trauma, severe pain, or occasionally following restraint.

Question 28

what is the pathogenesis of neurogenic shock?

Answer 28

massive autonomic nervous system discharge which disrupts vasomotor control and there is extensive venocapillary pooling of blood so it doesn’t get moved to vital organs

Question 29

true or false: the consequence of shock is that oxygen doesn’t get to cells

Answer 29

true

Question 30

what does anoxic injury to endothelial cells lead to?

Answer 30

increased vascular permeability and further loss of intravascular fluid, aggravating the hypovolemia and anoxia

Question 31

what is the result of insufficient renal and muscular perfusion?

Answer 31

metabolic acidosis, which further suppresses cardiac output

Question 32

what does insufficient myocardial perfusion cause?

Answer 32

anoxic injury to myocytes, further decreasing cardiac output.

Question 33

how does the body respond to shock?

Answer 33

by attempting to increase cardiac output and by shunting blood flow to vital organs such as brain, heart and kidneys and away from tissues such as the gastrointestinal tract, skeletal muscle, and skin

Question 34

how does the secretion of norepinephrine and epinephrine by the adrenal medulla support cardiac function?

Answer 34

increases heart rate.

Question 35

how does the production of aldosterone by the adrenal cortex support cardiac function?

Answer 35

stimulates retention of sodium and water, thus increasing blood volume

Question 36

how does the secretion of norepinephrine and epinephrine by the adrenal medulla support vascular changes?

Answer 36

stimulates vasoconstriction

Question 37

how does the renin-angiostensin system support vascular changes?

Answer 37

results in the eventual production of angiotensin II, which is a potent vasoconstrictor

Question 38

the lesions of shock are of what?

Answer 38

a. the various initiating causes (e.g., hemorrhages, burns, cardiac tampanode, etc.)
b. changes that reflect edema and venocapillary pooling of blood
c. degenerative changes in tissues subjected to anoxia.

Question 39

lesions of shock will cause severe organ congestion where?

Answer 39

liver, gastrointestinal tract, kidneys, and adrenal glands

Question 40

hemorrhage into the lumen of the GI tract follows congestion and anoxic necrosis of what?

Answer 40

superficial mucosa

Question 41

why is the lung considered a “shock organ”?

Answer 41

because of the frequent occurrence of severe edema, thrombosis, and degenerative changes associated with shock

Question 42

in horses, why is the large colon considered the shock organ?

Answer 42

because of the tremendous submucosal colonic edema that occurs with endotoxemia

Question 43

what type of response does shock elicit?

Answer 43

systemic

involving generalized cardiovascular collapse