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Surgical Biology > Shock > Flashcards

Shock Flashcards

1
Q

T/F: If vascular resistance or tone increases, afterload decreases with a resultant increase in cardiac output and perfusion.

A

False; If vascular resistance or tone increases, afterload increases with a resultant fall in cardiac output and perfusion.

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2
Q

T/F: Cardiac output=stroke volume x blood pressure

A

False; Cardiac output=stroke volume x Heart rate

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3
Q

T/F: Causes of increased preload include loss of volume, hypovolemia, decreases in vasomotor tone, and vasodilation

A

False; those are all causes of Decreased preload.

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4
Q

T/F: A severe fall in vascular resistance results in pooling of blood in capacitance vessels and a fall in blood pressure and preload.

A

True

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5
Q

T/F: Distributive shock is the result of a volume deficit.

A

False; Hypovolemic shock is the result of a volume deficit.

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6
Q

T/F: Distributive shock occurs when vasomotor tone is lost.

A

True

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7
Q

T/F: Distributive shock occurs when the cardiac muscle cannot pump out adequate stroke volume to maintain perfusion.

A

False; Cardiogenic shock occurs when the cardiac muscle cannot pump out adequate stroke volume to maintain perfusion

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8
Q

T/F: Distributive shock occurs when oxygen uptake is impaired because of mitochondrial failure.

A

False; Relative hypoxia or dysoxia occurs when oxygen uptake is impaired because of mitochondrial failure.

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9
Q

Which type of shock is caused by obstruction of ventilation or cardiac output?

A

Obstructive shock

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10
Q

T/F: In regard to early or mild shock, as blood volume initially decreases, pressure within the vessels increases.

A

False; As blood volume initially decreases, pressure within the vessels falls.

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11
Q

T/F: In regard to early or mild shock, baroreceptors and stretch receptors act to decrease inhibition of
sympathetic tone while increasing inhibition of vagal tone and decreasing release of ANP by cardiac myocytes.

A

True

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12
Q

T/F: In regard to early or mild shock, the increase in sympathetic tone and fall in atrial natriuretic peptide (ANP) results in vasodilation.

A

False; The increase in sympathetic tone and fall in atrial natriuretic peptide (ANP) results in vasoconstriction.

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13
Q

T/F: In regard to early or mild shock, increased sympathetic activity at the heart decreases heart rate and contractility.

A

False; Increased sympathetic activity at the heart increases heart rate and contractility.

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14
Q

In shock, the vasoconstrictive response will vary between organ systems. Which set of organ systems has the greatest vasoconstrictive response?

A

kidney, integument, and viscera

cerebral and cardiac flow is preferentially maintained

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15
Q

T/F: Regarding compensatory responses to restore blood flow in the face of shock, an increase in precapillary sphincter tone results in an increase in capillary hydrostatic pressure.

A

False; An increase in precapillary sphincter tone results in a drop in capillary hydrostatic pressure, favoring movement of fluid from the interstitium into the capillary bed.

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16
Q

T/F: Regarding compensatory responses to restore blood flow in the face of shock, a decrease in renal perfusion results in secretion of renin from
enterochromaffin cells located in the wall of the afferent arteriole.

A

False; A decrease in renal perfusion results in secretion of renin from Juxtaglomerular cells located in the wall of the afferent arteriole.

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17
Q

T/F: Regarding compensatory responses to restore blood flow in the face of shock, renin stimulates production of angiotensin I, which, after conversion to angiotensin II, increases sympathetic tone on peripheral vasculature and promotes aldosterone release from the adrenal cortex.

A

True

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18
Q

T/F: Regarding compensatory responses to restore blood flow in the face of shock, vasopressin is a potent vasoconstrictor and stimulates increased sodium reabsorption in the renal collecting ducts.

A

False; Vasopressin is a potent vasoconstrictor and stimulates increased Water reabsorption in the renal collecting ducts.
(aldosterone stimulates increased renal tubular sodium and water reabsorption)

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19
Q

Which set of clinical signs correlates to moderate hypotension/Shock Class II-III.

1. Normal to anxious mentation, tachycardia, cool to cold extremities.
2. Prolonged capillary refill time, decreased urine output, and cool extremities.
3. Obtunded mentation, normal extremity temperature, decreased urine output.
4. Agitated to lethargic mentation, normal extremity temperature, and anuria.
A
  1. Prolonged capillary refill time, decreased urine output, and cool extremities.
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20
Q

cool extremities, agitated to lethargic mentation, decreased urine output, prolonged CRT, tachycardia, tachypnea, and normal to decreased BP all describe a horse in which stage(s) of shock?

A

Moderate hypotension/shock class II-III

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21
Q

Cool to cold extremities, obtunded mentation, anuria, shortened CRT, severe tachycardia, tachypnea, and decreased BP are all consistent with a horse in which stage(s) of shock?

A

Severe hypotension/shock class III-IV

22
Q

What three functions dictate blood flow?

A

circulating volume, cardiac pump function, vasomotor tone/vascular resistance

23
Q

What is cardiac output?

A

CO= stroke volume x heart rate

24
Q

When blood loss of 15% circulating volume or less occurs, the circulating volume can be restored from what source?

A

the interstitium (“transcapillary fill”)

25
Q

What occurs with a circulating volume loss of greater than 15%?

A

uncompensated or hypodynamic shock; (ischemia to the brain and myocardium begins; inc. HR, inc. RR, decr. Pulses, cold extremities d/t vasoconstriction; progressive acidosis with inc. lactate and CO2 waste product buildup results in cell swelling and release of free radicals and inflammatory mediators.

26
Q

Ultimately as with hypoperfusion and the lack of energy, three things occur that lead to vasodilation (decompensated shock). List them:

A

accumulation of toxic metabolites, microthrombi formation, and inflammatory injury –> vascular smooth muscle failure and vasodilation

27
Q

In what ways does gastrointestinal disease lead to decreased blood volume?

A

mechanical compression on the caudal vena cava reducing blood return to the heart; third spacing of fluid; loss of mucosal barrier integrity resulting in endotoxin absorption and microcirculatory failure.

28
Q

The Americal College of Surgeons has four categories for progressive blood loss. Briefly describe each class:

A

Class I –> mild; less than 15% blood volume (compensated)
Class II –> 15-30%; onset of hyperdynamic shock and clinical signs
Class III –> moderate hypovolemic or decompensatory shock
Class IV –> circulatory collapse

29
Q

What is the recommendation of fluid therapy during acute blood loss?

A

conservative fluid therapy (prevent rapid increase in blood pressure and reduce risk of dislodging a clot)

30
Q

When using isotonic crystalloids, what percentage of fluid will be lost to the extravascular space?

A

80%

31
Q

If administering 10 liters of isotonic crystalloid solution, how much will remain in the vascular space?

A

2 liters (8L will be lost to the extravascular space)

32
Q

What type of cellular metabolism occurs during shock?

A

anaerobic

33
Q

What is the normal colloid oncotic pressure of plasma?

A

~ 20 mmHg

34
Q

What are the advantages of using a natural colloid?

A

provide protein (albumin, antibodies, critical clotting factors, etc.)

35
Q

Hypersensitivity reactions occur in ____% of horses receiving plasma.

A

10%

36
Q

What is the colloid oncotic pressure of hetastarch?

A

30 mmHg

37
Q

What is the recommended dose for hetastarch?

A

5-10 ml/kg iV q 36-48 hours (10 ml/kg will last ~ 120 hrs)

38
Q

List one potential complication from the use of large volumes of hetastarch.

A

decreases von Willebrand factor antigen and therefore results in increased bleeding time.

39
Q

What is the formula for calculating fluid replacement volumes?

A

percent blood volume (L/kg body wt x 100) x body weight

*blood volume = 7% - 9% in adult horse

40
Q

How does dobutamine improve perfusion?

A

beta1-adrenoreceptor agonist –> positive inotrophic action (it has a weaker affinity for beta2 and alpha receptors)

41
Q

What is the mechanism of action for norepinephrine?

A

strong beta1 and alpha-adrenergic affinity resulting in vasoconstriction and increased cardiac contractility.

42
Q

T/F: An intravenous infusion of hypertonic saline will expand the intravascular space 8 times the amount infused.

A

False; The osmolarity of this concentration range is approximately 8 times the tonicity of plasma. An intravenous infusion of hypertonic saline will expand the intravascular space 2 to 4 times the amount infused, pulling fluid from the intracellular and interstitial spaces.

43
Q

What is a normal central venous pressure (CVP) in a horse?

A

7 to 12 mmHg

44
Q

Normal urine output in an adult horse is _____; a decrease of urine output to _____ suggests significant volume depletion.

A

1 ml/kg/hr;

<0.5 ml/kg/hr

45
Q

a MAP of ____ is required to maintain adequate perfusion to the brain.

A

65 mmHg

46
Q

How much ATP does aerobic metabolism create?

A

36 moles ATP/molecule glucose

47
Q

How much ATP does anaerobic metabolism create?

A

2 moles ATP per molecule glucose

48
Q

Oxygen delivery depends on _________ ______ and ___ _______ of arterial blood.

A

cardiac output; O2 saturation

49
Q

As cardiac output decreases, the tissues respond by increasing oxygen extraction. How is O2ER calculated?

A

O2ER=SaO2-SvO2
Oxygen extraction = the difference between oxygen saturation of arterial blood (SaO2) and oxygen saturation of venous blood (SvO2)

50
Q

The physiologic response to trauma has two phases. Briefly describe these phases.

A 
Phase I ("ebb"): hypovolemia and low flow/perfusion to the injured site
Phase II ("flow"): perfusion is restored (there are two periods within phase II: the catabolic period --> may be shocky; and the anabolic period --> return to homeostasis)

Surgical Biology (8 decks)

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