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Phase 1 > Ch. 6 Shock > Flashcards

Ch. 6 Shock Flashcards

1
Q

what determines oxygen delivery

A

arterial oxygen content (mostly determined by hemoglobin)

cardiac output

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2
Q

what is hypovolemic shock

A

reduction in circulating intravascular volume –> causes impaired oxygen delivery through a reduction in venous return to the heart and then reduced cardiac output
ex. hemorrhagic, non hemorrhagic like burns/open wounds, severe diarrhea, urinary losses

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3
Q

what is cardiogenic shock

A

inability of the heart to propel the blood through the circulation
ex. systolic failure (arrhythmia, drugs, CHF, DCM)
diastolic failure (HCM, cardiac tamponade, tension pneumothorax)

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4
Q

what is distributive shock

A

maldistribution of the vascular volume and massive systemic vasodilation –> amount of blood in the circulation is inadequate to fill the vascular space creating a relative hypovolemia
ex. sepsis (but can lead to hypovolemic, cardiogenic, or hypoxic shock), anaphylaxis, drugs, neurogenic (loss of autonomic nervous stimulation on the vessels)

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5
Q

what is hypoxic shock

A

adequate tissue perfusion but inadequate arterial oxygen or cellular oxygen utilization
ex. toxins causing methemoglobinemia, anemia, hypoxemia, carbon monoxide poisoning

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6
Q

how does the Frank Starling mechanism relate to pre load?

A

an increase in end diastolic volume will augment the strength of cardiac contractions

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7
Q

why does increasing the fraction of inspired oxygen do little to increase arterial oxygen content

A

because oxygen is not well solubilized in plasma, once the hemoglobin is maximally saturated, increasing the fraction of inspired oxygen does very little to increase arterial oxygen content

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8
Q

what are the three main categories of abnormalities that can lead to a reduction in arterial oxygen content

A

anemia
altered hemoglobin function
hypoxemia

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9
Q

What is Fick’s equation

A

determination of venous oxygen content

CvO2 = Hb x SvO2 x 1.34 x PvO2 x 0.003

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10
Q

what is the anaerobic threshold

A

at higher oxygen delivery levels, the consumption of oxygen is independent of its supply
when oxygen delivery is low, however, the consumption becomes more supply dependent

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11
Q

what is the oxygen extraction ratio?

A

O2ER = VO2/DO2 x 100
this is the ratio between oxygen uptake and oxygen delivery as a percentage
represents an index of the efficacy of tissue extraction of oxygen from the capillary bed
oxygen extraction ratios of different organs are extremely variable

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12
Q

where does the acid in hyperlactatemia come from?

A

hyperlactatemia from lactate production from glucose does not generate hydrogen ions
hydrogen ions accumulate during anaerobic conditions because the degradation of ATP to ADP releases a H+. Usually, aerobic conditions allow H+ to be consumed but under anaerobic times, the H+ accumulates with lactate creating an acidemic state known as metabolic lactic acidosis

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13
Q

what causes defects in oxygen uptake

A 
diffusional shunting 
diffusional resistance
arteriovenous shunting
perfusion/metabolism mismatch
cytopathic hypoxia (mitochondrial dysfunction)
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14
Q

What are the four ways the body compensates for shock?

A

maintaining mean circulatory pressure
maximizing cardiac performance
redistributing perfusion
optimizing oxygen unloading

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15
Q

what are chemoreceptors sensing?

A

baroreceptors in the carotid and aortic bodies respond to a reduction in O2
chemoreceptors in the brainstem are sensitive to an increase in circulating H+ or CO2

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16
Q

why is a decrease in hematocrit and total protein seen in a shock patient?

A

there is constriction of the precapillary arterioles that leads to a fall in hydrostatic pressure in capillaries and then a net shift of body fluids from the interstitium into the intravascular space

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17
Q

what is calpain

A

a proteolytic enzyme involved in reperfusion injury
calpain becomes activated as intracellular calcium increases in shock
calpain will convert xanthine dehydrogenase to xanthine oxidase and then xanthine oxidase will make super oxide when tissues have oxygen again

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18
Q

what is the shock index?

A

the ratio between heart rate and systolic arterial pressure

ratios greater than 0.9:1 may be suggestive of shock

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19
Q

what would the central venous pressure be in a patient with cardiogenic shock

A

should be increased! possibly >10 cm H20

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20
Q

what is the gold standard for cardiac output measurements

A

thermodilution and placement of a pulmonary artery catheter (Swan-Ganz catheter)
also can aid in measuring pulmonary artery occlusion pressure

21
Q

What is type A lactic acidosis

A

inadequate oxygen delivery is the most common cause of increased blood lactate

22
Q

what is type B lactic acidosis

A

mitochondrial function is impaired but there is normal oxygen delivery
usually associated with diseases like sepsis, diabetes mellitus, neoplasia, drugs, toxins
prolonged states of hypoxia can damage mitochondria and lead to type a and b lactic acidosis

23
Q

what is sublingual capnometry

A

a regional perfusion measurement

measures partial pressure of CO2 from the sublingual area

24
Q

what is near infrared spectroscopy

A

an optical non-invasive technique used to monitor skeletal muscle tissue oxygen saturation
similar to pulse oximetry but also reflects the arterioles, capillaries, and venules

25
Q

what is the percent oxygen for flow by at 2-3 L/min

A

only about 25-40%

26
Q

what percent oxygen will you get with nasal cannulas at 100 ml/kg/min

A

40% for unilateral and 60% for bilateral

27
Q

how much fluid will remain in the intravascular space 30 min after a crystalloid is given

A

25%

28
Q

what is the goal of hypotensive resuscitation

A

for patients with active hemorrhage, the endpoint of presurgical resuscitation is targeted blood pressure in the lower range around 60 mmHg

29
Q

what is the goal of limited fluid volume resuscitation

A

restore intravascular volume using the smallest possible amount of fluid to get to close to physiologic pressure (like MAP 70 mmHg)

30
Q

based on human literature, what are the recommended SpO2 and hematocrit levels for resuscitation of a shock patient

A

> 94% SpO2

hct >24%

31
Q

why should you reperfuse hypothermic patients in shock prior to warming them

A

it is not really a hypothermia - just a redistribution of perfusion away from non vital regions such as the skin and colon
if you try surface rewarming while they are redistributing, you will cause peripheral vasodilation and a loss of compensation

32
Q

What receptors does dobutamine act on?

A

Most effect at beta 1 adrenergic receptors, then beta 2
some activity at alpha adrenergic
Leads to a strong increase in cardiac contractility but reduced effect on systemic vascular resistance

dose is 2-20 mcg/kg/min in dogs, 1-3 mcg/kg/min cats
May cause seizures in cats

33
Q

What receptors does low dose dopamine affect? what dose is low?

A

Causes vasodilation through activation of a dopaminergic receptor. has scant activity at the alpha and beta receptors.

dose is 0.5-2 mcg/kg/min

34
Q

What receptors does intermediate dose dopamine act on?

A

preferentially acts on beta receptors and stimulates cardiac contractility

dose is 5-10 mcg/kg/min

35
Q

what receptors does high dose dopamine act on?

A

in the high range, dopamine will preferentially act at the alpha receptors and then cause a vasoconstriction

dose is 10-20 mcg/kg/min

36
Q

what receptors does epinephrine act on

A

potent at alpha and beta receptors
0.05-1 mcg/kg/min

a lot of side effects

37
Q

what receptors does norepinephrine act on?

A

mostly alpha agonist

dose is 0.1-2 mcg/kg/min

38
Q

what receptors does phenylephrine act on

A

very potent vasoconstrictor acting at the alpha receptors but has potential side effects
dose is 1-3 mcg/kg/min

39
Q

what receptors does vasopressin act on?

A

acts on nonadrenergic V1 receptors

dose is 0.5-5 mU/kg/min

40
Q

what is the definition of SIRS (systemic inflammatory response)?

A

systemic inflammatory response triggered by infectious or non infectious insults

41
Q

what is the definition of bactermia

A

presence of viable bacteria in the blood

42
Q

what is the definition of sepsis

A

systemic inflammatory response to infection

43
Q

what is the definition of severe sepsis

A

sepsis complicated by organ dysfunction, hypoperfusion, or hypotension

44
Q

what is the definition of septic shock

A

state of acute circulatory failure associated with sepsis, with arterial hypotension despite adequate fluid resuscitation, along with the presence of perfusion abnormalities

45
Q

what is the definition of MODS

A

multiple organ dysfunction syndrome

presence of altered organ functionality such that homeostasis cannot be maintained without intervention

46
Q

what is the definition of ARDS

A

acute respiratory distress syndrome

acute fulminant respiratory failure leading to diffuse lung injury resulting from a variety of causes

47
Q

what is the criteria for veterinary ARDS

A
  • acute onset (<72 hours) of tachypnea and labored breathing at rest
  • presence of known risk factors
  • evidence of pulmonary capillary leak without increased pulmonary capillary pressure
  • evidence of insufficient gas exchange
  • evidence of diffuse pulmonary inflammation
48
Q

what are some categories for options for diagnostic biomarkers of shock

A

markers of infection like LPS or bacterial DNA
markers of cellular responsiveness like ICAM or CD11/CD18
products of inflammatory cells and humoral activation like interleukins
acute phase proteins

Phase 1 (35 decks)

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