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FA2 Anesthesiology > Lecture 18 11/7/24 > Flashcards

Lecture 18 11/7/24 Flashcards

1
Q

What factors can affect arterial oxygen content?

A

-hemoglobin conc.
-SaO2/hemoglobin saturation w/ O2
-PaO2/arterial pressure of O2

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2
Q

What is the treatment for anemia caused by low hemoglobin?

A

-blood transfusion
-fluids if hypovolemic

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3
Q

What is SpO2 a surrogate for?

A

PaO2

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4
Q

How does PaO2 relate to fraction of inspired oxygen (FiO2)?

A

PaO2 equals 4-5 times FiO2

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5
Q

What is the cutoff value for PaO2 in hypoxemia?

A

PaO2 < 80mmHg

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6
Q

Why is SpO2 not always the best indicator of PaO2 when the patient is on 100% oxygen?

A

the pulse ox will read 100% SpO2 when the PaO2 equals 100; cannot measure if the PaO2 reaches 400-500 like it should on 100% oxygen

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7
Q

What are the causes of hypoxemia?

A

-low fraction of inspired oxygen
-diffusion impairment
-hypoventilation
-shunt
-V/Q mismatch

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8
Q

What are the characteristics of hypoxemia due to low FiO2?

A

-uncommon
-can result from not turning on O2 in anesthesia
-low barometric pressure at high altitude leads to low partial pressure of inspired O2
-low partial pressure gradient leads to less drive of O2 into blood

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9
Q

What are the characteristics of hypoxemia due to diffusion impairment?

A

-uncommon
-thickening of blood/gas barrier occurs
-no increase in PaCO2
-seen in westies, pets of smokers, fibrosis cases, equine herpes

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10
Q

What are the characteristics of hypoxemia due to hypoventilation?

A

-decreased alveolar ventilation
-decreased EtCO2
-increased PaCO2
-neurologic or drug related
-treatment includes allowing pet to be apneic briefly; mechanical/manual ventilation if pet does not attempt to breathe

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11
Q

What are the characteristics of hypoxemia due to perfusion inequality?

A

-main cause of hypoxemia in anesthetized patients
-can have a blockage of the alveolus
-can have a blockage of the blood vessel

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12
Q

What are the characteristics of a high V/Q ratio?

A

-V/Q approaches infinity
-extreme skew means increased dead space
-wasted ventilation due to gas not going anywhere
-gas does not diffuse into blood

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13
Q

What are the characteristics of a low V/Q ratio?

A

-V/Q approaches zero
-extreme skew indicates right to left shunt
-air cannot reach the blood

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14
Q

What is compression atelectasis in horses?

A

-atelectasis of the portions of the lungs with the best perfusion
-occurs when horse is in dorsal recumbency
-diaphragm, colon, and liver sit on horse’s lungs

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15
Q

How can hypoxemia be treated?

A

-treat any known underlying causes
-increase FiO2
-ventilate
-PEEP/positive end expiratory pressure
-recruitment maneuver
-bronchodilator

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16
Q

Which factors promote heat loss and hypothermia?

A

-low body fat (neonates, young animals, emaciated)
-small patients/large surface area to body mass ratio
-circuit choice; circuits that do not warm inspired air

17
Q

What are the mechanisms of heat loss?

A

-radiation (most heat loss)
-conduction
-convection
-evaporation

18
Q

What are the characteristics of radiation heat loss?

A

-emission of electromagnetic energy
-accounts for 60% of heat loss
-caused by cold, ambient air
-can use radiant heat warmers or blankets to prevent patient heat loss

19
Q

What are the characteristics of convection heat loss?

A

-second most common source of heat loss
-“wind-chill” factor
-ambient air promotes heat loss
-cold anesthetic gases contribute

20
Q

What are the characteristics of conduction heat loss?

A

-transfer of heat to a surface
-can occur with stainless steel tables and cold lavage solutions

21
Q

What are the characteristics of evaporation heat loss?

A

-accounts for around 20% of heat loss
-occurs with open body cavities and dry anesthetic gases

22
Q

What are the consequences of hypothermia?

A

-decreases metabolic O2
-bradycardia and other arrhythmias
-shivering
-potential for overdose due to decreased metabolism
-prolonged recovery
-coagulation abnormalities
-delayed wound healing
-immunosuppression

23
Q

What is hypercapnia?

A

elevated PaCO2/PetCO2/EtCO2

24
Q

What occurs in the body as a result of hypoventilation?

A

CO2/acidosis detected peripherally via carotid body chemoreceptors and centrally in the medulla

25
Q

Which drugs can contribute to hypoventilation?

A

-propofol
-volatile inhalants
-opioids

26
Q

What are the consequences of hypoventilation?

A

-increased CO2 causes anxiety due to difficulty breathing
-sympathetic stimulus increases heart rate
-direct vasodilation
-narcosis

27
Q

What are the blood volumes in dogs, cats, and horses?

A

dog: 90 mL/kg
cat: 60 mL/kg
horse: 80 mL/kg

28
Q

What are the clinical signs of hemorrhage?

A

-hypotension
-tachycardia
-tachypnea
-pallor

29
Q

What are the characteristics of hemorrhage treatment from the anesthesia standpoint?

A

-hypotensive resuscitation until cause of hemorrhage is fixed
-be cautious with fluid boluses; could blow off clot
-restore vascular volume with crystalloids/colloids
-restore DO2 with whole blood or packed RBCs

30
Q

What are the characteristics of post-anesthetic myopathy?

A

-leads to altered blood flow, decreased blood flow, and ischemia of the muscles
-occurs in large animals most commonly

31
Q

What are the mechanisms of post-anesthetic myopathy?

A

-increased intra-compartmental pressure
-hypotension leads to decreased DO2 in muscles
-increased inflammatory cytokines
-pain
-reperfusion injury

32
Q

What are the factors influencing the development of post-anesthetic myopathy?

A

-padding
-positioning
-hypotension
-long duration of anesthesia
-heavily muscled animals

33
Q

How is post-anesthetic myopathy diagnosed?

A

-pain/lameness upon recovery
-increased creatine kinase and AST on chem.

34
Q

What are the treatments for post-anesthetic myopathy?

A

-volume expansion and diuresis (fluids)
-anti-inflammatories
-analgesics

35
Q

How can neuropathy be avoided during anesthesia?

A

-remove halters to prevent facial n. paralysis
-move down leg forward to prevent radial n. paralysis

36
Q

Which factors can result in prolonged recovery?

A

-hypothermia
-hypotension
-hypoglycemia
-myopathy/neuropathy
-drugs
-electrolyte imbalances

FA2 Anesthesiology (23 decks)

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