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5230 > Inhalation Anesthetics > Flashcards

Inhalation Anesthetics Flashcards

1
Q

FA (definition and determined by)

A 
Alveolar gas concentration
Determined by
-Uptake
-Ventilation
-Concentration effect, 2nd gas effect
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2
Q

FI (definition and determined by)

A 
Inspired gas concentration
Determined by 
-FGF rate
-Breathing circuit volume
-Circuit absorption
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3
Q

Sevo MAC

A

2%

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4
Q

Sevo blood/gas partition coefficient

A

0.6

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5
Q

Sevo oil/gas partition coefficient

A

50

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6
Q

Iso MAC

A

1.15%

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7
Q

Iso blood/gas partition coefficient

A

1.4

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8
Q

Iso oil/gas partition coefficient

A

99

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9
Q

N2O MAC

A

105%

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10
Q

N2O blood/gas partition coefficient

A

0.47

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11
Q

N2O oil/gas partition coefficient

A

1.4

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12
Q

Des MAC

A

5.8%

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13
Q

Des blood/gas partition coefficient

A

0.42

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14
Q

Des oil/gas partition coefficient

A

18.7

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15
Q

MAC

A

=dose

Minimum alveolar concentration required to achieve surgical anesthesia in 50% of patients exposed to a noxious stimulus

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16
Q

MAC awake

A

Alveolar concentration that inhibits response to command in 50% of patients

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17
Q

MAC bar

A

Alveolar concentration that blunts autonomic response to noxious stimuli
-Approx 1.6x higher than MAC

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18
Q

Blood/gas partition coefficient

A

Indicates speed of induction and emergence

-Higher number = slower drug

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19
Q

Oil/gas partition coefficient

A

Indicates potency once the drug gets to the brain

-Inversely proportional to the MAC (need lower dose for effect)

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20
Q

Blood/gas solubility vs Fa/Fi ratio

A
  • Decreased b/g solubility coefficient = faster increase in Fa/Fi
  • Except N2O is faster than Des due to the concentration effect (50-70% N2O vs 10% Des)
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21
Q

Ventilation effect on Fa/Fi (and which drugs affected more)

A

Fa/Fi increases faster when ventilation is increased

-More soluble drugs are affected more (iso) than less soluble (des)

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22
Q

Concentration effect on Fa/Fi

A

Increased dose/concentration = faster increase in Fa/Fi

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23
Q

V/Q Abnormality effect on Fa/Fi (and which drugs are affected more)

A

V/Q deficit slows the delivery of anesthetics

-Faster drugs (less soluble/des) are affected more than slower drugs (more soluble)

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24
Q

Second gas effect (2 necessary components)

A

1: Very low solubility agent (N2O) with an agent with a higher solubility
2: High concentrations of the faster (less soluble) drug

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25
Q

Cardiac output effect on Fa/Fi (and which drugs are affected more)

A

Increased cardiac output = slower increase in Fa/Fi (uptake from alveoli to blood is increased)

  • Only applies for induction/emergence
  • More soluble (slower) drugs are affected the most
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26
Q

Obesity effect on induction/emergence

A

No effect on induction
Emergence
-Takes longer, especially after a longer case
-Takes longer for more soluble drugs

27
Q

Diffusion hypoxia (and how to prevent)

A

Occurs when you stop N2O

  • You go from 79% N2O to 79% N2
  • N2O flooding out of the system dilutes O2
  • Give 100% O2 at the end of a case to prevent
28
Q

Pediatric effect on MAC and induction

A

MAC peaks at 6 months, then decreases with age
But, kids go to sleep faster because of an increased respiratory effort
-Despite different in drug solubility, increased cardiac output, and different body composition

29
Q

Pregnancy effect on Fa/Fi

A

Increased cardiac output and minute ventilation offset each other
-Fa/Fi increase is similar in pregnant and non-pregnant women

30
Q

Epi rules

A

No stronger than 1:100,000 (0.01mg/mL)
No more than 10mL in 10min (0.1mg)
No more than 30mL in 1hr (0.3mg)

31
Q

Anesthetic effect on HR (and how to treat/prevent)

A

Increased HR with Des (and Iso to a lesser extent)
-During initial induction, probably due to respiratory irritation
Treat with fentanyl, don’t increase des too fast
-Start at 3-6%, increase by 1% increments

32
Q

Factors that reduce MAC

A

Age, hypothermia, co-admin with other sedatives/analgesics, acute ethanol consumption, hypoxemia, hyponatremia, anemia, hypotension, lithium

33
Q

Factors that increase MAC

A

Young age, hyperthermia, hyperthyroidism, hypernatremia, acute administration of CNS stimulant drugs, red-headed females, chronic alcohol abuse

34
Q

N2O primary side effects

A

Expands closed gas spaces

  • Due to difference in solubility with the nitrogen it replaces and the high concentration required
  • Not used for inner ear surgery, bowel obstruction, neurosurgical procedures with air injections
35
Q

Vessel rich group (% body mass, % cardiac output, organs)

A 
Body mass
-10%
Cardiac output
-75%
Organs
-Brain
-Heart
-Kidney
-Liver
36
Q

Muscle group (% body mass, % cardiac output, organs)

A 
Body mass
-50%
Cardiac output
-18-19%
Organs
-Skeletal muscle, skin
37
Q

Fat (% body mass, % cardiac output)

A

Body mass
-20%
Cardiac output
-5-6%

38
Q

Vessel poor group (% body mass, % cardiac output, organs)

A 
Body mass
-20%
Cardiac output
-0-2%
Organs
-Bones, tendons, cartilage
39
Q

Chemical structure of des vs sevo vs iso

A

Des: 6 Fl atoms
Sevo: 7 Fl atoms
Iso: 5 Fl atoms, 1 Cl atom
^Halogenated agents: H atom in molecule was replaced with halogen (Fl, Cl)

40
Q

Inhalation anesthetic effect on CMRO2

A

CMRO2=Cerebral metabolic rate of oxygen consumption

CMRO2 decreases with inhalation anesthetic use

41
Q

Inhalation anesthetic effect on intraocular pressure

A

Decreased

42
Q

Inhalation anesthetic effect on intracranial pressure (& implications for practice)

A

Increased due to cerebral vasodilation, counteract it by modest hyperventilation (pCO2 30-35, low normal, CO2 causes further vasodilation)
-For neuro cases never do >1 MAC, usually 1/2 MAC

43
Q

N2O use in neuro cases (& effect on ICP)

A

Inconclusive study findings
Many still use it because of its rapid onset and termination without a “hangover”
ICP: 0 change or decreased

44
Q

Ways to facilitate adequate venous drainage in neuro cases

A

PEEP or cardiac failure will increase CVP and cause backup

Neutral head position, avoiding of ties/collars tight around neck

45
Q

Inhalation anesthetic effect on cerebral perfusion pressure

A

Decreased, because of decreased MAP

46
Q

Inhalation anesthetic effect on SSEP

A

SSEP: Somatosensory evoked potentials

Decreased with use, also MEP (motor evoked potentials) are decreased

47
Q

5 mechanisms that cause decreased BP with inhalation anesthetics (except N2O)

A
  • CNS depression
  • Direct cardiac depression
  • Decreased systemic vascular resistance
  • Baro-receptor depression
  • Hormonal changes such as decreased renin or vasopressin release (BP supportive hormones)
48
Q

Anesthetic preconditioning

A

Anesthesia induced protection, mimics ischemic preconditioning

  • Body response after MI, change in ATP/blood flow to heart
  • Occurs for 12-24 hours after
49
Q

Inhalation anesthetic effect on cardiac output (each gas)

A

Des: No change
Sevo: No change
Iso: Slight decrease
N2O: Decrease

50
Q

Inhalation anesthetic effect on SVR (each gas)

A

Des/Sevo/Iso: Decreased

N2O: Increased

51
Q

Inhalation anesthetic overall effect on respiratory system

A

Bronchodilation (all except N2O)
Dose dependent respiratory depression (except N2O)
-Depress TV before RR (opposite of opioids)
-Decreased ventilator drive in response to increased CO2
Hypoxic pulmonary vasoconstriction
-Shunt blood to oxygenated areas of lung
-Lungs aren’t as efficient, have to give >30% O2

52
Q

Inhalation anesthetic effect on renal system

A

All (except N2O) decrease BP -> decrease renal blood flow -> decrease GFR -> decrease UOP

  • Sevo is metabolized 6-8% (vs others none) and releases free Fl ions (strongest electronegative ion in body, can bind to cell membrane and lead to cell death)
  • Most still consider it safe but some avoid it in renal failure patients
53
Q

Inhalation anesthetic effect on GI system

A

Cause dose dependent decrease in GI function, which resolves when the patient wakes up
-Halothane hepatotoxicity -> don’t use in peds before puberty

54
Q

N2O and immune suppression

A

Only an issue with >6 hours of use

  • N2O inhibits/inactivates vitamin B12, which inactivates methionine synthetase (dependent on B12)
  • Normally methionine synthetase converts homocysteine to methionine->produce DNA/RNA
  • Interrupts production of DNA/RNA
  • Contraindicated if there is a known deficiency of enzyme or substrate in methionine synthase pathway
55
Q

Anesthetic technique effect on cancer (Volatiles, LA, Neuroaxial, NSAIDS, ASA, Opioids, Supplemental O2)

A

Volatile: Conflicting, insufficient to avoid
LA: Reduced cancer recurrence and mets (anti-inflammatory, direct effect on proliferation and migration of cancer cells)
Neuroaxial: Conflicting, thought to reduce cancer recurrence/mets (immunosuppressive stress response, opiate sparing)
NSAIDS: Tumor regression
ASA: Reduce mets
Opioids: Promote cancer progression, reduce long term survival
Supplemental O2: 80% O2 postop has shorter cancer free survival period

56
Q

Cortisol levels after anesthesia induction

A

Increased

57
Q

N2O use in pregnancy

A

Contraindicated, is teratogenic
Can be used in delivery
Pregnant CRNAs shouldn’t be in N2O rooms

58
Q

Volatile anesthetic use during pregnancy

A

Relax the uterus, should use <1 MAC

-Use during pregnancy is associated with an increased risk of postop miscarriage

59
Q

Developmental Neurotoxicity (FDA warning, study findings)

A

FDA: Repeated/lengthy use of general anesthetic/sedation drugs during surgeries/procedures in children<3yo or pregnant women during 3rd trimester may affected development of childrens brains (based on animal studies)
Studies: Single, relatively short exposure to general anesthetic/sedation drugs is unlikely to have negative effects on behavior/learning
-General anesthesia during emergent C sections isn’t associated with learning disabilities but shows possible association with increased risk of autism

60
Q

Postoperative cognitive dysfunction

A

Concern in the elderly

-No clinically significant association of major surgery/anesthesia with long term cognitive dysfunction

61
Q

Emergence phenomenon in children (& how to prevent and treat)

A

Emergence delirium occurs after sevo and des in preschool aged children in PACU, typically last 15 mins and resolve spontaneously

  • Prevent: Reduce postop anxiety and pain, provide quiet stress free environment for PACU
  • Treat: Small dose of midazolam, ketamine, fentanyl, clonidine or Dexmedetomidine, dexamethasone and NSAIDS (some may delay discharge)
  • Reuniting with parents is helpful
62
Q

Compound A

A

Forms when Sevoflurane interacts/reacts with carbon dioxide absorbants (new ones don’t react)
*Don’t use FGF <3LPM

63
Q

Preop pregnancy testing

A

Different facilities have different protocols
Incidence of positive HCG results was 0.3-1.3%, but in 100% of the cases the clinical management changed because of the positive result

64
Q

How much does MAC decrease each decade

A

6%

5230 (13 decks)

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