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Inhaled Anesthetics Flashcards

1
Q

Nitrous oxide

A

Molecular weight: 44

Boiling point:

Vapor pressure (mmHg 20°C): gas

Odor: sweet

Preservative necessary: No

Stability in soda lime (40°C): Yes

Blood:gas partition coefficient: 0.46

MAC w/ 100% O2 (middle age healthy pt): 104

MAC w/ 60-70% N2O:

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2
Q

Halothane

A

Molecular weight: 197

Boiling point: 50.2

Vapor pressure (mmHg 20°C): 244

Odor: Organic

Preservative necessary: Yes

Stability in soda lime (40°C): No

Blood:gas partition coefficient: 2.54

MAC w/ 100% O2 (middle age healthy pt): 0.75

MAC w/ 60-70% N2O: 0.29

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3
Q

Enflurane

A

Molecular weight: 184

Boiling point: 56.5

Vapor pressure (mmHg 20°C): 172

Odor: Ethereal

Preservative necessary: No

Stability in soda lime (40°C): Yes

Blood:gas partition coefficient: 1.90

MAC w/ 100% O2 (middle age healthy pt): 1.63

MAC w/ 60-70% N2O: 0.57

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4
Q

Isoflurane

A

Molecular weight: 184

Boiling point: 48.5

Vapor pressure (mmHg 20°C): 240

Odor: Ethereal

Preservative necessary: No

Stability in soda lime (40°C): Yes

Blood:gas partition coefficient: 1.46

MAC w/ 100% O2 (middle age healthy pt): 1.17

MAC w/ 60-70% N2O: 0.50

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5
Q

Desflurane

A

Molecular weight: 168

Boiling point: 22.8

Vapor pressure (mmHg 20°C): 669

Odor: Ethereal

Preservative necessary: No

Stability in soda lime (40°C): Yes

Blood:gas partition coefficient: 0.42

MAC w/ 100% O2 (middle age healthy pt): 6.6

MAC w/ 60-70% N2O: 2.83

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6
Q

Sevoflurane

A

Molecular weight: 200

Boiling point: 58.5

Vapor pressure (mmHg 20°C): 170

Odor: Ethereal

Preservative necessary: No

Stability in soda lime (40°C): No

Blood:gas partition coefficient: 0.69

MAC w/ 100% O2 (middle age healthy pt): 1.80

MAC w/ 60-70% N2O: 0.66

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7
Q

Alveolar partial pressure is an index of?

A

1) depth of anesthesia
2) recovery from anesthesia
3) anesthetic equal potency (MAC)

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8
Q

Minute ventilation

A

Sum of all exhaled gas volumes in 1 min

Tidal volume x breaths/min= 5L/min

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9
Q

Alveolar ventilation

A

Volume of inspired gases actually taking part in gas exchange in 1 min

(Tidal volume-dead space) x breaths/min

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10
Q

Dead space

A

Any volume of inspired breath that does not enter the gas exchange areas of the lungs

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11
Q

Time for equilibration (time constant)=

A

Amt of inhaled anesthetic dissolved in tissue/ tissue blood flow

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12
Q

For volatile anesthetics, 3 time constants =

A

5-15 min for brain

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13
Q

Lower tissue:gas ratios indicate?

A

The gas is relatively insoluble in tissues thus emergence will be more rapid

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14
Q

Stage I

A

Begins with induction of anesthesia

Ends with loss of consciousness (no eyelid reflex)

Still can sense pain

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15
Q

Stage II

A

Delirium excitement

Uninhibited excitation

Pupils dilated, divergent gaze

Potentially dangerous response to noxious stimuli: breath holding, muscular rigidity, vomiting,laryngospasm

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16
Q

Stage III

A

Surgical anesthesia

Centralized gaze with constriction of pupils

Regular respirations

Anesthesia depth is sufficient for noxious stimuli when the noxious stimuli does not cause increase sympathetic response

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17
Q

Stage IV

A

Stay away from. Too deep

Apnea

No reactive dilated pupils

Hypotension resulting in complete CV collapse if not monitored closely

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18
Q

How does nitrous cause diffusion hypoxia?

A

Once d/c’d the nitrous diffuses rapidly out of tissues and into the blood and alveoli. Rapid flood into alveoli dilutes alveolar gas and displaces O2

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19
Q

EEG effects

A

<0.4 MAC = increase in frequency & voltage similar for all volatile anesthetics

0.4 MAC= shift of voltage activity from posterior to anterior portions of brain.
Decrease in cerebral O2 requirements-may reflect transition from wakefulness to unconsciousness

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20
Q

_______ has fast frequency and high voltage on EEG indistinguishable from changes produced by seizure activity; twitching of facial muscle occurs and can be initiated from repetitive auditory stimuli

A

Enflurane

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21
Q

No seizure activity on EEG, suppress convulsants properties

A

Iso, des, sevo

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22
Q

Volatile anesthetics > 0.6 MAC produce what effect on CBF?

A

Cerebral vasodilation, decreased cerebral vascular resistance, dose-dependent increase in cerebral blood flow

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23
Q

At 1.1 MAC cerebral blood flow increases (greatest to least)

A

Halothane> Enflurane > Isoflurane=Desflurane

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24
Q

Cerebral Metabolic O2 Requirements dose dependent decrease (greatest to least) & how

A

Isoflurane= Desflurane= Sevoflurane > Halothane

Decrease metabolic requirement- decrease CO2 production- vasoconstriction that decreases CBF

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25
Decreased metabolic requirement =
Decreased CO2 production, vasoconstriction that decreases CBF
26
I’m CEA, CBF ischemic changes are lower with ____
Isoflurane
27
Increased ICP is parallel to
Increased CBF produced by volatile anesthetics
28
What opposes the tendency for increased ICP
Hyperventilation of lungs to decrease PaCO2
29
Cause similar dose dependent decreases in MAP due to decrease in SVR
Iso (most profound)> des > sevo
30
Causes decrease in MAP due to decrease in myocardial contractility
Halothane
31
Effects of N2O on MAP
No change or modest increase
32
Increase HR (greatest to least)
Des (most) > Iso > Sevo | sevo only >1.5 MAC
33
What effect does halothane have on HR?
No change
34
Halothane effect on CO/stroke volume
Dose dependent decrease CO
35
Effect of iso, des, sevo on CO/SV
No real effect
36
Sevo decreases CO up to ___ MAC; ____ MAC CO recovers
2; >2
37
N2O ____ CO slightly
Increases
38
N2O _____ PVR and is exaggerated in?
Increases; pulm. HTN, neonates, congenital heart disease
39
Coronary steal syndrome
Maldistribution of blood flow from ischemic to nonischemic areas
40
Coronary vasodilation (greatest to least)
Halothane, enflurane < Isoflurane < adenosine
41
To decrease risk of MI pretreat with?
Opioids or a beta blocker
42
______’s solubility characteristics make it a good choice to treat abrupt increases in systemic BP and HR associated w/ changes in intensity of surgical stimulation
Desflurane
43
Neurocirculatory response does not occur with abrupt increase in concentration of ________
Sevoflurane
44
_____ is the most potent of the volatile gases in clinical uses and is a potent coronary vasodilator
Isoflurane
45
Dose limit for exogenous Epi:
6mcg/kg for Iso, Des, Sevo
46
______ increases frequency of breathing at concentrations up to __ MAC, then no further increase occurs
Isoflurane; 1
47
_____ produces most profound decrease in SVR
Isoflurane
48
_______ selectively interferes with intercostal muscle function resulting in loss of chest wall stability
Halothane
49
________ has direct relaxing effects on airway smooth muscle (decreases _____ nerve traffic from CNS)
Halothane; vagal
50
______ causes modest increase in PVR
Nitrous oxide
51
Volatile anesthetics _______ PVR. Except for ______ which ____ PVR at MAC of 1.6
Decrease; Desflurane; increases
52
______ inhibits hypoxia pulmonary vasoconstriction (HPV)
Nitrous oxide
53
_______ acts as a hepatic circulation vasoconstrictor
Halothane
54
Hepatic effects greatest to least
Halothane > Enflurane > Isoflurane > Desflurane
55
Fluoride-Induced Nephrotoxicity sx
Polyuria, hypernatremia, hyperosmolarity, increased serum creatinine, inability to concentrate urine
56
Sevo effects on renal
No renal damage in pt without preexisting renal disease
57
Enflurane has greater _____ metabolism; Sevoflurane has greater ______ metabolism
Intrarenal; hepatic
58
Sevo and soda lime/Baralyme
CO2 absorbents react and eliminate hydrogen fluoride from its isopropyl moiety to form breakdown products- Compound A- nephrotoxin Use at least 2L/min fresh gas flow rate to minimize concentration of compound A accumulating in breathing circuit
59
_______ most potent trigger for MH of all VA
Halothane
60
Patho of MH
Increase and continuous leaking of Ca from Ryanodine receptors of SR
61
Earliest sign of MH
Succinylcholine induced masseter muscle rigidity (MMR)
62
Late sign of MH
Hyperthermia; can raise temp 1 degree C every 5 min
63
Other symptoms of MH
Rhabdomylosis, tachycardia, increased metabolism, HTN, mottled cyanosis, arrhythmia, dark urine
64
Most sensitive indicator of MH
Doubling or tripling of ETCO2
65
MH labs
``` Hyperkalemia Hypermagnesemia Reduced mixed venous O2 sat Increased serum myoglobin Increased creatinine kinase (CK) (peak 12-18 hrs later exceeding 20,000 IU/L) ```
66
Treatment for MH
``` Dantrolene 2.5mg/kg (max 10mg/kg) every 5 min until stops (after episode: 1mg/kg q 6 hrs for 24-48 hrs) Stop gas and succ immediately Change machines and bag/mask 100% O2 Correct acid-base/electrolyte imbalance No CCB! Cool pt til 38C ```
67
Dantrolene supply
20mg lyophilized order to be dissolved in 60ml sterile water. Takes 86 sec to reconstitute (new version 20 sec) Half life is 6 hrs
68
N2O metabolism
Very little metabolism, mainly by anaerobic bacteria in GI tract O2 concentration > 10% inhibits metabolism
69
Halothane metabolism
15-20% CYP450
70
Enflurane metabolism
3% CYP450
71
Isoflurane metabolism
0.2% CYP450
72
Desflurane metabolism
0.02% CYP450
73
Sevoflurane metabolism
5% CYP450
74
Carbon monoxide toxicity order
Desflurane > Enflurane > Isoflurane Halothane and Sevo have no CO production
75
___ of a MAC should produce MAC awake for volatiles
1/10
76
MAC BAR
Blunt Autonomic Responses to noxious stimuli
77
Factors that increase MAC
``` Hyperthermia Red hair Cocaine/methamphetamine/amphetamine Cyclosporine Hypernatremia ```
78
Factors that decrease MAC
``` Hypothermia Increasing age Preop meds Drug induced decrease catecholamine Alpha 2 Acute alcohol Pregnancy/postpartum Lidocaine Neuraxial opioids PaO2 <38 MAP < 40 Cardiopulmonary bypass Hyponatremia ```

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