Nitrous Oxide Flashcards
(139 cards)
1
Q
who synthesized nitrous oxide?
A
Joseph Priestly
2
Q
how did Priestly synthesize nitrous oxide?
A
mixed hot iron filings with nitric acid
3
Q
what did Priestly refer to nitrous oxide as?
A
“phlogisticated nitrous air”
4
Q
who proposed N2O for surgical operations?
A
Sir Humphry Davy
5
Q
who becomes addicted to N2O?
A
Sir Humphry Davy
6
Q
who administered N2O to patients to tx dental pain?
A
Horace Wells
7
Q
who was credited with discovering modern anesthesia?
A
Horace Wells
8
Q
what are the stages of the sedation continuum?
A
- minimal sedation
- moderate sedation
- deep sedation
- general anesthesia
9
Q
minimal sedation responsiveness
A
normal response to verbal stimuation
10
Q
minimal sedation airway
A
unaffected
11
Q
minimal sedation spontaneous ventilation
A
unaffected
12
Q
minimal sedation cardiovascular fx
A
unaffected
13
Q
moderate sedation responsiveness
A
“purposeful” response to verbal or tactile stimulus
14
Q
moderate sedation airway
A
no intervention required
15
Q
moderate sedation spontaneous ventilation
A
adequate
16
Q
moderate sedation cardiovascular fx
A
usually maintained
17
Q
deep sedation responsiveness
A
“purposeful” response after repeated or painful stimulus
18
Q
deep sedation airway
A
intervention may be required
19
Q
deep sedation spontaneous ventilation
A
may be adequate
20
Q
deep sedation cardiovascular fx
A
usually maintained
21
Q
general anesthesia responsiveness
A
unarousable even with painful stimulus
22
Q
general anesthesia airway
A
intervention often required
23
Q
general anesthesia spontaneous ventilation
A
frequently inadequate
24
Q
general anesthesia cardiovascular fx
A
may be impaired
25
why do some patients become more sedated than intended?
1. every patient is different
| 2. responds to sedative drugs in different ways
26
what must you understand before administering N2O?
1. be able to recognize the different levels of sedation
| 2. be able to rescue from a deeper plane of anesthesia
27
minimal alveolar concentration (MAC)
the concentration of a gas required to prevent movement in 50% of people to surgical stimulus
28
MAC of halothane
0.75%
29
MAC of isoflurane
1.2%
30
MAC of sevoflurane
2.0%
31
MAC of desflurane
6.0%
32
MAC of N2O
104%
33
expected responses from 10-20% MAC
1. body warmth
| 2. tingling of hands and feet
34
expected responses from 20-30% MAC
1. perioral numbness
| 2. numbness of thighs
35
expected responses from 20-40% MAC
1. numbness of tongue, hands, feet
2. droning sounds, distant hearing
3. sleepiness
4. euphoria (laughing)
36
expected responses from 30-50% MAC
1. sweating, nausea
2. increased sleepiness
3. mild amnesia
37
expected responses from 50-70% MAC
1. dreaming
2. laughing, giddiness
3. increased nausea/vomiting
4. sleepiness increasing toward unconsciousness
38
physical characteristics of N2O
1. colorless
2. sweet smelling
3. has high vapor pressure
39
N2O exists as a what?
gas
40
N2O is stored as a what?
liquid
41
uptake and distribution of N2O
quick onset/offset (low blood solubility)
42
N2O blood/gas partition coefficient
0.47
43
how long does it take for N2O to take effect?
1-3 minutes
44
how long does it take for N2O to have the MAXIMUM effect?
<5 min
45
how long does it take to have a complete recovery from N2O?
<5 min
46
what can N2O cause if pt is flushed with 100% O2 right after being given N2O?
diffusion hypoxia
47
T/F: N2O is easy to titrate
true
48
how long does it take to see changes in uptake of N2O?
~3-5 min
49
what can affect the uptake of N2O?
dependent upon fresh gas flow/size of circuit
50
signs and syms of over-sedation
1. complaints of feeling uncomfortable
2. nausea
3. irrational/sluggish responses
4. perspiration/sweating
5. non-compliant/combativeness
51
effects of N2O on CNS
1. modest CNS depression
2. sleepiness/mood alteration
3. depresses all sensations
4. inappropriate behavior
52
effects of N2O on CV system
1. HR unchanged
2. SV, SVR increases slightly
3. flushing
53
effects of N2O on CV system in anxious pts
BP and HR may decrease after N2O
54
effects of N2O on respiratory system
1. negligible effects
2. MV may slightly increase
3. not irritating, no mucous
55
what should be clearly described to the pt before administering N2O?
1. how the equipment works (esp mask and tubing)
2. how minimal/moderate sedation feels
3. what to do if they feel uncomfortable or nauseous
56
NPO instructions for clear liquids
2 hrs
57
NPO instructions for breast milk
4 hrs
58
NPO instructions for milk/dairy products
6 hrs
59
NPO instructions for light meal
6 hrs
60
NPO instructions for fatty meal
8 hrs
61
for minimal sedation, what should be avoided for 4 hrs?
"heavy meals"
62
for moderate sedation, what should be avoided?
ASA guidelines
63
reasons for failure of N2O
1. associated w poor pt selection
2. weak anesthetic
3. mild to mod fear (severe anxiety not good pts)
4. very young children, severe disabilities are poor pts
64
indications for N2O
1. alleviation of mild/mod anxiety
2. stress reduction in medically compromised
3. modification of excessive gag reflex
4. pain threshold elevation
65
contra-indications for N2O
1. pregnancy
2. deviated septum/nasal obstruction
3. upper resp tract infection
4. acute fear/anxiety
5. inability to communicate
6. pulmonary hypertension
7. vitamin B12 deficiency
8. MTHFR deficiency
9. CPOD/emphysema
10. closed spaces (e.g. ear or eye surgery, bowel obstruction)
11. fire hazard
66
side effects from abusing N2O in vitamin B12 deficient pt
1. hyperpigmentation (ep in distal digits)
2. hair changes
3. neuropathy/numbness
4. unsteadiness
5. depression
6. psychosis
7. Lichtheim's disease (degeneration of spinal corD)
8. megaloblastic anemia
9. increased risk of MI
10. increased risk of stroke
67
ventilation
passage of air from atmosphere to alveoli
68
how does air move?
via pressure gradient
69
how is the pressure gradient in ventilation produced?
diaphragm
70
T/F: ventilation has a conducting AND respiratory zone
true
71
conducting zone
1. oral and nasal pharynx --> 2. trachea --> 3. bronchi and bronchioles --> 4. "dead space"
72
respiratory zone
1. respiratory bronchioles --> 2. alveolar ducts --> 3. alveolar sacs
73
respiratory zone starts at what division?
16th
74
obstruction barriers to ventilation
1. physical barrier
2. laryngospasm
3. bronchospasm
75
restriction barriers to ventilation
1. lung compliance
2. habitus
3. scholiosis
76
paralysis barriers to barriers to ventilation
1. muscle weakness
| 2. nerve damage
77
oxygenation
diffusion of oxygen across
1. surfactant layer
2. alveolar epithelium
3. interstitial space
4. capillary endothelium
5. plasma
6. erythrocyte cell membrane
78
how does diffusion of oxygen work?
moves from areas of high partial pressure to areas of low partial pressure
79
what does oxygen bind to?
hemoglobin on RBC
80
barriers to oxygenation
1. low O2 partial pressure
2. small alveolar surface area
3. increased alveolar thickness
4. pulmonary edema
5. anemia
81
T/F: ventilation is oxygenation
false, you may be able to ventilate a patient but if you cannot oxygenate them... they will die
82
how can we monitor oxygenation and ventilation?
1. visual and auditory cues
2. auscultation
3. pulse oximetry
4. capnography
83
visual and auditory cues when monitoring pts under N2O
1. chest rise
2. tidal breathing vs bucking
3. nasal flaring
4. retraction of sternal notch
5. color of mucous membranes
6. wheezing or "crowing" sounds
84
Do visual and auditory cues monitor oxygenation or ventilation?
ventilation
85
which ausculation instrument gives you immediate recognition of apnea?
precordial stethoscope
86
Does ausculation monitor oxygenation or ventilation?
oxygenation
87
pulse oximetry follows what law?
Beer-Lambert law
88
Beer-Lambert law
relationship between absorbance and the concentration of an absorbing substance
89
what is the thing absorbed in Beer-Lambert law?
light
90
which wavelength is well absorbed by oxyhemoglobin?
660 nm - red light
91
which wavelength is well absorbed by deoxyhemoglobin (reduced or "empty" Hgb not bound to O2)?
940 nm - infrared light
92
positive cooperativity
when a substance (Hgb) binds to substrate (O2), it causes a conformational change in the substance that increases its affinity for the substrate
93
conditions that push rx to TENSED form positive cooperativity
1. increased temp
2. increased 2,3 BPG
3. increased CO2
4. decreased pH (acidosis)
94
conditions that push rx to TENSED form is commonly found where?
in the muscles
95
conditions that push rx to RELAXED form positive cooperativity
1. decreased temp
2. decreased 2,3 BPG
3. decreased CO2
4. increased pH (alkylosis)
96
conditions that push rx to RELAXED form is commonly found where?
in the lungs
97
O2 saturation drops soon if the oxyhemoglobin dissociation curve is "shifted" to what side?
right
98
normal O2 saturation on oxyhemoglobin dissociation curve
94-100%
99
O2 saturation on oxyhemoglobin dissociation curve to cause hypoxia
<94%
100
O2 saturation on oxyhemoglobin dissociation curve to cause quick desaturation
<90%
101
O2 saturation on oxyhemoglobin dissociation curve to cause organ compromise
<80%
102
A pt on supplemental O2 can be what for a long time before it registers as a drop in partial pressure of O2
apneic
103
pulse oximetry delay in healthy patients
1. 20-30 sec
| 2. longer w distal appendages
104
pulse oximetry delay in pt that is in shock
90 sec or longer
105
measurement errors with pulse oximetry
1. pt movement
2. decreased pt temperature (cold fingers)
3. low blood flow (e.g. hypotension, bradycardia)
4. dark fingernail polish
5. blood pressure cuff
6. ambient light
7. methemoglobinemia
106
does pulse oximetry monitor oxygenation or ventilation?
oxygenation
107
measurement of expired CO2 in mmHg on the capnograph
1. waveform
| 2. numerical value
108
sampling line to nose on capnograph
1. samples expired CO2
| 2. delivers O2
109
T/F: use of capnography is now required by law in add sedation and general anesthesia cases
true
110
phase 0 of capnography monitoring
inspiratory downstroke (D-E)
111
at what phase of capnography monitoring is the beginning of inspiration?
phase 0
112
what should be approaching baseline unless rebreathing of CO2 occurs of capnography monitoring?
phase 0
113
phase 1 of capnography monitoring
anatomic deadspace (A-B)
114
T/F: there is exchange in upper airway, nasopharynx in phase 1 of capnography monitoring
false
115
at what phase(s) of capnography monitoring are devoid of CO2?
phases 0 and 1
116
phase 2 of capnography monitoring
expiratory upstroke (B-C)
117
what happens in phase 2 of capnography monitoring?
1. rapid increase in ETCO2
| 2. emptying of proximal alveoli
118
phase 3 of capnography monitoring
alveolar plateau (C-D)
119
what happens in phase 3 of capnography monitoring?
1. slow increase inETCO2
| 2. emptying of distal alveoli
120
does capnogrpahy monitor oxygenation or ventilation?
oxygenation
121
how many standard leads are there in an ECG (EKG)?
3
122
lead placement of RA (white) cable for electrocardiogram
right arm ("right is white")
123
lead placement of LA (black) cable for electrocardiogram
left arm ("smoke over fire")
124
EKG leads monitor what?
atrial and ventricular depolarization (down and to the left)
125
lead 2 in EKG monitors what?
records depolarization at 60 degrees
126
which lead is the most commonly used on monitors?
lead 2
127
what manual method should be used to take non-invasive BP?
Korotkov method
| - inflated cuff placed around limb
128
systolic pressure of Korotkov method
appearance of 1st sound
129
diastolic pressure of Korotkov method
disappearance of all sound
130
what electronic method should be used to take non-invasive BP?
DINAMAP method
131
DINAMAP method
1. device for indirect noninvasive automatic mean arterial pressure
132
normal BP
<120 AND <80
133
elevated BP
120-129 AND <80
134
high BP (hypertension) stage 1
130-139 OR 80-89
135
high BO (hypertension) stage 2
≥140 OR ≥90
136
hypertensive crisis
>180 AND/OR >120
137
ADA guidelines of oxygenation monitoring for minimal sedation
1. need to use pulse oximetry
| 2. oxygen saturation must be evaluated by pulse oximetry continuously
138
ADA guidelines of ventilation monitoring for minimal sedation
1. dentist and/or appropriately trained individual must observe chest excursions
2. the dentist and/or appropriately trained individual must verify respirations
3. dentist must observe chest excursions continually
4. dentist must monitor ventilation and/or breathing by monitoring end-tidal CO2 unless precluded or invalidated by the nature of the pt, procedure or equipment
139
ADA guidelines of BP monitoring for minimal sedation
1. BP and HR should be evaluated pre-operatively, post-operatively and intraoperatively as necessary (unless pt is unable to tolerate such monitoring)
2. continuous ECG monitoring of pts w significant CV disease should be considered
