Nitrous Oxide Sedation Flashcards
1
Q
who discovered N2O and when
A
1776 by Joseph Priestley
2
Q
who started a practice using N2O first and when
A
1841 Horace Wells and William Morton
3
Q
who and when first used ether to remove tumor
A
1842 Crawford Long
4
Q
when did gardner colton demonstrate N2O
A
1844
5
Q
when was the first tooth extraction using N2O and who did it
A
1844 Colton had John Riggs extract Horace wells tooth
6
Q
1850s and 1860s were mostly dominated by _______
A
ether and chloroform
7
Q
who made addition of 20% O2 to N2O and when
A
1868 Edmund Andrews
8
Q
when was lidocaine introduced and replaced N2O as the ideal drug for eliminating pain
A
1945
9
Q
what does N2O do
A
decreases the inhibitions of the patient
increases the intensity of emotions
10
Q
what are the physical properties of nitrous
A
- only inorganic anesthetic gas in clinical use
- colorless and odorless
- capable of oxygen supporting combustion
11
Q
what are the effects of nitrous in cardiovascular system, respiratory, and renal
A
- CV: stimulation of catecholamines yet myocardial depression
- respiratory: stimulation of catecholamine, tachypnea and decrease tidal volume
- renal: reduced urine output
12
Q
what is the toxicity risk with nitrous
A
prolonged exposure, bone marrow depression, neurological deficiencies, peripheral neuropathies and pernicious anemia
13
Q
what is Nitrous made of
A
from ammoniium nitrate via 240 degree celcius heat
NH4NO3 -> N2O and 2H2O
14
Q
how is nitrous made
A
compressed in cylinder where 30% is liquefied
15
Q
N2O must be ____ pure
A
97%
16
Q
what are the impurities in nitrous
A
- N2, NO, NO2, NH4 ammonia, water vapor and CO
17
Q
what is the most dangerous impurity and why
A
NO
- combine with Hg and prevent O2 absorption and may also react with water vapor to form acid -> damage pulmonary epithelium -> pulmonary edema
- NO is formed when N2O is heated above 450 degrees celcius
18
Q
N2O is ______
A
anhydrous
19
Q
what are the properties of nitrous
A
- nonirritating, sweet smelling, colorless gas
- only nonorganic compound other than CO2 that has CNS depressant properties
- specific gravity if 1.53 vs air (1)
- wall of the cylinder may be cold due to heat needed for vaporization into gaseous state
20
Q
describe the solubility of nitrous
A
- relatively insoluble in the blood (0.47 blood gas solubility coefficient)
- rapid onset and recovery
- rapidly increase alveolar tension -> clinical action is quickly apparent
- oxygen in the N2O is not available for use by the tissue because N2O does not break down in the body
- N2O is not flammable nor explosive but will combust with other agents
21
Q
describe the potency of nitrous
A
least potent of the anesthetic gases
22
Q
N2O is ______ soluble in plasma than N2
A
35x more
23
Q
N2O is ______ in plasma than O2
A
100x more soluble
24
Q
N2O + O2 ->
A
CNS depression
- some may get delirium
- very few people will get stage III anesthesia
25
optimum concentration of N2O for production of analgesia while maintaining patient cooperation is ____
35%
26
20%:80% mixture N2O-O2 ->
10-15mg of morphine
27
what is the concentration effect of N2O
the higher the concentration of the gas inhaled the more rapidly arterial tension of the gas increases
- fresh gas will be pushed into the lunch from the anesthesia machine -> increase arterial N2O arterial tension
- so start nitrous slow
28
what is the 2nd gas effect
- occurs when a second inhalation anesthetic is administered along with N2O-O2
- extreme update of N2O will form a vacuum at alveoli that forces other air into the lungs
29
how does N2O work
- it is absorbed rapidly from the alveolar sacs into the pulmonary circulation
- primary saturation of the blood and brain with N2O is accomplished by the displacement of N2 from the alveoli and the blood and occurs within 3-5 mins
- pt should remain at given level of N2O of 3-5 mins before the inspired N2O concentration is increased
30
analgesic effect of N2O is ____ in nature because _____
opioid; may involve neuromodulator in the spinal cord
31
describe the anxiolytic effect of N2O
- similar to benzodiazepine: selected sub unit of GABA receptor
- N-methyl -D- aspartate (NMDA) receptor
32
what happens when the N2O session is over
- N2O diffused out of the blood and into the alveoli as rapidly as it diffused into the blood during the induction
- if patient simply breath room air and not O2, patient may get diffusion hypoxia
33
what is diffusion hypoxia
- as the N2O is rushed out of the body, it will take other airs out including CO2
- lowering CO2 tension in blood will cause respiratory depression
34
what are the signs and symptoms of diffusion hypoxia
headache, nausea, lethargy - > hangover effect
35
what is the prevention for diffusion hypoxia
administer 100% O2 for 3-5 mins at the termination of the procedure
36
what is the N2O effect on the CNS
- actual mechanism is unknown
- almost all form of sensation are depressed
- mild depression on CNS at cerebral cortex
- area postrema of medulla is not affected unless hypoxia or anoxia is present
37
what is the effect of N2O on CV system
- no clinically significant effect
- slight depression of myocardial contraction
- slight increase in vascular smooth muscle to norepinephrine
38
what is the effect of N2O on respiratory system
- not irritating to pulmonary epithelium
- ok for asthma
39
what is the effect of N20 on GI system
no clinically significant action
40
what is the effect of N2O on kidneys
no significant effect
41
what is the effect of N2O on hematopoiesis
- inhibits methionine synthetase -> impair B12 metabolism -> bone marrow function -> pernicious anemia (Vitamin B12 anemia)
- long term exposure (greater than 24 hour exposure) -> transient bone marrow depression
42
what is the effect of N2O on skeletal muscle
does not produce relaxation of skeletal muscle
43
what color is O2 cylinder and what is the PSI
green
- 1900 psi
44
what color is the nitrous cylinder and what is the PSI
blue
- 745
45
what are the advantages of inhalational sedation
- onset of action is similar to IV sedation
- fast recovery (3-5 mins)
- N2O is not metabolized by the body
- able to titrate
- no injection
- few side effect
- no adverse reaction to body organ/system
- nitrous does have analgesic properties
- 20% N2O equivalent to 10-15mg of morphine
46
what are the disadvantages to inhalational sedation
- equipment cost
- space
- not a potent agent
- chronic exposure to N2O is deleterious to health of dental personnel
47
what are the contraindications to inhalational sedation
- no absolute contraindication
- claustrophobic patients
- compulsive personality
- children with severe behavior problems
- upper respiratory tract infection
- COPD
- pregnancy
48
what are the indications for inhalational sedation
- anxiety
- medically compromised patients such as cardiovascular disease, respiratory disease, cerebrovascular disease, be aware of low O2 level
49
what is the armamentarium for inhalational sedation
- continuous flow unit
- inhalation sedation unit components: compressed gas cylinders, reducing valves (regulators), pressure gauges, flowmeters, reservoir bag, conducting tubing, scavenging nasal hood
50
compressed gas cylinders are designed to handle:
1.66 times the usual pressure
51
describe the handling of cylinders
- never use grease, oil or lubricant
- store in vertical position
- dont drop them
- avoid heat and fluctuating temperature
- close all valves tightly even when its empty
- cracked cylinder before use- let some gas out
52
what are the sizes for cylinders
from small A size to large HH size
53
portable nitrous units are what size
E cylinder for oxygen and N2O
54
what is the state of O2 cylinder
gas
55
what is the state of the nitrous cylinder
liquid
56
______ O2 E cylinder is used for every N2O E cylinder
2.5
57
what does the regulator do
reduce incoming cylinder pressure to 50 psi
58
describe the reservoir bag and what it does
-3 liter reservoir bag is commonly used
- provide addiitonal gas on demand if patient exceed the gas flow being delivered
- monitoring respiration
59
what does the scavenging nasal hood do
eliminated exhaled N2O from the ambient air
60
what is the preoperative instruction for nitrous
- no heavy metal 4 hours prior to N2O - O2 sedation
- determine proper flow rate for the patient: 6L/min flow of O2 for adult and 3-5L/min for peds
- COPD and CHF with partial obstruction may require larger volume
- reservoir bag
61
what is the minimum O2 delivering nitrous oxide to patient
30%
62
always begin and end with patient receiving
100% O2
63
what is the general algorithm for nitrous
- 6 L/min of oxygen and nasal hood on nose
- establish approriate flow of gas
- titrate N2O starting with 20%
- titrate N2O at 10% evert 60 seconds until ideal clinical sedation is reached
- perform procedure and constantly titrate the N2O to match the clinical need
- at the termination of the procedure, allow additional 3-5 mins of 100% O2 until pt returns to baseline
64
how do you determine the right flow volume
- the reservoir bag
- the bag remains partially inflated and deflates and inflates partially with each breath usually indicates that the minute volume is adequate
65
what are the causes of a totally deflated reservoir bag
- minute volume of gas is inadequate
- large leak at the nasal hood
- vacuum on the scavenging system
66
what are the causes of an overly inflated reservoir bag
- minute volume of gas is too great
- hose obstruction
67
what do you expect from the pt
- nothing
- light headedness
- tingling of arms, legs or oral cavity
- feeling of warmth, floating or heaviness
68
how do you know you are in the zone
- relaxation of hands
- slower verbal responses
- slower physical responses
69
what is the first clinical evidence of N2O effect
light headedness
70
what is the primary determinant of recovery from sedation
responses from the patient
71
what must be the vital signs for discharge
- BP: +/- 20mmHg/10mmHg from baseline
- heart rate and rhythm: +/- 15 beats per minute from baseline, same rhythm
- respirations: +/- 3 breaths per minute from baseline
72
what are the complications from nitrous
- expectoration
- behavioral problems
- shivering
- nausea and vomiting
73
success rate of nitrous decreases with ____ type patient
authoritarian
74
talkative patient will become:
more talkative
75
