Nitrous Oxide Sedation Flashcards
who discovered N2O and when
1776 by Joseph Priestley
who started a practice using N2O first and when
1841 Horace Wells and William Morton
who and when first used ether to remove tumor
1842 Crawford Long
when did gardner colton demonstrate N2O
1844
when was the first tooth extraction using N2O and who did it
1844 Colton had John Riggs extract Horace wells tooth
1850s and 1860s were mostly dominated by _______
ether and chloroform
who made addition of 20% O2 to N2O and when
1868 Edmund Andrews
when was lidocaine introduced and replaced N2O as the ideal drug for eliminating pain
1945
what does N2O do
decreases the inhibitions of the patient
increases the intensity of emotions
what are the physical properties of nitrous
- only inorganic anesthetic gas in clinical use
- colorless and odorless
- capable of oxygen supporting combustion
what are the effects of nitrous in cardiovascular system, respiratory, and renal
- CV: stimulation of catecholamines yet myocardial depression
- respiratory: stimulation of catecholamine, tachypnea and decrease tidal volume
- renal: reduced urine output
what is the toxicity risk with nitrous
prolonged exposure, bone marrow depression, neurological deficiencies, peripheral neuropathies and pernicious anemia
what is Nitrous made of
from ammoniium nitrate via 240 degree celcius heat
NH4NO3 -> N2O and 2H2O
how is nitrous made
compressed in cylinder where 30% is liquefied
N2O must be ____ pure
97%
what are the impurities in nitrous
- N2, NO, NO2, NH4 ammonia, water vapor and CO
what is the most dangerous impurity and why
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
N2O is ______
anhydrous
what are the properties of nitrous
- 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
describe the solubility of nitrous
- 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
describe the potency of nitrous
least potent of the anesthetic gases
N2O is ______ soluble in plasma than N2
35x more
N2O is ______ in plasma than O2
100x more soluble
N2O + O2 ->
CNS depression
- some may get delirium
- very few people will get stage III anesthesia
optimum concentration of N2O for production of analgesia while maintaining patient cooperation is ____
35%
20%:80% mixture N2O-O2 ->
10-15mg of morphine
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
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
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
analgesic effect of N2O is ____ in nature because _____
opioid; may involve neuromodulator in the spinal cord
describe the anxiolytic effect of N2O
- similar to benzodiazepine: selected sub unit of GABA receptor
- N-methyl -D- aspartate (NMDA) receptor
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
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
what are the signs and symptoms of diffusion hypoxia
headache, nausea, lethargy - > hangover effect
what is the prevention for diffusion hypoxia
administer 100% O2 for 3-5 mins at the termination of the procedure
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
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
what is the effect of N2O on respiratory system
- not irritating to pulmonary epithelium
- ok for asthma
what is the effect of N20 on GI system
no clinically significant action
what is the effect of N2O on kidneys
no significant effect
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
what is the effect of N2O on skeletal muscle
does not produce relaxation of skeletal muscle
what color is O2 cylinder and what is the PSI
green
- 1900 psi
what color is the nitrous cylinder and what is the PSI
blue
- 745
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
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
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
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
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
compressed gas cylinders are designed to handle:
1.66 times the usual pressure
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
what are the sizes for cylinders
from small A size to large HH size
portable nitrous units are what size
E cylinder for oxygen and N2O
what is the state of O2 cylinder
gas
what is the state of the nitrous cylinder
liquid
______ O2 E cylinder is used for every N2O E cylinder
2.5
what does the regulator do
reduce incoming cylinder pressure to 50 psi
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
what does the scavenging nasal hood do
eliminated exhaled N2O from the ambient air
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
what is the minimum O2 delivering nitrous oxide to patient
30%
always begin and end with patient receiving
100% O2
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
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
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
what are the causes of an overly inflated reservoir bag
- minute volume of gas is too great
- hose obstruction
what do you expect from the pt
- nothing
- light headedness
- tingling of arms, legs or oral cavity
- feeling of warmth, floating or heaviness
how do you know you are in the zone
- relaxation of hands
- slower verbal responses
- slower physical responses
what is the first clinical evidence of N2O effect
light headedness
what is the primary determinant of recovery from sedation
responses from the patient
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
what are the complications from nitrous
- expectoration
- behavioral problems
- shivering
- nausea and vomiting
success rate of nitrous decreases with ____ type patient
authoritarian
talkative patient will become:
more talkative
