6. Nitrous Oxide Flashcards
Advantages of N2O
- Ease of Use
- Wide margin of safety
- Rapid reversibility
- Analgesic and anxiolytic
Who first synthesized N2O
Joseph priestley
Who was credited the discoverer of N2O anesthetic
Horace Wells
Who first discovered the effects of inhaling N2O
Humphry Davy
Properties of N2O
- Odorless (or sweet smelling)
- Colorless
- Slightly heavier than air
- Anxiolytic and analgesic
- Minimal impairment of reflexes
- Low solubility in blood (rapid onset and recovery)
- Doesn’t bind hemoglobin or undergo biotransformation (held in serum portion of the blood)
Is N2O considered a general anesthetic
yes
What variable measures the potency of a general anesthetic and define in
MAC (Minimal alveolar concentration)= the concentration of anesthetic needed to cause immobility in 50% of patients
MAC of N2O is
105
Describe the mechanism of how N2O –> analgesia
- Increases the bodies production of endogenous opiods
- Direct interaction with opiod receptors
- Interaction with the GABA (A) receptor
30% nitrous is the equivalent to what dose of morphine
10-15mg
Describe the mechanism of the anxiolytic effects of N2O
Activation of the GABA A receptors through the benzo binding site
Objectives of N2O
- Reduce or eliminate anxiety
- Reduce movement and reaction to dental treatment
- Enhance communication and cooperation
- Increase tolerance for longer appointments
- Aid in treatment of mentally/physicalyl disabled or medically compromised patients
- Reduced gagging
- Potentiate the effect of sedatives
- Raise the pain threshold
Raising the pain threshold with N2O can be enhanced by
distraction
How does N2O increase the child’s pain threshold
-Analgesic properties
T/F N2O will not eliminate the need for LA in most kids
t
Disadvantages of N2O
- Low potency
- Relies of psychological reassurance (not a replacement for behavior guidance)
- Nasal hood in the way for a maxillary anterior injection
- Environmental and occupational health hazard
- Patient must breath through their nose (nasal polyps, deviated septum, URI and nasal obstruction prevent its use)
Indications for N2O
- Fearful, anxious or obstreperous patient
- Special care needs
- Profound LA can’t be obtained
- Lengthy procedure
- Reduce gag reflex
Adverse effects of N2O
-Most common adverse effect is Nausea and vomitting (occurs in 0.5% of patients)
How is vomitting exacerbated with N2O use
- Use for long amount of time
- Conc. N2O= too high
- Large fluctations of N2O conc.
- Rapid induction and reversal (titration not used)
Contraindications for N2O
-Can’t Everyone Please Be More Conscientious
COPD
- Not asthma (N2O may help by alleviating anxiety that can trigger and asthmatic attack)
- People with severe pulmonary diseases that use hypoxic drive to stimulate breathing rather than CO2 accumulation
- ^^These epopel are more sensitive to the sedative effects and can stop breathing)
Emotional Disturbances
- More sensitive to sedation
- More prone to hallucinations
Pregnant
- Spontaneous abortion
- Potential impact on developing fetus
Bleomycin Sulfate
- Anti-neoplastic drug
- High oxygenation isn’t advisable can cause respiratory failure
Methylenetetrahydrofolate reductase (MTHFR) deficiency
- MTHFR deficiency –> increased amounts of homocysteien
- N2O increases homocysteine conc.
Colbalamin (VitB12) deficency
- N2O irreversibly inhibits the cobalt atom of B12
- Decreased activity of B12 enzymes such as methionine and thymidylate synthetase
Effect of N2O on a patient with otitis media
- N2O is more soluble in blood than N2 which results in filling empty spaces with air
- Increases middle ear pressure –> pain
- Air may enter the tympanic space and rupture the ear drum
Entrapment of air is an issue where in the body
- Ear in otitis media
- GI in bowel obstruction
- Intraocular after retinal surgery
Have there been any reported allergies to N2O
no
NPO guidlines for N2O
Child doesn’t have to be NPO
-May recommend a light meal 2 hrs before
The smallest nasal hood is
Dynomite (disposable and scented nasal hood)
Define Tidal Volume
The amount of gas that flows in and out of the lungs during quiet breathing
Normal tidal volume for adults and kids is usually
Adult= 500 mL Child= 250 mL (1/2 the adult)
Define Minute Volume
- Product of the tidal volume and respiration rate
- Amount of air that is inhaled and exhaled per minute
Normal minute volume is
6-7 L/min
Gass flow should be the same as
the minute flow (notes say tidal volume??)
As the child ages the tidal volume (increases/decreases) and the respiration rate (increases/decreases)
increases…decreases
Flow rate of _-_L/min is generally acceptable for most patients
4-6L/min
How do you know if you should adjust the flow rate
Look at the reservoir bag
-Should be 2/3rds full and pulsate with breathing
Which technique is perfered (rapid inducation/titration)
titration (more safe)
Conc. of N2O shouldn’t exceed
50%
Typical patient requires -% N2O for ideal sedation
30-40
DESCRIBE THE TITRATION TECHNIQUW
- START N2O AT 10%
- Wait ~30-60 secs looking for signs of sedation
- Increase N2O by 5-10% intervals until optimal sedation
Signs of optimal sedation
- Ptosis of eyelids
- Staring off into space
- Relaxation of limbs and jaw
- Palms are warm, moist and open
- Pitch in voice changes
- Lowered heart rate
- Patient reports feeling relaxed
Describe the rapid induction technique
indicated when you have a kid that may be on the edge of losing coping abilities
-Administer 50% N2O immediately
Early sign of CNS effects of N2O
Tingling sensations in fingers and toes
-In kids instead of asking minimal or continual movement of fingers and toes is indication of CNS effects
Describe the technique to relax claustrophobic patients with N2O that don’t like the nasal hood
- N2O is slightly heavier than air
- Hod the hood at 30% O2 3 inches from face until kid relaxes
- bring hood closer until in position
Use of rubber dam (helps/inhibits) N2O effects
helps (facilitates nasal breathing)
O2 deliverance at the end of the procedure should be for how long
100% O2 for 3-5 min
Describe diffusion hypoxia
-Result of rapid release of N2O from alveoli resulting in dilution of O2
Side effects of inadequate oxygenation are
- dizziness
- Light headed
- Nausea
- *All can be relieved with oxygenation
When is diffusion hypoxia a concern
- High conc. of N2O used (70%)
- Closed system (full mask or endotracheal tube)
- AKA hospital/ OR setting
What are the benefits of delivering 100% O2 at end of procedure
- Expired nitrous into scavenging system in nasal hood
- Prevent diffusion hypoxia (even though unlikely)
What should be monitored during treatment
- Respiration rate
- Level of conciousness (spoken response= indication of breathing)
- Color
Documentatino after N2O use
- Informed consent
- Indication
- N2O dosage
- Duration of procedure
- Post treatment oxygenation procedure
Good O2 Hygiene includes
- Scavenging system
- Large operatory
- Rapid room air exchange
- Supplemental air movement (fans)
- Nasal hood adapts close to nose
- Periodic monitoring (dosimetry badge)
N2O occupational Hazards
- Spontaneous abortion (practitioner and spouse)
- Some cancers
- Liver disease (exposure longer than 3 hrs per week)
- Kidney disease
- Neurologic disease
- Long term exposure –> decreased fertility
- Congenital malformaitons
