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What is it? And what does it do?
Nitrous oxide (N2O) is simply a gas which you can breathe in. It's colorless, sweet-smelling, and nonirritating. It was discovered
in 1772. Gordon loves the stuff! And why wouldn't he... Humphrey Davy (1778-1829), one of the pioneers of N2O experimentation,
described the effects of N2O on himself following self-administration for a toothache and gum infection as follows:
Sounds like fun!! The extract above pretty much summarizes the effects of nitrous oxide: it kills pain - and it induces a
pleasureable feeling. After 5 minutes or so of breathing in the gas, you should feel a euphoric feeling spread throughout
your body. It really kind of feels like a 'happy drunk' feeling. Some people find that there are auditory or visual effects
as well. You will feel a bit light headed and often people get 'the giggles' (hence the name laughing gas!). As an interesting
aside, nitrous oxide was one of the drugs of choice for young people in the late1700s and early 1800s, when "laughing
gas demonstrations" were a popular source of entertainment and enjoyment!
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| � Mark Parisi - www.offthemark.com |
Since those days, it's been discovered that nitrous oxide (N2O) on its own can only safely be used for short periods of time
(because the lack of oxygen in pure N2O can lead to unconsciousness and even death) - but that it's safe to use for longer
periods of time if you mix it with oxygen (O2). Hence, the "laughing gas" used these days is called N2O-O2, and
contains at least 30% oxygen (that's all the machines used nowadays will permit!). Usually, the mix is about 70% oxygen to
30% nitrous oxide.
Depending on the concentration and length of administration of laughing gas, four levels of sedation can be experienced (after
an initial feeling of light-headedness):
(1) a tingling sensation, especially in the arms and legs, or a feeling of vibration ("parasthesia"), quickly
followed by
(2) warm sensations, and
(3) a feeling of well-being, euphoria and/or floating ("drift"). During heavier sedation, hearing may dissolve
into a constant, electronic-like throbbing.
(4) At a deeper level of sedation again, sleepiness, difficulty to keep one's eyes open or speak ("dream") can
occur. Should nausea set in, it means you're definitely oversedated!
During relative analgesia, you should be maintained within the first three stages. The "dream" stage is indicative
of too high an N2O concentration or too lengthy administration, and is associated with ill side effects such as nausea and
other potentially unpleasant sensations, including flashbacks of bad experiences. These are definitive signs of oversedation.
N2O concentration should always be gradually increased ("titrated") at each visit, because people's tolerance can
vary from day to day, depending on both psychological and physiological factors. If you've had bad experiences with laughing
gas in the past, it is highly likely that these were due to improper administration and too high a concentration of N2O.
Interestingly, the actual mechanism of action of N2O is still unknown (it appears that there are quite a few different mechanisms
at work)! However, it's been observed that N2O depresses almost all forms of sensation - especially hearing, touch and pain,
and that it seems to disinhibit some emotional centers in the brain. The ability to concentrate or perform intelligent acts
is only minimally affected, as is memory.
How is it administered?
The equipment used for delivering "happy gas" is quite simple. It consists of a supply of compressed gases and an
apparatus which delivers the gases to the client. By turning some knobs and flipping on/off switches, the administrator can
produce the desired mix of N2O-O2 in the desired quantities. Flowmeters and pressure gauges allow the administrator to keep
an eye on the flow of gases.
The desired N2O-O2 mix is fed through a tube to which a nasal hood or cannula is attached. This hood is put over your
nose. All you have to do now is breathe normally through your nose - bingo!
| The white inner mask (sticking out) |
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| comes in vanilla, strawberry, and mint |
In modern machines there is a sort of "double mask" where the outside mask is connected to a vacuum machine to suck
away the waste gas - you wouldn't want your dentist to get a face full of N2O... The white inside mask, which is placed over
your nose, comes in lots of yummy scents - vanilla, strawberry, and mint! The one pictured to the left is scented with vanilla
(that's the one I'd go for), but Gordon likes the minty one best...
| The grey "outer mask" ensures that your |
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| dentist doesn't leave work with a headache |
The twin tubes running to the mask are for "gas in" and "gas out". The "gas out" line is attached
to the vacuum machine, while the "gas in" line is attached to the RA (short for relative analgesia) machine. The
inner mask is attached to the "line in", you breathe out through a one-way valve in the inner mask, and the exhaust
gas is collected inside the outer grey mask (pictured to your right) and sucked into the vacuum machine.
What are the advantages?
* Happy gas works very rapidly - it reaches the brain within 20 seconds, and relaxation and pain-killing properties develop
after 2 or 3 minutes.
* The depth of sedation can be altered from moment to moment, allowing the person who administers the gas to increase
or decrease the depth of sedation. Other sedation techniques don't allow for this. For example, with IV sedation, it's easy
to deepen the level of sedation, but difficult to lessen it. Whereas with gas, the effects are almost instant.
* Other sedation techniques have a fixed duration of action (because the effects of pills or intravenous drugs last for
a specific time span), whereas gas can be given for the exact time span it's needed for. It can also be switched off when
not needed and then switched on again (though to avoid a roller-coaster effect, you shouldn't do this too abruptly).
* There's no "hangover" effect - the gas is eliminated from the body within 3 to 5 minutes after the gas supply
is stopped. You can safely drive home and don't need an escort.
* With nitrous oxide, it's easy to give incremental doses until the desired action is obtained (this is called "titration").
So the administrator has virtually absolute control over the action of the drug, preventing the possibility of accidental
overdoses. While giving incremental doses is possible with IV sedation, it's not possible with oral sedation (as a result,
oral sedation can be a bit of a hit-and-miss affair).
* Unlike IV sedation, no injection is required. In cases of very severe needle phobia, getting laughing gas first can
help you feel relaxed enough to allow the needle required for IV sedation to be inserted in your arm or hand. The very deep
state of sedation achievable through IV sedation may then allow you to accept local anaesthetic.
* Inhalation sedation is very safe. It has very few side effects and the drugs used have no ill effects on the heart,
lungs, liver, kidneys, or brain.
* For certain procedures, especially those involving soft tissues (e. g. deep cleaning), inhalation sedation may be used
instead of local anaesthesia. N2O acts as a painkiller; however, its pain-relieving effects vary a lot from person to person
and can't be relied upon. So if you're determined to give the needle a miss, you and your dentist will have to try and see
what happens...
* Inhalation sedation has been found to be very effective in eliminating or at least minimizing severe gagging.
Are there any disadvantages?
* Some people are not comfortable with the effects of laughing gas (either because they're afraid they might lose control
or because it makes them feel nauseous - this is quite rare, though, and usually due to oversedation). If you're prone to
nausea, it's a good idea to have a meal (not a huge one) about 4 hours before your appointment. If that's not possible (e.
g. an early morning appointment), make sure your stomach isn't completely empty - but don't stuff yourself straight beforehand
either. According to Gordon, who's a bit of an expert in the field, the normal working concentration of gases is about 70%
oxygen to 30% nitrous oxide: "It's rare to go beyond that because that's what brings on the nausea, more than 45% N2O
and you're going to have the patient puke on you :-)" Ahh... nothing like a bit of straight talk!
* Some people will not achieve adequate sedation with permissible levels of oxygen.
* On rare occasions, people have a bad experience with N2O. Usually this is due to oversedation. This is easily reversible
by reducing the amount of N2O in the mix. For example, a few people have reported auditory and "physical" hallucinations,
dizziness, or vertigo:
Don't panic should you experience any symptoms of that nature. While they're usually due to the N2O concentration being too
high for you, the machines used nowadays have built-in safety features preventing an accidental overdose. Nonetheless, these
sensations can be unpleasant - if you start feeling nauseous or experience any other unpleasant symptoms, communicate these
to your dentist asap so that he or she can adjust the percentage of N2O. Laughing, becoming giddy, crying, or uncoordinated
movements are other signs that the NO2 concentration is too high, but these will easily be spotted by your dentist. Alternatively,
just rip the mask off your nose, and you'll be fine :-) !
Don't confuse "dizziness" with the normal feeling of lightheadedness which many people who've never had N2O
before experience after maybe 60 or 90 seconds. The feeling of lightheadedness will pass as the concentration of N2O is increased.
* Some people are unable to breathe through their noses (see above on how nitrous oxide is administered), or they feel too
claustrophobic when something is put over their nose. If you have the snuffles and you can't breathe through your nose, it
can't be used.
* Depending on where you live, a dentist who offers nitrous oxide may be hard to come by.
Apart from that, most of the disadvantages of inhalation sedation do not affect the client, but the dental team: there's
training required, the equipment is quite bulky and takes up a lot of space, and there is a possibility that dental staff
who are chronically exposed to nitrous oxide might develop health problems. The cost of the equipment and gases is high, so
you'll have to contribute to the cost - but it's quite a bit cheaper than IV sedation.
When should I not use it?
There aren't any major contraindications to RA, except for emphysema and some exotic chest problems. It hasn't been proven
to be safe during the first trimester of pregnancy, so you can't use it then. Because you have to breathe it in through your
nose, it's not suitable for people who have a cold or some other condition which prevents them from breathing through their
nose. M.S. is another contraindication.
You can't be allergic to N2O. It's also safe to use if you suffer from epilepsy, liver disease, heart disease, diabetes,
or cerebrovascular disease. It is also used quite successfully in many people with respiratory disease - but it depends on
the exact nature of the disease, so check with your dentist!
How do I know if it's for me?
Why not ask if you can have a 5 minute 'sample' so that you know what to expect on the day of your procedure? Some dentists
offer that service to patients to help them with the decision of what to do. Your dentist may not like the idea of doing this
(costs, time, etc.), but there is no harm in asking!
Links to other sedation methods: Oral Sedation,Inhalation Sedation
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