Nitrous Oxide: The most popular sedative

Fadi Kass DMD, Msc, FRCD(c)

November 15, 2008

1426 McPhillips St

Winnipeg, MB

888-KIDS

Some statistics:

• United States

– 89%1 and 86%2 of pediatric dentists

– 35%3 of general dentists

• Manitoba

– 52 out of 610 registered dentists (8.5%)

– 4 out of 16 Pediatric dentists (25%)

MDA stipulates . . .

• Have taken a nitrous licensing course– University of Alberta– Dalhousie University

• Site audit for the initial setup

• Office audit every 3 years to upkeep your initial site audit allowing the use of nitrous

Some history . . .• Discovered in 1772 but primarily used as

recreational drug

Pertinent history . . .

• In 1884, Horace Wells first dentist to recognize its value– Saw it at a show– Extracted own

tooth next day

Benefits of Nitrous

1. Safe and effective

2. Increase patient comfort and enjoyment

3. Visually shields child's eyes from work

4. Potential practice building tool

5. Short recovery time

6. Short duration of onset

7. Easy to administer

What is it?• N2O

• Colorless

• Odorless except for faint sweet smell

4How does it work?

• Exact mechanism unknown

• Widely accepted that the analgesic effect is mediated through interaction with opioid receptors.

• The anxiolytic effect is mediated through interaction with the GABA-A receptors. Closely resembles the effect of ethanol.

5How it works . . . • Rapidly absorbed upon inhalation• As a result of lower tissue/blood partition

coefficients, the equilibration of nitrous oxide in most tissues occurs rapidly

• Nitrous oxide is not metabolized in the body. • The blood/gas partition coefficient is low and most

of the inhaled nitrous oxide is rapidly eliminated through the lungs, though small amounts diffuse through the skin

Equipment . . .

• Need to deliver a mixture of nitrous oxide and oxygen from the the tanks to the child's lungs

Equipment . . .

• Modern equipment employ “fail-safe” mechanisms that allow a minimum of 30% oxygen to be used.– By contrast, air we breath is 22% oxygen– Body is never oxygen starved

Equipment . . .

• Use of digital delivery units

• Digital units deliver pure oxygen during “flush” function instead of simply mixing more nitrous to the bag

1Monitoring equipment

• Clinical observation of the patient’s responsiveness, color, and respiratory rate and rhythem must be performed.

• According to the American Academy of Pediatrics, if nitrous is used with any other sedatives, monitoring should be done in accordance to the protocol of deep sedation

• According to the American Academy of Pediatric Dentistry, oxygen analyzers use in the office are only a recommendation unless nitrous is used in concentrations greater than 80%.

Does nitrous work?

My experience . . .• Anecdotally, based on case selection, nitrous use

seems to assist significantly.• Children under 3 are not candidates for nitrous as

they are pre-cooperative• 3-6 yr old patients are only good candidates if you

think they will wear the nose piece without panicking

• 6 yrs + are ideal candidates as they are capable of understanding instructions given by the clinical team

Biggest benefit for me . . .

Fear reduction using nitrous4

• Study looking at two groups of children– Behavior Management– Behavior Management + Nitrous

• Anxiety scores were significantly lower

• At semi annual check-ups, Nitrous group did significantly better

• Concluded that nitrous helps children lower anxiety levels during a long period after treatment

Ideal flow rate

• Range between 5-6 L/min

• Look for bag movement with inspiration / expiration

Percentage of Nitrous?• Depending on the patient

• Ranges between 25%-50%

• The mean alveolar concentration of N2O considered the ED50 for general anesthesia (the dose at which 50% of patients will experience anesthesia) is 105%.

• Nitrous alone can not be used to bring on general anesthesia.

3Normal distribution curve

0

5

10

15

20

25

% p

atie

nts

idea

lly s

edat

ed

10 20 30 40 50 60 70

% N2O for ideal sedation

Prepare the child• When child receives nitrous for first time,

the dentist or assistant should explain what they will feel– Tingling of hands and feet– Slight floating sensation– Chest is going to feel funny– General disconnect (“weird”) feeling– THEY ARE ALWAYS IN CONTROL– THEY WILL NOT FALL ASLEEP

• At correct therapeutic levels, it will be a positive experience for most patients

• If the nitrous levels are too high– Experience slight/severe

nausea– Uncontrollable giggling– May even experience a

greater sense of anxiety

Sequence . . .

• Start with 100% oxygen

• Progress to 25% nitrous over 2 mins

• Increase by 5% every 30 seconds until ideal levels area reached

• Flush oxygen when giving local

• Restart back to ideal level for procedure assuming rubber dam use

• Finish with 3-5 mins at 100% oxygen

Problems with nitrous use . . .

Diffusion hypoxia

• Occurs when the nitrous is discontinued at the end of a procedure which produces a “hang over” type effect

• Rapid diffusion of nitrous from the blood back into the alveoli results in displacement of oxygen and a drop in pO2.

• This can be easily avoided by breathing 100% O2 for 3-5 mins.

Contraindications• Women who are in the first trimester of pregnancy

– Some evidence linking its use to a higher risk of miscarriage in dental assistants

• Persons with chronic obstructive pulmonary disease (COPD)– Bronchitis or emphysema related to cigarette smoke

– PO2 is their primary stimulant for respiration

• Patients undergoing bleomycin sulfate treatment.– Anticancer drug

Thank You

Bibliography

1. Wilson S. A survey of the American Academy of Pediatric Dentistry membership: nitrous oxide and sedation. Pediatr Dent. 1996 Jul-Aug;18(4):287-93.

2. Adair SM, Waller JL, Schafer TE, Rockman RA. A survey of members of the American Academy of Pediatric Dentistry on their use of behavior management techniques. Pediatr Dent. 2004 Mar-Apr;26(2):159-66.

3. Malamed SF, Clark MS. Nitrous oxide-oxygen: a new look at a very old technique. J Calif Dent Assoc. 2003 May;31(5):397-403. Erratum in: J Calif Dent Assoc. 2003 Jun;31(6):458.

4. Veerkamp JS, Gruythuysen RJ, Hoogstraten J, van Amerongen WE. Anxiety reduction with nitrous oxide: a permanent solution? ASDC J Dent Child. 1995 Jan-Feb;62(1):44-8

5. Reynolds JE. Martindale: The Extra Pharmacopoeia. The Pharmaceutical Press: London 1982..