Chapter 17: Contemporary Issues Surrounding Nitrous Oxide

Question 1

With increased use of N2O-O2 has come a greater concern for the safety of personnel who are in contact with it for the greatest length of time– the dentist and dental staff. What are the three categories addressed in this regard?

Answer 1

1) potential biohazards from long-term exposure to trace anesthetic gas
2) recreational abuse of N2O
3) sexual phenomenon and N2O

Question 2

what is the maximum exposure limit for personnel in the dental limit? (in ppm)

Answer 2

50 ppm

Question 3

what is the standard (in ppm) set by NIOSH for the operating room?

Answer 3

25 ppm

Question 4

What does NIOSH stand for?

Answer 4

National Institute for Occupational Safety and Health

Question 5

What does OSHA stand for?

Answer 5

Occupational Safety and Health Administration

Question 6

What can nitrous do to methionine synthase?

Answer 6

The specific biologic issue is the inactivation of methionine synthase. This enzyme is linked to vitamin B12 metabolism. Vitamin B12 is necessary for DNA production and subsequent cellular reproduction. N2O does affect methionine synthase and does, in high concentration and under long exposure (24 hours or greater), have an effect on reproduction. However, to date, there is no evidence that a direct causal relationship exists between reproductive health and scavenged low levels of N2O.

Question 7

Who wa sthe first to link reproductive problems in humans with long-term N2O exposure?

Answer 7

Sweeney

Question 8

What is the deoxyuridine suppression test?

Answer 8

a sensitive test to accurately determine the first signs of this biologic effect in humans.. They found that long-term exposure levels of 1800 ppm of N2O DID NOT exert any detectable biologic effect in humans. They suggest that a level of 400 ppm is a reasonable exposure level that is both attainable and significantly below the biologic threshold.

Question 9

What is the name of a neurologic disorder associated with long-term N2O exposure?

Answer 9

myeloneuropathy; symptoms such as sensory and proprioception impairment, may be permanent, but are usually temporary with a slow recovery.

Definition: Myeloneuropathy is characterized by simultaneous damage of the tracts of the spinal cord and peripheral nerves in the lower limbs. Clinical manifestations of myeloneuropathy include difficulty in walking, weakness of lower limbs, ataxic gait, and sensory manifestations in glove and stocking distribution.

Question 10

N2O and leukopenia

Answer 10

N2O in very high nontherapeutic doses can cause leukopenia and reduction in megaloblastic erythropoiesis resembling pernicious anemia

Question 11

what is the optimum and recommended vacuum flow rate

Answer 11

45 L/min; at this rate, leakage of N2O-O2 into the room is prevented even when the maks is removed from the patient and a gas flow of 4L of each N2O and O2 is delivered through the nasal hood

Question 12

Should you allow the patient to adjust the mask?

Answer 12

yes because adjusting the mask will invariably create a snugger fit and seal of the nasal hood periphery than the administrator would be able to achieve alone

Question 13

what are air sweeps?

Answer 13

simple oscillating fans that can be placed in such. away as to “sweep” the trace N2O from a specific area

Question 14

What is the breathing zone?

Answer 14

the 12-inch area between the patients mouth and the operators face, sometimes called the breathing zone, contains high concentrations of gas that may be directed toward the venting system

Question 15

what is the number one cause of N2O contamination in the office?

Answer 15

from patient talking

Question 16

what is the most accurate and effective method of determining N2O levels in ambient air?

Answer 16

infrared (IR) N2O analyzer

Question 17

What is the advantage of IR spectrophotometry?

Answer 17

it can detect minute levels of gases, such as N2O, in ambient air at levels as low as 1 ppm

Question 18

IR analyzer can detect what range of ppm of gases?

Answer 18

1 to 2000 ppm; the machine is extremely accurate to within one-half of a percentage point

Question 19

IR analyzers price and how do you get one?

Answer 19

they are very expensive but can be rented from a gas service company and allow you to analyze N2O

Question 20

what are TWM devices?

Answer 20

time weighted monitoring devices are commonly used in medical and dental offices. they detect the amount of N2O absorption over a given period. it’s worn by anyone who desires to know the amount of N2O he or she has been exposed to in a particular setting. they’re not as accurate as IR but they serve a useful purpose

Question 21

what kind of products or agents can cause euphoria?

Answer 21

solvents, model glue, nail polish remover, typewriter correction fluid

Question 22

N2O is used for ____ alteration, sedation and analgesia. It is the _____ of all the general anesthetic agents

Answer 22

mood; weakest

Question 23

What happens when you depress the patient’s inhibitions by depressing the CNS?

Answer 23

you make it easier for them to “let out” whatever it is they are feeling at the time, thus the common term “laughing gas” for nitrous oxide

Question 24

What can cause a patient to dream?

Answer 24

when sedative drugs are administered in higher doses, the level of CNS depression increases and patients may dream. dreams can also be of sexual nature

Question 25

how long does it take to titrate N2O to achieve the desired effect?

Answer 25

5-6 minute period of time; on the normal distribution curve (“bell shaped curve”) the “average” patient will require between 35% and 45% N2O. some require higher concentrations and others less.

Question 26

what is the built in “fail safe device”

Answer 26

a contemporary N2O delivery system cannot deliver more than 70% N2O and no less than 30% O2.

Question 27

what percentage of oxygen is there in atmospheric air?

Answer 27

21%