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Anesthesia Supporting Your Practice

Focusing the Medical History When Administering Nitrous Oxide


In this short video, Dr. Joonyoung Ji speaks to Dr. John O’Keefe about the absolute and relative contraindications for the use of nitrous oxide guide by the dental clinician.


Nitrous oxide is often used to allay patient fears and anxiety that may occur during dental treatment. However, it should be used only after a thorough medical history by the dentist.

Absolute contraindication

  • Pregnancy
  • Bowel obstruction
  • Bleomycin
  • Recent surgery in closed spaces such as eyes or middle ear

Relative contraindications

  • Pulmonary hypertension
  • Intracranial pressure
  • Folate deficiency
  • Predisposition to nausea and vomiting

In some instances, modifications can be made for patients with relative contraindications to the use of nitrous oxide. These may include using oral sedation over nitrous oxide, keeping appointments short for folate deficient patients or those taking methotrexate and prescribing Ondansetron (Zofran®) for patients to use prior to a nitrous oxide appointment to lessen nausea and vomiting.


Here is a sample of questions suggested by Dr. Ji which you should consider when using nitrous oxide:

  1. Are you or do you think you could be pregnant?
  2. Do you receive injections or infusions as part of your chemotherapy?
    1. Is Bleomycin part of the chemotherapy?
  3. Have you ever been treated for bowel obstruction?
  4. Have you had any ear surgeries in the past 6 months?
  5. Have you had any eye surgeries in the past 6 months?
  6. Have you ever seen a heart or lung specialist for pulmonary hypertension?
    1. Do you take medications such as Viagra for pulmonary hypertension?
  7. Have you ever had a brain tumor, brain infection, very high blood pressure, or stroke?
    1. Are you experiencing any episodes of headache, blurred vision, fainting, or unusual difficulty with memory?
  8. Do you take methotrexate as part of your medication regimen?
  9. Do you have folate or vitamin B deficiency?
  10. Do you get carsick often?

1 Comment

  1. Martha Knopp March 9, 2017

    I am confused because you recommend to take 4mg of Zofran sublingually to manage patients who are non smokers but get car sick . You also though list it in the absolute contraindication category .
    Can you please clarify

    Dr Martha KNOPP


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