Nitrous Oxide in Dental Anesthesia

Joseph Priestley

Discovered nitrous oxide (1733-1804)

Sir Humphrey Davy

Identified nitrous oxide's analgesic properties (1778-1829)

Dr. Horace Wells

Attempted the first dental use of nitrous oxide

Wells' public N2O demonstration

The patient cried out; Wells was ridiculed and later took his own life.

Ideal characteristics of nitrous oxide for inhalational anesthesia

Analgesic, anxiolytic, amnestic, rapid onset/recovery, titratable, minimal side effects.

Indications for nitrous oxide use in dentistry

Pain/anxiety management, medically compromised patients, gag reflex management.

Fear of dental treatment

40% (~35 million people) avoid dental treatment due to fear.

Medically compromised conditions where N2O may help

Cardiovascular disease, hepatic disease, epilepsy.

Blood-gas solubility coefficient of N2O

Low — leads to rapid onset and recovery.

MAC (Minimum Alveolar Concentration) of N2O

105%, indicating it is not potent enough for general anesthesia alone.

Second gas effect

High concentrations of N2O enhance the uptake of a more potent anesthetic (e.g., sevoflurane).

Diffusion hypoxia

O2 dilution in alveoli post-procedure; prevent with 100% O2 for 3-5 minutes.

Elimination of N2O from the body

Exhaled unchanged via the lungs.

Primary site of action for N2O

Cerebral cortex.

N2O doses > 80%

Slight myocardial depression.

Minimal sedation according to VA regulations

Anxiolysis, inhalation analgesia, or both.

Required equipment features in VA for N2O-only sedation

BP monitor, positive-pressure oxygen, hand respiratory bag, suction apparatus.

Storage of nitrous oxide in E cylinders

In liquid form.

Color of nitrous and oxygen tanks in the U.S.

N2O - Blue; O2 - Green.

Pin index safety system

Prevents mixing up O2 and N2O tank connections.

Initial N2O dose during administration

20%, increasing by 10% every 2 minutes.

Patient response to 30% N2O

80% of patients respond well.

Post N2O administration care

100% O2 for 3-5 minutes; assess vital signs and recovery.

Modified Romberg Test

Eyes closed, feet together, touch nose with finger — tests balance post-sedation.

Signs of nitrous oxide overdose

Restlessness, disorientation, unresponsiveness, sweating, nausea.

Management of N2O overdose

100% O2, remove mask, reassure patient, use reservoir bag as needed.

Stages of anesthesia

I - Analgesia, II - Delirium, III - Surgical anesthesia, IV - Respiratory paralysis.

Symptoms of Guedel's Stage I (Sedation/Analgesia)

Lightheadedness, numbness, warmth, euphoria.

Early excitement symptoms

Hearing/vision changes, anxiety, hyperventilation, sweating.

Overdose symptoms (Guedel's Stage II)

Nausea, amnesia, loss of airway, snoring, unresponsiveness.

Absolute contraindications for N2O

Acute URI, nasal obstruction, active bronchitis, 1st trimester pregnancy, pneumothorax, bowel obstruction, inner ear infection.

Relative contraindications for N2O

Pregnancy after first trimester, psychiatric instability, severe COPD, recent eye surgery (consult needed).

Major occupational exposure risk of N2O

Spontaneous abortion, reduced fertility, birth defects, neurological damage.

NIOSH's N2O exposure limit

50 ppm over 8 hours; ideally under 25 ppm.

Minimizing occupational N2O exposure

Use scavenging systems, reduce patient talking, ventilate, calibrate equipment.

Side concerns of N2O use

Hallucinations, dreams, potential for sexual misconduct accusations — always have an assistant present.

Advantages of N2O sedation

Rapid onset/recovery, titration, no escort needed, low side effects.

Disadvantages of N2O sedation

Requires cooperation, low potency, risk of abuse, space and equipment costs.