Anesthesia and Nitrous Oxide Quiz

Nitrous Oxide & Oral Sedation

• Nitrous oxide (N₂O) and potent volatile halogenated agents make up inhalation anesthetics.
• N₂O is inhaled and travels from the alveoli to the pulmonary vasculature, entering the blood-brain barrier to affect the brain.
• N₂O is minimally metabolized and excreted unchanged back into the alveoli.
• Plasma concentrations of inhalation anesthetics depend on the gas concentration in the alveoli, the solubility characteristics of the individual gases, and cardiac output.
• Minimum Alveolar Concentration (MAC) is the end-tidal concentration of an inhaled anesthetic at 1 atm that prevents skeletal muscle movement in response to pain in 50% of patients.
• MAC values are general guidelines and individual anesthetic requirements can vary based on factors like higher altitudes, pregnancy, hypothermia, and hyponatremia.
• Factors that decrease MAC include higher altitudes (lower barometric pressure), pregnancy, hypothermia, and hyponatremia. Opioids and calcium channel blockers also decrease MAC.
• Factors that increase MAC include increased central neurotransmitter levels (MAOIs, cocaine, ephedrine, levodopa), hyperthermia, and chronic alcohol use.
• In adults, a 1.3 MAC level prevents movement in 95% of patients, and a 1.5 MAC level blocks adrenergic responses in 95% of patients.
• A MAC level of less than 0.3 will likely result in patient awareness.

Inhalation Anesthetics

• Nitrous oxide (N₂O) is combined with oxygen (O₂).
• N₂O is commonly used in dental offices for anxiolysis and mild sedation.
• The procedure does not usually necessitate an escort after completion.
• At the end of a procedure, 3-5 minutes of 100% O₂ is administered to prevent diffusion hypoxia.
• N₂O has low blood-gas solubility (0.47).
• It can be administered to intubated patients during general anesthesia.

Laughing Gas in 1845

• N₂O use became a trendy activity at social events and in university settings.

Nitrous Oxide Overview

• N₂O in combination with O₂ is the most commonly used sedative agent in dental offices for anxiolysis and mild sedation.
• It does not require an escort after the procedure is complete.
• Administering 100% oxygen for 3 to 5 minutes at the procedure's conclusion prevents diffusion hypoxia.
• The low blood-gas solubility of N₂O (0.47) contributes to its rapid onset and recovery.
• N₂O can be administered to intubated patients for general anesthesia.

Middle Ear Surgical Procedures with N₂O

• N₂O diffuses from the blood into the middle ear.
• N₂O concentrations increase until equilibrium with alveolar concentrations are reached.
• Higher inspired N₂O concentrations lead to increased middle ear pressure, potentially causing complications like tympanic membrane rupture.

Pharmacokinetic Properties of N₂O

• N₂O is a nonirritating, sweet-smelling, and colorless gas.
• Its blood-gas solubility is 0.47.
• Onset of action can range from a few seconds to 3-5 minutes.
• N₂O rapidly crosses the blood-brain barrier.
• It is rapidly eliminated, primarily through exhalation from the lungs, and is not significantly metabolized by the liver or kidneys.
• N₂O isn't stored in tissues.

Blood Gas Solubility

• The speed at which a gas saturates blood depends upon its blood-gas solubility.
• Insoluble gases saturate the blood quickly.
• Highly soluble gases saturate the blood slowly.

Diffusion Hypoxia

• When N₂O is discontinued, it leaves the blood more quickly than nitrogen, decreasing the blood's O₂ concentration in the alveoli.
• This can lead to hypoxia.
• To counteract diffusion hypoxia, 100% oxygen is administered for 5 minutes, replacing the N₂O.
• The mask should be positioned to receive exhaled nitrous oxide from the patient instead of releasing it into the room.

Clinical Properties

• Nitrous oxide is an anxiolytic, similar to oral versed.
• It's used as an analgesic for minor and minimally invasive procedures.

Advantages of N₂O

• Rapid onset and complete recovery with quick titration to the desired effect.
• Relatively safe procedure.
• No adverse effects on the liver, kidneys, brain, or cardiovascular systems.
• Suitable for providing analgesia and anxiolysis.
• Can be used in combination with local and other volatile anesthetics.

Percent of Nitrous Oxide Administered

• This data shows the percentages of N₂O based on various liters per minute of N₂O and O₂.

Disadvantages of N₂O

• Initial equipment costs and maintenance expenses for sedation can be high.
• It may require a significant amount of space.
• N₂O may not achieve the same clinical effect in all patients.
• Patient cooperation is necessary.

Indications for N₂O

• Helpful for reducing dental anxiety and in shorter procedures.
• Useful for patients with comorbidities like cardiovascular disease, asthma, and hepatic issues.
• Helpful in IV starts.
• Helpful in laceration repairs and I&D.

Precautions and Contraindications for N₂O

• Patient selection is crucial.
• Be cautious with young patients and those with a pre-existing psychiatric history.
• N₂O should be used with caution in pregnant women.
• Medical contraindications include current otitis media, sinus infections, COPD, and recent MVCs,
• Avoid using N₂O for patients with compulsive behaviour issues, claustrophobia, and acute upper respiratory tract infections.

Additional Contraindications for N₂O

• Patients with compulsive or behavioral problems.
• Claustrophobic patients.
• Patients with upper respiratory infections or acute respiratory conditions.

Fasting Before N₂O/O₂ Sedation

• Fasting may not be necessary for N₂O/O₂ sedation, but the operator might use ASA guidelines for reference.
• Avoid fatty, fried, or greasy food consumption just before the procedure.
• A light meal including carbohydrates is safe to consume about 1 to 2 hours prior to the procedure.

Sexual Phenomena Associated With Nitrous Oxide

• Reports suggest that N₂O abuse can induce hallucinations and altered sexual perceptions.
• Cases of accusations of sexual impropriety against health practitioners after patient sedation have been reported.
• Recommendations include continuous supervision and limiting nitrous oxide concentrations to prevent potential overmedication.

Administration of N₂O

• Attach the N₂O delivery system to wall suction for proper scavenging.
• Visually inspect for leaks in the system prior to use.
• Ensure equipment is appropriately positioned and is out of the way, easily visible, during the procedure.
• Administer 5 minutes of pre-oxygenation before sedation.

Monitoring Equipment

• A patient under N₂O sedation must be closely monitored, typically by an anesthesia monitor, for responses to verbal stimulation, and for oral mucosal color, and to watch for preoperative and postoperative vital signs.

Anatomy of the Mask

• Details of the N₂O mask's components and connections are presented.

Nitrous Oxide/Oxygen Breathing Circuits

• Noncorrugated tubing in the breathing circuit may become occluded by bending around the dental chair's sides.

Traditional Portable N₂O Unit

• Key components of N₂O delivery devices are noted.

Centralized N₂O System

• The centralized N₂O system components are shown, including connections and leak sources.

How to Administer N₂O

• Open both O₂ and N₂O tanks.
• Turn on/off switches.
• Adjust the green and blue levers for a 50/50 O₂/N₂O mixture.
• Ensure the mask is suitably sealed on the patient to begin administration.

Nitrous Oxide/Oxygen Administration Technique

• Assemble and check all necessary equipment.
• Confirm functioning scavenging systems.
• Review the patient's medical history and ensure informed consent is obtained.
• Initiate O₂ flow; fill the reservoir bag.
• Use proper minute volume adjustments.
• Begin nitrous oxide titration, assessing patient responses promptly.
• Continue to adjust N₂O levels to maintain the optimal level of sedation.
• Terminate N₂O, and provide 5 minutes of 100% oxygen post-procedure.
• Monitor recovery, document treatment, and dispose of used equipment properly.

Informed Consent for Nitrous Oxide and Oxygen Sedation

• Details about obtaining informed consent from the patient and/or guardian are delineated in this format.

Components of the Sedation Record

• Components of a comprehensive sedation record for a patient undergoing N₂O with O₂ are described.

N₂O/O₂ Sedation Record

• Record of the sedation session, including patient information, ASA classification, pain and anxiety levels, medical history, informed consent, procedural data, blood pressure, pulse, respiration, SpO2, minute volume, duration of administered drugs, and post-procedure observations

Nitrous Oxide and Oxygen Sedation Record

• Record of procedures including patient details, ASA classification, procedural data, drugs, vital signs, and post-procedure observations

Administration of Nitrous Oxide and Oxygen Sedation Clinical Competency Evaluation

• Evaluation criteria for competence in a nitrous oxide and oxygen sedation procedure are presented.

Oral Sedation

• The oldest route of drug administration, and frequently used in dentistry.
• Oral sedation aims to reduce patient stress before and during dental treatments.

Oral Sedation Advantages

• Universally accepted by most patients due to its ease and affordability.
• Low cost.
• Decreased incidence and severity of adverse reactions.
• No needles or special equipment is needed.

Oral Sedation Disadvantages

• Oral sedation relies heavily on the patient complying with dosage and timing instructions.
• Absorption of medications can be erratic and not completely effective.
• Difficult to titrate to the precise level of sedation needed.
• Sedative effects can persist for a prolonged period.
• Difficult to quickly adjust or reduce sedation levels.

Oral Benzodiazepines in Dentistry

• Ideal for managing anxiety.
• Acts by binding to GABA receptors and causing hyperpolarization.
• Potential for prolonged drowsiness, fatigue, and ataxia.
• Increased risk of paradoxical reactions such as agitation, hallucinations, insomnia, and uncontrolled behavior in patients.
• Contraindicated with other CNS depressants (drugs like opioids and alcohol).
• Pregnant women (especially during the first trimester).

Effects on CNS, Respiratory, Cardiovascular Systems

• Reduces anxiety/aggression; acts as CNS depressant.
• Potential respiratory depression (especially with larger doses).
• Administered alone, in low doses, will not normally inhibit respirations.
• Has minor impact on cardiovascular function.
• Metabolized primarily in the liver.
• Excreted by the kidneys.
• Can induce dependence.

Onset of Peak Plasma Levels of Oral Benzodiazepines

• Data table showing onset of peak plasma levels for various oral benzodiazepines.

Properties of Benzodiazepines

• Table describing peak plasma levels, half-lives, and active metabolites for several benzodiazepines.

Benzodiazepines in Children

• Oral diazepam tablets are not recommended for children younger than 6 months old.
• Recommended pediatric diazepam dosage is 0.15 to 0.3 mg/kg.
• Oral Chlordiazepoxide and oxazepam are not recommended for children under 6.
• Clorazepate is not recommended for children under 18.

Chlordiazepoxide (Librium)

• Drug class: benzodiazepine.
• Slow onset of effects (peak plasma levels developing in 4+ hours) and a gradual reduction in anxiety (may take 1-2 hours).
• Not the ideal choice compared to newer benzodiazepines.

Diazepam (Valium)

• More potent anti-anxiety effects compared to Librium.
• Faster peak plasma levels (within 2 hours).
• Can be administered 1 hour before the procedure.

Oxazepam

• Short half-life, no active metabolites.
• Relatively fast onset and is absorbed quickly.
• Effective in cases requiring rapid anxiety reduction or minimal sedation.
• Recommended dosage: 10 to 15 mg 3 times daily (TID) for adults.
• 10 mg TID for elderly patients.

Alprazolam (Xanax)

• Peak plasma levels in 1-2 hours.
• Relatively long half-life (12-15 hours), meaning the medication remains active longer.
• No active metabolites.
• Dosage: 0.25 to 0.5 mg three times daily (TID) for adults.
• 0.25 mg twice daily or three times daily in elderly patients.
• Suitable for short to medium half-life circumstances.

Benzodiazepine Sedative-Hypnotics

• List of benzodiazepines useful as sedatives.

Flurazepam

• Peak plasma levels are achieved within 30-60 minutes.
• Metabolized in the liver with a long half-life (47-100 hours).
• Side effects include dizziness, drowsiness, lightheadedness, staggering, and ataxia.
• Contraindicated in pregnant women.

Temazepam

• Absorption is slow after oral administration.
• Peak plasma levels take 2-3 hours.
• Has a shorter half-life (10 hours) compared to flurazepam.

Triazolam (Halcion)

• Short half-life (1.5-5.5 hours) enabling faster onset, useful in dental settings.
• Absence of active metabolites.
• Suitable for pediatric patients requiring anxiety relief in dental procedures.
• Over-dosing is possible.

Lorazepam (Ativan)

• Peak plasma levels in 2 hours.
• Relatively long half-life (12 hours).
• Effective in anxiety and insomnia, suitable for patients with liver dysfunction.
• Contraindications include narrow-angle glaucoma.
• Side effects include sedation, dizziness, weakness, loss of coordination.

Midazolam (Versed)

• Rapid onset (peak effect within 30 minutes).
• Actions less noticeable after 8 hours due to faster metabolism.
• Offered in syrup form (2 mg/mL).
• Dosage varies widely dependent on patient age, weight, and liver function.

Histamine H₁ Blockers (Antihistamines)

• CNS depressant properties; useful for inducing sedative effects.
• Commonly used to treat allergies, motion sickness, and Parkinsonism.
• Available as sedative hypnotics.

Promethazine (Phenergan)

• Used as an antiemetic for nausea and vomiting, and as a pre-operative sedative.
• A phenothiazine tranquilizer.
• May cause extrapyramidal reactions (involuntary muscle movements).
• Dosage is up to 50 mg administered one hour before treatment.

Hydroxyzine

• Derived from diphenylethanes, with sedative, antiemetic, antispasmodic, and anticholinergic properties.
• Effective 15-30 min after ingestion; full effectiveness in 2 hours.
• Two available forms: hydrochloride and pamoate.
• 50-100mg 1 hour before the procedure.

The Oral Sedation Appointment (Adult)

• Patient should report 1 hour before the appointment.
• Oral sedative is administered in the dental office with 8oz water.
• Continuous monitoring is essential.
• Assess for appropriate response to sedation at 45 minute mark.
• Assist them to the treatment room, and apply appropriate monitoring (pulse oximetry and BP cuff).
• Emphasize that sedation won't completely replace local anesthetics.

References

• Various papers citing information on oral and nitrous oxide sedation.