RDA Assisting with Administration of Anesthesia and Sedation 2 — Questions and Answers
Question 1: Which local anesthetic agent is classified as an amide and is the most commonly used in dentistry?
- Procaine
- Benzocaine
- Lidocaine (Correct answer)
- Tetracaine
Correct answer: Lidocaine
Lidocaine (Xylocaine) is an amide-type local anesthetic and is the most widely used local anesthetic in dentistry, often combined with epinephrine as a vasoconstrictor.
Lidocaine is an amide-type local anesthetic that blocks sodium channels to prevent nerve depolarization. It is available in 2% concentration with or without 1:100,000 epinephrine. Amide anesthetics are metabolized in the liver, making them safer for patients with ester allergies. Procaine and tetracaine are esters; benzocaine is a topical ester anesthetic.
Question 2: What is the recommended maximum dose of epinephrine in local anesthetic for a patient with cardiovascular disease?
- 0.04 mg (Correct answer)
- 0.2 mg
- 0.4 mg
- 1.0 mg
Correct answer: 0.04 mg
For patients with significant cardiovascular disease, the maximum dose of epinephrine is 0.04 mg (two cartridges of 1:100,000 epinephrine) per appointment.
Epinephrine is a vasoconstrictor added to local anesthetics to prolong duration and reduce systemic absorption. For healthy patients, the maximum is 0.2 mg per appointment. However, for patients with cardiovascular compromise, the ADA and AAOM recommend limiting epinephrine to 0.04 mg (approximately 2 cartridges of 1:100,000 epi) to avoid cardiac stimulation, hypertension, and arrhythmias.
Question 3: Which route of administration is used for nitrous oxide/oxygen sedation?
- Intravenous
- Inhalation (Correct answer)
- Intramuscular
- Oral
Correct answer: Inhalation
Nitrous oxide/oxygen conscious sedation is administered via inhalation through a nasal hood, making it an inhalation route of administration.
Nitrous oxide (N2O) combined with oxygen is delivered via a nasal hood inhalation device. It produces anxiolysis and mild analgesia while maintaining a conscious state. The patient retains protective reflexes and can respond to verbal commands. Recovery is rapid because N2O is eliminated through exhalation. The RDA must monitor the patient's respiration, color, and level of consciousness throughout the procedure.
Question 4: What should the RDA do FIRST if a patient develops syncope (fainting) during a procedure?
- Administer oxygen immediately
- Call 911
- Place patient in Trendelenburg (supine with feet elevated) position (Correct answer)
- Administer epinephrine
Correct answer: Place patient in Trendelenburg (supine with feet elevated) position
For syncope, the first step is to place the patient in the Trendelenburg position (supine with feet elevated above the heart) to restore blood flow to the brain.
Syncope (vasovagal fainting) is the most common medical emergency in the dental office. It results from a sudden decrease in cerebral blood flow due to peripheral vasodilation and bradycardia. The immediate action is to recline the patient to a supine position with legs elevated (Trendelenburg), which uses gravity to return blood to the brain. Oxygen may follow, and vital signs should be monitored. Calling 911 is reserved for unresponsive patients or those who do not recover promptly.
Question 5: Which of the following is a contraindication to the use of nitrous oxide sedation?
- Dental anxiety
- Obstructive nasal passages (Correct answer)
- Mild hypertension
- Fear of injections
Correct answer: Obstructive nasal passages
Obstructive nasal passages (e.g., severe nasal congestion, deviated septum) are a contraindication to nitrous oxide because the gas is delivered via nasal inhalation.
Nitrous oxide is delivered through a nasal hood, so any condition that impairs nasal breathing is a contraindication. These include nasal obstruction, chronic obstructive pulmonary disease (COPD — N2O can cause hypoxia), first trimester of pregnancy, recent middle ear surgery (N2O diffuses into closed spaces), and severe psychiatric conditions. Dental anxiety, fear of injections, and mild hypertension are actually common indications for N2O sedation.
Question 6: What percentage of oxygen is included in a nitrous oxide/oxygen sedation mixture at minimum?
- 10%
- 20% (Correct answer)
- 30%
- 50%
Correct answer: 20%
The minimum oxygen concentration in a nitrous oxide/oxygen sedation mixture is 20% (equal to or greater than atmospheric oxygen), ensuring the patient does not experience hypoxia.
Modern nitrous oxide delivery units have a fail-safe mechanism that prevents the oxygen concentration from falling below 20% (some machines are set at 30% minimum). This safeguard prevents hypoxic mixtures from being delivered. Typical sedation mixtures range from 30–50% N2O with the remainder being oxygen. At the end of the procedure, the patient must breathe 100% oxygen for at least 3–5 minutes to prevent diffusion hypoxia.
RDA Assisting with Administration of Anesthesia and Sedation 2
Which local anesthetic agent is classified as an amide and is the most commonly used in dentistry?