APC 102

Local Anesthetic Cautions

• Injection into a blood vessel
• Infected area
• Localized toxic reaction
• Systemic toxic reaction
• Temporary numbness
• Paresthesia

How is injection of local anesthesia into a blood vessel prevented?

Why is infiltration of local anesthesia into an infected area not advised? ([1] Inadequate anesthesia resulting from the different pH of infected tissue and [2] the risk of spreading infection.)

What is paresthesia? (Loss of feeling—numbness that lasts beyond the expected duration of the local anesthetic.) 

Inhalation Sedation

• Nitrous oxide/oxygen (N²O/O²) is a combination of gases inhaled by the to help eliminate fear and to aid relaxation. 
• History
  • The use of nitrous oxide dates back to 1844.
  • Dr. Horace Wells was the first to use nitrous oxide on patients. 
• Effects
  • N²O/O² is nonaddictive.
  • Onset is easy, side effects are minimal, and recovery is rapid.
  • N²O/O² produces stage I anesthesia. 
  • N²O/O² dulls the perception of pain. 

Why should local anesthesia always be used in conjunction with nitrous oxide? 

Although nitrous oxide and oxygen are nonaddictive, dental professionals and members of the public may easily become addicted to the feeling they experience when they inhale this gas. 

Advantage of Using N_²O/O_²

• Administration is simple and
  easily managed.
• The services of an anesthetist or other special personnel are not required.
• N_²O/O_² has an excellent safety record.
• Side effects are minimal.
• The patient is awake.
• Recovery is rapid.
• N_²O/O_² can be used with patients of all ages.

It is important for the patient to remain awake throughout administration to permit proper titration of the gases according to the patient’s signs and symptoms.

When administering nitrous oxide to a child, make sure to have children’s nasal masks available. Regardless of the patient’s age, a qualified dental team member should stay with the patient at all times. 

Contraindications to the Use of N_²O/O_²

• Pregnancy: first trimester
• Nasal obstruction: problems inhaling through the nose
• Emphysema: increased O_²
• Multiple sclerosis: breathing difficulties
• Emotional stability: altered perception
  of reality

What is an example of a common nasal obstruction? (Deviated septum.)  

In some medical conditions the use of N_²O/O_² is actually desirable because of the additional oxygen being delivered.

The dental assistant should also be familiar with the unit because he or she may be required to deliver pure oxygen to a patient in an emergency.

Inhalation Sedation Equipment

• Cylinders: Gases are dispensed from steel cylinders, which are colored green for O_² and blue for N_²O.
• N_²O machines are portable or part of the dental unit.
  • Control valves control the flow of each gas.
  • A flowmeter indicates the rate of flow of the gases. 
  • The two gases are combined in a reservoir bag, which the patient draws on for breathing.
• Gas hose 
  • Carries the gases from the reservoir bag to the mask or nosepiece. 
• Masks: supplied in sizes for adults and children
  • The nosepiece through which the patient breathes the gases
• Scavenger system
• Protection from the occupational risks of N_²O.

If portable units are in place, the valves are not usually opened unless the unit is about to be used.

Before the use of nitrous oxide, both cylinders should be checked for adequate remaining gas levels.

All parts of the delivery system should be in acceptable working condition. The reservoir bag should be checked frequently for leaks.

Be aware that a large amount of facial hair (especially a moustache) may interfere with an adequate seal of the nosepiece, decreasing the amount of the sedative delivered to the patient and perhaps increasing the amount of leakage to the surrounding environment and exposure to the dental team. 

A scavenger system is essential for safely gathering and disposing of any unused or exhaled nitrous oxide outside the building. 

Nitrous Oxide gas lines are color-coded.

What color represents nitrous oxide? (Blue.)

What color represents oxygen? (Green.) 

The metal plate in the wall is an outlet for the nitrous oxide and oxygen supplies, as well as an outlet for the scavenging system to prevent nitrous oxide from accumulating.

Exposure to Nitrous Oxide

• Used only for patient treatment
• Never administered for recreational purposes
• How to reduce N_²O hazards to dental personnel 
  • Use a scavenger system. 
  • Use a patient mask that fits well.
  • Discourage the patient from talking. 
  • Vent gas outside the building. 
  • Routinely inspect equipment and hoses for leaks. 
  • Use a monitoring-badge system to detect N_²O.

Why is it important to discuss with patients the steps in the administration of nitrous oxide, as well as what they may expect from the dental procedure itself, before beginning a procedure?

An office should have a schedule in place for routine inspection of nitrous oxide equipment for safety and maintenance.

Scavenger system attached to mask and evacuation
unit to redirect unused nitrous oxide gas.
(From Clark M and Brunick A: Handbook of nitrous oxide and oxygen sedation, ed 3, St Louis , 2008, Mosby.) (Courtesy of Accutron.)

This photo depicts the nasal mask that is placed over the patient’s nose to deliver nitrous oxide, in combination with the scavenging device that collects excess or exhaled nitrous.

It is important that the mask be placed with the corresponding end over the bridge of the nose for a proper fit.

The nosepiece is placed over the nose and the tubing is secured behind the headset of the dental chair.

Patient Preparation for Inhalation Sedation

• Review the patient’s health history.
• Obtain baseline vital signs.
• Describe the procedure of administering the gases. 
• Describe the use of the mask and the importance of nasal breathing. 
• Describe the sensations that the patient will experience. 
• Reassure the patient. 

Should the baseline vitals be recorded? If so, where? 

Discussing what the patients may or should expect, as well as addressing his other questions or concerns, will help avoid or alleviate any unwarranted anxiety during the procedure.

Assisting the Administration of Inhalation Sedation

• Start with pure oxygen while establishing the patient’s tidal volume.
• Slowly titrate the nitrous oxide until the desired results are achieved. 
• The patient should refrain from talking or
  mouth-breathing. 
• The N_²O/O_² analgesia should end with the administration of 100% O_² for 3 to 5 minutes. 
• Obtain postoperative vital signs and compare them with the preoperative recordings.  

The tidal volume is the amount of air inhaled and exhaled with every breath.

Starting with pure oxygen will help patients get accustomed to having the nasal mask in place and practice breathing through their nose.

What does inhaling 100% oxygen at the end of the procedure help prevent? (Diffusion hypoxia.)

Antianxiety Agents

• Sedatives are the drug of choice for physicians and dentists seeking to relieve anxiety in their patients. 
• Criteria for use
  • A patients is very nervous about a procedure. 
  • A procedures is long or difficult. 
  • The patient is mentally challenged. 
  • The patient is a very young child requiring extensive treatment.   

Antianxiety medications are used as an adjunct to dental treatment.

Patients with extreme dental fear may require this type of medication for the first few visits.

Anxiolytics are also sometimes prescribed to mentally challenged patients who may be  uncooperative.

Commonly Prescribed Sedatives

• Secobarbital sodium (Seconal)
• Chlordiazepoxide hydrochloride (Librium) 
• Diazepam (Valium) 
• Triazolam  (Halcion)
• Chloral hydrate (Noctec): for children

Diazepam is a benzodiazepine that is available in 2-, 5-, and 10-mg tablets; it may also be given intramuscularly, IV, or as an oral solution. 

Secobarbital is a sedative-hypnotic barbiturate, chlordiazepoxide a benzodiazepine, and chloral hydrate a sedative-hypnotic, used more often in pediatric dentistry.