|Sedation in Dentistry|
Four stages of anesthesia:
4. Respiratory paralysis
IV sedation and Nitrous oxide
results in a patient in stage I.
Dinh X. Bui, D.D.S., M.S.
Sedation in Dentistry
Sedation in dentistry is the art and science dealing
with management of fear, anxiety, and pain by influencing
the state of consciousness in a patient by the use
of drugs. As a periodontist performing full mouth
reconstruction, I believed that sedation is a very
integral part of dental treatment. It not only allows
the dentist to provide anxiety management to his patient
and better prepare him or her for the medical compromise
population, but most importantly, the dentist became
very efficient in the field of emergency dental medicine
due to his knowlege of advance cardiac life support,
airway management, and the pharmaceutical action and/or
mechanism of those procedures in emergency medicines.
It allows the dentist to operate in a very relaxing
situation, knowing that his or her patient is not
in any kind of pain or discomfort during even the
most complicated dental procedure. It should be noted
that term sedation must be differentiated from general
anesthesia. Sedation is the calming of a nervous,
apprehensive individual through the use of a drugs,
without inducing the loss of consciousness. General
anesthesia is the elimination of all sensation, accompanied
by loss of consciousness. Sedation is one of the stages
of general anesthesia in which the patient is still
conscious but under the influence of a drug. The term
conscious means the patient is capable of an appropriate
response to command, with protective reflexes intact,
including the ability to maintain the patent airway.
In sedation, patient may or may not amnesic depends
on the type of drug used in sedation.
What are the stages of general
Four stages of general anesthesia
is classified by Guedel as:
- Stage of analgesia
- Stage of delirium
- Stage of surgical anesthesia
- Stage of respiratory paralysis
Stage of analgesia, or stage I of anesthesia, is
characterized by the patient consciousness and his or
her ability to response to command and may or may not
become amnesic. It begins with the inital admininistration
of CNS depressant drug and continues until the patient
loses consciousness. In this stage, pain and pain threshold
may be present and unaltered, however, the patient's
response is diminished. All the techniques of oral,
rectal, intramuscular, submucosal, inhalation, and intravenous
sedation, results in a patient in stage I, i.e., stage
Stage II, or stage of delirium or excitement, begins
with the patient lose consciousness from stage I. Early
in stage II, the breathing patern may become irregular,
reflexes may be exaggerated and there is a tendency
to overreact to stimulation. In response to stimulation
(such as pain), the patient will cry out and attempt
to move the extremities. However, he or she suffers
from amnesia and will not remember these activities.
As stage II deepen, the breathing becomes more regular,
with lateral nystagmus (eyeballs oscillate involuntarily),
normal pupil reaction to light, muscle tonus first increase
at early stage II and more relax in deep stage II, and
finally the laryngeal and pharyngeal reflexes become
more obtunded as stage II deepens. When performing intravenous
sedation, entry into stage II should be avoided as it
is the sign of oversedation.
Stage III is the stage of surgical anesthesia.
In this stage, the respiration becomes regular, automatic
and involuntary. Muscular tonus is lost with patient
head and mouth can be manipulated with ease. This stage
is furthered divided into four planes by Gillespie in
1943. The following summarizes these planes. Plane 1
is characterized by full, regular, automatic respiration,
nystagmus and normal pupil response, swallowing and
vomiting reflexes disappear, and finally, tears are
secreted throughout plane 1. Plane 2 characterized with
cease of nystagmus, thoracic respiration decrease, depth
of breathing diminished, and tidal volume decrease.
Laryngeal closure disappear, respiratory response to
skin incision disappears, and secretion of tears diminishes.
Plane 3 is entered when thoracic respiration decreases
and abdominal respiration increases. Inspiration now
is shorter duration than inhalation. Tidal volume decreases.
Plane 4 begins with the paralysis of intercostal muscle
until the arrest of respiration. Diaphragm weaken until
spontaneous breathing ceases entirely. No muscle tonus
and pupils dilate.
Stage IV is the stage of respiratory paralysis
(medullary paralysis). This is usually encountered when
there is drug overdose. Management of patient in stage
IV is basic and advance cardiac life support and oxygen
When we perform intravenous sedation in our office,
we always stay in stage I. I preferred my patient to
be relaxed and stable, with anterograde amnesia (with
the use of Midazolam or Versed). He or she should be
conscious but coperative with the vital signs barely
altered, protective reflexes are intact, and most importantly,
the patient is able to maintain a patent airway.
What is nitrous and how does
Nitrous oxide is a nonirritating, nonallergenic, sweet-smelling,
colorless gas. It is the least potent of the anesthetic
gases. However, it is absorbed rapidly from the lungs
into the cardiovascular system. The higher the concentration
of gas inhaled, the more rapidly the arterial tension
of that agent increase. N2O replaces N2 in the blood
and this occurs within 3 to 5 minutes from the onset
of nitrous oxide administration. This is why the patient
should be remained at a given level of nitrous for 3-5
minutes before increasing the N2O concentration. Also
at the completion of nitrous oxide administration, patient
should be allowed to breath 100% oxygen for at least
3-5 minutes to avoid the phenomenon of diffusion hypoxia.
Diffusion hypoxia refers to rapid diffusion of N2O from
blood back into the alveoli (reverse of the beginning)
and is responsible for the headache, nausea, and lethargy
after nitrous oxide administration. The common term
for it is "hang over".
At the therapeutic level, nitrous oxide does not
depress the central nervous system. However, it depresses
all forms of sensation included sight, hearing, touch,
and pain. Memory is affected only to slight degree,
as is concentration and thinking. Nausea and vomitting
are very uncommon unless diffusion hypoxia occurs. There
is no changes in heart rate or cardiac output. Blood
pressure should be stable with an insignificant drop
due to vasodilation. Nitrous oxide is not irritating
to the pulmonary epithelium and therefore it can be
used in asthmatic patient. Change in breathing rate
or depth is due to the sedation effect. Nitrous oxide
has no significant effect on gastrointestinal tract
and kidney. Moreover, it can be used on pregnant women.
There is no contraindication to the use of nitrous oxide
as long as minimum of 25% oxygen is supplied. Finally,
to answer the similar question toward oxygen, the inhalation
of 100% oxygen has no effect on central nervous system,
with a slight fall in heart rate and cardiac output,
slight increase in diastolic, no change in systolic
and blood pressure. Breathing 100% oxygen for 2 minutes
slightly depresses the minute volume.
Our office, Cosmetic Dentist of Katy, is equipped
with nitrous oxide and oxygen provided for every operatory.
The monitoring equipments includes EKG, pulse oxymeter,
and real time blood pressure/temperature monitor. We
also have a mobile unit and the oxygen crash cart for
What is intravenous sedation
and how does it work?
Intravenous sedation is a procedure
of which sedation is achieved with the drug administered
via parenteral. It is beneficial because the rapid onset,
ability for drug titration for the desired clinical
effect, easily application of emergency medicine as
we have the IV line already established. The dangerous
effect is due to the rapid onset, the action of the
drugs are more pronounced. As mentioned above, the rapid
onset of the drugs allows the dosage to be tailored
to fit the need of the patient. The level of sedation
can be fine tuned, and also the recovery of the intravenously
administered drugs will be significantly shorter than
any other route except for nitrous oxide administration.
The patient vein is maintained during the entire procedure
to facilitate injection of any drugs and also for emergency
drugs should the complication arises. The side effect
of nausea and vomiting are very uncommon with IV sedation,
as is the gag reflex, motor disturbance (seizure). The
salivary secretion can be controlled easily by addition
of other medication through IV. Disadvantages are the
procedure of venipuncture, thrombophlebitis may occur
at the venipuncture site, and more intensive monitoring
process required. Recovery from IV drugs is not complete
at the end of dental treatment and patient must be escorted
to and from the dental office by a responsible companion.
Keep in mind that it is not easily reversed the intravenous
drug. The rule of thumb is try NOT to over sedate
the patient if possible.
Contraindication for IV sedation are:
- Dentist must be trained and certified in performing
- Pregnancy is relative contraindication because
most CNS depressant will cross the placenta into the
fetus and may produce birth defect
- History of significant hepatic disease is a
contraindication due to the fact that liver is the
place where the drugs undergo biotransformation thus
the effect of medication might be prolonged or profounded.
- Thyroid dysfunction is a relative contraindication
for the use of IV sedation. Hypothyroid patient are
particularly sensitive to CNS depressants such as
sedative hypnotic, antianxiety agents, and narcotic
analgesic. Clinically hypothyroid patient should not
be IV. Hyperthyroid patient, on the other hand, is
very extremely difficult to sedated due to the high
metabolism and heart rate. Atropine and scopolamine
therefore should be avoided in these patients.
- Adrenal insufficiency, as in patients who received
chronic corticosteroid therapy or those of Addison's
disease, is a relative contraindication for the use
of IV sedation. They will not be able to handle the
stress thus light to moderate sedation only is recommended.
- Patients with MAOIs or tricyclic antidepressants
should be carefully evaluated for potential synergistic
action with narcotic agonist and barbiturates.
- IV sedation is not contraindicated in patient
with psychiatric disorders
- Obsese patient may pose the venipunture problem
and also the decrease in cardiovascular and pulmonary
reserves. Other forms of sedation (such as nitrous)
should be considered first.
- IV sedation is contraindicated if the patient
is allergic to the drugs used in sedation. Patient
may experience asthma with the narcotics and barbiturates
and pophyria with the barbiturates. Other contraindication
is the use of anticholinergics in glaucoma and prostatic
In summary, IV sedation provides amnesia
(use of midazolam, diazepam) and anxiety management
which are desired in a complicated dental procedure.
However, even though IV sedation is a very effective
form of sedation, I only employed the sedation when
there is a specific indication for it. After all, the
best patient is the patient that can be managed without
the use of any drugs. I have removed countless number
of complete bony third molar extraction under just local
anesthesia, and the patient behaves very well (Over
500 cases, perhaps only two or three cases with IV sedation).
I performed IV sedation on numerous medical compromises
patients of which the stress reduction protocol is mandatory.
I choose a narcotic agonist and a sedative hypnotics,
in conjunction of oxygen administration. My favorite
narcotic agonist is meperidine (Demerol) and that of
the sedative hypnotics is midazolam (Versed).
What do we expect from the
drug interaction and the intravenous procedure using
Midazolam (Versed) is a benzodiazepine. Its average
sedative dose is 2.5-7.5mg. Its maximal dosage is 10mg.
It posesses several favorable characteristic such as
anterograde amnesia (patient will not remember from
the point of administration on), short duration (1 hour
typical), and has minimal effect on cardiovascular and
respiratory system. Its most usual side effect is dizziness.
The medical history of the patients receiving diazepam
should be checked for benzodiazepine allergy, acute
pulmonary insufficiency, and respiratory depression.
Meperidine (Demerol) is a narcotic agonist which
is the most frequently used IV narcotic in dentistry.
Its onset is approximately 2-4 minutes, and its duration
of action is 30-45 minutes. The recommended dose is
50mg (maximum), with the average sedative dose is 37.5mg-50mg.
Meperidine produce atropine properties such as reduction
of salivary secretion and increase heart rate (minimal
with 50mg maximal dose). The notable side effect of
meperidine is the phenomenon of "tracking",
i.e., the skin overlying the vein into which meperidine
is injected will appear red and iching is present. The
reddening may continue following the path of the vein.
Management of meperidine-induced histamine release is
simply to allow it to dissipate spontanneously, which
occurs over the next 10-15 minutes. The medical history
of patiets receiving meperidine should be checked for
narcotic anagesics allergy, MAO inhibitors taken within
14 days (synergistic effect), Asthma, and COPD and decreased
I always preferred to use EKG, pulse oximeter,
and real time blood pressure on the intravenous sedation
of patient. Oxygen administration is mandatory (in my
opinion) as to maintain oxygen saturaion pressure at
96-99%. Most importantly, the medical history should
be screen and checked with the patient carefully prior
to any sedation procedure.
These points of discussion reflect
Dr. Bui's view point on the topic of sedation in dentistry.
He has been performing intravenous sedation since 1998.
He is certified in oral, inhalation, IM, and IV sedation.
His office equipped with EKG, pulse oxymeter, real time
blood pressure and temperature monitor, and finally,
oxygen and nitrous are plumbed to every operatory.