The preoperative visit usually
involves the following actions:
- Review of medical history, family history and social
habits
- Physical examination
- Request for additional examinations
- Risk assessment
- Explanation of the GA procedure and risks
- Informed consent form
- GA procedure planning
- Prescription of premedication
- Pre-operative instructions
The first step of the pre-anesthetic
evaluation is the review of the patient’s medical history (health conditions
and medications), family history, and social history.
Medical History
Reviewing of the past medical
history of the patient is an essential part of the preparation for general
anesthesia. Your dentist anesthesiologist needs to know about your past and
present health conditions.
The existence of diseases such as
asthma, diabetes, tuberculosis, seizures or any chronic major organ
dysfunction, but particularly diseases of the cardiovascular and respiratory
systems, is a significant factor in deciding if a patient is a suitable
candidate for general anesthesia, or which anesthetic drugs should be used.
Identification of pregnancy in the
first trimester is a contraindication to GA due to the risk of teratogenicity.
Pregnant women are generally at a higher risk of regurgitation and aspiration
of gastric contents during general anesthesia. It is also generally agreed that
the elderly are subject to increased risks of anesthesia.
Previous anesthesia history -
Adverse reactions to anesthesia
Your dentist or anesthesiologist
must be notified if you (or any other member of your family) have a history of
problems or adverse reactions to general anesthesia, such as allergic
reactions, intubation problems, anesthesia awareness during GA, or
postoperative nausea and vomiting. Several related problems are caused by
hereditary disorders which need special attention.
Medications usage
Several common medications may
interact with anesthesia drugs either enhancing or reducing their effect.
Failure to fully disclose medication usage can increase the risks associated to
general anesthesia, because many drug interactions can be potentially dangerous.
Provide the dentist anesthesiologist
with a full list of all the medications you take regularly (both prescription
and over-the-counter medications), and any other medication you may have taken
in the last days. Do not forget to include in the list and any herbal products,
natural supplements or alternative medicines you take, because some of them
(e.g. valerian, and ginseng) can also interact with certain general anesthesia
drugs. Your dentist must also know about any allergic reactions you've had to
medicines in the past.
The anesthesiologist will advise you
if you have to adjust the dosage or suspend taking certain medications prior or
after the general anesthesia procedure.
Family history – Hereditary problems
Some hereditary conditions can cause
dangerous complications during general anesthesia, if the anesthesiologist is
not made aware of them. Family medical history is useful in identifying
possible hereditary conditions such as:
- Malignant hyperthermia. Malignant hyperthermia (MH) is
an inherited disorder with a high mortality rate, which may occur during
GA causing uncontrolled rise of body temperature.
- Porphyria. A rare hereditary blood disorder in which
the hemoglobin is abnormally metabolized, resulting in excessive
production of porphyrins. The condition may be triggered by some drugs
used in GA such as barbiturates.
- Suxamethonium apnea. It is a rare condition where the
patient’s body metabolizes very slowly the drug suxamethonium
(succinylcholine) which is used in general anesthesia procedures as a
muscle relaxant. As a result the patient may remain paralyzed and unable
to breath for longer periods, requiring ventilation support.
Social history and habits (smoking,
alcohol, drug usage)
Patients with social habits such as
smoking, alcohol or drug usage are more susceptible to complications during or
after GA. Any such usage must be disclosed to the dentist anesthesiologist in
order to adjust accordingly the anesthesia planning (drug selection and
dosage), or suggest another alternative solution.
- Smoking. Smoking has negative effects on the
respiratory tract and function, reducing the oxygen-carrying capacity of
the blood, and increasing the incidence of respiratory infection and
postoperative respiratory morbidity. Patients should stop smoking for at
least 12 hours before anesthesia (ideally they should stop smoking for 6
weeks before anesthesia) to reduce this risk.
- Alcohol. Regular consumption of alcohol may have caused
liver damage affecting the metabolism and lead to tolerance to anesthetic
drugs.
- Drug abuse. Except of the obvious problem due to drug
interactions, other issues for general anesthesia in drug abusers include
possible inadequate venous access and increased risk for existence of
infectious diseases such as HIV or hepatitis. Drug and alcohol abusers are
at a much higher risk of anesthesia awareness.
Physical examination
A full physical examination is
important to complement the preanesthetic evaluation. The dentist
anesthesiologist will particularly focus on the patient's airway, inspecting
the mouth and pharynx soft tissues, and neck’s flexibility. The patient will
also be checked for loose teeth, dentures, or crowns.
The vital signs of the patient (e.g.
blood pressure, heart rate, oxygen saturation) will be checked and recorded. A
more extensive physical examination may be required for medically compromised
patients.
Request for additional examinations
Although healthy patients under 40
years old may not require further preanesthetic examinations, a blood and urine
test, and a chest x-ray are typically recommended. These tests can reveal
conditions related to the lung, heart, liver, or kidney function, diabetes or
other problems that the patient may be unaware of.
Additional examinations may be asked
for patients with a history of health conditions, in order to determine their
exact health status.
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