Local anesthetics

Avoiding local anesthetics: indications for general anesthesia

In outpatient dental practice, the decision to switch from local anesthesia to general anesthesia is made by the anesthesiologist. There are several key factors predetermining this choice:

• Allergic reactions. Any history of allergic manifestations to the administration of a local anesthetic (ranging from skin rash, pruritus, and hyperemia to a drop in blood pressure and anaphylactic shock).
• Hypersensitivity (toxicity). Development of clinical symptoms of intoxication even upon administration of a standard therapeutic or reduced dose of the drug.
• Ineffectiveness or impossibility of local injection. Local anesthetics may fail in foci of purulent inflammation. Furthermore, performing adequate local anesthesia is difficult in the presence of pronounced tissue scar changes or anatomical defects.
• Patient's mental status. Overwhelming fear of the procedure, panic at the sight of instruments, as well as mental disability (e.g., oligophrenia or sequelae of meningitis).
• Scope of the procedure. High invasiveness of the procedure and surgical interventions in infants and toddlers.

Specifics of outpatient anesthesia and preparation

Outpatient general anesthesia has a number of strict limitations. The drug must ensure rapid induction and recovery (post-anesthesia period no longer than 1–1.5 hours), cause no severe side effects, and be non-explosive. A specific feature of dental appointments is the sitting or semi-recumbent position of the patient, which requires mandatory isolation of the pharynx with a gauze or foam sponge to protect the trachea from the aspiration of blood and saliva.

Mandatory minimum examination:

1. Collection of a detailed anamnesis (past illnesses, medication use, bad habits).
2. Measurement of blood pressure and pulse rate.
3. Performance of basic respiratory tests.
4. Verification of the time of the last meal (strictly on an empty stomach).
5. For women — clarification of pregnancy status and menstruation dates (risk of collapse in case of blood loss).

In outpatient settings, pharmacological preparation (premedication) is minimized. Hypnotics and narcotics are undesirable. Patients with a labile psyche are prescribed minor tranquilizers 2–3 days prior, and 45 minutes before the procedure, atropine sulfate (0.1% solution) is administered subcutaneously to suppress glandular secretion and relieve vagal tone.

Inhalational anesthetics

For mask anesthesia in outpatient settings, several groups of volatile liquids and gases are used:

• Dinitrogen oxide (nitrous oxide). The safest colorless gas. It does not depress respiration and circulation, but does not provide deep sleep or relax the masticatory muscles. It is used in the stage of analgesia for minimally invasive procedures (extraction of 1–2 teeth, opening of abscesses).
• Halothane (Fluothane). A potent anesthetic, 50 times superior to nitrous oxide. It excellently relaxes the masticatory muscles, but can cause bradycardia and a decrease in blood pressure. It is dangerous due to rapid overdosage.
• Trichloroethylene. Possesses a strong analgesic effect and induces amnesia. It preserves the tone of the floor of the mouth muscles and pharyngeal reflexes, which minimizes the risk of aspiration.
• Cyclopropane. A gas that can be used in diabetes and liver diseases. Its main and critical drawback is the formation of explosive mixtures. It is strictly forbidden to use a dental drill, electrosurgical unit, and any sparking devices while working with it.

Intravenous drugs and neuroleptanalgesia

Classical barbiturates (hexobarbital, thiopental sodium) are extremely rarely used in outpatient clinics due to the risk of laryngospasm and prolonged secondary sleep.

Instead, preference is given to ultra-short-acting drugs:

• Propanidid (Sombrevin). Sleep occurs in 15–30 seconds and lasts up to 4.5 minutes. Ideal for short-term tooth extractions and opening of phlegmons. The patient can be discharged home as early as half an hour after waking up. The disadvantage is poor controllability.
• Ketamine. Provides a rapid effect, widely used in maxillofacial surgery.
• Fentanyl. An analgesic 100 times stronger than morphine. It can depress respiration and cause bronchospasm. All side effects are reversed by a specific antidote — nalorphine.
• Dehydrobenzperidol (Droperidol). A neuroleptic with a strong antiemetic and hypotensive effect. It suppresses reflexes but does not cause bronchospasm.

The combination of potent analgesics (e.g., fentanyl or tramadol) with tranquilizers (diazepam) allows for ataralgesia — a state of deep calmness and pain relief while maintaining spontaneous breathing.

Class and exam questions

What else to study on this topic

• Complications of inhalation anesthesia in outpatient practice.
• Influence of concomitant diseases on the choice of anesthetic.
• Features of the use of muscle relaxants in maxillofacial surgery.
• Mechanisms of potentiation in neuroleptanalgesia and ataralgesia.
• Pharmacokinetics of ultra-short-acting barbiturates.

Other topics in "Chapter 12. Dental Anesthesia"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.