Restrictions on Vasoconstrictors
The use of anesthetic drugs containing vasoconstrictive components requires special vigilance. Ignoring the medical history can lead to life-threatening conditions. Drugs with vasoconstrictors are not recommended if the patient has been diagnosed with the following pathologies:
- Severe forms of cardiovascular diseases (including sinus bradycardia and paroxysmal tachycardia).
- Angle-closure glaucoma.
- Serious endocrine disorders, such as diabetes mellitus or thyrotoxicosis.
The administration of a vasoconstrictor in itself can provoke a sharp increase in heart rate, excessive sweating, and a specific reactive state. These factors can act as a trigger for the development of an emergency.
Excipients and the Risk of Acute Reactions
Often, the cause of acute conditions, including asthma attacks and anaphylaxis, is not the anesthetic itself, but the auxiliary additives in the carpule or ampoule. Each of these components carries specific risks.
| Component | Role in the solution | Potential risks and side effects |
|---|---|---|
| Sodium sulfite | Antioxidant. Binds free oxygen, protecting the vasoconstrictor from degradation. | Causes allergy, sudden sweating, tachycardia, asphyxia. Particularly dangerous in hormone-dependent asthma and sulfur sensitivity. |
| EDTA (Sodium Edetate) | Chelating agent. Binds heavy metal ions (tin, aluminum) from the glass of ampoules. | At high concentrations, causes nausea, vomiting, headache, and a sharp deterioration in well-being. |
| Methylparaben | Preservative of the paraben group. | Provokes cross-allergy in individuals with intolerance to PABA derivatives (procaine, furosemide, sulfonamides). |
A patient's history of allergy to para-aminobenzoic acid derivatives is an absolute contraindication to the use of paraben-containing drugs.
Pharmacokinetics of Sympathomimetics
To prevent systemic complications, it is necessary to consider the pathways of distribution of adrenaline and noradrenaline in the patient's body:
- Blood-Brain Barrier (BBB): Sympathomimetics are unable to penetrate this barrier into the structures of the central nervous system.
- Placental Barrier: The drugs freely cross the placenta, affecting the fetus.
- Lactation Period: Active substances are excreted in breast milk.
The clinical significance of these features lies in the need for extremely careful selection of local anesthesia when treating pregnant and breastfeeding women.
Topical Anesthesia as a Safe Alternative
To minimize systemic risks during minimally invasive procedures, topical or surface anesthesia (from Latin applicatio — application) is used. This method ensures the psychological comfort of both the patient and the doctor.
The mechanism of action consists in impregnating the superficial layer of the oral mucosa or skin. Due to the high concentration of the active substance, the drug rapidly penetrates to a depth of 2–3 mm, blocking peripheral nerve fibers. The most important feature of such solutions, ointments, gels, and films is the complete absence of vasoconstrictors, which eliminates many cardiovascular risks.
Indications for use:
- Extraction of mobile permanent or deciduous teeth.
- Opening of superficial submucosal abscesses.
- Painful manipulations at the gingival margin and on the oral mucosa.
- Anesthesia of the site prior to needle injection.
It should be remembered that using a physical method of anesthesia (severe cooling due to the spraying and evaporation of ethyl chloride) in the oral cavity is inadvisable. This is due to the high risk of aerosol aspiration into the respiratory tract and negative impact on intact teeth.
Fundamentals of Safety and Dosage Selection
The foundation of local anesthesia safety is the appropriate choice of drug and precise calculation of its dosage. To prevent the development of emergencies, the doctor must consider:
- The planned scope of the surgical intervention.
- Patient's age.
- The functional characteristics of the systems responsible for the biotransformation and elimination of the anesthetic from the body.
Patients from risk groups require special caution: pregnant women, children, overweight individuals, elderly and senile patients, as well as those with concomitant systemic pathologies.
Briefly: answers to topical questions
What are the clinical signs of impending hypoglycemic coma in a patient with diabetes mellitus during a dental procedure?
The clinical picture of impending hypoglycemic coma develops rapidly and includes two main groups of symptoms. Autonomic and adrenergic precursors include a sharp feeling of hunger, general weakness, increased sweating, muscle tremor, palpitations, skin pallor, and pupillary dilation. Neuroglycopenic signs are caused by glucose deficiency in the central nervous system and manifest as dizziness, headache, impaired concentration, movement coordination disorders, confusion, drowsiness, and paresthesias.
To remember drugs that cause cross-allergy with methylparaben (PABA derivatives), use the acronym: «Patient Cannot Function Properly» (PABA, Procaine, Sulfonamides, Furosemide) [Note: translated conceptually to English medical mnemonic if applicable, but keeping sense].
Class and exam questions
Do vasoconstrictors from the carpule cross the blood-brain barrier?
No, sympathomimetics do not cross the BBB, however, they freely cross the placental barrier and are excreted in breast milk.
Why do patients with bronchial asthma need careful anesthetic selection?
Solutions often contain the antioxidant sodium sulfite, which in individuals with hormone-dependent asthma can provoke an allergy, tachycardia, and an asthma attack.
Can ethyl chloride spray be used for mucosal anesthesia in the oral cavity?
This is inadvisable. The use of cooling sprays carries a high risk of their aspiration into the respiratory tract and can damage intact (healthy) teeth.
What else to study on this topic
- Features of the biotransformation of local anesthetics in the liver and blood plasma.
- Detailed drug selection protocols for patients with cardiovascular pathology.
- Mechanisms of allergic reactions to paraben preservatives.
- Principles of calculating a safe anesthetic dose taking into account the patient's body weight and age.
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Other topics in "Chapter 4. Anesthesia in Oral Surgery (S.A. Rabinovich, S.T. Sokhov)"
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