Dental Anaesthesia Study

Dental Anaesthesia Study Notes

• Dental Anaesthesia: Provided by Dr. Omar Hraibat
• Contact Information: WhatsApp 0792149318
• Vasoconstrictors in Local Anaesthetics:
  • Vasoconstrictors are used to oppose the vasodilatory effects of local anaesthetics, reducing blood flow and absorption rate.
  • This reduces the risk of LA toxicity and increases the duration of action for local anaesthetics.
  • Vasoconstrictors also help to decrease bleeding at the site of treatment, which is useful during surgical procedures.
  • Common vasoconstrictors include epinephrine, norepinephrine, and dopamine.
• Types of Vasoconstrictors:
  • Catecholamines: Chemically similar to sympathtic nervous system mediators (e.g., epinephrine, norepinephrine, levonordefrin, isoproterenol, dopamine).
  • Noncatecholamines: Amphetamine, methamphetamine, ephedrine, mephentermine, hydroxyamphetamine, metaraminol, methoxamine, phenylephrine (a synthetic analog of vasopressin or ADH).
• Pharmacologic Actions:
  • Myocardium: Stimulates beta-1 receptors increasing the force and rate of contraction (positive inotropic, positive chronotropic).
  • Pacemaker Cells: Stimulates beta-1 receptors, increasing irritability, and can cause dysrhythmias (ventricular tachycardia, premature ventricular contractions).
  • Blood Pressure: Usually raises systolic pressure and lowers diastolic pressure.
  • Vasculature: Causes peripheral vasoconstriction (alpha-1).
  • Bronchial Dilation: Causes dilation via beta-2 receptors.
  • CNS: If crosses blood brain barrier (BBB), may exert an effect on the central nervous system.

Modes of Action

• Direct-Acting Drugs: Directly activate adrenergic receptors (alpha and beta).
• Indirect-Acting Drugs: Release norepinephrine from adrenergic nerve terminals.
• Mixed-Acting Drugs: Exert both direct and indirect actions on adrenergic receptors.
  • Epinephrine acts on both alpha and beta receptors and is often most preferred for dentistry.

Epinephrine Overdose Symptoms

• CNS Stimulation: Fear, anxiety, tension, restlessness, throbbing headache, tremor, weakness, dizziness, pallor, respiratory difficulty, and palpitation.
• Cardiac Dysrhythmias: Ventricular fibrillation is a possible consequence, especially in cases of overdose.
• Dramatic Blood Pressure Increase: Systolic and diastolic blood pressure increases dramatically (may lead to cerebral hemorrhage).
• Anginal Episodes: Increased risk in patients with coronary artery insufficiency.
  • Toxic reaction is usually brief due to rapid inactivation of epinephrine.

Clinical Implications of pH and Local Anesthetic Activity

• Most LA without a vasoconstrictor have a pH between 5.5 and 7.
• Injecting into tissue causes the pH to return to the normal 7.4.
• Adding sodium (meta)bisulfite to LA containing epinephrine may retard oxidation, increasing the effectiveness and shelf-life of the drug.
• pH of LA containing epinephrine may range from 2.8 to 5.5.
• Buffering capacity of tissues tends to maintain normal tissue pH, requiring a longer period for maximum effectiveness of the LA.

Dilutions of Vasoconstrictors

• Allowed doses of local anesthetics and vasoconstrictors are low.
• Dilute in a solvent to easily dispense (ratio e.g., 1:1000).
• 1:1000 means 1 gram of solute is present in 1000 mL of total solution.
• 1 mg = 1000 mcg or µg
• It is often better to use 1:100,000 dilution instead of 1:1000 to reduce the dose.

ASA Classification

• This is a risk-stratifying system for assessing the risk of surgical procedures, evaluating preoperative risks, and helps select the appropriate surgical procedure as well as dosages.

Contraindications to Vasoconstrictors

• Significant cardiovascular disease (ASA 3 and 4)
• Thyroid dysfunction (mainly hypothyroidism)
• Diabetes mellitus
• Sulfite sensitivity
• Patients receiving MAO inhibitors, tricyclic antidepressants, and phenothiazines.
• Severity of disorder should inform the use of vasoconstrictors.

Local Anesthetic Selection

• This selection depends on the duration of pulpal/soft tissue anaesthesia needed, potential self-mutilation, postoperative pain management, and hemostasis.

Local Anesthetic Duration of Action

• Short Duration: Pulpal anaesthesia approximately 30 minutes (Mepivacaine HCl 3%)
• Intermediate Duration: Pulpal anaesthesia approximately 60 minutes (Prilocaine HCl 4%, Articaine HCl 4% + epinephrine 1:100,000, 1:200,000, Lidocaine HCl 2% + epinephrine 1:50,000, 1:100,000, Mepivacaine HCl 2% + levonordefrin 1:20,000, Prilocaine HCl 4%).
• Long Duration: Pulpal anaesthesia approximately 90+ minutes (Bupivacaine HCl 0.5% + epinephrine 1:200,000).

Lidocaine Preparations

• 2% Lidocaine with 1:100,000 epinephrine is preferred for most procedures
• Lidocaine hydrochloride or base is available in various topical forms, 5% base, 2% hydrochloride.

EMLA Cream

• A eutectic mixture of lidocaine and prilocaine (2.5% of each)
• Topical use, applied one hour prior to procedure and lasts 1-2 hours.
• Can be used prior to injection for pain relief if needle phobic patient.

This quiz covers essential concepts in dental anaesthesia, particularly focusing on the role of vasoconstrictors in local anaesthetics. Learn about different types of vasoconstrictors, their mechanisms, and clinical applications. Enhance your understanding of how these agents improve patient safety during dental procedures.