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Questions and Answers
What is the recommended approach to drug dosing?
How does a patient's health status influence drug dosage?
What does MRD stand for in the context of drug dosing?
What is the potential risk when exceeding the MRD?
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Which of the following groups may be at higher risk for overdose?
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In which scenario is the use of postoperative opioid analgesics considered to be less necessary?
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What population is generally advised against the use of postoperative opioids due to risks associated with self-mutilation?
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Why are opioids rarely indicated for children in the context of postoperative pain management?
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What is a relative contraindication for opioid use in postoperative pain management?
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How does the requirement for postoperative opioid analgesics in certain patients compare to general expectations?
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Why is the use of ADH analog contraindicated in pregnancy?
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What potential effect does ADH analog have on uterine blood flow during pregnancy?
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What is a major risk associated with the use of ADH analog in pregnant women?
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Which statement best describes a reason for the contraindication of ADH analog in pregnant patients?
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In terms of pregnancy safety, which of the following is a concern regarding ADH analog?
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What is the effect of increased irritability of pacemaker cells?
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Which of the following dysrhythmias is commonly associated with increased irritability of pacemaker cells?
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What happens to systolic blood pressure when there is increased irritability of pacemaker cells?
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Which of the following is NOT commonly a result of increased irritability of pacemaker cells?
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What contributes to the occurrence of premature ventricular contractions (PVCs) in patients with increased pacemaker cell irritability?
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What is the effect of adding epinephrine to prilocaine?
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Which of the following statements is true about prilocaine when used without a vasoconstrictor?
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What is the dilution of epinephrine typically used with prilocaine for prolonged anesthesia?
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Which of these anesthetics is comparable to prilocaine in terms of efficacy when used without a vasoconstrictor?
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What characteristic distinguishes the use of prilocaine with epinephrine?
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What is a key property of Articaine HCl?
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Which statement about Articaine is true?
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How does Articaine compare to other local anesthetics regarding tissue diffusion?
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Which of the following is NOT a characteristic of Articaine HCl?
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In what way does Articaine enhance its effectiveness in clinical settings?
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Study Notes
Dental Anaesthesia Study Notes
- Dental Anaesthesia: Provided by Dr. Omar Hraibat
- Contact Information: WhatsApp 0792149318
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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.
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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).
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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.
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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).
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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.
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Description
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.
