Chapter 6 - Vasoconstrictors in Dentistry Flashcards
Q6-1: How do vasoconstrictors enhance the effects of local anesthetic drugs?
A6-1: Vasoconstrictors constrict local vessels, increasing safety by slowing systemic absorption. This constriction also prolongs the local actions of the drugs, provides hemostasis, and increases the profoundness of anesthesia.
Q6-2: When are vasoconstrictors useful in dental settings?
A6-2: Vasoconstrictors are useful in dental settings where long durations and more profound anesthesia are routinely required.
Q6-3: Name two vasopressors that are routinely included in dental local anesthetic drugs in North America.
A6-3: There are two vasoconstrictors, also known as vasopressors, which are routinely included in dental local anesthetic drugs in North America — epinephrine and levonordefrin.
Q6-4: Define epinephrine.
A6-4: Epinephrine is a naturally occurring catecholamine. It is both a hormone and a neurotransmitter. It is a direct-acting sympathomimetic drug, and is used in some local anesthetic solutions.
Q6-5: Define levonordefrin.
A6-5: Levonordefrin is a synthetic catecholamine. It is a direct-acting sympathomimetic drug, and is used in some local anesthetic solutions.
Q6-6: Are vasoconstrictors used in dentistry direct-acting, indirect-acting, or mixed-acting sympathomimetics?
A6-6: Vasoconstrictors used in dentistry are direct-acting sympathomimetics.
Q6-7: Using Table 6-1, provide the names of common sympathomimetic amines.
Catecholamines Noncatecholamines **
Epinephrine* Amphetamine
Norepinephrine* Methamphetamine
Levonordefrin Ephedrine
Dopamine* Phenylephrine
*Naturally occurring chemicals
** All are examples of chemicals found in street drugs, diet pills, and cold medications
Q6-8: Explain why the lack of profound anesthesia can result in a spike in blood pressure.
A6-8: The lack of profound anesthesia can result in unmanageable pain, which in turn can lead to a spike in blood pressure due to the release of endogenous epinephrine in response to the pain. This endogenous release may be much greater than doses of exogenous epinephrine typically administered.
Q6-9: What are the possible local and systemic effects of adrenergic vasoconstrictors?
A6-9: Adrenergic vasoconstrictors used in dental procedures typically do not produce noticeable effects but are capable of causing undesired local and systemic reactions. Local effects may include ischemia and necrosis while systemic effects may include changes in arterial blood pressure, palpitations, dysrhythmias, and even permanent injury or death due to ventricular fibrillation, heart attack, or stroke. Overdose, intravascular administration, drug interactions, and intolerance increase the likelihood of adverse events.
Q6-10: Why are most adverse events related to the use of vasoconstrictors short-lived?
A6-10: Most adverse events related to the use of vasoconstrictors are short-lived due to their efficient reuptake in synapses, and the rapid removal and biotransformation of any residual portions that enter the bloodstream.
Q6-11: Name the types and subcategories of adrenergic receptors.
A6-11: Two types of adrenergic receptors were identified by Ahlquist in 1948, alpha (α) and beta (β). Since that time, subcategories have been identified which explain specific actions of vasoconstrictors
Q6-12: Which receptors are responsible for smooth muscle contraction in peripheral arterioles and veins?
A6-12: Alpha (α) receptors are responsible for smooth muscle contraction in peripheral arterioles and veins throughout the body (peripheral vasoconstriction).
Q6-13: Which receptors are responsible for smooth muscle relaxation such as bronchodilation and vasodilation?
A6-13: Beta 2 (β2) receptors are responsible for smooth muscle relaxation such as bronchodilation and vasodilation.
Q6-14: What concentrations of epinephrine are available in local anesthetic solutions in North America?
A6-14: Epinephrine is added to local anesthetic solutions in North America in concentrations of 1:50,000, 1:100,000, and 1:200,000.
A6-15: A patient calls the office approximately six hours after a tooth extraction to report an increase in bleeding. What is a likely cause of increased bleeding?
A6-15: Epinephrine provides nearly equal α and β effects, but not at the same time. Initial α vasoconstriction of peripheral vasculature allows time for the anesthetic drugs to bind to receptor sites. Later, β2 vasodilation predominates. This has been observed before and after surgery where epinephrine has been administered. Initially, α effects enhance profound, durable anesthesia and reduce hemorrhaging at surgical sites. Postoperatively, the dominant β2 effects can result in increased bleeding approximately 6 hours after surgery.
A6-16: What is the maximum dose of epinephrine for use in dentistry in a healthy individual?
A6-16: The maximum dose of epinephrine for use in dentistry in healthy individuals has been determined to be 0.2 mg per appointment.
Q6-17: Give examples of situations in which the dose of epinephrine should be reduced.
A6-17: In individuals with significant cardiovascular compromise (ASA categories III & IV), and other medical situations, including elderly populations and in the presence of a number of specific drug interactions, the dose of epinephrine should be reduced.
