L.A 2 Flashcards
Classification of Vasoconstrictors used
in L.A
- Catecholamines:
Epinephrine, norepinephrine, levonordfrin , dopamine - Noncatecholamins:
e.g. Felypressin, Amphetamine, ephdrine
Functions of vasoconstrictor agents
1) To prolong the duration of action of L.A.
2) To reduce the systemic toxicity
3) To reduce the volume of anesthetic agent to be used.
4) To reduce bleeding at the site of surgery
5) It potentiates the action of L.A.
6) To increases the depth anesthesia
Mode of Action
- Direct-acting drugs: Attach to and directly stimulate adrenergic receptors.
- Non-direct acting drugs: Act indirectly by provoking the release of endogenous catecholamine from intraneuronal storage sites.
- Mixed-acting drugs: Combination of 1 and 2.
Adrenergic receptors
• Activation of alpha receptors: contraction of smooth muscles in blood vessels (vasoconstriction).
• Activation of beta receptors: produces smooth muscle relaxation (Vasodilation and bronchodilation)
and cardiac stimulation
(increased heart rate and strength of contraction)
• Beta 1: Stimulation of cardiac smooth muscle.
• Beta 2: Bronchodilation, vasodilation.
Epinephrine 3 points
• Most potent vasoconstrictor
• Concentrations of 1:50,000 to 1:200,000
• sodium bisulfite is usually added to epinephrine solutions to delay this deterioration.
Systemic effects of epinephrine include
• Vasoconstriction of small arterioles
• Bronchodilatation.
elimination and reuptake of epinephrine
• The action is terminated primarily by its reuptake by adrenergic nerves.
• Epinephrine that escapes reuptake is rapidly inactivated in blood by the enzyme
enzyme Catechol-O-methyltransferase (COMT) and Monoamine
oxidase (MAO)
epinephrine Side effects and overdose
• Max. Dose of epinephrine for otherwise healthy adult is 0.2 mg per appointment.
• Max. Dose for patients with significant cardiovascular diseases (ASA III or IV) is 0.04 mg per appointment.
Clinical applications for Epinephrine
- Management of acute allergic reactions.
- Management of bronchospasm.
- Treatment of cardiac arrest.
- As vasoconstrictor for hemostasis.
- As vasoconstrictor in L.A to decrease
absorption into the circulation and to
increase duration of action of L.A. - To produce mydriasis.
Epinephrine Availability in dentistry
– Lidocaine with following epinephrine dilutions ( 1:50 000, 1:80 000, 1:100000, 1:200000).
– Articaine ( 1:100 000, 1:200 000).
– Bupivacine ( 1:200 000).
Contraindications of epinephrine
• Patients with blood pressure over 200 systolic or 115
diastolic.
• Uncontrolled hyperthyroidism.
• Post myocardial infarction (less than 6 months).
• Daily attacks of angina pectoris or unstable angina.
• Cardiac dysrhythmia despite appropriate therapy.
• Patient on Beta blockers, MAO inhibitor, tricyclic antidepressants or GA with halogenated anesthetic
(halothane)
Norepinephrine 3 points
alpha receptors (90%
,beta receptors on the heart (10%).
• The degree and duration of ischemia noted following norepinephrine infiltration into the palate have led to soft tissue necrosis.
25% as potent a vsopressor as
epinephrine
Levonordefrin 4 points
• Its a synthetic vasoconstrictor, it acts more on alpha receptors (75%).
• It is 15% as potent an epinephrine.
• It can be obtained with mepivacaine in a 1:20 000 dilution.
• Maximum dose for all pateints should be 1 mg
Felypressin (Octapressin )
• It’s a synthetic analogue of the antiuretic hormone vasopressin.
• It acts as a direct stimulant of vascular smooth muscle.
• Felypressin have no direct effects on the myocardium and CNS; thus it may be safely administered to hyperthyroid patient and to anyone receiving MOA inhibitors or tricyclic antidepressant, also patients with cardiovascular diseases (ASA III, ASA IV)
• Felypressin has a oxytoxic action + not recommended for hemostasis
Selection of a vasoconstrictor According to:
- Lenght of the dental procedure.
- Requirement for hemostasis.
- Medical status of the patient.
