3. pharmacolgy of vasoconstricors local.ppt

pharmacology of vasoconstrictors local anesthesia

1. Pharmacology of
Vasoconstrictors
Local anesthesia
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2. What happens if you don’t use a vasoconstrictor?
*Plain local anesthetics are vasodilators by nature
1)Blood vessels in the area dilate
2)Increase absorption of the local anesthetic into the cardiovascular
system (redistribution)
3)Higher plasma levels increased risk of toxicity
4)Decreased depth and duration of anesthesia diffusion from site
5)Increased bleeding due to increased blood perfusion to the area
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3. Why You Need Vasoconstrictors
Vasoconstrictors resemble adrenergic drugs and are called sympathomimetic,
or adrenergic drugs
1)Constrict blood vessels decrease blood flow to the surgical site
2)Cardiovascular absorption is slowed lower anesthetic blood levels
3)Local anesthetic blood levels are lowered lower risk of toxicity
4)Local anesthetic remains around the nerve for longer periods
increased duration of anesthesia
5)Decreases bleeding
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4. Chemical Structure
Classification of Adrenergic Drugs
• Classification by chemical structure is related to the presence or absence of
a catechol nucleus
• Catechol is orthodihydroxybenezene
• Sympathomimetic drugs that have a hydroxy (OH-) substitution in the 3rd
and 4th positions of the aromatic ring are termed catechols
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5. CatecholaminesIf the 3rd and 4th positions contain an amine group (NH2)
attached to the aliphatic side chain, they are then called catecholamines
natural catecholamines of sympathetic NS
Epinephrine
Norepinephrine
Dopamine
synthetic catecholamine
Isoproterenol and Levonordefrin.
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8. 2 Types of Adrenergic Receptors:
Alpha
-contraction of smooth muscle in blood vessels
-vasoconstriction
-Alpha 1 excitatory; post-synaptic
-Alpha 2 inhibitory; post-synaptic
Beta
-smooth muscle relaxation
-vasodilation/bronchodilation
-cardiac stimulation, i.e., increased rate and strength of contraction
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9. 2 Types of Beta Receptors:
1)Beta 1 -found in heart and small intestines -produces cardiac
stimulation and lipolysis
2)Beta 2 -found in bronchi of the lung, vascular beds and uterus -
produces bronchodilation and vasodilation
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11. The dilution of vasoconstrictors is commonly referred to asa ratio
i.e., 1:50,000; 1:100,000; 1:200,000 etc,… A concentration of 1:1,000
means that there is 1 gram (1000 mg) of solute (drug) contained in
1000 ml (1 L) of solution, therefore, 1:1,000 dilution contains 1000 mg
in 1000 ml or 1.0 mg/ml of solution (1000 ug/ml) The concentration of
1:1,000 is very concentrated (strong); a much more dilute form is used
in dentistry for example, 1:50,000 > 1:100,000 > 1:200,000
(1:100,000 = 0.01 mg/1 ml of solution)
per 1.8 ml cartridge of anesthetic
1:50,000= .036 mg epinephrine, 1:100,000= .018 mg epinephrine,
1:200,000= .009 mg epinephrine decreasing potency of epinephrine
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13. 1:50,000 epinephrine is used to stop bleeding in asurgical area; this
amount of epinephrine is not used for block anesthesia
1) Bleeding areas that require resin from any trauma
2) Nick the papilla with a bur; resin or alloy
3) Oral surgery root tip removal; bloody socket
4) Works awesome for short period of time
5) Use as alternative to electrosurgery unit
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14. Resting plasma epinephrine levels are doubled when onecartridge of
2% Lidocaine 1:100,000 epinephrine is injected
• Recent evidence suggests that epinephrine plasma levels equivalent to
those achieved during moderate to heavy exercise occur after intraoral
injection
• Moderate increase in cardiac output and stroke volume occurs
• Blood pressure and heart rate are minimally affected
• IV administration of .015 mg of epinephrine with Lidocaine can increase
heart rate 25 to 75 beats and increase systolic blood pressure 20 to 70
mmHg “Epinephrine reaction” causes tachycardia, sweating,
apprehension and pounding in the chest (palpitations
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15. Norepinephrine
• Norepinephrine lacks Beta 2 actions (bronchodilation and vasodilation) and
produces intense peripheral vasoconstriction with possible dramatic
elevations in blood pressure
• Norepinephrine’s side effect ratio is 9 times higher than epinephrine
• Norepinephrine’s use in dentistry is not recommended and its use is
diminishing around the world
• Epinephrine remains the vasopressor of choice in dentistry
*Norepinephrine is not used because of its many side effects
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16. Epinephrine
Sodium Bisulfite antioxidant added
18 months shelf life
Acts directly on Alpha and Beta receptors
Beta effects predominate
Increases force / rate of contraction
Increases stroke volume
Increases myocardial O2 use
Increases cardiac output / heart rate
Increases dysrhythmias and PVCs
Increases coronary artery perfusion
Increases systolic blood pressure
Decrease in cardiac efficiency
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17. Alpha receptor stimulation leads to hemostasis initially
Beta 2 actions predominate leading to vasodilation 6 hours after a surgical
procedure Potent bronchodilator (asthma) Not a potent CNS stimulant
Increases oxygen consumption in all tissues of the body Reuptake by
adrenergic nerves terminates epinephrine action Ventricular fibrillation
is possible
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19. 1.8 ml Cartridge of 2% Lidocaine 1:100,000 epiMaximum
Epinephrine: 11 Cartridges Maximum Anesthetic: 300 mg 1.8 ml
Cartridge of 2% Lidocaine 1:200,000 epi Maximum Epinephrine: 22
Cartridges Maximum Anesthetic: 300 mg
The maximum amount of 2% Lidocaine 1:100,000 epinephrine that
can be used is 300 mg which is 8.3 cartridges regardless of the
patient’s weight; so the maximum epinephrine will only be achieved
after you have already surpassed the maximum amount of anesthetic
allowable 8.3 cartridges
American Heart Association says that thetypical concentrations of
vasoconstrictors in local anesthetics are not contraindicated in patients
with cardiovascular disease so long as aspiration, slow injection and the
smallest effective dose is administered; ASA III and ASA IV pose the
largest risk
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20. How much Epinephrine in CV patients?Maximum Epinephrine .04 mg
Two cartridges of 1:100,000 epinephrine
Clinical Applications of Epinephrine1) Management of acute allergic
reactions 2) Management of bronchospasm 3) Management of cardiac
arrest 4) Vasoconstrictor for hemostasis 5) Vasoconstrictor to decrease
absorption into CVS 6) Vasoconstrictor to increase depth of anesthesia
7) Vasoconstrictor to increase duration of anesthesia 8) To produce
mydriasis (excessive pupil dilation)
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21. Levonordefrin
Levonordefrin is freely soluble in dilute acid solutions
Sodium bisulfite is added to delay its deterioration Synthetic vasoconstrictor
Acts through direct Alpha receptor stimulation (75%) Acts through
some Beta activity (25%)
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22. Levonordefrin produces less cardiac and CNS stimulation
thanepinephrine • Levonordefrin is eliminated via COMT (catechol-O-
methyl transferase) and MAO (monamine oxidase) • Levonordefrin is
obtained via Mepivacaine 1:20,000; used at a higher concentration, i.e.,
1:20,000 because it is • 1/6th as potent as epinephrine • Levonordefrin
has a maximum recommended dose of 11 cartridges
-Levonordefrin is only 1/6th as strong as Epinephrine,therefore,
using a ratio of 1:20,000 Levonordefrin is like using a ratio of
1:120,000 of Epinephrine -you will need more Levonordefrin because it
is only 15% as effective as Epinephrine
2 vasoconstrictors are available in North America:1) Epinephrine 2)
Levonordefrin Selection of a vasoconstrictor depends on: 1) Length of
the dental procedure 2) Requirement for hemostasis 3) Requirement for
post-operative pain control 4) Medical status of the patient
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24. Contraindications to Using Vasoconstrictors1) Blood pressure >
200/115 mm Hg 2) Severe cardiovascular disease ASA IV+ 3) Acute
myocardial infarction in the last 6 months 4) Anginal episodes at rest 5)
Cardiac dysrhythmias that are refractory to drug treatment 6) Patient is
in a hyperthyroid state of observable distress 7) Levonordefrin and
Norepinephrine are absolutely contraindicated in patients taking tricyclic
antidepressants (Elavil, Sinequan)
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25. References
Malamed, Stanley: Handbook of Local Anesthesia. 5th Edition. Mosby. 2004
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