question

Duration of action

answer

classified as either short (20-40 minutes of pulpal anesthesia), intermediate (last up to 70 minutes) and long (up to 8 hours). All anesthetics have an approximate duration of action. This is approximate because many factors can affect the duration of anesthesia of an anesthetic drug

question

Factors that can affect the duration of anesthesia of an anesthetic drug

answer

1. Individual response to a drug 2. Accuracy of injection technique 3. Tissue status at side of deposition 4. Anatomic variation 5. Type of injection used (block vs. infiltration)

question

Variation in LA response

answer

most patients will respond normally (~70%), ~15% will hyperrespond and ~15% will hyporespond. The patients you should be aware of are not those who respond normally or those who are numb for slightly longer than you would expect, but rather those who hyporespond (those who are anesthetized for shorter periods of time than you would expect).

question

Two groups of patients are particularly vulnerable from overly high LA blood levels:

answer

1. Smaller, lighter-weight children 2. Debilitated elderly individuals Patients with decreased liver function are especially susceptible to amide LA drugs since the 1/2 lives (rates at which drugs are removed from the circulation by the kidneys) of these drugs are dramatically increased.

question

Allergy to LA drugs (amides)

answer

Allergies to amide anesthetic drugs are extremely rare and virtually nonexistent. In addition, amide drugs also have low cross-reactivity, meaning that if an allergic reaction is elicited by one drug, there may not be a response to another amide drug. This gives amides a major clinical advantage over ester-type drugs which have been known to elicit allergic (hypersensitivity) reactions.

question

Allergy to LA drugs (Esters)

answer

Esters all share a common metabolite (PABA) which is thought to be an allergen in ester hypersensitivity reactions. Because esters are primarily used as topical anesthetics in dentistry, a hypersensitivity reaction will most likely occur upon topical anesthetic application about 30-60 minutes of tissue contact.

question

Cocaine

answer

Despite its highly addictive and toxic properties, no discussion of local anesthetic agents would be complete without the mention of cocaine. Cocaine was the precursor to all dental anesthetics due to its numbing effects. Cocaine is an ester local anesthetic now used solely via topical application. Injection is strongly contraindicated because of the availability of safer drugs. Cocaine is characterized by a relatively rapid onset (within 1 minute) and long duration of action (roughly 2 hours). A particularity of cocaine is its quality to function both as a local anesthetic and vasocontrictor consistently. The addition of vasoconstrictors to cocaine is therefore contraindicated and can be potentially dangerous, possibly leading to dysrhythmias including ventricular fibrillation. Despite its anesthetic capabilities, the euphoric and addictive properties of cocaine continued to preclude its use as an anesthetic.

question

Procaine

answer

Procaine was subsequently developed and marketed as novocaine in 1905. Its main advantage was that it produced local anesthesia without cocaine's adverse effects. Procaine is an ester anesthetic (as its name indicates) and is included in this discussion in the event that you encounter a patient with an allergy to all other amide dental LA drugs. Procaine can therefore be obtained as a medical vial and used as a substitute. Unlike cocaine, procaine is a vigorous vasodilator and is quickly metabolized by cholinesterase. It therefore has a very short duration of action (15-60 minutes as most) and has been associated with incomplete pain control during dental appointments. Due to this fact, its very low potency (1/2 as potent as lidocaine, mepivicaine, and prilocaine) compared to amide injectable LA drugs and its high incidence of inducing allergic reactions (because it is an ester), procaine has been replaced by more effective LA drugs and is no longer available in dental cartridges in the US.

question

Lidocaine

answer

Lidocaine has become the drug of choice for dental LA, mostly because of its rapid onset (3-5 minutes), low risk of hypersensitivity, pulpal anesthesia of 60+ minutes, and soft tissue anesthesia of up to 5 hours. Lidocaine is available as: 1. 2% plain (no longer available in North America) 2. 2% lidocaine, 1:100,000 epinephrine 3. 2% lidocaine, 1:50,000 epinephrine

question

Lidocaine duration of action

answer

Lidocaine is a vigorous vasodilator and so necessitates the use of vasoconstrictors to provide profound anesthesia. With a vasoconstrictor (epinephrine), lidocaine has an intermediate duration of action, usually providing 60+ minutes of pulpal anesthesia and 3-5 hours of soft tissue anesthesia for BOTH 1:50,000 and 1:100,000 dilutions.

question

Maximum recommended dose of lidocaine

answer

.2 mg/lb or 7.0 mg/kg Lidocaine-induced overdose is different from that of other amides in that the initial excitatory phase may be short-lived or non-existent

question

Potency of LA drugs

answer

idocaine is as potent as mepivacaine and prilocaine, but it is less potent than articaine and much less than bupivacaine. Procaine < Lidocaine = Prilocaine = Mepivacaine < Articaine << Bupivacaine

question

Toxicity of LA drugs

answer

Lidocaine more toxic than prilocaine, similar to articaine and mepivacaine, and much less toxic than bupivacaine. Procaine < Prilocaine < Mepivacaine < Lidocaine = Articaine << Bupivaicaine

question

pKa and onset time of LA drugs/Lidocaine

answer

-The most useful pKa range for LA falls between 7.6 and 8.1. Drugs in this range provide more rapid onset of anesthesia. With a pKa of 7.7, lidocaine has a relatively fast onset time of 2-3 minutes. -As a general rule, there is clinically no significant or noticeable difference between all amide injectable drugs, with the exception bupivacaine which has a relatively long onset.

question

When would understanding of the concept of drug half-life have the greatest impact on safety?

answer

Understanding the concept of half-life is relatively less important when only a single carpule is administered. The same goes for multiple carpules as long as maximum dosing hasn't occurred. Half-life is most important after maximum dosing has occurred. A shorter half-life drug such as articaine can be administered sooner after achieving maximum dosing because its circulating level will drop below the maximum recommended level faster. When more than one drug is administered, as long as the combination doesn't result in maximum dosing, the situation is similar to single or multiple carpule administration below the maximum recommended dose.

question

Topical preparations of lidocaine

answer

Lidocaine is one of two anesthetics available as as both an injectable and topical anesthetic. Lidocaine is an effective topical anesthetic and is available in concentrations ranging from 2-10% in the form of ointments or solutions.

question

Pregnancy category

answer

In general, lidocaine and prilocaine (category B) are safe to use during pregnancy with no evidence of adverse effects or harm to the fetus. However, a strong rationale for the need to use articaine, bupivacaine, and mepivacaine (category C) is necessary prior to use in pregnant patients. However, these guidelines are currently under FDA review and may change in the near future.

question

What is the significance of the ester component added to articaine?

answer

- It increases its rate if biotransformation: This is the best response since as stated previously, articaine is primarily biotransformed in the blood by cholinesterase (90-95%) rather than by the liver's p450 enzyme system (5-10%) as are most other amide anesthetics.

question

Articaine is available as:

answer

1. 4% articaine, 1:100,000 epinephrine 2. 4% articaine, 1:200,000 epinephrine

question

Articaine duration of action

answer

Articaine has a similar duration of action as lidocaine, categorized as intermediate, usually providing 60+ minutes of pulpal anesthesia at the 1:100,000 epinephrine concentration and 45-60minutes at the 1:200,000 epinephrine

question

Maximum recommended dose of articaine

answer

3.2 mg/lb or 7.0 mg/kg Articaine has the same MRD as lidocaine.

question

Potency of articaine

answer

Articaine is 1/3 more than lidocaine, mepivacaine, and prilocaine, but it is 1/3 less potent than bupivacaine. Procaine < Lidocaine = Prilocaine = Mepivacaine < Articaine << Bupivacaine

question

Toxicity of articaine

answer

Procaine <Prilocaine< Articaine = Mepivicaine < Lidocaine << Bupivicaine Importantly, articaine has also been shown to be associated with a higher than normal incidence of post-operative injury (parasthesia), especially when it is used as a block such as the inferior alveolar block. However, while some research suggests extremely low rates (as low as 3 per million for articaine, which is by far the highest rate among all injectable anesthetics), other research suggest that the incidence of permanent nerve damage by all LA drugs including articaine may be much greater than previously thought (1 per 26,000 or 1 per 160,000 depending on the study) when used in IA blocks (Basset et al)

question

pKa and onset time of Articaine

answer

The most useful pKa range for LA drugs fall between 7.6 and 8.1. Drugs in this range provide more rapid onset of anesthesia. With a pKa of 7.8, articaine has a relatively rapid onset time of 2-3 minutes (nerve block) and1-2 minutes (infiltration). Of all injectable LA drugs, articaine provides the most rapid onset of anesthesia when given as an infiltration. While its pKa is slightly higher than that of lidocaine (7.7) which would logically give it a mildly slower onset time, articaine is more lipophillic giving it a higher affinity for nerve membranes and possibly resulting in its reported slightly faster/comparable onset of anesthesia as compared to lidocaine

question

Pregnancy category of Articaine

answer

In general, lidocaine and prilocaine (category B) are safe to use during pregnancy with no evidence of adverse effects or harm to the fetus. However, a strong rationale for the need to use articaine, bupivacaine, and mepivacaine (category C) is necessary prior to use in pregnant patients. However, these guidelines are currently under FDA review and may change in the near future.

question

Mepivacaine

answer

Mepivacaine is a close relative of lidocaine in its pharmacological behavior. Its duration, onset of action, potency, and toxicity are all similar to lidocaine's. Unlike lidocaine however, mepivicaine is a weak vasodilator and is therefore effective for short durations without a vasoconstrictor.

question

Mepivacaine formulation

answer

Mepivacaine is available as: 1. 3% mepivacaine plain 2. 2% mepivacaine, 1:20,000 levonordefrin

question

Mepivacaine duration of action

answer

1. 3% mepivacaine plain - 20-40 minutes pulpal (short duration) 2. 2% mepivacaine, 1:20,000 levonordefrin - 60 minutes pulpal and 3-5 hours of soft tissue anesthesia (intermediate duration)

question

Mepivacaine maximum recommended dose

answer

3.0 mg/lb or 6.6 mg/kg

question

Mepivacaine potency

answer

Mepivacaine is as potent as lidocaine and prilocaine, but it is less potent than articaine and much less than bupivacaine. Procaine < Lidocaine = Prilocaine = Mepivacaine < Articaine << Bupivacaine

question

Mepivicaine toxicity

answer

Mepivicaine more toxic than prilocaine, similar to articaine and lidocaine, and much less toxic than bupivicaine. Procaine <Prilocaine< Articaine = Mepivicaine < Lidocaine << Bupivicaine

question

Mepivicaine vasoactivity

answer

Mepivacaine is the weakest vasodilator which allows it to be used without vasoconstrictors. This makes it ideal for short-term procedures in both infiltrations and nerve-blocks in plain solutions.

question

Mepivicaine pKa and onset time

answer

The most useful pKa range for LA drugs fall between 7.6 and 8.1. Drugs in this range provide more rapid onset of anesthesia. With a pKa of 7.6, mepivacaine has a relatively fast onset time of 1.5-2 minutes. This short onset can be advantageous. For example, some clinicians elect to administer 3% mepivacaine plain as an initiating drug prior to administering bupivacaine which has the slowest onset time but longest duration of anesthesia.

question

Mepivicaine vasoconstrictor

answer

3% mepivacaine, 1:20,000 levonordefrin provides a similar depth and duration of anesthesia as 2% lidocaine, 1:100,000 epinephrine. Levonordefrin however is less effective as a hemostatic agent than epinephrine and so epinephrine remains the preferred vasoconstrictors in patients who are able to tolerate its side-effects.

question

Mepivicaine pregnancy category

answer

In general, lidocaine and prilocaine (category B) are safe to use during pregnancy with no evidence of adverse effects or harm to the fetus. However, a strong rationale for the need to use articaine, bupivacaine, and mepivacaine (category C) is necessary prior to use in pregnant patients. However, these guidelines are currently under FDA review and may change in the near future.

question

Prilocaine

answer

In the same way that mepivacaine and lidocaine are close relatives, prilocaine is very similar to mepivacaine. Mepivacaine is a close relative of lidocaine in its pharmacological behavior. Its duration, onset of action, potency, and toxicity are all similar to lidocaine's. Unlike lidocaine however, mepivicaine is a weak vasodilator and is therefore effective for short durations without a vasoconstrictor.

question

Prilocaine is available as

answer

1. 4% prilocaine plain 2. 4% prilocaine, 1:200,000 epinephrine

question

Prilocaine duration of action

answer

1. 4% prilocaine plain as an infiltration - 10-15 minutes pulpal (short duration) 2. 4% prilocaine plain as a block - 40-60 minutes pulpal (intermediate duration) 3. 4% prilocaine, 1:200,000 epinephrine - 60-90 minutes pulpal (intermediate duration)

question

Prilocaine maximum recommended dose

answer

4.0 mg/lb or 8.8 mg/kg

question

Prilocaine potency

answer

Prilocaine is as potent as mepivicaine and lidocaine, but it is less potent than articaine and much less than bupivicaine. Procaine < Lidocaine = Prilocaine = Mepivicaine < Articaine << Bupivicaine

question

Prilocaine toxicity

answer

Procaine <Prilocaine < Articaine = Mepivicaine < Lidocaine << Bupivicaine

question

Prilocaine metabolism

answer

Prilocaine metabolism is unique in that it is metabolized into orthotoluidine which can induce methemoglobinemia, thereby reducing the blood's oxygen-carrying capacity (sometimes enough to cause observable blue cyanosis or coloring of the lips, mucous membranes, and nails). Vasoactivity Prilocaine is a weak vasodilator which allows it to be used without vasoconstrictors.

question

Prilocaine pKa and onset time

answer

The most useful pKa range for LA drugs fall between 7.6 and 8.1. Drugs in this range provide more rapid onset of anesthesia. With a pKa of 7.9, prilocaine has a relatively fast onset time of 2-4 minutes, slightly slower than lidocaine, mepivacaine, and articaine.

question

Prilocaine topical preparations

answer

Prilocaine is one of two dental anesthetics available as as both an injectable and topical anesthetic. It is an effective topical anesthetic and is only available combined with lidocaine in concentrations 2.5% lidocaine/2.5% prilocaine in the form of ointments or solutions.

question

Prilocaine pregnancy category

answer

In general, lidocaine and prilocaine (category B) are safe to use during pregnancy with no evidence of adverse effects or harm to the fetus. However, a strong rationale for the need to use articaine, bupivacaine, and mepivacaine (category C) is necessary prior to use in pregnant patients. However, these guidelines are currently under FDA review and may change in the near future.

question

Bupivacaine

answer

Distinguished by its long onset time and duration of action, bupivicaine has some important indications: 1. When extended post-op pain control is necessary (for example, when overnight pain relief is necessary) 2. When durable and deep anesthesia is necessary and has failed with other available drugs 3. When you expect the procedure to require more than 60-90 minutes. This long duration of action can however be a problem in certain patient populations. For example, it may put young children at higher risk for self-inflicted post-op trauma such as cheek or tongue biting.

question

Bupivacaine is available as

answer

1. 0.5% bupivacaine plain, 1:200,000 epinephrine

question

Bupivacaine duration of action

answer

1. 0.5% bupivacaine plain, 1:200,000 epinephrine - up to 12 hours pulpal and soft tissue (long duration) Given its strong vasodilating properties, you wouldn't expect bupivacaine to have such long duraction of action. In fact, bupivacaine owes its long duration to its strong protein binding characteristics.

question

Bupivacaine maximum recommended dose

answer

90mg absolute maximum Because of bupivacaine's increased cardiotoxicity, overdoses tend to be more severe and less easily reversed.

question

Bupivacaine potency

answer

Bupivacaine is the most potent LA drug, nearly 3x more potent than articaine. Procaine < Lidocaine = Prilocaine = Mepivicaine < Articaine << Bupivicaine

question

Bupivacaine toxicity

answer

Bupivacaine is the most toxic LA drug, nearly 4x more potent than lidocaine, mepivacaine, and articaine. The two main factors that contribute to its increased toxicity are its lengthy 1/2 life and its early CVS involvement. Procaine <Prilocaine< Articaine = Mepivicaine < Lidocaine << Bupivicaine

question

Bupivacaine vasoactivity

answer

Bupivacaine is the 2nd most potent vasodilator (after procaine which is no longer in use in dentistry, but still available in medicine).

question

Bupivacaine pKa and onset time

answer

The most useful pKa range for LA drugs fall between 7.6 and 8.1. Drugs in this range provide more rapid onset of anesthesia. With a pKa of 8.1, bupivacaine has the slowest onset time, 6-10 minutes

question

Bupivicaine pregnancy category

answer

In general, lidocaine and prilocaine (category B) are safe to use during pregnancy with no evidence of adverse effects or harm to the fetus. However, a strong rationale for the need to use articaine, bupivacaine, and mepivacaine (category C) is necessary prior to use in pregnant patients. However, these guidelines are currently under FDA review and may change in the near future.

question

Topical Anesthetic

answer

In general, the concentration of topical anesthetic is still higher than if that same drug were to be used as an injectable drug. This is to facilitate diffusion through the mucous membrane. Conventional topical anesthetics cannot diffuse through intact skin, but are useful on mucous membranes and abraded skin (sunburned skin). Conventionally, topical anesthetics are effective only on surface tissues (2-3mm) and are ineffective on tissues deeper to the area of application.

question

Main use of topical anesthetic

answer

1. allow atraumatic needle penetration of the mucous membranes 2. relief of discomfort during: a. radiographic film placement b. periodontal evaluation and treatment c. placement of retraction cords and rubber dams d. superficial manipulation of mucosal tissues.

question

Factors that affect topical anesthetic toxicity

answer

1. Concentration 2. Ability to penetrate tissue 3. Speed of systemic absorption 4. Total area of coverage

question

Local adverse reactions

answer

Reactions may occur when anesthetic is applied to abraded tissue, for extended periods of time, or when there is an undiagnosed hypersensitivity to a particular agent. Reactions at the site of application include: - Sloughing - Edema - Delayed hypersensitivity - Redness - Pain - Burning These reactions are readily treated with palliative strategies.

question

Systemic reactions

answer

It is common for patients to ask if swallowing topical anesthetic has any harmful effects. In fact, no significant systemic uptake occurs during swallowing of anesthetic. The greatest risks are associated with the rare occurrence of allergic reactions, or more commonly, overdose reactions. These may induce CNS and CVS depression ranging from subclinical symptoms (restlessness, agitation, and increased heart rate) to life-threatening (respiratory and cardiovascular collapse).

question

Benzocaine (topical)

answer

Benzocaine is an ester drug and one of the most widely used topical anesthetic

question

Formulation, onset time, and duration of action of Benzocaine (topical)

answer

It is available in concentrations ranging from 6-20% with 20% being the most commonly used formulation. At this concentration, a topical effect will occur within 30 seconds of application with a peak effect at 2 minutes. Anesthesia however can last anywhere between 5-15 minutes.

question

Benzocaine Toxicity (topical)

answer

It is almost entirely present in its base form making it insoluble in water and therefore slowly absorbed into the CVS and less likely to produce an overdose reaction. It has however been known to cause methemoglobinemia, especially when used in excessive amounts in its spray forms (Hurricane 20%) on small children.

question

Dyclonine HCl (topical)

answer

This is a nonester, nonamide, ketone topical anesthetic that is used most commonly when both ester and amide anesthetics (benzocaine and lidocaine) cannot be used. It is available as a 0.5% formulations for dental use.

question

Dyclonine HCl onset and duration of action (topical)

answer

It is has a slow onset of 2-10 minutes, but has a duration of action of about 30 minutes (greater than that of benzocaine).

question

Lidocaine is available in (topical)

answer

1. Lidocaine base at 5% concentration: - As are most base preparations, this formulation is poorly soluble in water, thereby decreasing its toxicity. - Indicated for use on ulcerated, abraded, or lacerated tissue 2. Lidocaine HCl at 2% concentration: - Water-soluble formulation which penetrates tissue more effectively than its base form, BUT systemic absorption is also greater, providing a greater risk of toxicity.

question

Lidocaine topical onset and duration of action

answer

Onset usually occurs at 1-2 minutes, peaks at 10 minutes, and lasts for a total of 15 minutes.

question

Tetracaine HCl

answer

As its name indicates, tetracaine is a long-duration ester similar to benzocaine. It is usually used at a 2% concentration for topical purposes.

question

Tetracaine HCl onset and duration of action

answer

Tetracaine has a slow onset, peaking only at 20 minutes but lasting for up to 1 hour.

question

Tetracaine HCl toxicity

answer

A potent anesthetic, tetracaine can lead to serious adverse reactions when applied in excessive dosing and too frequently. An MRD of 20mg is recommended when used topically.

question

Kovanase Mist

answer

Currently undergoing clinical trials, a new tetracaine formulation available as an intra-nasal spray may become available in the near future to provide both pulpal and soft-tissue anesthesia.

question

Eutectic mixtures: (EMLA) and Oraqix

answer

EMLA cream is an emulsion of lidocaine and prilocaine while Oraqix is a dual phase liquid/gel of the same two drugs. Both are formulated at a 1:1 ratio and 2.5% concentrations of each anesthetic.

question

EMLA

answer

This is the only topical anesthetic used in dentistry that is also effective on intact skin. It is most commonly used in a variety of procedures that do not involve the deep tissues and only require short-term anesthesia, such as metal splints used to contain fractures or other superficial procedures in pediatric dentistry. EMLA has an onset time of 5-10 minutes no information is available with regards to its duration of action on oral mucosa, but peaks at 2-3 hours after application on skin and lasts for 1-2 hours after removal from skin.

question

Oraqix

answer

This mixture is dual phase (liquid at RT and gel-like when applied subgingivally) and is most commonly applied subgingivally into the sulcus of periodontal pockets prior to periodontal probing or scaling and root planning. It takes about 1 minute for an anesthetic effect to take place and can last up to 20 minutes. Overdose risks are similar to those of injectable lidocaine and prilocaine and occurs in the same sequence (CNS excitation followed by depression).

question

Vasopressors

answer

The main action of vasopressors is to constrict the blood vessels. They are added to dental anesthetic drugs to: 1. Increase safety of LA drugs by slowing systemic absorption 2. Provide hemostasis 3. Increase duration and depth of anesthesia Only two vasopressors are available in North America: epinephrine and levonordefrin. The former is naturally occurring while the latter is a synthetic drug. Both stimulate adrenergic receptors on the smooth muscle walls of blood vessels and are direct-acting (directly stimulate the receptors). Vasoconstrictors are expressed as dilution ratios. For example: 1:1000 epinephrine = 1 gram of epinephrine per liter of solution = 1000 mg/1000 mL = 1 mg/mL

question

Local side effects of vasoconstrictors

answer

May result in ischemia and tissue necrosis

question

Systemic side effects of vasoconstrictors

answer

Vasopressors are particularly relevant in dentistry due to their potential for systemic effects. These are intimately tied to the fact that dentistry is stressful for many patients and that endogenous epinephrine released from the adrenal glands may increase before and during appointments. As such, by providing exogenous vasopressors, we are increasing and potentially stimulating the dose of vasopressors already present in the body, thereby inducing undesirable side effects. These may range from CNS stimulation side effects such as tension, restlessness, headache, and tremor to changes in blood pressure or palpitations to arrhythmias, ventricular fibrillation, MI, or stroke, sometimes resulting in death. Patient screening and assessment is paramount prior to deciding whether to use a local anesthetic drug containing a vasopressor.

question

Allergies vs. overdose of vasoconstrictors

answer

Vasoconstrictors in some individuals may cause nausea, restlessness, racing heart, anxiety, weakness, and tremor even at low doses. However, these effects pass rather quickly and may sometimes be misinterpreted by patients as an "allergy" to the vasoconstrictor in anesthetic. While these responses may be due to intravascular deposition of the anesthetic and subsequent dissemination of epinephrine in the blood stream, it is more commonly due to a hyper-response to absorbed doses. This is not an allergenic response because there is no humoral, cell-mediated, or antibody response and true epinephrine allergies are impossible given that epinephrine in dental anesthetic is identical to endogenous epinephrine. Rather, it is due to rapid stimulation of the adrenergic receptors.

question

Contraindications of vasopressors

answer

1. ASA III or IV patients 2. Patients with certain noncardiovascular diseases such as thyroid dysfunction, diabetes, and sulfite sensitivity 3. Patients on MAO inhibitors, tricyclic antidepressants, and phenothiazines For these patients, it is necessary to determine the degree of severity of the condition and weigh the risks and benefits of vasopressor use.

question

Epinephrine mechanism of action

answer

Epinephrine provides equal α and β stimulation. Initially, the α receptors are stimulated resulting in vasoconstriction of the peripheral vasculature, thereby allowing the LA drug to bind to its receptor site and reducing bleeding at the site of deposition. Later, a rebound effect via β2 stimulation occurs resulting vasodilation, which commonly translates into increased bleeding 6 hours or so post-operatively.

question

Epinephrine Effects on the CVS

answer

- Epinephrine stimulates β1 receptors of the CVS increasing cardiac output and heart rate. This action irritates the pacemaker cells of the heart and may increase the incidence of dysrhythmias. - In addition, systolic pressure will increase in response to epinephrine while dyastolic pressure will decrease when small doses are administered but increase when large doses are present. - All in all, epinephrine will: 1. Increase blood pressure 2. Increase cardiac output 3. Increase stroke volume 4. Increase heart rate 5. Increase strength of contraction 6. Increase myocardial oxygen consumption 7. Increase hemostasis 8. Increase bronchodilation 9.increase pacemaker cell irritability

question

Epinephrine effects on the respiratory system

answer

- Epinephrine provide β2 stimulation which results in bronchodilation.

question

Termination of action and elimination of epinephrine

answer

Epinephrine undergoes either: 1. Reuptake by the adrenergic nerves 2. Inactivation by COMT and MAO which are both present in the liver.

question

Epinephrine concentrations

answer

In North America, epinephrine is available in concentrations of: - 1:50,000 - 1:100,000 (2x less epinephrine than 1:50,000) - 1:200,000 (4x less epinephrine than 1:50,000) Duration of anesthesia is equal in all forms; only the hemostatic effects are altered. It is generally agreed upon that there is little need for 1:50,000 dilution and that 1:100,000 dilutions should be used with lidocaine whenever possible.

question

Maximum dose of epinephrine

answer

The maximum dose is limited to 0.2mg per appointment for ASA I patients and 0.04mg per appointment for ASA III or IV patients. Current recommendations are to limit or avoid exposure of vasoconstrictors in ASA III or IV patients (or those with ischemic heart disease) whenever possible. However, the risk of epinephrine administration should be weighed against the risk of its inclusion (Malamed).

question

Levonordefrin

answer

-synthetic vasoconstrictor -It acts primarily on α receptors (75%) with only 25% of β stimulation. In general, levonordefrin is only 15% as potent as epinephrine as a vasoconstrictor. As such, it produces the same effects, but to a lesser degree, on the CNS and CVS as epinephrine.

question

Levonordefrin concentration

answer

In North America, levonordefrin is only available in combination with mepivacaine plain. Due to its decreased potency (15% as potent as epinephrine), it is available at higher concentrations than epinephrine: 1:20,000. At this concentration, it has the same effect as epinephrine at lower concentrations (1:100,000).

question

Levonordefrin maximum dose

answer

The maximum dose is 1mg per appointment for ALL patients (or 20 mL of a 1:20,000 dilution resulting in approximately 11 cartridges).

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