Diagnosis sheet # 12 - Hanan Msle7

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Diagnosis sheet # 12 - Hanan Msle7

Post by Shadi Jarrar on 6/8/2011, 4:51 pm

بسم الله الرحمن الرحيم

Dr. Shayab
Lecture #12
The local anesthetic carpule that we use is mainly composed of the local anesthetic drug, the vasopressor drug (vasoconstrictor), and sodium bisulfite which is a preservative (an antioxidant) and it prevents the deterioration of the vasoconstrictor; all these are dissolved in distilled water. As we took in the previous lecture, the vasoconstrictor is always accompanied by the preservative sodium bisulfate (an antioxidant) which preserves and protects it. In the past other additives and preservatives were used; other than sodium bisulfate; but they were later prohibited because they caused allergic reactions.
The local anesthetic drug is composed mainly of the lipophilic part connected to the hydrophilic part by the intermediate chain. The intermediate chain determines the type of the local anesthetic, whether it's an ester or an amide.

We took about the tissues, and why we add a vasoconstrictor to the local anesthetic; in order to improve the properties of the plain local anesthetic. The vasoconstrictor is added to increase the depth of anesthesia, to decrease the absorption of the local anesthetic in the bloodstream, and to decrease the toxicity. However, by adding the vasoconstrictor the ph of the local anesthetic will decrease. Lower ph means a longer onset of action. When the ph is close to or even higher than the ph of the tissues, then the onset of action is shorter.
There are two groups of vasoconstrictors that can be used in combination with the local anesthetic. The first is the sympathomimetic/adrenergic (sympathetic); the second group is the non-sympathomimetic/non-adrenergic drugs

The addition of these vasoconstrictors will lead to an action similar to the activation of the sympathetic nerves. The action of these drugs is on the adrenergic receptors (alpha α, and beta β).
These drugs also subdivide into two groups; the catecholamines, and the non-catecholamines.
In these drugs, the amine group as well as the catechol group are present. Catechol is the OH (hydroxyl group). Amine is NH or sometimes NH2 . So if these two groups are present in the vasoconstrictor structure, then they are called catecholamines. The catechol group is usually present in the third or fourth position on the aromatic ring.
The catechol group is NOT present on the aromatic ring. But the amine group is present.
_Ephedrine: used usually as a nasal drop especially in acute sinusitis.
_ phenylephrine
_ amphetamine
They do not act on the adrenergic receptors.
Dilution of vasoconstrictors
1:1000 1g:1000mL 1000mg:1000mL 1mg:1mL
1:10,000 1g:10,000mL 1000mg:10,000mL 1mg:10mL 0.1mg/mL
The most commonly used is the 1:100,000 especially in America. Whereas in Britain its 1:80,000.
1:100,000 1000mg:100,000mL 1mg:100mL 0.01mg/mL
This is very important and we must memorize it, since it is the most commonly used ratio in the dental local anesthetic carpules.
There will be atleast 2-3 questions in the final exam about dilutions.
The cartridge that we use contains 1.8mL of solution.
In 1.8 mL of a 1:100,000 solution, how much is there epinephrine??
1.8 mL 0.018 mg of epinephrine.

In the past, it was believed that the epinephrine that is added to the local anesthetic didn’t cause any risks, that what caused the risk is the endogenously secreted epinephrine rather than the exogenously administered epinephrine. This was believed for quite a while, until about 1996/1997. So the patients fear was the main factor (fear causes the endogenous secretion of adrenaline {fight, flight, and fright}). This is true, but there is a risk from the exogenously administered epinephrine as well.
Recent research states that the level of epinephrine after the administration of a local anesthetic carpule would be similar to the level that would be achieved during moderate exercise (e.g. jogging, or a brisk walk) . This exercise causes an elevation in the epinephrine level in the blood, and this level equals the level that is attained from the administration of a local anesthetic carpule. This means that there is a risk from the exogenously administered epinephrine that is added to the local anesthetic, there's an effect on the heart rate and the cardiac output.
ÓThe sites of action of the vasoconstrictor/epinephrine/adrenergic drugs:
The first group (the sympathomimetic/adrenergic):
As we said they act on the adrenergic receptors; alpha α, and beta β.
The activation of the alpha receptors leads to constriction. A common mistake is when we assume that epinephrine causes constriction of all the vessels, since it's called a vasoconstrictor. But this is not true; it causes constriction of some vessels and dilation of other blood vessels. It’s a vasoconstrictor to the peripheral blood vessels (or certain types of blood vessels), but it is
a vasodilator for the blood vessels in the skeletal muscles.
Also, epinephrine is a bronchodilator, so it is the drug of choice for an acute asthmatic attack or anaphylactic shock.
Ó The alpha receptors are commonly found in the mucosa or the skin, so their activation leads to the constriction of the blood vessels found in those areas.
Ó Beta 1 receptors are commonly found in the heart and small intestine, activation of them leads to an increase in the cardiac output (tachycardia), or stimulation of the myocardium.
Ó Beta 2 receptors are commonly found in the bronchi and the skeletal muscles, their activation leads to bronchodilation or vasodilation of the blood vessels found in the skeletal muscles; so once the epinephrine is injected the diastolic blood pressure drops initially.
In the oral mucosa alpha and beta 2 receptors are found, in the bronchi you only find beta 2 receptors, in the heart beta 1, in the liver beta 1 and 2, in the kidney alpha, in the skeletal muscles beta 2 and alpha.

The local anesthetic in addition to the epinephrine is first injected in the oral mucosa. The site of the epinephrine determines which receptors are predominately affected by it. For example in the oral mucosa, skin, and kidneys the alpha receptors are the predominately activated ones, not the beta 2 receptors. Therefore, the primary action of the epinephrine after its deposition in the oral mucosa is vasoconstriction. That’s why it's used in the local anesthetic carpule, that’s also why it's used as a hemostatic agent. (Always alpha denotes vasoconstriction, beta2: bronchodilation, or vasodilation, beta1: stimulation of the myocardium)
Once it reaches the blood stream, it goes to the myocardium and stimulates it (the beta1 receptors); this stimulation creates an elevation in the blood pressure. However, it also goes to the skeletal muscles and predominately stimulates the beta2 receptors (much more than its stimulation of the alpha receptors in this site; remember it all depends on the site of action), and this causes vasodilation of the blood vessels in the skeletal muscles; which creates a fall in the diastolic blood pressure; this results in further stimulation of the myocardium to compensate for this drop in the blood pressure. The final effect is an elevation in the blood pressure, an elevation in the diastolic blood pressure, an elevation in the cardiac output, an increase in the Oxygen consumption; an overall increase in the work and activity of the myocardium. This increase in the myocardium's work results in a decrease in the cardiac efficacy.
Once it reaches the kidneys it works as a vasoconstrictor, in the liver it induces glycogenolysis; and this is why we try to avoid giving a diabetic patient epinephrine with the local anesthetic, because it raises the blood glucose level. Nevertheless, this fact isn’t very accurate, because you need about 4 dental carpules of the local anesthetic (with a concentration of epinephrine of 1:100,000) for it to result in a rise in the blood glucose level. This is theoretically speaking, in practice it's not always necessarily so.
In the liver, the epinephrine is metabolized by enzymes that are secreted by the liver; but work in the blood. Enzymes such as: MAO mono amino oxidase, COMT Catechol-O-methyltransferase; these enzymes are produced by the liver but work in the blood. They degrade and inactivate the epinephrine, then its excreted by the kidney.
A common use of epinephrine is to treat anaphylactic shock, sometimes people with unknown allergies may ingest aspirin or penicillin for example, and they may go into anaphylactic shock. The drug of choice in such cases is epinephrine 1:1000 subcutaneously or intramuscularly NOT intravenously because then it may cause sudden contraction of the myocardium and result in cardiac arrest.
***Why do we give a patient who underwent cardiac arrest epinephrine??
The reason is because of its action as a bronchodilator NOT because of its work as a vasoconstrictor. In cardiac arrest cases, what concerns us is conducting a life-saving procedure, so epinephrine works as a bronchodilator to reduce the laryngeal edema.

Epinephrine is also used to treat an acute asthmatic attack; although theoretically local anesthetic carpules that contain epinephrine are contraindicated in asthmatic patients, theoretically we should use a local anesthetic carpule without epinephrine for asthmatic patients.
***Why is epinephrine contraindicated for asthmatic patients when it is the drug of choice for treating an acute asthmatic attack???
This is due to the preservative that is added to the epinephrine (we took previously that epinephrine should be accompanied by the preservative sodium bisulfite), this preservative may cause an allergic reaction in an asthmatic patient; since they are more susceptible to allergies.

Epinephrine can be used in several concentrations: 1:50,000 / 1:80,000 / 1:100,000 / 1:200,000 / 1:300,000 .
Epinephrine may be added to different kinds of local anesthetics; lidocaine; articaine; kelocaine…etc.
Later on we'll learn about the maximum dose, we should know how many carpules we could give the patient, and what the limit is whether it's 4, 5, 6, 10 carpules….we'll take this later on.
****There's a difference between a theoretical risk and a clinical risk; theoretical risk is when in theory we consider it a risk however no cases were reported to have happened to establish that risk. Once a case is reported the theoretical risk turns into a clinical one.
ÓWhat serious complications could you expect if the recorded blood pressure is 300/200??
This patient has very high blood pressure, normal blood pressure is 120/80, so the expected complications are cardiac arrest, stroke, and thrombosis NOT heart failure.

**Heart failure (HF) often called congestive heart failure (CHF) is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body.
Felypressin (Octapressin)
It is a non-sympathomimetic amide; it does not act on the adrenergic receptors , which is why it may be indicated where epinephrine is contraindicated. Therefore, patients with hyperthyroidism (hyperthyroidism is associated with many manifestations, one of which is hyper-excitability of the brain due to the increased blood flow to the brain) epinephrine given to these patients may increase this hyper-excitation; whereas felypressin which is an analogue of vasopressin (antidiuretic hormone (ADH)) does not act on the CNS, does not act on the adrenergic receptors so it is not contraindicated in hyperthyroid patients.
Mono amino oxidase inhibitors (MAOI), in the past they used to say that they are contraindicated with epinephrine, whereas nowadays they are considered to be RELATIVELY contraindicated to epinephrine; which means that they may be given with epinephrine but only in small doses and with care, and even then there is still some risk.
An example on a relative contraindication: a pregnant patient who suffered from a stroke that was caused by thrombosis; do we or do we not give her aspirin? In such a case we do give her aspirin because this is a life-saving treatment.
This differs than an absolute contraindication; in which cases you must not give the patient the drug at all, because it will definitely be a risk to the patient.
An example on an absolute contraindication: a patient suffered from a stroke that was caused by bleeding (not thrombosis), in this case we do NOT give aspirin because it will exacerbate the bleeding and cause death.
Again Felypressin is indicated where epinephrine is contraindicated, like hyperthyroidism, diabetes, or patients taking MAOI which are a type of antidepressants.
The concentration of felypressin used is 0.03IU/ml (IU: international unit) with 3% prilocaine. 3% prilocaine is produced in Germany, whereas the rest of Europe produces 4% plain prilocaine (without felypressin).
Felypressin is contraindicated in pregnant patients, it could lead to an oxytocic action (abortion).
In general, we use epinephrine with the local anesthetic for two reasons; the first is to control the pain, because the epinephrine prolongs the duration of action of the local anesthetic so this aids in controlling the pain for a longer period of time, the second reason is for hemostasis; so that there isn’t too much blood in the area we're working in, which provides good access and good vision.
In order to achieve high-quality hemostasis, we need a concentration of 1:50,000 of epinephrine. A concentration of epinephrine of 1:50,000 gives twice as much bleeding control (hemostasis) as a concentration of 1:100,000. On the other hand, in relation to pain control and prolonging the duration of anesthesia, a concentration of 1:50,000 of epinephrine gives the same effect as a concentration of 1:100,000. So, if the procedure requires good bleeding control (hemostasis); then we use a concentration of 1:50,000 of epinephrine. However, if the patient isn't medically fit; if he has a cardiovascular problem then we use a concentration of 1:100,000 of epinephrine, because 1:50,000 is a high concentration of epinephrine and this may lead to adverse effects.
Duration of action of local anesthetics without and without epinephrine:

Nerve Block (min)
Infiltration (min)
Local Anesthetic Agent
Lidocaine (B category)
Without epinephrine
With epinephrine
Mepivacaine (C category)
Without epinephrine
With epinephrine
Without epinephrine
With epinephrine
˜The nerve block method always gives a longer duration of anesthesia since it is applied to the trunk of the nerve.
˜Mepivacaine is contraindicated in pregnant patients since it belongs to category C, for pregnant patients they may be given a drug belonging to category B but NOT category C.
**The following is extra information about the pregnancy categories, obtained from Wikipedia:

United States FDA Pharmaceutical Pregnancy Categories
Pregnancy Category A
Adequate and well-controlled human studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy (and there is no evidence of risk in later trimesters).
Pregnancy Category B
Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women OR Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus in any trimester.
Pregnancy Category C
Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
Pregnancy Category D
There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
Pregnancy Category X
Studies in animals or humans have demonstrated fetal abnormalities and/or there is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience, and the risks involved in use of the drug in pregnant women clearly outweigh potential benefits.

This is a question that'll be on our exam, slightly different wording but with the same concept:
Ahmad is a dental student and has the following six choices to nerve block his patient for endodontic treatment, which is expected to last for 40 minutes??
A. 2% lidocaine without vasoconstrictor
B. 3% mepivacaine without vasoconstrictor
C. 4% prilocaine without vasoconstrictor
D. 2% lidocaine with vasoconstrictor (adrenaline) (1:50,000)
E. 2% mepivacaine with adrenaline (1:100,000)
F. 4% prilocaine with adrenaline (1:200,000)
™˜The answer is all of the above EXCEPT A. 2% lidocaine without vasoconstrictor (which only gives 10-20 minutes duration of anesthesia).
Best Wishes
كل عام وانتو بخيرJ

Done by: Hanan Musleh

Last edited by Shadi Jarrar on 6/8/2011, 11:17 pm; edited 1 time in total
Shadi Jarrar
مشرف عام

عدد المساهمات : 997
النشاط : 12
تاريخ التسجيل : 2009-08-28
العمر : 26
الموقع : Amman-Jordan


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