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What is a Vasoconstrictor?

What is a Vasoconstrictor?

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Vasoconstrictor

Vasoconstrictor is the one which causes constriction of the blood vessels. Vasoconstriction is the contraction of the blood vessels resulting from contraction of the muscular wall of the vessels, mainly the large arteries, small arterioles and veins. Vasoconstriction method is the opposite of vasodilation, the widening of blood vessels. The process is mainly significant in stopping hemorrhage and acute blood loss. When blood vessels constrict, the flow of blood is limited or reduced, thus, maintaining body heat or rising vascular resistance. This makes the skin turn paler due to the less blood reaches the surface, decreasing the radiation of heat. On a larger level, vasoconstriction is one mechanism by which the body regulates and maintains an average blood pressure in a person. Vasoconstrictors or vasopressors are the substances that are causing vasoconstriction. Vasoconstrictor is any substance that makes the layer of smooth muscle in the blood vessels to contract and as a result constricting the width of the blood vessel. vaso refers to blood vessels and constriction means to close down. General vasoconstriction typically results in an increase in systemic blood pressure, but it may also take place in particular tissues causing a confined reduction in blood flow. The degree of vasoconstriction may be slight or severe depending on the substance or condition. Several vasoconstrictors also cause pupil dilation, a physiological response that varies the size of the pupil of the eye.

 

What are the medications that cause vasoconstriction?

Medications that cause vasoconstriction include:

  • Antihistamines
  •  Decongestants
  •  Stimulants that are used to treat ADHD.
  •  Vasoconstrictor eye drops are available without a prescription, but are not recommended for long-term use. These drops can cause "rebound redness" in which the constricted blood vessels relax, dilate and cause even more redness than before.

 

How does vasoconstriction take place in anesthetics?

The local blood vessels start to absorb the unused anesthetic as soon as it is injected, whatever may be the pace in which the anesthetic agent enters a nerve. With the intention of slowing down this process, manufacturers of these solutions add a substance that in low concentrations in order to cause the local blood vessels to constrict, or narrow down. This limits or controls the quantity of blood and plasma entering and leaving the area of the injection which has the net effect of slowing the vascular absorption of the anesthetic solution. This makes the unused anesthetic solution to stay in place longer and extends the action of the drug. This action is performed by a substance called a vasoconstrictor. The vasoconstrictor used is the naturally occurring hormone epinephrine or one of its analogs named levonordefrin.

 

Why is Epinephrine a perfect vasoconstrictor?

Epinephrine, also known as adrenaline is a naturally occurring hormone and a neurotransmitter. Epinephrine is a perfect vasoconstrictor because it is produced naturally by the body as adrenaline, occasionally called the "fight or flight hormone". If it enters the normal circulation, it can cause an increased heart rate and stronger heart beat with a feeling of anxiety, besides causing a constriction of blood supply. So, it increases heart rate, constricts blood vessels, dilates air passages and participates in the acute stress response of the sympathetic nervous system, one of the three parts of the autonomic nervous system. These side effects describe for the "rush" that some people feel after getting an anesthetic shot.

 

What is the concentration of vasoconstrictor in Anesthesia?

The concentration of vasoconstrictor in any given carpule of anesthesia is represented by a ratio of vasoconstrictor per mL of solution. For instance, a solution may be labeled as 1:100,000. This concentration represents 1000mg/100,000mL or 0.01mg/mL, or 1 gram per 100 Liters. A 1:1000 solution translates to 1 mg vaoconstrictor per mL of solution, or 1 gram per Liter. Most anesthetic solutions contain the minimum amount of anesthesia required to constrict local blood vessels and extend the action of the anesthetic. A few, however, contain a higher concentration of vasoconstrictor for use in controlling bleeding for specific purposes, such as periodontal surgery. For instance, general purpose lidocaine contains epinephrine in the amount of 1/100,000 for producing deep, extended anesthesia. On the other hand, lidocaine also comes with epinephrine at twice the normal concentration (1/50,000) used mostly by periodontists who need to control gingival bleeding during surgery.

 

What is the advantage of anesthetics that don't have a vasoconstrictor?

  • The majority of anesthetic solutions have added vasoconstrictor. Only two, mepivicaine and prilocaine are sold with or without vasoconstrictor. Mepivicaine and prilocaine have the advantage of producing only minor vasodilation and, though both are short acting without their vasoconstrictor added. However, they still produce sufficient anesthesia for short procedures. The most important advantage of using an anesthetic without a vasoconstrictor is that there are virtually no interactions with other drugs the patient may be taking. 
  • Also, carpules that do not contain vasoconstrictor do not contain preservatives either. This is a vital point, because it is most often the preservatives, and not the anesthetics themselves which play a role in allergic reactions. There has never been a recognized case of allergy to the modern amine based anesthetics themselves; nevertheless, many people are allergic to the preservatives linked with the vasoconstrictor.

 

What is the disadvantage of anesthetics that don't have a vasoconstrictor?

The use of vasoconstrictor has a disadvantage. These naturally occurring hormones are not very stable, and must be stabilized by the addition of an acidic preservative. The presence of the preservative can lower the PH of the anesthetic solution to the range of 3.8 to 5.0, thus reducing the amount of the neutral basic radical (RN) and slowing the beginning of action of the anesthetic. This effect is, however not particularly major, and anesthesia with vasoconstrictor is a very popular choice among practitioners when other medical considerations authorize its use.

 

When should a vasoconstrictor be avoided?

Vasoconstrictors are not used in any part of the body in which the blood supply must "double back" on itself. This includes such blind ended appendages as the tip of the nose, or the fingers or toes. In these areas, a vasoconstrictor may block all blood flow to the appendage causing tissue necrosis. Vasoconstrictors may not be used with certain types of blood pressure medications or tri-cyclic antidepressants.

  • Uncontrolled hypertension
  • Uncontrolled hyperthyroidism
  • Patients with angina
  • patients who have lately had a myocardial infarction
  • Patients taking non-selective Beta Blockers, such as carteolol (Cartol), carvedilol (Coreg), labetolol (Normodyne, Trandate), nadolol (Corgard), penbutolol (Levatol), pindolol (Visken).
  • Patients taking tri-cyclic antidepressants, such as amitriptyline (Elavil), amoxapine (Asendin), clomipramine (Norpramin), doxepin (Sinequan), Imipramine (Tofranil), nortriptyline (Aventyl, Pamelor), protriptyline (Vivactil), trimipramine (Surmontil). If the patient is taking one of these, the amount of vasoconstrictor must be limited to no more than 3 carpules of 1/100,000.
  •  Cocaine is always hazardous with vasoconstrictor.

 

Are vasoconstrictors safe?

The use of vasoconstrictor in dentistry has been proven to be very safe for approximately all patients. Actually, the use of vasoconstrictor is highly recommended due to the increase in effectiveness and prolonged existence of dental anesthesia. There are no absolute contraindications to the use of vasoconstrictors in dental local anesthetics, as epinephrine is an endogenously produced neurotransmitter. According to the American Heart Association and the American Dental Association, the characteristic concentrations of vasoconstrictors present in local anesthetics are not contraindicated with cardiovascular disease so long as preliminary objective is accomplished, the agent is injected gradually, and the smallest effective dose is offered. 

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