Anesthetics

.. amount of side effects. Throughout the country there are many different types of anesthetics used. Some of the most popular anesthetics are used in U.S. hospitals across the region.

Among general anesthetics, cyclopropane, ethylene, and halothane are the most popular. Cyclopropane and ethylene are used with caution because they are highly explosive. Halothane is the most prefered over the three because it is neither inflammable or explosive. Amongst intravenous anesthesia, Pentothal sodium is the most popular. This is because it produces the least amount of side effects during and after a surgical procedure. Block anesthesia is the most common and popular of the group known as local anesthetics.

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Block anesthesia is often called this because it blocks the nerves, to that specific area, off so that the patient feels no pain within that immediate area. The two most popular types of block anesthesia are spinal and caudal. They are both administered during the child bearing process. The most common drug used in these blocks are procaine hydrochloride. As far as topical anesthetics go, xylocaine is the most popular. It is used extensively when the patient is receiving stitches or going through simple dentistry procedure.

These are among the most useful and important in the anesthetic industry. Since the early 18th century, many advances have been made in the field of anesthetics. Inhalation anesthesia has had three main advances in the course of its history. These advances include sevflurane, desflurane, and xenon. Sevoflurane was first synthesized in 1960, but has just recently become widely distributed for general use.

Sevoflurane is a methylpropyl ether because it is highly insoluble. For example it is three times more soluble in blood than halothane is. Since sevofl- urane has low solubility, it enables the anesthesia to act faster in the human body. Recovery from sevo- flurane is also rapid. When inhaling sevoflurane it does not irritate the airways.

This allows a rapid as well as pleasant induction and awakening. Sevoflurane has become extremely popular, especially among children. There is a downfall however, it is too expensive to produce in large quantities. Desflurane was also first synthesized in 1960, but has just recently been introduced to the medical world. Basically, des- flurane has the same properties as sevoflurane, but it is an irritant to the airways when inhaled. Over 50% of the people who use this product develop some form of laryngospasm.

Although this is a major down fall, the drug is very inexpensive to produce. This allows for more research to be done to improve the drug because there is a greater amount of left over funds after producing the drug. Xenon, another important inhalant, is an inert gas. Xenon is still prohibited for medical use because it is a fairly new discovered drug that seems to have anesthetic properties. It is extremely insoluble in the blood. This causes it to have an extremely fast induction and recovery. It is not extremely potent when it is used by itself, but could someday replace nitrous oxide as a general anesthetic. Xenon exhibits all the analgesic properties to eventually become an important anesthetic in the medical world.

Many advances have also been made to intravenous anesthetics as well. One of the newest types of intravenous anethesia is propofol. It is the newest intravenous drug to date. It was introduced to the medical world in 1984. Since then there have been incredible advances made in the administration, distribution, and maintenance of the drug, propofol.

The drug has very few side effects, which include a mere nausea and drowsiness. It has a very fast recovery and induction. One major disadvantage, though, is that it is difficult to acheive the desired plasma concentration by manual control of the infusion rate. In order to maintain a constant flow the infusion rate must be changed frequently. This is when the target controlled infusion rate technique takes place.

Target controlled infusion is what allows the anesthesiologist to set a desired plasma concen- tration, which the software inside the infusion pump produces rapidly, but safely by controlling the infusion rate according to complex, but standard pharmacokinetic equations (basically medical equations). Remifentanil is a new potent, yet synthetic opiod that is ideally suited for infusion during anesthesia. Unlike other opiods, remifentanil contains a methyl ester in its structure which causes a rapid metabolism of the drug within the body. Remifentanil is now used as a neuroanesthetic and in the future will probably be used as a cardiac and cardiovascular anesthetic. Many advances have also been made in the medical world concerning local anesthetics. Amongst these local anesthetics, the most popular and up to date are bupivacaine and ropivacaine. Bupivacaine is frequently used in postoperative pain releif.

Induction to this anesthetic is rapid and lasts very long. It can last for several hours depending on the dose given. The bupivacaine molecule exhibits stereoisomerism in each one of the two enantiomers, which are R(+)bupivacaine and S(-) bupivacaine. The R(+) form of bupivacaine is 3-4 times more likely to cause cardiovascular toxitity in rabitts, sheep, and humans. Ripovacaine is very similar to bupivacaine, but it is only prepared as S(-) ripovacaine isomer. Ripovacaine was proven safer than bupivacaine in many clinical studies. Anesthesia has an unusual property.

It is known as the cutoff phenom- enon. The cutoff refers to the loss of anesthetic potency in the homologous series of alkanes and their derivatives when their size becomes too large. Apparently the potency increases with the length of the chain until the chain reaches fourteen carbons. At the fourteen carbon mark, the anesthetic has no potency whatsoever. The anesthetic potency increases rapidly from a two carbon chain (ethanol) up to a ten carbon chain (decanol). From the eleven carbon chain to the thirteenth carbon chain the potency remains the same.

When the carbon chain finally reaches the forteenth carbon, the potency suddenly disappears. Scientists predict that this happens because the binding site is not large enough to accomodate long chained alcohols or because of the low water solubility of longer 1- alkanols limits their access to the action sight. Scientists studied this through changing the 1- alkanol series to DPPC ( dipalmitoyl-L-a-phosphatidylcholine). They did this through a procedure known as hydrogen bonding. Through hydrogen bonding transitional phases occured. In these phases scientists proved that in between the transition of temperature, which also changed the state of matter, there was a certain point at which there was no affect on the DPPC.

Scientists also learned that the primary action site for anesthetics are the macromolecules of water. In conclusion C2-C10 are known as anesthetics and C14+ are known as nonanesthetics. In anesthesia, high polarizability causes hydrogen bond breaking which causes anesthesia to work (e.g. cyclopropane). Also increased hydrophobicity along with relaxaion of membranes and proteins cause anesthesia to work. Anesthetics have many advantages.

They are great in eliviating pain before, during, and after a surgical procedure. They also make the procedures much more easier. Anesthetics give a desired affect which is good because it helps us as a patient to relax and feel calm and pleasant. Anesthetics have been around since the begging of the 1700’s. Scientists have gathered a tremendous amount of information concerning anesthetics. Many advancements have been made and will continue to be made. Throughout history man has searched for a way to stop pain. Whether it be a sore tooth or a broken limb, man has tried many different things to try and to get rid of that pain that he feels.

The most modern way to eliviate pain is through the use of anesthetics. Although many of them have side effects, they are improving and as long as our world and economy keep moving ahead and technologically advancing, we will be able to perfect all of the anesthetics. In the future there will prob- ably be new techniques used to administer and distribute anesthetics, but for now these drugs seem to be doing the trick. As we enter into this new millennium, I hope to see more advances concerning anesthesia in this colorful world that we call the U.S. Bibliography Anesthesia: The Curing Sleep.

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