Anesthetics Essay, Research Paper

Anesthesia is a partial or complete loss of sensation or feeling induced by the admin-

istration of various substances. For many decade, people have used one form of an anesthetic during

surgical procedures. Some people also use some of these anesthetics as recreational drugs, e.g.

laughing gas (a.k.a. Nitrous Oxide). The term anesthetic literally means “without feeling”. There are

many different types of anesthesia, but they are usually put into three groups. These groups are gene-

ral anesthetics, local anesthetics, and spinal anesthetics. A general anesthetic causes a complete loss

of consciousness. They are used when having a serious operation or in the case of an emergency

operation. It works to the surgeon’s advantage because the anesthesia reacts with the body in a matter

of seconds. There are two different ways in which general anesthetics are administered, they are

intravenous and inhalation. The most popular procedure is intravenous. This is where the anesthetic is

put into the body by way of a needle in the vein, which is usually located in the hand or elbow. Although

intravenous is more popular, it is usually used by itself during short procedures. In the case of longer

procedures, intravenous anesthesia is also accompanied by inhalation anesthesia. Inhalation anesthesia

is administered by way of a mask and in the form of gas. Usually during long procedures, the mask will

remain on while the fluids from the intravenous anesthesia work through your body. The second group

of anesthesia is local anesthesia. Local anesthesia is used when a doctor wants to numb a certain part

of the body while you maintain total consciousness. Local anesthetics are usually administered through

a gel or cream on the surface of the skin, but can also be injected underneath the skin, e.g. lidocane. If

the anesthetic is placed on the surface of the skin than the numbing effect should take place within a few

seconds. If injected underneath the skin, it can take up to a few minutes to take effect. Both forms of

local anesthesia are used when dealing with minor surgery such as dentistry, etc. The third and last

group of anesthetics is the topical group. This group is associated with childbirth, gynecological

procedures, and spinal operations. A spinal injection gives relief to pain, but at the same time allows

for total consciousness. Usually the syringe is injected into the epidural layer of the spine. The effects

of the spinal injection can be felt within minutes of the injection.

As I have already discussed, there are three different methods of distribution

among anesthetics, inhalant, intravenous, and infusion. An inhalant is an anesthetic in the form of a gas

which is administered by way of a gas mask. Intravenous anesthesia is administered by way of a needle

into the vein. Infusion anesthetics are administered by way of a catheter. These three methods operate

in four steps. The first of these steps is premedication or induction stage. This step involves the nurse or

practitioner to administer a form of a sedative or muscle relaxant. This step is not always required, only

when having major surgery. The second stage is when the actual anesthesia is administered. The patient

falls into a deep, pleasant state of unconsciousness. The third stage is when the drug is in full effect. The

patient now experiences a loss of consciousness, although the patients reflexes still remain active and

breathing is a little irregular. In the last stage, the fourth stage, the patient is totally unconscious.

Muscels are fully relaxed and breathing becomes regular and quiet.

Anesthesia has a long history which started in the middle 1700’s. In 1769,

an English chemist, Joseph Priestley discovered the first recognized anesthetic, nitrous oxide. Nitrous

oxide is more commonly known as laughing gas. Although the gas was discovered in 1769, it wasn’t

until 1844 when an American dentist by the name of Horace Wells, first put the nitrous oxide to use

during a dentistry procedure. The wonderful world of anesthesia was growing and becoming more and

more popular throughout the United States as well as in England. The next important discovery took

place in 1829. In 1829, an American, Micheal Faraday reported that the inhalation of ether caused a

person to go into a state of unconsciousness. Using ether as an anesthetic was not very popular, though.

It was first used in 1842 when, an American doctor, Crawford W. Long removed a tumor off of the neck

of one of his patients. The second recorded use of ether was by the American dentist, Thomas Green

Morton in 1846. Morton along with the help of Charles Thomas Jackson, an American chemist, devel-

oped a technique for painless tooth extraction with the assistance of diethyl ether. In 1831, an American

physician and chemist, Samuel Guthrie was the first to discover chloroform and its uses. The first to use

chloroform during a surgical procedure was Sir James Y. Simpson. Simpson was a Scottish obstetrician

whom was not satisfied with the action and reaction of ether. Simpson was the first to adopt chloroform

as a useful anesthetic in surgical procedures. In 1884, Sigmund Freud was the first to report cocaine’s

anesthetic properties. An Austrailian physician, Karl Koller, took this report of cocaine as an anesthetic

and applied it to surgical procedures. Koller’s surgical procedure was even more important because it was

the first procedure to take place while using what we now call “local anesthesia”. Cocaine was the first

local anesthesia to be discovered and used in a surgical procedure. William Stewart Halsted, a profesor

of surgery at John Hopkins University in Baltimore, was the first to use cocaine to anesthetize whole areas

of the body by directly injecting the cocaine into the nerve. In 1898, Karl Gustav Bier injected cocaine

into vertebral canal and obtained paralysis of the lower extremities of the body. He used this method in

surgical procedures. Since then this procedure that he discovered is know as spinal anesthesia and is

widely used today. At around 1901, J.L. Corning used cocaine to produce a useful spinal anesthetic,

which in turn produced two important cocaine derivatives, novocaine and procaine.

Many other important analgesics and their uses came about between 1800 to

1900. Ethyl chloride which was introduced to us in 1848, was too short lived. Surgeons needed an anesth-

etic that was non-toxic and non-inflammable. So in 1929, cyclopropane was introduced to the medical

world, but soon enough the medical world found out that the drug was inflammable. In 1934, trichloreth-

ylene was first used. This drug on the other hand came along with two advantages. It reduced the

awareness of pain while maintaining full consciousness, which made the drug ideal for childbirth use.

In 1874, Ore of Bordeaux, was the first to achieve an intravenous anesthesia.

He used Chloral to achieve this intravenous anesthesia. In 1902, Emil Fischer performed a synthesis of

Veronal. The synthesis caused the use of intravenous anesthesia to be widely excepted and performed.

After Veronal many other analgesics were produced and discovered. After 1945, two specific drugs came

into use with anesthesia. These two drugs are curare and succinylcholine. Both of these drugs are used in

anesthetics as a muscle relaxer. Curare prevents the nervous impulses fromreaching the muscels. Thus

blocking the it at the neuromuscular junction where the nerve transmitter substance, acetylcholine, is

stored. The curare that is used in anesthesia is refered to as tubocurarine. Succinylcholine is used to

neutralize the action of acetylcholine in the neuromuscular junction. These anesthetics and their

derivatives are still used today.

Another form of anesthetic used on the body is hypothermia. This is where

the body temperature is lowered by about ten degrees. Hypothermia is achieved by cooling the patient

with ice, wet sheets, and fans. Although this helps in cooling the body it does not stop the body’s natural

responses to the cold. These responses are centered around the part of the brain called the hypothalamus.

Some of these responses are shivering, etc. The body has these responses because it is trying to keep the

body’s heart, temperature, and blood pumping at a constant rate. In order to stop these responses

doctors use a drug called chlorpromazine or they use promethazine, which also has a tranquilizing

effect. This whole process is used because it lowers the amount of oxygen consumed by the

tissues in the body. This also causes vital organs in the body to consume a lower amount of oxygen.

The less oxygen the smaller amount of blood that is rushed to the brain and other vital organs within

the body during surgery. In turn the brain and other vital organs will still function just at a slower pace.

This is an advantage to brain and heart surgery because these operations require more time and this

allows for it without causing permanent damage to the body.

There are many different effects of anesthesia on the body. There can

be a dramatic drop or rise in blood pressure. A person’s blood pressure may also drop or rise if the

patient goes into shock or has lost too much blood. Some anesthetics cause nausea and sickness.

A rare reaction that sometimes occurs when administered general anesthesia is juandice. Doctors

try to choose an anesthetic that induces unconsciousness rapidly and has the least 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. 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

Bibligraphy

Anesthesia: The Curing Sleep. Swift, W. Bradford. Cats Magazine. South Daytona . January 1990

Vol. 47, Iss. 1, Pg.17.

Best Medicine: Under and Out. Saline, Carol. Philadelphia Magazine. Philadelphia. November 1988

Vol. 79, Iss. 11, Pg. 45.

Anesthesia Cutoff Phenomenon: Interfacial Hydrogen Bonding. Chiou, Jang-Shin. Science. Washington.

May 4, 1990. Vol. 248, Iss. 4955, Pg. 583-586.

Tropospheric Lifetimes of Halogenated Anesthetics. Brown, A.C. Nature. London. October 19, 1989

Vol. 341, Iss.6243, Pg. 635-638.

Anesthesiology-First of two parts. Wiklund, A. Richard. The New England Journal of Medicine. Boston

October 16,1997. Vol. 337, Iss. 16, Pg. 1132-1142.

An Anesthesia Mask Gas-Scavenging System. Schapera, Anthony. Journal of Occupational Medicine.

Baltimore. November 1993. Vol.35, Iss.11, Pg. 1138.

Ludovici, L.J. The Discovery of Anesthesia. New York. Cone of Oblivion. 1961.

United States Pharmacopeia. Complete Drug Reference. Yonkers, New York. United States

Pharmacopeial Convention Inc. 1992.