Anesthetics

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.

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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
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
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
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.


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