Anesthesia is a partial or complete loss of sensation or feeling induced by the administration 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 aving 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 ccompanied 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. . lidocane.
If the anesthetic is placed on the surface of the skin han 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 njection. 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 ajor 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 nesthetic, 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 atisfied 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 f 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 nalgesics 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 ntravenous 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, cetylcholine, 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 ypothalamus. 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 urgery. 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 xample 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 roperties 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 xtremely 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 nfusion 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 opular 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 leven 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 dvantages. 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 et 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.
