Inhalation Anesthetics

In the early 16th century, Vale brings successfully synthesis the diethyl, and in the relative peace which was written by Cordus and Paracelsus, it mentions that the diethyl has the ability to kill the pain. In the middle of the 18th century, Priestley discovered the Nitrous Oxide which is well known as the ‘laughing gas’ in 1782, in 1788 Davy proved that the ‘laughing gas’ has the ability to kill the pain based on Priestley's discovery. In 1782 Black analyzed the appearance of the carbon dioxide; based on this Hickman found the fact that if animal sucked in the highly concentrated carbon dioxide, the animal will be anaesthetized, but it has never been tried out on the human body. In 1818, Faraday found the anaesthetize character of diethyl. In 1849, the Inhalation anaesthesia really came into people’s eyesight. Because an American country doctor Long successfully used the diethyl as the inhalation anaesthetic before he did the surgery of removing the tumour from the patient’s neck in 1842. Even though this is a huge thing in the anaesthetics’ history for this is very first surgery used the diethyl clinically, but the public got to know that at 1849 just because he did the surgery in the suburb, thus no one noticed that until 1849. Two years after the success of Long, Chemist Colton showed to the public that the ‘laughing gas’ is able to make the patients lost their feelings. This presentation really catches the attention of the doctor Wells, thus he tried Colton’s method while he was pulling out his own teeth and he proved Colton’s presentation was actually working in the clinical condition. In 1845 Wells did the presentation again; however, this time because he used too concentrated Nitrous Oxide, the cyanosis appeared on him after the anaesthesia has completely gone. In 1846 dentist Morton and chemist Jackson worked together and did the first experiment of the combination of the dentist surgery and the anaesthetic effect caused by the diethyl vapour, and it ended up with success. In the same year in Massachusetts, there was a big surgery had successfully been done by using the diethyl anaesthetic. All of these show the diethyl anaesthetic is completely working in the clinical environment, and this shows the starting of the modern aesthetics. In 1950s Halothane and Methoxyflurane appeared. In 1963 Terrell successfully synthesized the Enflurane. Because of the development of these new drugs the diethyl anesthetic is slowly getting forbidden, because diethyl is explosive, flammable and have a strong pungent smell, because of these characters it will stimulate the air tube and cause the increasing of the Glandular Secretion, the other reason why it is getting forbidden is it is easy to cause accident.

Here are some of the individual samples which are in details.

Halothane (Fig (3.1.1).1), one of the Inhalation anaesthetic drugs. It is colourless, easy to flow and have a pleasant smell. The character of it is not so stable, for it will decomposition into Haloid acid when it meets the light or heat. Also, it can easily mix with the ethanol, Chloroform or diethyl.

It has a strong property in anesthetic than the diethyl, and the thing good about the Halothane is it does not stimulate the mucous membrane. Compare to other types of anesthetic drugs it takes a shorter time to finish the Anesthesia induction process which brings a lot of benefits such as not a lot of secretion has been produced, not going to cause coughing and so on. Even though it has so many advantages but still there are other points which it is weak at just like all the other drugs. Halothane has a strong effect om depressing the heart and it is weak at the result of anesthetic effects and the muscle-relaxing effects. So because of these properties it is normally used as the general anesthesia and the anesthesia induction in the big surgery.

After we have seen something about the Halothane, let us move onto the Nitrous Oxide. Nitrous Oxide has another name called ‘Laughing gas’. It is a gas which has a sweet smell, thus when the patients use it they will feel pleased and relaxed. Because of its short anesthetic indication time period, it is a perfect gas to be used in anesthetic indicate area. So Normally we always mix it up with other anaesthetics in order to achieve the aesthetic result which we want to achieve. In the lab we heat up the ammonium nitrate in order to make the thermal decomposition happens on it, which means the water and the Nitrous Oxide will both be formed. The mainly way of using the Nitrous Oxide is in the medical area but it also has been used in other areas; like it is used as an oxidation agent in the rocket. The benefits of using the Nitrous Oxide instead of other agents is it is not toxic, stable under the room temperature and easy to store and to use during the fly. In the medicinal area as we all know that it is used as an anesthetic drug. Nitrous acid has a structure of straight line of (N-N-O), the central N atom uses Sp hybridization and it forms two Sigma bonds and two Pie bonds, the oxidation number for the N is +1. After we had a look at the basic chemistry information about the Nitrous Oxide, I think it is a good time to look at the method of how to use it in the clinical environment and how much to use as well. Because Nitrous Oxide is an inhalation anesthetic so the only method for using it will be sucking it into the lung. However, the pure Nitrous Oxide is not suitable for that because it may cause the suffocation owning to the strong effect of anesthetic. Thus it must be used by mixing up with the oxygen. Because of its short anesthetic introduction time period, either human or animals can wake up shortly if there is no further more of it is supplied. About how much we should use? Well, it depends, it depends on the weight and the size of the animal or human who is taking it, normally for a small animal the mixture of 75%of Nitrous Oxide and 25% of Oxygen will be suitable.

Fig (3.1.1).1 Halothane