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The Science Of Anesthetics

by — 2014-10-26 in Drugs & Medications
Pain is a feeling that we are all afraid of, but thanks to the work of doctors, we don´t have to worry about it anymore. The introduction of anesthetics into the medical world has made surgical treatments not only pain free but also safer.

Physical pain is certainly an unpleasant feeling to deal with and scientists and doctors have always looked for alternatives to reduce it in order for them to be able to carry out medical procedures than can go from a tooth extraction, which is actually not as simple as it may sound, to an open heart surgery. In the past, pain during surgical procedures was something that could not be avoided and patients had to put on with excruciating pain  but the discovery of inhaled anesthetics came to revolutionize the whole concept around pain and consciousness.

A bit of history

In 1846, in the Massachusetts General Hospital in Boston, the first surgical procedure using ether to anesthetize a patient was performed. Although this type of sedative had already been used before, this was the first publicized attempt of using ether as an anesthetic agent.

After ether, chloroform was also introduced as a general anesthetic due to its effectiveness, even though it had more side effects that its predecesor.

Then, in 1877 the concept of local anesthesia began with the use of cocaine as a sedative, event that promoted the search for less invasive and more effective procedures to reduce or avoid pain.

Following cocaine, local infiltration, nerve blocks and spinal and epidural anesthesia made it possible to perform medical procedures without driving the patients into a complete sedated state and of course, allowing doctors a better control of the whole process.

Types of anesthesia

There are three types of anesthesia, depending on how they are administered and the region that is intended to be sedated.

Local anesthesia is used to stop the sense of pain in a small region of the body. For example, a local anesthetic, which can be in the form of a spray, a liquid that is injected or a cream or gel, can be used to numb the area of a wound, in order for the doctor to be able to clean it and stitch it. When you are under local anesthesia, you remain conscious since only a specific area is sedated and the amount of anesthesia used is not enough to reach your brain.

Local anesthetics only affect the nerves that process pain and that are present in the region where the anesthesia is applied.
These nerves are blocked and cannot send signals all up to your brain in order for it to codify pain signals and send the response back, which is the actual feeling of pain.

There are several local anesthetics, including lidocaine and novocaine. Sound familiar? They are very similar to cocaine, but are not as strong in terms of causing addiction. The effect of local anesthesia lasts for a few hours and pain can be felt after the effect wears out. 

Dealing With Sedation And Consciousness 

If the doctor has to perform a more invasive medical procedure that involves the exposure of a wider body area, for example the leg, the type of sedation to use would be regional anesthesia. But if the surgery comprises a more complicated procedure, such as the removal of a tumor or a kidney, general anesthesia would be used. Both of them involve the use of stronger dosis of anesthetic and the constant monitoring of the specialist. 

Regional anesthesia 

There are two types of regional anesthesia. The first one is called spinal anesthetic because it is applied in the subarachnoid space that surrounds the spinal cord and it is used to numb the lower abdominal, pelvic, rectal and lower limbs body regions. The second one, the epidural anesthetic, is similar to the spinal type but it is applied outside the subarachnoid space and is mainly used to sedate the lower limb region in women during labour and childbirth.

Both spinal and epidural anesthetics require constant infusions of the sedative substance, which are usually the same synthetic anesthetics used for local anesthesia, but in higher doses.

In order to avoid several injections in this area, the anesthesiologist leaves a small catheter during the first injection, through which it is possible to administrate more anesthetic if required.

Regional anesthesia involves more risks than the local one, because it is applied in a very delicate area of the nervous system and because it basically blocks the nerves of a wider body area, but the patient is constantly monitored by the specialist during the procedure. 

General anesthesia

General anesthesia causes a state of unconsciousness and the inability to move. This type of sedation is used in major surgeries and can be achieved by using inhaled anesthetics, anesthetics in solutions that are administered directly into the bloodstream or both.

How does it work? Scientists are not quite sure about the mechanisms involved in general anesthesia, but they believe it acts at three different levels of the nervous system.

First, it acts at the level of the spinal cord, affecting the ability of the patient to move; second, it blocks signals in the brain stem, causing unconsciousness, and third it reaches the cerebral cortex.

Because the patient is unconscious under general anesthesia, it is necessary to externally control the breathing process by introducing a breathing tube into the windpipe of the patient, to help him or her breathe during the surgery.
The administration of the sedative agent is administered constantly and is monitored during the whole procedure by the anesthesiologist.

See Also: Brain Recovery After Anesthesia

When the surgery ends, the administration of the sedative is ceased gradually in order to bring the patient into a conscious state again.

Just as any other medical procedure, anesthesia has intrinsic risks, specially related to unexpected allergic responses to the anesthetic; however, anesthesiologists are well prepared specialists that, after a complete evaluation of the health state of the patient and the type of surgery to be performed, will determine if the patient can undergo surgery and will monitor the patient´s state before the surgery starts, during the period of unconsciousness and until after the patient wakes up from anesthesia. 

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