The Chemistry of General Anesthesia

Introduction

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General Anesthesia is used in surgeries to control pain and tramea (anglesia), blood pressure and heart rate ( hemodynamic stability). It induces no memory (amnesia), unconsciousness (hypnosis), and immobility through action on the spinal Cord. General Anesthesia uses intravenous drugs( inserted into the veins), and inhaled drugs.


I chose to study the chemistry of the effects of general amnesia on the body because whenever I got surgery, it was such an interesting experience, I was curious to how it worked. General Anesthesia is practiced all the time in surgeries dating back to 1846. Without the modern technology to make General Anesthesia a safe practice, many surgeries would not be performed with success.


General Anesthesia has changed the way I think about common medical procedures. I’ve had three surgeries where I went under General Anesthesia, and always remembered the beginning, and waking up. All I knew was that I  was being injected with chemicals and  had no idea what they did to my body. This sparked my interest that led to a whole research project.


Composition of ...

Inhaled Gases:


  • Desflurane C3H2F6O

  • Isoflurane C3H2CLF5O

  • Sevoflurane C4H3F7O

  • Ethyl Ether ( CH3CH2)2O

Intravenous drugs

  • Propofol C12H18O


Main Chemicals, Compounds, Components

  • Intravenous drugs: Propofol C12H18O

Propofol is a chemical administered through the veins(Intravenous) that travels through the whole body and works in the brain, since the brain is has good blood supply. Propofol travels into the brain and stimulates the  GABA receptors ( major neurotransmitter to the central nervous system), which produces sedation effects. Profol affects the central nervous system by a prominent reduction in gamma band sequences through cell membranes, making the level of unconsciousness in a person extremely deep.

  • Inhaled Gases, specifically: Sevoflurane C4H3F7O

    • Sevoflurane is an inhaled gas that predominantly has effects in the spinal cord, and central nervous system, as well as GABA receptors. Sevoflurane is a highly fluorinated Ether, commonly used with short surgeries. It is an antagonist that works on the glycine receptors (amino acid neurotransmitter glycine) decreasing mitochondrial connectivity, and arterial pressure, and an increased respiratory rate. It is thought to have direct effects on the lipid membranes, affecting gate properties of ion channels.

Chemistry's Role

All the compounds of General Anesthesia are man made in a lab. While propofol is a liquid and is injected based on weight ( 2-2.5 mg/kl),  Sevoflurane is a liquid but is made into a vapor by a machine. Because most of the Sevoflurane inhaled comes out unmetabolized in the lungs, the exhaled gas is put through a CO2 filter to be recycled again. MAC ( Minimum Alveolar Concentration) is used to determine the concentration of vapour in the lungs needed to prevent motor response (total Immobility), in fifty percent of patients. after Induction (putting the patient to sleep with Propofol).  Propofol works on  the GABA receptors in the brain. By  stimulating the GABA receptors, it produces a sedation effect on the body. The Sevoflurane vapors are then turned on to the right percent, which works in the spinal cord, central nervous system, as well as GABA receptors. It is mostly thought by scientists to have effects on  the lipid membranes of cells, affecting gate properties of ion channels, so no pain can be felt. Most surgeries paralyze the patient, so it is important to know if they are asleep or not. A way to test this is an electronic nerve stimulator. It measures patient's movements in certain nerves to test if muscle relaxants are effective. It is also used at the end of surgeries, to make sure the patient’s nervous system is responding to landing emergence (waking the patient up with less anesthesia and more oxygen).

Background Research

General Anesthesia was first publicly demonstrated by William T. G. Morton in 1846 in what is known as the Ether Dome. He used diethyl ether as an anesthetic. Sevoflurane is a highly fluorinated ether used as an anesthetic in surgery today. This type of ether is made in a lab, and the impurities and differences in certain labs that make is low. However Sevoflurane is susceptible to chemical degradation to Lewis Acids ( metal oxides and metal halides). Chemical degradation of this drug can become toxic quickly, which is why a high fluoride amount indicates drug degradation. Propofol is also man made in a lab, It is formulated containing soybean oil, egg lecithin, and glycerol. Propofol has a milky, white appearance and produces the effects of hypnosis, and analgesia. Propofol and Sevoflurane are commonly used in General Anesthetic procedures, because they're so fast acting. The work quickly, and wear off quickly because they are broken down and metabolized very efficiently in the liver.

Resources

http://blog.pedsedation.org/?p=136

Medical article to explain correlations with propofol and egg allergies.

http://www.apsf.org/newsletters/html/2007/fall/03_sevoflurane.htm

How Sevoflurane is manufactured, and the risks behind its manufacture. Like its highly corrosive quality.

http://www.scienceclarified.com/Al-As/Anesthesia.html

This article described the history of how medical professions controlled pain, as well as the difference between general, and local anesthesia. It also included the gases and chemicals used to maintain unconsciousness or pain levels.

http://humantouchofchemistry.com/how-does-an-anaesthetic-put-you-to-sleep.htm

This website showed what the three A’s of anesthesia: Analgesia (no pain), Amnesia (no memory), Anaesthesia (no consciousness)

Most common use anaesthetic-ethyl alcohol (temporary paralysis of nerve endings)

Dentists use mixture of nitrous oxide and Novocain

https://paulingblog.wordpress.com/category/theory-of-anesthesia/

Two theories of how anesthesia works:

Lipid hypothesis- anesthetic lodges in the lipid membrane of a cell, changing the shape and the way it functions.

Protein Hypothesis- interacts directly with proteins, changing shape, therefore function.

https://en.wikipedia.org/wiki/Theories_of_general_anaesthetic_action

There is no obvious structure and activity relationship, making it hard to determine how anesthetics work on the body

Commonly used chemicals are: Ethanol, Chloroform, Diethyl Ether, Fluroxene, methoxyflurane, Enflurane, Halothane, Enflurane, Isoflurane, Desflurane, sevoflurane

https://www.nlm.nih.gov/medlineplus/ency/article/007410.htm

During surgery, Doctors regulate certain doses of chemicals to put the person being given the drug into different states of consciousness.

Anesthesia can cause pain to vocal chords, stroke, heart problems, vomiting, and other strange effects like mental confusion.

https://www.nlm.nih.gov/medlineplus/ency/article/007410.htm

1 or 2 people in every 10,000 may experience unintended intraoperative awareness be partially awake, but cannot move due to muscle relaxants, and cannot speak due to the tube down their trachea.

Eyes are taped shut during operations because anesthesia reduces tonic contraction in 59% of patients, and so they eyes do not dry out while in surgery.

http://pubchem.ncbi.nlm.nih.gov/compound/sevoflurane

Sevoflurane’ s structure and properties.

http://www.openanesthesia.org/

Diagram for how General Anesthesia affects the cell membrane.

http://www.authorstream.com/Presentation/bhardwajshaels-1358890-general-anesthesia/

Helpful powerpoint explaining the basics of General Anesthesia, its effects, and how it operates.

About the Author
Holland Howe is a current student at Billings Senior High, and has many interests. She enjoys skiing, biking, science, art, and animals.  She is in Student Council, HOSA, STEM Society, Senior Advocates, cross country and skis for Silver Run Ski Team.   She plans on living in the mountains on a farm, and might  be an explorer for National Geographic, or a Nurse Practitioner.
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