Tag Archives: anesthesia

Anesthesia, Safe or Not?

Throughout my life I’ve had a couple of surgeries. Every time I have received surgery, my mother always asked the doctor, “Do you have to use general anesthesia?”. In times like that I have always told myself, why does my mom even ask, of course the doctors are going to use general anesthesia, why not?  One day I asked my mother “Why do you ask the doctors the same question every time?”, and she told me that general anesthesia was very dangerous, and if it is unnecessary it would be better not to use it. This is why I chose to research general anesthesia. I would like to formulate my own conclusions about the dangers of general anesthesia. The way I will do this is through a careful analysis of the facts, side effects and the way general anesthesia works. I will also use my knowledge of chemistry to aid me in making my conclusion.

The functions of anesthesia include: analgesia (no pain), amnesia (loss of consciousness), impairment of skeletal muscle, and weakened autonomic responses. The most important part of anesthesia is that after the surgery all of these effects can be reversed.  Not all anesthetics will provide all of these effects. For example, barbiturates are not analgesics, but will bring loss of consciousness. This is often why most anesthesias are a combination of many anesthetics.

Anesthetics have many side effects. The first one is a decrease in respiration. Anesthesiologists deal with this by attaching all patients to ventilators during surgery. The second most common side effect is nausea, when a patient is under general anesthesia, their lower esophageal sphincter is relaxed. To avoid death by aspiration, doctors use endotracheal tubes to provide ventilation.

Endotracheal tube

Picture 1: Endotracheal Tube

The third side effect is hypothermia. To prevent this side effect is one of the major goals for anesthesiologists. Anesthesiologists prevent hypothermia by warming the fluids (anesthesia), which are injected into the human body.

How does anesthesia work? Anesthetics block certain protein receptors, inhibiting the protein from performing its task. For example, the NMDA (N-methyl-D-aspartate) receptor is one of the main mediators of excitatory neurotransmission. The receptor is an ion channel, which permits the movement of calcium, sodium and potassium across the post-synaptic membrane. Anesthesiologists inhibit this protein receptor by depolarizing the cell with the anesthesia, which then results in the protein receptor not completing its task. Anesthesia depolarizes the cell inducing the cell with a net positive charge.  (Gambulos)

NMDA receptor

Picture 2: NMDA Receptor

The Ca2+ and Na+ enter the cell and induce a net increase of 3+. The anesthesias, which are involved, are Xenon, Ketamine (C13H16ClNO), and nitrous oxide (N2O). (Gambulos)

Anesthesias are really useful in putting you to “sleep”, but once surgery is over and you wake up you don’t want these chemicals to linger around in your body.This diagram shows how propofol (C12H18O) interacts with your metabolism in order to exit the human body.

Propofol and your metabolism

Picture 3: Propofol exiting the body

The propofol interacts with the liver glucuronate and sulfate conjugation. Then is excreted into the urine to exit the body. Usually 70% of the propofol is gone in 24 hours, and about 90% is gone in 5 days.

Before I started this blog assignment I thought anesthesia was the “simple” part of surgery. After doing all this research I have realized that the anesthesiologists must consider many things before using an anesthesia.  For example, if the anesthesia will interact correctly with the patients protein receptors. The anesthesiologist’s job doesn’t stop there, while the patient is “under” they must ensure that they are ready to deal with any side affects that might occur from the anesthesia, and after surgery is complete the anesthesiologist must then ensure that the anesthesia administered must exit the human body safely.

In conclusion, general anesthesia is safe. The side effects are all dealt with appropriately. For example, the hypothermia is dealt with warm anesthesia pumped through your veins. After examining the way anesthesia works, obstructing the function of protein receptors, I have realized that drugs work the same way. The reason why drugs are so dangerous is because often it is difficult to stay within the therapeutic window. Anesthesiologist deals with this by constantly staying by your side, ensuring that the drugs in your system do not exceed the toxic level or go under the therapeutic level. Finally the last part of anesthesia is the way it exits your body. Your body does this through a reaction of the anesthetics with your liver glucuronate and sulfate conjugation. Then the anesthetic proceeds to your urine. At first I thought this was dangerous, but then I remembered that almost every adult drinks alcohol, and 90% of the ethanol, from alcohol, is broken down by your liver. Therefore I concluded that the way anesthesia leaves your body is not so dangerous after all.

References

Garcia, Paul, Scott Kolesky, and Andrew Jenkins. “General Anesthetic Actions on GABAA Receptors .” PMC. Bentham Science Publishers, n.d. Web. 25 Mar 2013. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2866459/>.

Gambulos, Rachel. N.p., 20 04 2008. Web. 25 Mar 2013.

Gordon, G. (2010, August 31). Propofol-3. Retrieved from http://www.anesthesiawiki.net/metrohealthanesthesia/MHAnes/edu/ivanes/propofol3.htm

Lundbeck Institute. (n.d.). Nmda receptor, showing different subtypes. Retrieved from http://www.cnsforum.com/imagebank/item/hrl_rcpt_sys_NMDA/default.aspx

Oda, Yutaka. Hamoka, N. Hiroi, T., Imaoka, S., Hase, I., Tanaka K., Funae Y., Involvement of Human Liver Cytochrome P4502B6 in the metabolism of Propofol. The British Journal of Pharmacology. 51. 281-285. 2001.

Thomas, Shawn. Drug Reference for FDA Approved General Anesthetics @ Neurotransmitter.net. 2007.