What is Anesthesia?

A reversible lack of awareness caused by the inhalation (of gases) or injection of (liquid) drugs
It is used to minimize pain, discomfort, and shock for surgical patients
It can put medical staff at ease knowing that they won’t hurt the patient

General Anesthesia

A loss of consciousness in the patient accomplished through injected and inhaled drugs
Purpose: provides loss of pain response, loss of memory, loss of motor reflexes
The anaesthetic affects the brain
Used for lengthy surgeries or where the patient needs to be held in a specific position

A loss of sensation in a certain area of the body through injected drugs
Is achieved when the anaesthetic “freezes” the nerves around a specific area of the body
Some common local anaesthetics are: procaine, bupivicaine and proparicaine
Much safer that general anesthesia, as only one part of the body is receiving the drug

For most of history, all surgical procedures were performed without any effective painkillers
Alcohol, opium, cocaine, blood letting, extreme cold and concussions were used as first anaesthetics
In Canadian/American wars, solders had to get amputations without any painkillers
Beginnings of Modern Anesthesia
The first major breakthrough in anesthetics occurred on October 16 1846 when William T.G. Morton performed the first successful live demonstration of diethal ether anesthesia on a patient
The anesthesia allowed Morton to painlessly remove a tumor from the back of his patients neck
Ether was among the first of successful anesthetics to be used but it had several drawbacks: it induced vomiting and was very flammable

Over time, anesthesia has improved and new chemicals that create an anesthetic effect have been discovered through trial and error
These include nitrous oxide[N2O] Halothane [CF3CHClBr] and Isofluorine[CF3CHClOCHF2] (for general anesthesia)

Must be non toxic, with minimal side effects
Must be non-flammable
Must have a reasonably high blood (water) solubility to make sure it can be transported from the lungs to the brain (but not too high so the anaesthetic stays too long in the bloodstream)
Has to have a high solubility in the fatty tissues of the brain so it will concentrate onto the cells of the nervous system to cause unconsciousness

Gay Lussacs law states that Temperature and pressure are directly proportionate.
The solubility of gas decreases with pressure (Henry’s Law)
The solubility of gas decreases with temperature
In anesthetics, the gas must have a boiling point slightly above room temperature so that the gas will be highly soluble
Low temperature = low pressure
However,the pressure of the gas cannot be too low because the gas needs a high enough pressure to enter the lungs

The anesthetics we have today aren’t perfect
Minor side effects can include nausea, shaking, extreme drowsiness for all types of anesthesia
For general anesthesia, side effects can include heart attack, bruising, coordination problems, muscle pain, stroke, sharply falling blood pressure, and even death