Effects and Types of Anesthetics

Effects and Types of Anesthetics

Anesthetics are depressant drugs that cause a total or

partial loss of the sense of pain. The effect an anesthetic has

on the body depends on several factors. What type of anesthetic

is used determines the effect along with the dosage and a person

(or animal’s) body weight.

The word anesthesia was first introduced by Oliver Wendell

Holmes in 1846 about four weeks after the first demonstration of

ether anesthesia at the Massachusetts General Hospital. Ether

was the first type of anesthesia used and was demonstrated as a

means of allowing a patient to be unconscious and free from

surgical pain.

Stages of Anesthesia

Stage one is known as analgesia and results from an increase

in circulating endorphins. There is a mild depression of

cortical centers and this type of anesthesia is also known as

twilight sleep.

Stage two is characterized by a loss of consciousness. It

is a critical period because delirium and increased involuntary

activity, as well as hypersecretion, can occur. It is best to

get through stage one and stage two as quickly as possible and

this stage, along with stage one, are known as induction.

Stage three is the stage of anesthesia known as surgical

anesthesia, and most surgical procedures are performed in this

stage. There is usually a loss of spinal reflexes and muscle

tone.

Stage four is an undesirable stage and is characterized by

respiratory depression and other manifestations of overdose.

Most general anesthetics are non-specific agents, meaning

that their activity depends on their lipid solubility rather that

their structure. Inhaled and exhaled gas containing the agents

equilibrates with the lung tissue, and then with the blood. In

the brain, the agent equilibrates between the blood and neural

tissue, depressing neurons and causing the pharmacological

effect.

Types of Anesthesia

Though ether was the first type of anesthesia, there are now

many different types. Ether, along with chloroform, are known as

the anesthetics from hell because they have all of the negative

traits of this class of drugs. Ethyl ether is potent and fairly

safe, but it is also flammable and explosive. It forms peroxides

and it produces a very unpleasant induction phase. Also, it is

irritating and causes nausea and vomiting during recovery.

Chloroform is just as potent and relaxes the skeletal muscle

fairly effectively, but has a narrow margin of safety, produces

liver and kidney toxicity, and has been known to fairly

frequently cause cardiac arrest. In addition, it can also cause

severe hypertension.

Another type of general anesthetic agent is non halogenated

hydrocarbons. All of these work well and the longer the chain,