General Anesthetics

 

General aesthetics

General anesthetics are CNS depressants that cause partial or complete loss of sensation, consciousness, or pain. The effect is reversible and is commonly used to induce anesthesia during painful surgeries. 

General anesthetics bring about descending denervation of the central nervous system, beginning with the cerebral cortex, basal ganglia, cerebellum, and finally the spinal cord.

Stages of general anesthesia

• Stage I (Stage of analgesia)

It is the period from the start of anesthetic administration to loss of consciousness. The patient progressively loses pain. This stage is also called the stage of analgesia.

• Stage II (Stage of Delirium)

This period extends from the loss of consciousness through a stage of irregular and specific breathing to the re-establishment of regular breathing. Respiration is normal. The patient may laugh, vomit, or struggle and hence it is called the excitement phase or stage.

• Stage III (Stage of surgical anesthesia)

In this phase, excitability disappears and the skeletal muscles relax. Most of the surgeries are done at this stage.

• Stage IV (Stage of medullary depression)

Overdose of the anesthetic may bring the patient to this stage. At this stage, respiratory and circulatory disorders occur.

An ideal characteristic of aesthetics.

1. It should be inert, potent, and non-flammable.

2. It should be economical.

3. It should not produce nausea, vomiting, and severe hypotension.

4. It should be stable in heat, light, and alkalis.

Classification of general aesthetics

Volatile inhalation general anesthetics:

They are administered by inhalation and further distributed subcutaneously:

1. Gas:

2. Liquids:

Non-volatile or intravenous anesthetics:

They are unstable at room temperature and are administered via the IV route.

1. Barbiturates:

2. Non-barbiturates:

These are used to produce rapid unconsciousness for surgical and basal anesthesia. These drugs induce anesthesia during surgery which is then maintained by inhalation anesthetics and used in every operation in the body.