General Anesthesia

General anesthesia is the term given to describe the utilization of a combination of injectable drugs with inhalant agents to induce and maintain a deep level of unconsciousness during the performance of a surgical procedure.

This type of anesthesia has long been the benchmark in this field, and until recent years where other anesthetic variations have come into wider use and popularity, was used almost universally in the surgical environment.

Why use general anesthesia?

There are several advantages to the use of a general anesthetic: The patient is unconscious, so there is no psychological demand placed upon him/her.

General anesthesia allows for complete control of the airway, breathing and blood pressure by the anesthesia caregiver.

It allows for surgery to be performed in different areas of the body simultaneously.

It enables the patient to remain motionless for extended periods of time.

So, what are the components of a general anesthetic?

First, the intravenous drugs:

There are many different types of intravenous drugs used in a general anesthesia scenario. Some are narcotics, some anti-anxiety agents (anxiolytics), while others may be anti-nausea, and sedative/hypnotic agents. Some medications control blood pressure, while others are designed to dry up secretions in the mouth and throat. Next the Inhalants:

These agents are typically in liquid form until placed into an anesthesia machine where it becomes a vapor to be inhaled.

The flow of these “gases” is strictly controlled and is usually administered in combination with pure oxygen. Each type of inhalant agent works a bit differently to achieve various results.

Of course, nitrous oxide (aka "laughing gas")is still routinely used. It is typically administered as a percentage of a mixture with oxygen and never gives "straight".

One drug which can be used both for anesthesia or sedation levels of consciousness is called Propofol. The brand name is Diprivan.

Diprivan is a white, milky, "emulsion" that, when given intravenously, can produce a quick-onset anesthesia, or when utilized with an "infusion pump" can produce and maintain a steady dream state or sedation during procedures that don't require a deep level of anesthesia.

There are essentially three main stages of general anesthesia:

I: Pre-medication

II: Induction

III: Maintenance

In the premedication phase, patients are given different drugs to either calm them, decrease anxiety, and/or to preemptively treat anticipated post-operative pain. The goal here is to prepare the patient for a calm and relaxed entry into the operating room.

The induction phase is characterized by the transformation of an awake patient to an anesthetized one. For the most part, this is accomplished by the use of intravenous induction agents such as sodium pentothal (we’ve all heard of that one), or propofol (Diprivan). These agents work rapidly to achieve a state of unconsciousness, followed by the slower absorption of anesthetic vapors from breathing, which maintains this deep level of anesthesia

The maintenance phase begins as the induction agents start to wear off. Consequently, the level of anesthesia must be maintained primarily through ventilation and breathing of the anesthetic gases. Depending on the depth of anesthesia required, the patient may be breathing on his/her own, or may be assisted by a ventilator if deep muscle relaxation is needed for the surgical procedure.

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