General anaesthetic

From ArticleWorld

A general anaesthetic is any drug that can induce a reversible and titratable unconsciousness for the purposes of eliminating the pain and awareness of surgery. In nearly all surgeries involving general anaesthesia, a nurse anesthetist or an anesthesiologist regulates the medication given to the patient.

Types

There are two basic medication types used in general anesthesia. Injectable anaesthetics are often used to induce the state of unconsciousness but can be used to maintain the state if given repeatedly or in an intravenous drip. Injectable anaesthetics include etomidate, barbiturate medications, benzodiazepines such as midazolam (Versed) and ketamine are often given to induce the unconscious state fairly rapidly.

Versed is also used alone in smaller doses to relax a patient and induce amnesia during minor procedures. Ketamine is given to children more often than adults as adults can have hallucinations if given the medication. Versed is also sometimes combined with Fentanyl, a powerful opioid medication to have the combined effect of pain reduction and relaxation.

Gases or vapors are used in many surgical situations to maintain the unconscious state. Desflurane and sevoflurane are commonly used inhaled anaesthetics and are delivered along with oxygen and sometimes nitrous oxide by means of a mask or through a tube placed in the patient’s trachea.

Action

It is believed that general anaesthetics act by modifying the cellular ion channels in the neurons of the brain so that electrical activity is diminished. It is possible the medications alone block the ion channels or that they modify some other brain molecule that in turn blocks the cellular ion channels.

Complications

General anaesthesia is not without its risks. The patient loses the ability to breathe spontaneously and if the airway is not maintained properly, the brain can become deprived of oxygen. Errors in the gaseous mixture can lead to an excess of medication and prolonged unconsciousness can result.

A little known phenomenon that can occur in general anaesthesia is patient awareness. Some patients can be paralyzed during surgery but are not sufficiently unconscious to obtain pain relief. Thus, they feel the intense pain of surgery but cannot relay that information to anyone. Some facilities use brain wave monitoring as a way to detect if the patient has any awareness of the surgery.