What Are the Types of General Anesthesia?

02 June, 2020
General anesthesia can be administered via inhalation or intravenous. It can only be administered by a medical professional. It has some side effects that should be controlled to avoid complications.

General anesthesia is a type of pharmaceutical drug that doctors use in an operating room to induce anesthesia. This state is characterized by progressive and controlled depression of central nervous system functions.

When a person is under the effects of different types of general anesthesia, they lose consciousness. Plus, they don’t react to painful stimulants. Depending on the effect they want to achieve, doctors use different types of general anesthetic. However, they usually achieve similar results.

For example:

  • Insensitivity to pain.
  • Loss of reflexes.
  • Complete amnesia about everything that happened in surgery.
  • Skeletal muscle relaxation.
  • Loss of consciousness.

Overall, all these effects come from different areas of the central nervous system. To get them all with just one medicine would require very high concentrations. For this reason, they use combinations. This prevents irreversible depression of vital areas of the brain.

Characteristics of general anesthesia

There have been many great advances in anesthetic science.  However, scientists still don’t know exactly which structures are affected and on which molecules these medicines act. Nevertheless, they do know that they cause sedation and hypnosis. They do this by deeply modifying several processes and pathways.

Overall, some scientific hypotheses as to how they work are:

  • General anesthesia takes an unspecified action on the properties of the neuronal membrane.
  • The Meyer and Overton lipid theory states that these medicines act on lipid targets or fats. Therefore, the potency depends on their solubility in fats.
  • They’re medicines that act on protein receptors or ion channels.
  • Voltage-dependent channels and ligand-dependent ion channels are implicated in the action.

On the other hand, when doctors administer general anesthesia, they have to evaluate three factors:

  1. How quickly you get the anesthesia.
  2. The duration for a specific dose.
  3. The potency, depth, and intensity of the anesthesia.
Doctor administering general anesthesia to patient.
General anesthesia can be inhaled or intravenous.

Inhalation anesthetics

This type of anesthetic is a substance that, when inhaled through the respiratory tract, causes general anesthesia. Additionally, they aren’t irritating medicines. Plus, they’re usually used to maintain anesthesia along with intravenous inducers.

In fact, the potency of these pharmaceuticals depends on the partial pressure or tension that the anesthetic reaches in the brain. Generally, they estimate the partial pressure in the blood.

Some examples of these inhalation general anesthetics are:

  • Nitrogen protoxide
  • Halothane
  • Isoflurane
  • Desflurane
  • Sevoflurane

All of these are absorbed and pass through mucous membranes until they reach the brain. Then, this absorption or diffusion normally happens in three stages:

  1. Lung inhalation stage: The less soluble ones will have a quick induction speed. Meanwhile, the more soluble ones cause anesthesia more slowly.
  2. Distribution in tissues.
  3. Elimination.

Read also: Medications that May Lead to Drowsiness

Intravenous anesthetics

Doctor holding anesthesia mask toward camera.
Only medical professionals can use general anesthesia.

On the other hand, there are general anesthetics that doctors administer through the veins. Here, the goal is to induce and maintain anesthesia during surgery. These are substances with hypnotic, analgesic, anxiolytic, and muscle relaxing properties.

Intravenous anesthesia facilitates the rapid induction of anesthesia. However, it isn’t as easily controlled as inhaled general anesthesia. Health professionals use the minimum infusion rate (MIR) to calculate the requirements for clinical anesthesia.

Overall, some examples of intravenous general anesthetics are:

  • Sodium thiopental
  • Propofol
  • Etomidate
  • Ketamine

Overall, all of these medications can cause a series of adverse effects. These include respiratory depression, apnea, muscle stiffness, blurry vision, and mood swings, among others.

Also, you might like to read: Care After Getting Your Wisdom Teeth Pulled

General anesthesia as a medical procedure

Overall, general anesthesia is a delicate process. Therefore, only trained professionals should perform it. 

They have to be very careful about the medicine they use and the dose they administer. After all, misuse could end up seriously harming the patient. Nowadays, we have a large variety of general anesthesia. Thus, they allow doctors to reduce the adverse effects and risks that often come with them.

  • Evers, A. S., Crowder, C. M., & Balser, J. R. (2007). Anestésicos generales. In Goodman & Gilman: Las bases farmacológicas de la terapéutica.
  • Perouansky, M., Pearce, R. A., & Hemmings, H. C. (2010). 10 – Anestésicos inhalatorios: mecanismos de acción. In Miller Anestesia. https://doi.org/10.1016/B978-84-8086-713-9.00010-2
  • Matute González, E., & Gilsanz Rodríguez, F. (2003). Mecanismo de acción molecular de los anestésicos generales. Actualizaciones En Anestesiologia y Reanimacion.