General anesthetics can be inhalational or intravenous. Its use can only be administered by a medical professional. They have some adverse effects that must be controlled to avoid complications.
General anesthetics are a series of drugs that are used in the operating room to induce general anesthesia. This state is characterized by the progressive and controlled depression of the functions of the central nervous system.
When a person is under the effects of different types of general anesthetics, he has loss of consciousness and reactivity to painful stimuli. Both effects are reversible.
Thus, depending on the objective to be achieved, different types of general anesthetics will be used. However, common objectives are always sought, such as:
- Insensitivity to pain
- Reflex loss
- Complete amnesia of everything that happens in the surgical act
- Skeletal muscle relaxation
- Loss of consciousness
All of these effects originate from different locations in the central nervous system, and achieving them with a single medication would require very high concentrations. That is why combinations are used to avoid irreversible depression of vital brain areas.
Characteristics of general anesthesia
Despite the great advances in the area of anesthetic science, the structures affected and the molecules involved in this type of medicine are still not exactly known. It is known that they obviously produce sedation and hypnosis, profoundly modifying multiple processes and pathways.
Some of the hypotheses that professionals have described are:
- General anesthetics have a nonspecific action on properties of the neuronal membrane.
- Meyer and Overton’s lipid theory : it consists in that these drugs act on lipid targets , that is to say fats, and therefore, their potency will depend on the solubility they present in fats.
- They are drugs that have an action on receptor proteins or ion channels.
- Voltage dependent channels and ligand dependent ion channels are involved in the action.
On the other hand, when administering a general anesthetic, three factors must be assessed, above all:
- Speed with which anesthesia is obtained
- Duration for a given dose
- Power, depth and intensity of anesthesia
Inhalation general anesthetics
These types of general anesthetics are substances that, inhaled through the airways , produce general anesthesia. They are not irritating drugs and are usually used for maintenance of anesthesia together with intravenous inducers.
The anesthetic potency of these drugs depends on the partial pressure or tension that the anesthetic reaches in the brain. Normally, it is always close to the partial pressure in blood. Some examples of these general anesthetics are:
- Nitrogen protoxide.
- Halothane.
- Isofluorane.
- Desflurane.
- Sevofluorane.
All of them are absorbed and pass through the mucosa until reaching the brain. This absorption or diffusion is carried out in three stages:
- Pulmonary inhalation stage : the least soluble will have a rapid induction rate and the most soluble will produce anesthesia more slowly.
- Distribution in the tissues.
- Elimination.
Intravenous general anesthetics
On the other hand, we find general anesthetics that are administered intravenously in order to induce and maintain anesthesia before a surgical procedure. They are substances with hypnotic, analgesic, anxiolytic and muscle relaxant properties.
Intravenous anesthesia quickly facilitates induction of anesthesia, but is much less well controlled than general inhalation anesthesia. Health professionals in this specialty use the infusion rate parameter (IMV) to meet the requirements of clinical anesthesia.
Some examples of general anesthetics are:
- Sodium thiopental.
- Propofol.
- Etomidate.
- Ketamine.
All these drugs can produce a series of adverse effects, such as respiratory depression, apnea, muscle stiffness, blurred vision, and mood changes, among others.
Anesthesia as a medical procedure
General anesthesia is a delicate process in which you have to be very careful with the drugs used , as well as with the dose administered since their misuse could lead to the death of the patient. Today we have a wide variety of general anesthetics that allow us to reduce the adverse effects and the risks associated with them.