The term anesthetic is very general and is used for many active ingredients that cause insensibility locally or throughout the body. A local anesthetic is used for local anesthesia . It is used almost exclusively to eliminate pain during operations or pain therapy .

It contains analgesics as the only active ingredient group. A general anesthetic, in turn, is used for general anesthesia ( narcosis ). In addition to painkillers, general anesthetics also contain substances that switch off consciousness, dampen motor activity and inhibit vegetative reactions. Accordingly, they consist of a mixture of hypnotics (sleeping pills), analgesics (painkillers) and relaxants (for muscle relaxation).

Anesthetics can be inhaled or injected intravenously. Due to the large number of substances contained, there is no uniform mechanism of action. Although the anesthetics used today can be described according to the Meyer-Overton correlation, the underlying assumptions about the mechanism of action are outdated.

Function, effect & goals

There are basically two groups of anesthetics. On the one hand, there are drugs that act locally and, on the other hand, they affect the entire body. Local anesthetics must be applied in such a way that they cannot spread throughout the body but remain in place. Therefore, they must not get into the bloodstream when injected.

In addition to an injection, it can also be used in the form of gels, ointments, sprays or patches . All local anesthetics contain aminoamides or aminoesters as active ingredients. These substances work by blocking the sodium channels on the membranes of nerve cells. This prevents the stimulus transmission and numbs this area. In contrast to local anesthetics, the use of narcotics is associated with greater challenges. Anesthetics always consist of a mixture of several substances that have very different effects.

Sleeping pills, painkillers and muscle relaxants must be combined effectively. The combination of active ingredients should be selected in such a way that there are no undesirable cross-reactions between the individual substances. Before the anesthetic is used, the anesthetist must first carry out a preoperative assessment of the individual risk using the so-called ASA risk classification. According to the ASA risk classification, the perioperative risk is divided into six degrees of severity. The composition of the anesthetic is then based on this assessment. Furthermore, the anesthetist must also decide how the anesthesia is to be induced.

There are two ways to do this. Anesthesia can be induced either by inhalation or by injection. This also depends on various factors. Different active ingredients are used for both forms of anesthesia induction. Gaseous anesthetics such as isoflurane or sevoflurane are used for inhalation . In addition, muscle relaxants must also be used during intubation. Induction of anesthesia via an intravenous injection requires soluble substances such as ketamine. According to current knowledge, the mode of action of the various substances is based on their complex interaction with receptors and ion channels.

The GABA, NMDA and opioid receptors play a prominent role here. How the anesthetics affect the receptors is currently the subject of research. In the past, it was assumed within the framework of the Meyer-Oberton hypothesis that inhalation anesthetics have a non-specific effect on the lipid components of the central nervous system. Although the effect of anesthetics can still be well described today using the so-called Meyer overtone correlation, this hypothesis can no longer be maintained unconditionally. However, she is not excluded.

Risks, side effects & dangers

Side effects and complications can occur with the use of both local anesthetics and anesthetics. If large amounts of this substance get into the blood through an unnoticed intravenous injection of local anesthetics , the body becomes intoxicated , which can lead to fatal circulatory collapse . In addition, local anesthetics of the ester type in particular can sometimes cause allergies . This should be clarified before using them.

However, the implementation of an anesthetic poses greater challenges for the doctor. Therefore, it may only be performed in the presence of a specially trained anesthetist. First of all, it is important to explain the patient comprehensively about the anesthetic and its possible effects. For risk assessment, the general operation risks, problems with the administration of anesthesia and previous illnesses of the patient are included in the assessment. The ASA status (ASA risk classification) should be determined. In the risk assessment, the patient’s advanced age and possible other illnesses are of particular importance.

However, the mortality induced specifically by anesthetic procedures plays only a subordinate role overall. Today it is between 0.001 and 0.014 percent. The main focus of anesthesia must be the monitoring of respiration . The main causes of anesthesia-related mortality are to be found in respiratory problems, incorrect treatment of cardiovascular problems, inadequate anesthetic care or incorrect medication administration. The main challenge, however, is airway management.

If the patient cannot be supplied with oxygen despite all the measures taken, the last resort is to open the airways . Problems can arise from the ingress of foreign bodies into the airways, acute narrowing of the bronchi or spasms of the larynx muscles . Cardiovascular disorders, intraoperative wakefulness, allergic reactions or malignant hyperthermia can also occur as further anesthetic-related complications. Even after the operation, nausea , vomiting , postoperative tremors or disorders of the cognitive brain functions are still possible due to the use of anesthetics.