Indication & Application

Local anesthetics serve to inhibit pain. They are therefore used for operations on the body that cause pain and where the patient is not anaesthetised. During anaesthesia, other substances are used to inhibit pain.

There are four types of local anesthesia. In surface anaesthesia, the medication is applied to the surface of the (mucous) skin and diffuses from there to the sensitive nerve fibers. In infiltration anesthesia, the drug is usually injected into the tissue through a syringe and then spreads in the area of interest.

In conduction anesthesia, the drug is injected close to the nerve root, thus inhibiting pain transmission. A distinction is made here between peripheral and spinal procedures. Peripheral procedures include, for example, brachial plexus anesthesia of the arm.

Procedures near the spinal cord include spinal anaesthesia and epidural anaesthesia (also known as epidural anaesthesia). In spinal anaesthesia, a cannula is used to puncture the subarachnoid space where the cerebrospinal fluid (liquor) is located. Here lie the spinal nerves with their front and rear roots.

The procedure in epidural anesthesia is similar, but the cannula is not advanced as far as in spinal anesthesia. The dura mater (hard cerebral membrane) is not punctured during epidural anesthesia, so that the medication approaches the spinal nerve to be anesthetized by diffusion. The decisive difference between the two methods is that the drug is distributed much more widely in the liquid-filled subarachnoid space during spinal anesthesia than in the connective and fatty tissue epidural space during epidural anesthesia.

For example, spinal anaesthesia in the lumbar spine region anaesthetizes the entire lower half of the body, whereas epidural anaesthesia mainly involves the area into which the anaesthetic has been injected. The last procedure is intravenous local anesthesia, where the drug is injected into the vein after a tourniquet has been applied. In ophthalmology, local anesthetics are administered by syringe, e.g. for operations on the eyelid such as corrections or tumor removal.

On the other hand, anaesthetic eye drops are also used, especially for operations directly on the eyeball. They are also used for painful diseases such as corneal injuries. Another area of application is the measurement of intraocular pressure.

Since pressure is applied directly to the cornea, the examination would not be possible without anaesthetic eye drops. Local anesthetics are also available in the form of ointments. Just like powders, gels and sprays, which contain narcotic substances, they are used for surface anaesthesia.The ointment is applied to the desired area of the skin or mucous membrane.

It is now absorbed and reaches the sensitive nerve endings, which are then anaesthetised and thus no longer transmit the sensation of pain. Local anesthesia by means of ointments is usually used for minor procedures on the skin or the anus, e.g. for the treatment of hemorrhoids. An example of a local anaesthetic ointment is lidocaine ointment, which is used for tattoos or piercings in addition to procedures.

Contraindications for local anesthetics are an allergy to the active substance and a large-area application in already damaged skin. This increases the risk of an undesirable systemic effect, as more of the active ingredient can penetrate deeper into the tissue. Just like ointments, anaesthetic sprays are also used for surface anaesthesia.

This means that you spray on the desired area and wait briefly until the local anesthetic takes effect. It numbs the sensitive nerve endings located in the skin or mucous membrane. Sprays are often used on the mucous membranes of the mouth and throat, e.g. before endoscopic operations or at the dentist. An example of a local anesthetic spray is the xylocaine spray.