Peripheral nerve blocks

definition

The job of peripheral nerves is to relay information such as pain information from the body to the brain, where it is switched over and processed.
Furthermore, the brain and spinal cord pass on their commands, for example to move muscles, via the same nerves to the corresponding target organ.

With a nerve block, it is possible to numb individual nerves with the help of a drug, usually a local anesthetic, such as the “sciatica”, which extends over the buttocks to the foot, or the ulnar nerve, better known as musician's bones.
However, there is also the possibility of switching off entire nerve plexuses, so-called plexus (singular plexus), which are located on the arms and legs and from which the individual nerves arise. In addition, the nerve root can be anesthetized immediately after exiting the spinal cord.
The local anesthetic is applied to the nerve using a syringe or a catheter. The switching off of the peripheral nerves can take place briefly or permanently.

General

The peripheral nerve block of the femoral nerve (nervus femoralis) is a form of regional anesthesia that enables targeted pain relief in the leg. At the same time, the leg can also be controlled to a limited extent, as feeling and strength are also temporarily reduced.

Materials and drugs used for peripheral nerve block have been specially developed to minimize the risk of nerve damage. For this reason, permanent damage from a peripheral nerve block is extremely rare and the numbing effect can largely be centered on the area of ​​the surgical procedure.

After a single injection of local anesthetics, it leads to an anesthetic lasting several hours in the treated area.

If long-term anesthesia is required, the anesthetic medication can also be administered continuously via a catheter (fine plastic tube).

Read more about this under Femoral catheter

execution

To find the nerve to be anesthetized, weak electrical impulses are passed into the tissue at the beginning of the anesthesia via an injection needle. As soon as the impulses stimulate the nerve to be anesthetized, characteristic involuntary muscle twitches occur.
After the correct position of the injection needle has been ensured in this way, the nerve is anesthetized.
The leg is made up of two major nerves, the Femoral nerve and Sciatic nerve provided. The femoral nerve runs in the inguinal canal and is therefore anesthetized just below the groin.
For this about 15-20ml Local anesthetics (e.g. Xylonest1% ® or Naropin0.75% ®).

Side effects

The nerves are using a Local anesthetic stunned.
As a result, it can be present in very rare cases Allergies against the means used, to intolerance reactions, which in the worst case in the Circulatory shock end up. This can be partially counteracted by informing the doctor performing the treatment of known allergies before the treatment.
After the blockage has ended, it is possible for a rule reversible loss of strength, as well as a Insensitivity remain temporarily in the event of contact. For this reason, if the procedure is to be carried out on an outpatient basis, it should ideally be accompanied by a person, as it is no longer possible to actively participate in road traffic.

During the local anesthetic injection, the Damage to blood vessels come. This can result in an internal bruise on the nerve, which can push it off or injure it, which in the best case can result in reversible insensitivity or abnormal sensations in the nerve supply area. The risk of this risk increases with the use of blood-thinning medication, such as ASS, Marcumar or Eliquis (Apixaban), which for this reason should be discontinued by the attending physician a few days before a planned procedure.

Since there are accompanying vessels near the nerves, there is a risk of injecting the local anesthetic into them. This can lead to problems with the cardiovascular system Cardiac arrest to lead. However, this complication can be circumvented if, after the needle has been pierced, the doctor performing the procedure creates a negative pressure in the syringe by pulling it and blood becomes visible in the syringe if a vessel has been pierced. The doctor would now reposition the needle.

By piercing the skin, if the previous skin disinfection was insufficient bacteria get into the puncture site and there a infection cause.
In the worst case, a so-called abscess, a purulent bacterial encapsulation that can pinch off and damage the surrounding nerve / nerve.
Thorough disinfection is very important as a preventive measure. However, this risk is particularly high in the case of a longer-lasting nerve block, in which a small catheter is placed that transports the drug to the nerve (s), for example in the case of a postoperative pain management.
If an infection and / or abscess formation occurs, this requires further antibiotic and possibly surgical treatment. Ultimately, there is also the risk that the needle will damage the nerve directly and, in the worst case, permanently.

Complications

The possible side effects of the femoral block are those of peripheral regional anesthesia:

• Nerve damage from injuries with the cannula
• Nerve damage due to the toxic effects of local anesthetics
• Bruise ("bruise")
• Cardiovascular complaints (low blood pressure, Cardiac arrest, Etc.)
• Complaints with the central nervous system (Seizures, impaired consciousness)