Regional anaesthesia methods
There are several ways to perform local anesthesia: The complications of an anaesthesia close to the spinal cord are minor. However, an incorrect injection of the medication can lead to problems. Depending on the injection site, paralysis of the respiratory muscles and a subjective feeling of breathlessness may occur.
In addition, especially under strong anesthesia, a pronounced vasodilatation can occur, resulting in a strong decrease in cardiac output and blood pressure. This can be prevented or treated by administering volume and plenty of fluid before the anesthesia. Headaches may occur after the treatment.
The exact cause of this is unknown, but experts discuss headaches as a result of a loss of cerebrospinal fluid or as a consequence of an inflammatory brain nerve irritation. Neurological persistent damage, however, is very rare. Since patients are awake and fully conscious during regional anesthesia, it is important to explain the exact procedures in advance.
- Surface anaesthesia: In this procedure of local anaesthesia the surface nerves are anaesthetised by applying a local anaesthetic to the skin or mucous membrane. The medication can be applied to the affected area in the form of sprays, powder, solutions or ointments.
- Infiltration anesthesia: During infiltration anesthesia, the anesthetic drug (local anesthetic) is injected into the area to be anesthetized using a needle. After a short waiting period the anesthetic takes effect and the treatment can be carried out.Depending on the puncture site and the sensation of pain, the injection of the medication can be felt as unpleasant to painful.
This form of local anesthesia is a very common and uncomplicated type of anesthesia.
- Anaesthesia near the spinal cord: This includes the so-called spinal and epidural anaesthesia (also called peridural anaesthesia/PDA). In both procedures, the nerve fibers are blocked directly at their point of exit from the vertebral bodies. This is why it is also called central nerve blockage.
The main areas of application for these procedures are operations on the legs, up to the groin, as well as obstetric or urological procedures.
In spinal anaesthesia of local anaesthesia, the anaesthetic is injected into the liquor space near the spinal cord. In order to avoid injuries to the spinal cord, the anesthetic is injected below the 3rd lumbar vertebra. Since the spinal cord in humans grows more slowly than the vertebral bodies, in the area below the 1st lumbar vertebra, there are usually only the nerve roots in the cerebrospinal fluid.
In order not to injure the spinal cord under any circumstances, the anesthetic should be injected into the intervertebral area L3/4. The puncture of this local anesthetic can be performed on a sitting or lying patient. There are then two options for anesthesia: The advantage of a lying catheter is the possibility of post-operative injection during surgery and post-operative analgesia.
The drugs are usually heavier than the cerebrospinal fluid and therefore spread depending on the position of the patient. Thus, the anaesthesia of the local anaesthesia can be controlled by the patient’s position, but also by the height of the injection site and the quantity and density of the anaesthetic.
- One-time injection: This involves directly injecting a dose of anesthetic and then removing the needle.
- Indwelling catheter: The needle is not removed after injection of the anesthetic.
Instead, a thin plastic catheter is inserted into the liquor space via the needle. The catheter remains in the cerebrospinal fluid space, so that it is always possible to administer another dose of local anesthetic.
Epidural anaesthesia is also one of the spinal cord anaesthesias of local anaesthesia. In contrast to spinal anaesthesia, the anaesthetic is not injected directly into the liquor space, but into the dura space.
Since the anesthetic has to diffuse through the hard meninges before it takes effect, it takes 20-30 minutes before the anesthetic takes effect. In addition, more anaesthetic must be injected. As in spinal anaesthesia, the anaesthetic is injected into the intervertebral space L3/4.
However, it can also be carried out in the other areas of the vertebrae, since it does not directly puncture the cerebrospinal fluid space, and thus there is no danger to the spinal cord. Nevertheless, the correct position of the catheter/needle should be checked after the puncture in order to rule out a spinal position. The dose of anaesthetic given during epidural anaesthesia can be up to 5 times higher and would lead to a much too strong spinal anaesthesia in case of misalignment.
Indications for epidural anaesthesia are longer lasting procedures, longer postoperative pain therapy and obstetrics. In addition to the spinal anaesthesia there is also the possibility of peripheral nerve blockage. In this case, the anesthetic is injected in the immediate vicinity of the plexus or individual nerves, thus enabling an anesthesia that is limited to the surgical area.
The advantage of such local anesthesia is a low complication rate compared to general anesthesia. Tumescent local anesthesia, which was developed in plastic and reconstructive surgery, is used to anesthetize large areas of the body without general anesthesia. Tumescent local anesthesia (TLA) is a regional anesthesia in which large amounts of a previously diluted local anesthetic are infiltrated into the skin and subcutaneous fatty tissue.
In addition to a large-area anaesthesia, this also leads to a strong swelling of the tissue, hence the name tumescent anaesthesia (tumescere = swelling). The main area of application of tumescent local anesthesia is liposuction. Here the special feature of this form of anaesthesia is used to remove large amounts of fat without the need for a general anaesthetic. The local anaesthetic solution used is usually a mixture of sodium chloride water and the local anaesthetic lidocaine.In order to keep blood loss as low as possible even during major surgery, adrenaline is usually added. Adrenaline causes a narrowing of the blood vessels, which leads to a lower blood circulation and thus to a lower blood loss in the surgical area.
