Introduction
Pain is a major topic in all areas of medicine. In acute cases, pain can strain the circulation, aggravates the subjective experience of an illness and can also become a long-term burden. Sometimes pain can no longer be controlled with conventional medication in tablet form. It is then possible to switch from a so-called peripheral pain therapy to an invasive procedure close to the spinal cord, the so-called epidural anaesthesia.
Definition and implementation
Epi- or epidural anaesthesia (PDA) is a method of analgesia, i.e. pain therapy, and has nothing to do with conventional anaesthesia in the sense of (general) anaesthesia. In epidural anaesthesia, a painkiller or anaesthetic is applied directly to the spinal nerves and can thus block the transmission of pain signals via the spinal cord to the brain. This means that there is no need to take a detour via the digestive tract, as is the case with conventional tablets.
Instead, the mechanism of pain transmission at the nerve is used to specifically disrupt it (effect via sodium channel blockade). Substances such as bupivacaine are used for this purpose. Drugs that act on the sodium channel often have the suffix -cain in their name.
Occasionally opiates are also used. The epidural anaesthesia is performed by the anaesthetist (anaesthetist), usually the patient is awake, sitting in a forward bent position or sometimes lying down. It is important that the back is curved so that the distance between the spinous processes is greater and access to the spinal canal is easier.
The spinous processes are the bone points that protrude centrally from the back and make the course of the spinal column visible under the skin. The skin above the spinal section concerned is disinfected several times and covered with sterile drapes. From now on, sterile work is performed, i.e. with sterile gloves, gowns and covers.
To prepare the puncture, the area is first injected with a local anesthetic. After a short exposure time, the special puncture needle for epidural anesthesia is now inserted at an oblique angle upwards. The following layers are now punctured one after the other: the skin and the subcutaneous fatty tissue beneath it, the ligamentous apparatus between the two spinous processes of the spinal column, the outer leaf of the hard spinal cord skin, and now the tip of the needle is in the epidural space, i.e. in the space between the inner and outer leaf of the hard spinal cord skin (dura = Latin hard).
The anesthetist feels the entry into the epidural space by a sudden loss of resistance of the needle. Now it should be possible to inject sterile saline solution without any problems, because the epidural space is only filled by a loose network of connective tissue and small blood vessels. The anesthetic can now either be injected directly through the needle once or a fine tube can be inserted.
In both cases the needle is pulled out again and the area is covered with a plaster. If a longer-lasting anaesthesia is desired, painkillers can be pumped through the fine tube into the epidural space either continuously or in batches, this is called an epidural catheter. Once injected into the epidural space, the painkiller is distributed evenly in a certain segment and can now take effect. The analgesic must be dosed in such a way that the pain fibers are blocked, but the motor nerve fibers responsible for muscle movement are not affected. In this way, freedom from pain is achieved while maintaining mobility.
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