Regional anesthesia is a large and important subspecialty of anesthesia. Along with infiltration anesthesia and surface anesthesia, it is part of the higher-level field of local anesthesia. Regional anesthesia procedures are used to eliminate pain and, in some cases, to block motor innervation (nerve supply to the musculoskeletal system). In contrast to general anesthesia, the patient is conscious during regional anesthesia. If both forms of anesthesia are performed together, it is called a combination anesthesia. Procedures that specifically block a nerve cord or nerve bundle are referred to as conduction anesthesia. These include spinal cord anesthesia and peripheral conduction anesthesia:
Spinal cord near conduction anesthesia – blocking the nerve roots or nerve cords near the spinal cord, for example:
- Peridural anesthesia (PDA) (synonym: epidural anesthesia).
- Spinal anesthesia
- Combined spinal / epidural anesthesia
Peripheral conduction anesthesia – blockade of individual peripheral nerves, e.g.:
- Upper extremity: interscalene block, infraclavicular block, axillary block, ulnar nerve block, radial nerve block, median nerve block, musculocutaneous nerve block, and wrist block.
- Lower extremity: femoralis blockade, blockade of the lumbar plexus (nerve plexus in the lumbar region), ischiadicus nerve, obturator nerve, saphenous nerve, as well as blockades in the area of the foot.
Another form of regional anesthesia is formed by intravenous regional anesthesia according to Bier, in which the local anesthetic is injected into a previously tied vein. This procedure is used for minor procedures on the forearm, hand, lower leg and foot. Detailed aspects of this procedure will be explained later in the course.
Indications (areas of application)
Regional anesthesia is used to treat pain in both minor and major surgical procedures. It is mainly used when general anesthesia carries too high risks for the patient. This is the case with:
- Alcoholized or not sober patients
- Respiratory patients, unless regional anesthesia affects the respiratory tract
- In addition, if the need for continuous anesthesia via a catheter system.
Contraindications
Absolute contraindications
- Lack of patient consent
- Allergy to local anesthetics
- Anatomical changes that prohibit proper puncture.
- Blood clotting disorders – Both genetic conditions and those caused by medications.
- Expectation of high blood loss during surgery.
- Infection (inflammation) in the affected area.
- Sepsis (blood poisoning)
- Shock and/ or hypovolemia (volume deficiency).
Relative contraindication
- Hypovolemia – volume deficiency
- Long duration of surgery
- Neurological diseases – For forensic reasons, regional anesthesia is not performed in some cases, as deterioration of these diseases may otherwise be seen in this context; for example, multiple sclerosis.
- Little cooperative or anxious patients.
Before regional anesthesia
Preoperatively, the patient’s medical history (anamnesis) is first taken. Important here is information on allergies to medications, especially local anesthetics, as well as systemic diseases that can lead to complications during the procedure (eg, cardiovascular disease). In the further course, a physical examination, the interpretation of laboratory values, and patient education take place. In particular, the coagulation parameters (Quick, TTP, platelet count) must be checked in the case of near-spinal cord conduction anesthesia. This is followed by administration of premedication (administration of medication before a medical procedure), which in this case is primarily for anxiolysis (anxiety resolution).
The procedure
A number of local anesthetics are considered for regional anesthesia, and their use is individualized. Some anesthetics include procaine, tetracaine, lidocaine, prilocaine, mepivacaine, bupivacaine, etidocaine, and ropivacaine. In addition to the local anesthetics, a vasopressor, usually adrenaline, (drug that has a vasoconstrictor effect) is also injected, which improves the blockade and reduces the risk of a toxic reaction to the anesthetics.However, adrenaline must not be used for the anesthesia of end-stream areas, e.g., on the fingers, since otherwise enormous vasoconstrictions (vasoconstrictions) can result in necrosis (tissue destruction due to lack of blood flow). After careful consideration of the necessity, as well as the decision for the most sensible form of regional anesthesia, the puncture area is first prepared sterilely. Immediately prior to anesthesia, blood pressure and heart rate are measured. These vital signs (measures that reflect basic functions of the human body) are monitored throughout the procedure. This is followed by the placement of venous access. Depending on the differences in the procedure, the anesthesiologist locates the puncture site and first applies surface anesthesia to make the puncture painless for the patient. The local anesthetic is then applied (if necessary under ultrasound guidance) and the procedure can be performed. Depending on the procedure, there are individual requirements that are not explained in detail here. Intravenous regional anesthesia according to Bier is performed as follows: First, the affected limb is tied off or wrapped so that the vascular system empties. To cut off further blood supply, a blood pressure cuff is applied, which prevents the spread of the local anesthetic throughout the procedure. The local anesthetic, usually one with very low toxicity, is now injected peripherally into a vein in the hand or arm via an indwelling vein cannula into the bloodless vessels, and from here it reached the tissue. The anesthesia takes effect after about 5-10 minutes and the procedure can be performed. The cuff must not be opened for at least 30-45 minutes, otherwise there is a risk of intoxication.
After the operation
Depending on the form of regional anesthesia, various follow-up measures must be taken. Close follow-up, especially monitoring of the cardiovascular system, is recommended in all cases.
Possible complications
Depending on the form and type of regional anesthesia, complications vary, sometimes considerably. For this reason, they are highlighted in a superordinate manner.
- Allergic reactions – To local anesthetics.
- Intoxication affecting the cardiovascular system – On the one hand, tachycardia (racing of the heart; sustained heart rhythm of more than 100 beats per minute) and hypertension (high blood pressure) due to the addition of epinephrine and, on the other hand, bradycardia (slowing of the heart action; sustained heart rhythm of less than 60 beats per minute) and hypotension (drop in blood pressure) due to the local anesthetic.
- Intoxication affecting the central nervous system – logorrhea (unrestrained speech), motor agitation, anxiety, euphoria, convulsions, respiratory depression (suppression of respiratory drive).
- Procedural complications – Eg. E.g., injury to surrounding structures, and specific complications depending on anatomic location.
- In addition – vagovasal reaction (“blackening of the eyes”, collapse).
