What Is Regional Anesthesia?

Local anesthesia, also known as local anesthesia, refers to the application of local anesthetics to a part of the body when the patient is conscious, temporarily blocking the sensory nerve conduction function in one part of the body, and maintaining motor nerve conduction intact or at varying degrees. Blocked state. This block should be completely reversible without causing any tissue damage. The advantages of local anesthesia are simplicity, safety, patient sobriety, fewer complications, and small impact on patients' physiological functions.

Basic Information

English name: local anesthesia

Visiting department: Department of Anesthesiology

Characteristics of local anesthesia

Compared with general anesthesia, local anesthesia has unique advantages in some aspects. First of all, local anesthesia has no effect on consciousness; secondly, local anesthesia can also play a certain degree of postoperative analgesia; in addition, local anesthesia has easy operation, safety, fewer complications, and has little impact on patients' physiological functions, which can block Discontinue various adverse neurological reactions, alleviate the stress response caused by surgical trauma and quick recovery.

However, local anesthesia and general anesthesia often complement each other clinically, and these two anesthesia methods cannot be completely separated, but should be regarded as part of individualized anesthesia programs adopted for specific patients. For pediatric, psychiatric or unconscious patients, it is not appropriate to use local anesthesia to complete the operation alone, and it must be supplemented with basic anesthesia or general anesthesia; and local anesthesia can also be used as an auxiliary means of general anesthesia to enhance the effect of anesthesia and reduce the amount of general anesthesia.

Local anesthesia

Local anesthetics are those drugs that can temporarily, completely, and reversibly block nerve conduction within a limited range of the human body, that is, a part of the human body loses sensation under the condition that the consciousness has not disappeared to facilitate surgical operation. The fundamental difference between a local anesthetic and a general anesthetic is that after the local anesthetic is combined with certain specific sites on the sodium ion channel on the nerve membrane, the sodium ion through the sodium ion channel decreases to change the nerve membrane potential, leading to the conduction of nerve impulses It is blocked to achieve anesthesia effect; general anesthetics play an anesthetic role by affecting the physical properties of the nerve membrane, such as the fluid properties and permeability of the membrane.

Local anesthesia method

Common types of local anesthesia include surface anesthesia, local infiltration anesthesia, regional block, and nerve block. The latter can be divided into neural stem blocks, epidural blocks and spinal anesthesia. Intravenous local anesthesia is another form of local anesthesia ^[1] .

Surface anesthesia

(1) Definition The contactless local anesthetic with local mucous membranes to make it pass through the mucosa and block the superficial nerve endings is a painless state. Local anesthetics used for surface anesthesia are difficult to reach under the epithelial nociceptors, and can only relieve the discomfort caused by the mucosa. Can be used for corneal, nasal, throat, trachea and bronchial surface anesthesia.

(2) Precautions Before filling the surface of the mucosa with cotton pads impregnated with local anesthetic, squeeze out excess liquid to prevent toxic reactions caused by excessive absorption. Cotton pads should be applied under a headlight or laryngoscope to facilitate proper placement ^[2] . Mucosa absorbs local anesthetics at different rates. Generally speaking, the application of high-concentration and high-dose local anesthetics on large mucosa is prone to toxic reactions, and in severe cases, it is fatal. The speed of mucosal absorption of local anesthetics is the same as that of intravenous injections, especially the tracheal and bronchial spray methods. Local anesthetics are absorbed fastest, so the dose should be strictly controlled, otherwise the local anesthetics can inhibit the myocardium and the patient quickly collapses, so you should prepare in advance Resuscitation equipment and medicine. Atropine should be injected before surface anesthesia to dry the mucous membranes and avoid saliva or secretions from interfering with the contact between local anesthetics and mucous membranes. The local anesthetic ointment applied to the outer wall of the tracheal tube is best to be water-soluble. It should be noted that the onset time of the anesthesia takes at least 1 minute, so it is not expected that the tracheal tube can prevent coughing once it is inserted. Spray surface anesthesia of throat, throat and tracheal mucosa.

2. Local infiltration anesthesia

(1) Definition The local anesthetic is injected in layers along the surgical incision line to block nerve endings in the tissue, which is called local infiltration anesthesia. Take an intradermal injection needle, and the bevel of the needle is close to the skin. After entering the skin, the local anesthetic solution is injected, resulting in a white orange peel-like mound. The puncture needle should be inserted from the site that was infiltrated last time to reduce puncture pain. Local injection of local anesthesia solution should be pressurized to form tension infiltration in the tissue and make extensive contact with nerve endings to enhance the anesthetic effect.

(2) Precautions The local anesthetic should be injected deep into the underlying tissues and infiltrated layer by layer. The nerve endings are distributed most at the membrane surface, submuscle and periosteum, and large nerves often pass through. Increase the concentration if necessary. There are few nerve endings in myofiberic pain, as long as a small amount of local anesthetic can produce a certain muscle relaxation effect. The puncture needle should be inserted slowly. When changing the direction of the puncture needle, the needle should be retracted to the skin first to avoid the needle from bending or breaking. Suction should be performed before each injection to prevent local anesthetic solution from being injected into the blood vessels. After the local anesthetic solution is injected, you must wait 4 to 5 minutes to complete the effect of the local anesthetic solution. The tissue should not be cut open immediately to cause the liquid to overflow and affect the effect. Do not exceed the maximum amount of each injection to prevent local anesthetic toxicity. Local infiltration and anesthesia should not be used for infection and cancer.

3. Regional block

Local anesthesia is injected around and around the surgical area to block access to the nerve trunk and nerve endings in the surgical area. This is called regional block anesthesia. It can be injected by surrounding the resected tissue, or by injecting around its base. The main points of operation of regional block are the same as those of local infiltration. The main advantage is to avoid puncture of pathological tissues, suitable for minor outpatient surgery, and also suitable for frail or elderly patients with poor physical conditions.

4. Intravenous local anesthesia

(1) Define the local tourniquet on the proximal end of the limb. Anesthesia by injecting local anesthesia from the distal vein to block the limbs below the tourniquet is called intravenous local anesthesia. It is suitable for distal limb surgery where a tourniquet can be safely placed. Due to the limitation of the tourniquet, the operation time is generally within 1 to 2 hours. If combined with severe ischemic vascular disease of the limb, this method should not be used. The lower limb is mainly used for foot and calf surgery. A calf tourniquet should be used below the fibula neck to avoid compressing the superficial peroneal nerve.

(2) Precautions The main complication of intravenous local anesthesia is the toxic reaction caused by a large number of local anesthetics entering the systemic circulation after relaxing the tourniquet or leaking air. Therefore, you should pay attention to: carefully check the tourniquet and inflating device before operation, and calibrate the pressure gauge; the pressure should be at least 100mmHg of the side systolic pressure during inflation, and the pressure gauge should be closely monitored; should not relax within 20 minutes after injection Tourniquet, it is best to take intermittent deflation when putting the tourniquet, and observe the patient's mental state.

5. Nerve and plexus block

(1) Cervical plexus block The superficial cervical plexus block can be used for superficial clavicle and superficial neck surgery, while deep neck surgery, such as thyroid surgery, carotid endarterectomy, etc., requires deep cervical plexus. Block. However, because the neck has the last four pairs of cranial nerve innervation, the effect of cervical plexus block alone is not perfect, and auxiliary drugs can be used to reduce pain.

(2) Brachial plexus block includes five methods including transcervical brachial plexus block, intermuscular sulcus block, upper clavicle block, lower clavicle block, and axillary brachial block. Approach. The effects of the five brachial plexus approaches vary depending on the anatomy of each site and the innervation of the upper limbs varies. Therefore, the most appropriate approach should be selected based on the innervation of the surgical site.

(3) Upper limb nerve block Upper limb nerve block is mainly suitable for forearm or hand surgery. It can also be used as a remedy for incomplete brachial plexus block. It mainly includes median nerve block, ulnar nerve block and radial nerve block, which can be blocked at the elbow or wrist. If finger surgery is performed, interdigital nerve block is also feasible.

(4) Lower limb nerve block All lower limb anesthesia needs to block lumbar nerve plexus and phrenic nerve plexus at the same time. Due to the need for multiple injections and inconvenient operation, the clinical application is not widespread. However, lumbosacral plexus block can be applied when the area where anesthesia is needed is limited or intra-spinal anesthesia is contraindicated. In addition, lumbosacral plexus block can also be used as an adjunct to general anesthesia for postoperative analgesia.

Although lumbar plexus block and intercostal nerve block can be used for lower abdominal surgery, it is rarely used clinically. The combined sacral inferior sacral nerve and sacral inguinal nerve block is a simple and practical method of anesthesia, which can be used for surgery of the sacral inferior sacral nerve and sacral inguinal innervation area. Hip surgery needs to block all lumbar nerves except the sub-sacral and sacral inguinal nerves. The easiest way is to block the lumbar nerve plexus (lumbar plexus lumbar plexus block). The thigh surgery requires anesthesia of the lateral femoral cutaneous nerve, femoral nerve, obturator nerve, and sciatic nerve. It is possible to use the psoas muscle space lumbar plexus block combined with sciatic nerve block. Anterior thigh surgery is possible with combined or separate lateral femoral cutaneous nerve and femoral nerve. The "three-in-one" method can also be used. Pure lateral femoral cutaneous nerve block can be used for skin anesthesia in skin grafts. Simple femoral nerve block Postoperative analgesia for femoral shaft fractures, quadricepsplasty or patella fracture repair. The combination of lateral femoral cutaneous nerve and femoral nerve block plus sciatic nerve block usually prevents tourniquet pain, because the obturator nerve innervates the skin area very little. Open knee surgery requires blocking of the lateral femoral cutaneous nerve, femoral nerve, obturator nerve, and sciatic nerve. The easiest way is to implement the psoas muscle space lumbar nerve plexus block combined with sciatic nerve block. Combined femoral and sciatic nerve block can also meet the requirements of surgery. Distal knee surgery requires blocking of the sciatic and femoral nerve branches, and ankle block can be used for foot surgery.

Adverse effects of local anesthesia

It mainly involves local anesthetic allergies, tissue and neurotoxicity, and cardiac and central nervous system toxic reactions.

Tissue toxicity

The factors involved include traumatic injection methods, high drug concentrations, malabsorption and other mechanical factors that cause damage to the naked eye or microscopic tissue. In fact, commonly used anesthetics do not have tissue toxicity. If local or subcutaneous injection of hypertonic concentration is injected into the skin, it can cause temporary edema: although the adrenaline can improve the degree of edema, it will further increase the toxicity of the tissue. . Injection of procaine, lidocaine, and mepivacaine solutions below 1% will not affect wound healing.

2. Neurotoxicity

Direct injection of anesthetics into nerves or nerve bundles can cause functional or structural changes, which are not caused by the drug itself, but are related to physical factors (stress).

3. High-sensitivity reaction

Individual patients have very different tolerances to local anesthetics. When a small dose of local anesthetic is used, or its dosage is lower than the usual amount, the patient will have early symptoms of toxic reactions and should be considered a hypersensitivity reaction. Once a reaction occurs, dosing should be stopped and treatment given.

4. Allergies

The allergic reaction is due to the attachment of the cytophilic immunoglobulin to the surface of mast cells and basophils. When the antigen meets again with the reactin antibody, histamine and serotonin are released from the mast cell particles. During these cycles, biogenic amines can trigger a rapid and severe systemic defensive response with airway edema, bronchospasm, dyspnea, hypotension, and vascular edema due to increased capillary permeability, and urticaria on the skin. Measles with itching. Those with severe reactions can endanger patients' lives. The incidence of allergic reactions accounted for 2% of local anesthetic adverse reactions. Allergic reactions caused by ester local anesthetics are far more common than amides. It is generally believed that ester local anesthetics and immunoglobulin E form haptens, and at the same time, local anesthetic preservatives can also form haptens, which is another potential factor causing allergic reactions.

5. Central nervous system toxicity

The central nervous system toxicity of local anesthetics is the initial excited phase and the terminal inhibitory phase. It initially manifests as patient anxiety, anxiety, paresthesia, tinnitus, and numbness around the mouth, which in turn causes facial muscle spasm and systemic convulsions, which eventually develop into severe Central nervous system depression, coma, and respiratory arrest.

6. Cardiotoxicity

The early stages of the cardiovascular system are tachycardia and hypertension indirectly due to the excitement of the central nervous system. In the later stages, arrhythmias, hypotension, and myocardial contraction are caused by the direct action of local anesthetics.

7. Prevention and treatment of toxic reactions

(1) The prominent manifestation of the prevention of severe toxicity of local anesthetics is convulsions. At this time, due to the uncoordinated and strong contraction of the airway and chest and abdominal muscles, it is bound to affect the respiratory and cardiovascular systems, which can be life-threatening. Therefore, the toxic reaction should be actively prevented: the safe dose of local anesthetics; in the local Epinephrine is added to the anesthetic solution to slow absorption and prolong the narcotic effect; To prevent the local anesthetic from being injected into the blood vessel by mistake, you must carefully suck with or without blood return; before injecting the full dose, you can inject the reagent to observe the reaction; Be wary of the precursor symptoms of toxic reactions, such as panic, sudden fall asleep, multilingualism, and muscle twitching. Injection should be stopped at this time and hyperventilation should be used to increase the threshold of cerebral convulsions. If convulsions continue to progress, controlled breathing is needed to maintain adequate oxygenation of the heart and brain; use diazepam and other benzodiazepines as pre-anesthetic medications.

(2) Treatment Due to the rapid dilution and distribution of local anesthetics in the blood, the duration of a seizure should not exceed 1 minute. Pay attention to protect the patient from accidental damage when convulsions occur; Inhale oxygen and assist or control breathing; Open intravenous infusion to maintain hemodynamic stability; Intravenous thiopental sodium or other rapid buses Pharmacy, but do not apply too much to prevent respiratory depression; Diazepam can also be injected intravenously.

Complications caused by local anesthesia puncture

Nerve injury

Nerve can be directly damaged during puncture, especially with paraesthesia. The use of short bevel needles and neurostimulator positioning can reduce the incidence of nerve damage. Intravenous injections should also be avoided during puncture.

2. Hematoma formation

Occasionally, hematoma formation can be seen during peripheral nerve block. Hematoma has an impact on the local anesthetic diffusion and puncture location. Therefore, before the puncture operation, you should ask about the bleeding history, use as fine a puncture needle as possible, and be careful when operating near the vascular rich area.

3. infection

The sterility principle is not strict during operation or the infection can spread further through puncture through infected tissues. Therefore, local infection should be considered as a contraindication to local anesthesia.

References

1. Zhuang Xinliang, Zeng Yinming, Chen Bozhen. Modern Anesthesiology. Third Edition. People's Medical Publishing House, 2010

2. Chinese Anesthesiology Guide: Expert consensus on prevention and treatment of complications of spinal canal block