About The Location Of Local Anesthesia

Common local anesthesia includes topical anesthesia, local infiltration anesthesia, regional block, and nerve conduction block. The latter can be divided into nerve trunk block, epidural block and spinal anesthesia. Intravenous local anesthesia is another form of local anesthesia [1].

1. Topical anesthesia

(1) Define the painless state produced by contacting the local anesthetic with strong osmotic effect with the local mucosa to block the superficial nerve endings through the mucosa, which is called topical anesthesia. Local anesthetics used in topical anesthesia are difficult to reach the pain receptors under the epithelium, and can only relieve the discomfort caused by the mucosa. It can be used for surface anesthesia of cornea, nasal cavity, throat, trachea and bronchi.

(2) Precautions ① Before applying the cotton pad impregnated with local anesthetic on the mucosal surface, squeeze out the excess liquid medicine to prevent the toxic reaction from being absorbed too much. Padding should be performed under a headlamp or laryngoscope to facilitate proper placement [2]. ②The rate of absorption of local anesthetics by the mucosa of different parts is different. Generally speaking, the application of high concentrations and large doses of local anesthetics on large mucosal areas is prone to toxic reactions, and severe cases can be fatal. The absorption rate of local anesthetics from the mucosa is equal to that of intravenous injection, especially in the tracheal and bronchial spray method. The local anesthetics are absorbed the fastest, so the dose should be strictly controlled. Resuscitation kits and medicines. ③ Before topical anesthesia, atropine must be injected to dry the mucous membranes and avoid saliva or secretions that hinder the contact between local anesthetics and mucous membranes. ④The local anesthetic ointment applied to the outer wall of the tracheal tube is preferably water-soluble. It should be noted that the onset time of anesthesia should be at least 1 minute. Therefore, it cannot be expected that the tracheal tube can be prevented from choking once it is inserted. Spray topical anesthesia of the mucous membranes of the pharynx, larynx and trachea.

2. Local infiltration anesthesia

(1) Define the layered injection of local anesthetic along the surgical incision line to block the nerve endings in the tissue, which is called local infiltration anesthesia. Take an intradermal injection needle, the bevel of the needle is close to the skin, and after entering the skin, inject the local anesthetic liquid to form a white orange peel-like skin mound, and then pierce through the skin mound and inject the drug in layers. The puncture needle should be inserted from the site that has been infiltrated last time to reduce puncture pain. The injection of local anesthetic liquid should be pressurized to form a tension infiltration in the tissue and make extensive contact with nerve endings to enhance the anesthetic effect.

(2) Precautions ① The injection of local anesthetic should penetrate deep into the underlying tissue and infiltrate layer by layer. The nerve endings are most distributed in the membranous surface, subsarcolemma, and periosteum, and thick nerves often pass through. The amount of local anesthetic solution should be increased. The concentration can be increased if necessary. There are few nociceptive nerve endings in muscle fibers, and only a small amount of local anesthetic can produce a certain muscle relaxation effect. ② The puncture needle should be inserted slowly. When changing the direction of the puncture needle, the needle should be withdrawn to the subcutaneous surface first to avoid bending or breaking of the needle shaft. ③Aspirate before each injection to prevent the local anesthetic liquid from being injected into the blood vessel. After the injection of the local anesthetic liquid, it is necessary to wait for 4 to 5 minutes so that the effect of the local anesthetic is perfect. ④ Do not exceed the maximum amount of each injection to prevent local anesthetic toxicity. ⑤ It is not advisable to use local infiltration anesthesia for the site of infection and cancer.

3. Regional block

Around the surgical area, local anesthetic is injected around and at the bottom to block the nerve trunks and nerve endings entering the surgical area. This is called a regional block anesthesia. Surround injection can be performed by surrounding the resected tissue, or around its base. The operating points of the regional block are the same as those of the local infiltration method. The main advantage is that it avoids puncturing of pathological tissue, it is suitable for outpatient minor surgery, and it is also suitable for frail or elderly patients with poor physical condition.

4. Intravenous local anesthesia

(1) Define the tourniquet on the proximal end of the limb, and inject local anesthesia intravenously from the distal end to block the limb below the tourniquet. The anesthesia method 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. This method should not be used if combined with severe limb ischemic vascular disease. The lower extremity is mainly used for foot and calf surgery. A calf tourniquet is used, which should be placed below the fibular 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 amount of local anesthetics entering the systemic circulation after loosening the tourniquet or air leakage. Therefore, attention should be paid to: ① Carefully check the tourniquet and inflatable device before operation, and calibrate the pressure gauge; ② When inflating, the pressure should reach at least 100mmHg of the systolic pressure on the side, and monitor the pressure gauge closely; ③ Do not relax within 20 minutes after injection Tourniquet, it is best to take intermittent deflation method when placing tourniquet, and observe the patient's state of mind.

5. Nerve and plexus block

(1) Cervical plexus block Superficial cervical plexus block can be used for superficial supraclavicular neck surgery, while deep neck surgery, such as thyroid surgery, carotid endarterectomy, etc., still requires deep cervical plexus block. However, because the neck is still innervated by the last four pairs of cranial nerves, the effect of cervical plexus block alone is not perfect, and adjuvant drugs can be used to relieve pain.

(2) Brachial plexus block includes transcervical brachial plexus block, intermuscular groove block, supraclavicular brachial plexus block, subclavian brachial plexus block, and axillary brachial plexus block. approach method. The block effect of the five brachial plexus approaches varies due to the anatomy of each part, and the innervation of each part of the upper extremity is also different. Therefore, the most appropriate blockade approach should be selected according to the innervation of the surgical site.

(3) Upper extremity nerve block Upper extremity nerve block is mainly suitable for forearm or hand surgery, and can also be used as a remedy for incomplete brachial plexus block. Mainly include 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 possible.

(4) Lower extremity nerve block All lower extremity anesthesia needs to block the lumbar plexus and sacral plexus at the same time. Because of the need for multiple injections and inconvenient operation, it is not widely used in clinical practice. However, lumbosacral plexus block can be used when the site requiring anesthesia is limited or when neuraxial 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 combined with intercostal nerve block can be used for lower abdominal surgery, it is rarely used clinically. Combined iliohypogastric nerve and ilioinguinal nerve block is a simple and practical method of anesthesia, which can be used for surgery in the area innervated by the iliohypogastric nerve and the ilioinguinal nerve. Hip surgery requires blocking of all lumbar nerves except the iliohypogastric and ilioinguinal nerves. The easiest way to do this is to block the lumbar plexus (lumbar plexus block in the psoas space). Thigh surgery requires anesthesia of the lateral femoral cutaneous nerve, femoral nerve, obturator nerve and sciatic nerve, and a lumbar plexus block in the psoas major space combined with sciatic nerve block can be performed. The lateral femoral cutaneous nerve and the femoral nerve can be combined or blocked separately for the anterior thigh surgery, and the "three-in-one" method can also be used. The lateral femoral cutaneous nerve block alone can be used for skin graft anesthesia, and the simple femoral nerve block is suitable for Postoperative pain relief for femoral shaft fractures, quadriceps plasty or ilium fracture repair. A combined lateral femoral cutaneous and femoral nerve block combined with a sciatic nerve block usually prevents tourniquet pain because the obturator nerve innervates very little skin. Open knee surgery requires block of the lateral femoral cutaneous nerve, femoral nerve, obturator nerve, and sciatic nerve. Combined femoral nerve and sciatic nerve block can also meet the surgical requirements. Distal knee surgery requires blocking of the saphenous nerve branches of the sciatic and femoral nerves, and ankle blocks can be used for foot surgery.

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