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null 局 部 麻 醉 Local Anesthesia 局 部 麻 醉 Local AnesthesiaSection 1 IntroductionSection 1 IntroductionLocal anesthetic drugs act by producing a reversible block to the transmission of peripheral nerve impulses. Preservation of consciousness, simplicity of administration, sympathetic blockade, minimal depression of ventilation and reduction in the incidence of major postoperative complications are often considered to be advantages of local anesthesia. nullIn some circumstances, regional anesthesia may have distinct advantages over general anesthesia, but it may have disadvantages in others. Local anesthesia should be compensated by sedative or centrally acting anesthetic drugs when performed in pediatric and incorporated patients. The incidence of complications may be minimized by ensuring adequate supervision and training in local anesthetic techniques. Sufficient expertise and equipment must be available to deal with potential complications. Section 2 The clinical features of local anesthetic agentsSection 2 The clinical features of local anesthetic agents1 Local anesthetic drugs clarification All the local anesthetic drugs have a three-part structure----aromatic group , amine and an intermediate chain bond at the center. There are two types of the intermediate chain: ester and amide. Ester agents include procaine , chloroprocaine and tetracaine. Amide agents include lidocaine, bupivacaine and ropivacaine.nullThe Features of individual anesthetic drugs nullMixtures of local anesthetics should be considered to have roughly addictive toxic effects: A solution containing 50% of the toxic dose of lidocaine and 50% of the toxic dose of bupivacaine will have roughly 100% of the toxic effects of either drug.null2. Individual drug properties Procaine,普鲁卡因 Procaine is a low potent and short duration anesthetic agent. Because of low toxicity, it is commonly used for local infiltration anesthesia. The incidence of allergic problems, short shelf-life and brief duration of action of procaine have resulted in its infrequent use at the present time.null Tetracaine,丁卡因 Tetracaine is a commonly used drug of high toxicity. It is also very potent and is the standard drug for topical anesthesia and nerve block. It has a prolonged duration of action, but also a slow onset time. nullLidocaine, 利多卡因 Having been used safely and effectively for every possible type of local anesthetic procedure, lidocaine is currently the standard agent. It has no unusual features and is also a standard antiarrhythymic.nullBupivacaine ,布比卡因 A number of deaths have occurred after the accidental intravenous administration of large doses of bupivacaine, and some concern has been expressed that this drug might have a more toxic effect on the myocardium than other local anesthetic agents.null Ropivacaine, 罗哌卡因 Ropivacaine is slightly less potent than bupivacaine, and produces a slightly shorter duration. At equipotent concentrations, ropivacaine appears to be less likely than bupivacaine cardiac collapse and arrhythmias, and resuscitation is more likely to be successful if cardiotoxicity does occur.null3 Side-effects of local anesthetic drugs (1)Toxicity 毒性反应 If the plasma concentration of drug is higher than a value result from overdosage , the toxicity may occur and the most severe result is death. （hypersusceptibility， 高敏反应） The common causes of systemic toxicity: ①Absolute overdosage ②Inadvertent intravascular injection ③The sites of injection have high blood supply and the anesthetic solution has no adrenaline ④The tolerability of the patients decreasednullThe clinic features of toxicity Numbness or tingling of tongue and circumoral area. Light-headed, anxious, drowsy and complain of tinnitus. Consciousness is lost and this is proceeded or followed by convulsion. Coma and apnea may develop subsequently. Cardiovascular collapse may result from direct myocardial depression and vasodilatation, but more commonly it is a result of hypoxaemia secondary to apnea. Prevention and treatment of toxicity null(2)Allergic reaction 过敏反应 Allergic reaction is extremely rare and most reactions result from systemic toxicity, overdosage with vasoconstrictors, or are manifestation of anxiety. The clinical features of allergic reaction Urticaria寻麻疹、larynx edema咽喉水肿、constriction of bronchioles支气管痉挛、hypotension低血压、swelling血管神经性水肿、anaphylactic shock过敏性休克，可危及病人生命。 发生过敏，应予肾上腺糖皮质激素、抗组胺药物，必要时予肾上腺素。 用酰胺类药物可减少过敏反应的发生。null(3)Reaction of overdosage with vasoconstrictors When adrenaline was used with concentration greater than 1:200,000 or the maximum dose exceeding 0.5mg, it produced systemic toxicity. The clinical features include pale, anxious, palpitation（心悸）, panting（气促）, nausea and vomiting, and hypertension.Effect on organ systemsEffect on organ systemsCardiovascular system Respiratory system Neurological system Immunologic system Musculoskeletal system Hematologic system Section 3 Local anesthetic techniquesSection 3 Local anesthetic techniques1 Topical anesthesia , 面麻醉 Topical anesthesia means the local anesthetic agents are spread on mucosae or applied on skin (e.g. Emla) to produce anesthetic effect. Topical anesthesia is often used for operations on eye, nose, larynx, tracheal , and urethra or venepuncture in children. Tetracaine 1-2% and lidocaine 2% are commonly used as topical solution for anesthesia. When used on airway and urethra, the dosage should be reduced because the absorption is rapid. 2 Local infiltration anesthesia, 局部浸润麻醉 沿手术切口线分层注射局麻药，阻滞组织中的神经末梢，称为局部浸润麻醉。 when a large volume of local anesthetic is to be injected, use of dilute concentration and addition of epinephrine (1:200,000)help reduce systemic absorption and the likelihood of systemic toxicity. Attention !Attention !局部浸润麻醉的注意事项: (1)注入组织内的药液要有一定容积, 使局麻药在组织内形成张力, 以便借水压作用能与神经末梢广泛接触, 从而增强麻醉效果. (2) 避免穿刺针在组织内弯曲或折断。 (3)每次注药前都要回抽, 以免药液误注入血管,或者边注药边推进穿刺针. (4)局部感染或癌肿部位不宜注药。null3 Regional anesthesia, Field block,区域阻滞 在手术区的四周和底部注入局麻药, 阻滞通入手术区的神经纤维, 称为区域阻滞. 区域阻滞的优点:①可避免穿刺肿瘤组织; ②不会因局麻药浸润后, 组织水肿使小的肿块不易扪及; ③不会使手术区的局部解剖因注药而难于辨认.null4.Intravenous regional anesthesia(IVRA),静脉局部麻醉 IVRA involves isolating an exsanguinated limb from the general circulation by means of an arterial tourniquet and then injecting local anesthetic solution intravenously. Analgesia and weakness rapidly occur and result from local anesthetic action on peripheral nerve endings.nullChoice of drugs for IVRA 0.25%procaine 100~150ml 0.5%procaine 60-80ml 0.5%lidocaine 40ml Relevant problems Tourniquet pain Systemic toxicity Insufficient analgesia nullnull5 Nerve block，神经阻滞 在神经干、神经丛或神经节的周围注射局麻药，阻滞其冲动传导，使受它支配的区域产生麻醉作用，称神经阻滞。 Good surgical anesthesia is obtained only when local anesthetic is injected in close proximity to the nerve or nerves that are to be blocked. Injection techniques include use of a field block, reliance on fixed anatomic relationship, elicitation of paresthesias, and use of nerve stimulation. nullThe principal disadvantages of nerve block anesthesia are that it may require patient cooperation and there is a risk of systemic toxicity from local anesthetics. Techniques performed in a blind fashion Failure rate related to clinical experience Early resolution Unanticipated prolongation of the surgery Inadequate and necessitate general anesthesia Premedication with small doses of hypnotics or opioids helps reduce anxiety and raise the pain threshold. null(1)、Cervical plexus block, 颈丛神经阻滞 颈神经由C1-4神经的前支组成，它们构成颈浅丛和颈深丛。浅丛分布于颌下和锁骨上整个颈部、枕部区域的皮肤和浅层组织。深丛分布于颈前及颈侧的深层组织。 颈丛神经阻滞的适应症：颈部表浅短小外科手术。 颈浅丛阻滞的方法 颈深丛阻滞的方法 nullTechnique for superficial cervical blocknullComplications：toxic reaction, the phrenic blockade, the recurrent laryngeal nerve blockade, Horner’s syndrome, hematoma, inadvertent epidural injection, and total spinal blockade. null(2)、Brachial plexus block,臂丛神经阻滞 臂丛由C5-8和T1的脊神经前支组成，至肌间沟被肌膜包裹形成鞘膜，在锁骨上方形成锁骨下动脉鞘膜，在腋窝形成腋鞘。阻滞臂丛神经一般就在肌间沟、锁骨上、锁骨下血管旁和腋窝进行。 臂丛神经阻滞适应症：适用于上肢手术、肩关节手术和上肢关节复位术。 Techniques for brachial plexus blockTechniques for brachial plexus blocka.Interscalene brachial plexus block nullb.Axillary brachial plexus block c.Supraclavicular brachial plexus blockc.Supraclavicular brachial plexus blocknullComplications: toxic reaction, the phrenic blockade, the recurrent laryngeal nerve blockade, Horner’s syndrome, inadvertent epidural and subarachnoid injection, and pneumothorax. The axillary approach to brachial plexus is associated with a very low complication rate, providing intravascular injection is avoided. Postoperative neuropathies, hematoma, and infection are very rare. nullCase discussion: Dyspnea following interscelene block An anxious 54-year-old woman with a humeral fracture desires regional anesthesia for open reduction and internal fixation. An interscalene block with 25ml of 2%lidocaine with epinephrine (1:200,000)is administered using an “immobile needle” with incremental injection and careful aspiration. After 5 minutes, the patient notes numbness of the operative arm but starts to complain of increasing dyspnea. What would be appropriate management? What are the most likely causes? null(3)、Digital nerves block 指（趾）间神经阻滞 Digital nerves in one digit include two dorsal nerves and two palmar nerves. Injecting large volumes of local anesthetic or epinephrine-containing solution may compromise blood flow to the digit and cause the digit to necrosis.