Torp Klaus D., Metheny Eric, Simon Leslie V.
Mayo Clinic Florida
Integris Southwest Medical Center
Lidocaine is a local anesthetic drug that produces a transient loss of sensory, motor, and autonomic function when the drug is injected or applied in proximity to neural tissue. It is the most commonly used local anesthetic in nearly all medical specialties. It is also commonly used as an antiarrhythmic agent to suppress ventricular arrhythmias. Infusions of lidocaine (and procaine) have been used to supplement general anesthetic techniques, as they are capable of reducing the minimum alveolar concentration of volatile anesthetics by up to 40%, while also providing pain relief in the perioperative phase. It is in the class of the local amide anesthetics, which, compared to the ester-type local anesthetics, is usually well tolerated with only rare occasions of allergic reactions. Amide local anesthetics are metabolized (N-dealkylation and hydroxylation) by microsomal P-450 enzymes in the liver. Applied either by injection, inhalation, or as a topical agent to provide anesthesia, lidocaine has a good safety margin before reaching toxic blood levels. Since it can be administered in various forms to the same patients, care must be taken to track the total dose administered to minimize systemic toxicity. In addition, clinicians should consider the dose of any other local anesthetics that may have been administered to the same patient, as toxic doses appear to be additive. Lidocaine toxicity is not only determined by the total dose (usually 4.5 mg/kg) but also by the rate of absorption, which is dependent on the blood flow of that tissue. To reduce blood flow to the injection site and the absorption rate, vasoconstrictors such as epinephrine 1:200000 are frequently used and may increase the toxic dose to 7 mg/kg. Lidocaine toxicity to muscles and peripheral or neuraxial nerves can occur locally at the site of injection. Transient neurologic symptoms (TNS) after high-concentration lidocaine spinal anesthetics have been described multiple times and have led to either reducing the concentration of the dose or switching to a different agent. In addition to direct nerve toxicity, systemic toxicity affecting the brain or cardiac muscle can lead to sudden and dramatic changes in the patient’s vital signs. Finally, there are the side effects of a relative overdose at the site of injection, which can be quite dramatic. Examples include total spinal anesthesia or subdural injection of the drug that can cause severe hemodynamic compromise, such as hypotension or bradycardia, up to cardiac and respiratory arrest.
利多卡因是一种局部麻醉药，当将其注射或应用于神经组织附近时，会导致感觉、运动及自主神经功能出现短暂丧失。它是几乎所有医学专科中最常用的局部麻醉药。它还常用作抗心律失常药，以抑制室性心律失常。输注利多卡因（和普鲁卡因）已被用于补充全身麻醉技术，因为它们能够将挥发性麻醉药的最低肺泡浓度降低多达40%，并在围手术期提供疼痛缓解。它属于局部酰胺类麻醉药，与酯类局部麻醉药相比，通常耐受性良好，仅有罕见的过敏反应情况。酰胺类局部麻醉药在肝脏中通过微粒体P-450酶进行代谢（N-脱烷基化和羟基化）。利多卡因通过注射、吸入或作为局部用药来提供麻醉，在达到中毒血药浓度之前有良好的安全范围。由于它可以以多种形式应用于同一患者，必须注意记录所给予的总剂量，以尽量减少其全身毒性。此外，临床医生应考虑可能已给予同一患者的任何其他局部麻醉药的剂量，因为中毒剂量似乎具有相加性。利多卡因毒性不仅取决于总剂量（通常为4.5mg/kg），还取决于吸收速率，而吸收速率取决于该组织的血流情况。为了减少注射部位的血流和吸收速率，常使用肾上腺素1:200000等血管收缩剂，这可能会将中毒剂量增加到7mg/kg。利多卡因对肌肉和外周或神经轴索神经的毒性可在注射部位局部发生。高浓度利多卡因脊髓麻醉后出现的短暂性神经症状（TNS）已被多次描述，这导致要么降低剂量浓度，要么改用其他药物。除了直接的神经毒性外，影响大脑或心肌的全身毒性可导致患者生命体征突然发生显著变化。最后，在注射部位存在相对过量的副作用可能会相当严重。例如全脊髓麻醉或药物硬膜下注射，可导致严重的血流动力学损害，如低血压或心动过缓，直至心脏和呼吸骤停。
