Local anesthetic agents are used primarily to prevent the patient from feeling pain for varying periods of time after the agents have been administered in the peripheral nervous system. In increasing concentrations, local anesthetics can also cause loss of the following sensations (in this sequence): Temperature, touch, proprioception (position sense), and skeletal muscle tone. If these other aspects of nerve function are progressively lost, recovery occurs in the reverse order of the loss.
The local anesthetics are very powerful nerve blockers, and it is very important that their effects be limited to a particular area of the body. They should not be absorbed systemically. Systemic absorption could produce toxic effects on the nervous system and the heart (e.g., severe CNS depression, cardiac arrhythmias).
Local anesthetics are classified as esters or amides. The agent of choice depends on the method of administration, the length of time for which the area is to be anesthetized, and consideration of potential adverse effects. Esters include benzocaine (Dermoplast, Lanacane, Unguentine), chloroprocaine (Nesacaine) and tetracaine (Pontocaine). Amides include bupivacaine (Marcaine, Sensorcaine), dibucaine (Nupercainal), lidocaine (Dilocaine, Solarcaine, Xylocaine, Lidoderm, Octocaine), mepivacaine (Carbocaine, Isocaine, Polocaine), prilocaine (Citanest Dental), and ropivacaine (Naropin). Pramoxine (Tronothane, PrameGel, Itch-X, Prax) is a local anesthetic agent that does not fit into either of these classes.
Local anesthetics work by causing a temporary interruption in the production and conduction of nerve impulses. They affect the permeability of nerve membranes to sodium ions, which normally infuse into the cell in response to stimulation. By preventing the sodium ions from entering the nerve, they stop the nerve from depolarizing. A particular section of the nerve cannot be stimulated, and nerve impulses directed toward that section are lost when they reach that area.
The way in which a local anesthetic is administered helps to increase its effectiveness by delivering it directly to the area that is causing or will cause the pain, thereby decreasing systemic absorption and related toxic effects. Local anesthetics are indicated for infiltration anesthesia, peripheral nerve block, spinal anesthesia, and the relief of local pain. In 2005 the U.S. Food and Drug Administration approved a local anesthetic product that combines lidocaine and tetracaine in a dermal patch, called Synera.
esters – n. 酯类
benzocaine – n. 苯佐卡因 Dermoplast – n.止痛喷雾 Lanacane – n. 止痒膏 Unguentine – n. 苯佐卡因商品名
chloroprocaine – n. 氯普鲁卡因 Nesacaine – n. 纳塞卡因（盐酸氯普鲁卡因制剂）
tetracaine – n. 丁卡因 Pontocaine – n. 潘妥卡因
amides – n. 酰胺
bupivacaine – n. 布比卡因 Marcaine – n. 麦卡因 Sensorcaine – n. 噻瑟卡因
dibucaine – n. 地布卡因 Nupercainal – n. 地布卡因商品名
lidocaine -- n. 利多卡因 Dilocaine – n. 地罗卡因【奥】 Solarcaine – n.塞罗卡因【奥】, Xylocaine – n. 赛洛卡因 Lidoderm – n. 利多卡因贴片 Octocaine – n. 奥妥卡因
mepivacaine – n. 甲哌卡因 Carbocaine – n. 卡波卡因 Isocaine – n. 氨苯异丁酯 Polocaine – n. 普鲁卡因
prilocaine -- n. 丙胺卡因 Citanest Dental – n. 丙胺卡因制剂商品名
(标【奥】者为本站临时译名，只供学员记忆用，不得作为临床参考依据)
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★Video ★
Local Anesthetics
★Test ★
1. Which of the following statements about shivering is correct?
A. Shivering is a response controlled by the brainstem.
B. Shivering can occur in the absence of hypothermia.
C. Shivering is effectively treated with small doses of naloxone.
D. Shivering is an uncomfortable, though harmless, effect of anesthesia. 2. A preoperative patient receives atropine before induction of anesthesia. The nurse caring for this patient understands that this agent is used to prevent:
A. Anxiety.
B. Bradycardia.
C. Dry mouth.
D. Hypertension.
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答案 Answer 1. B. Shivering can occur in the absence of hypothermia. Rationale: Shivering can also appear after surgery. This is known as postanesthetic shivering. 2. B. Bradycardia. Rationale: Atropine, an anticholinergic drug, is used as an adjunct to anesthesia to counter the effects of vagal stimulation, which is caused by surgical manipulations that trigger parasympathetic reflexes, resulting in bradycardia. Atropine is not an anxiolytic. Atropine causes dry mouth and sometimes is used to minimize bronchial secretions.
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