Local anesthetics for facial plastic procedures.

The use of local anesthetic in facial plastic surgical procedures is well established as an effective and safe mode of anesthesia delivery. Local infiltration of anesthesia may be used alone for minor surgical procedures, or it may be used with general anesthesia or intravenous sedation and analgesia for more complex, lengthy procedures. When considered independently, the use of local anesthetic agents has undeniable limitations. Local anesthetics can cause toxicity and side effects. Injection of local anesthetics for subcutaneous infiltration frequently is painful until sensory anesthesia occurs. Local anesthetics have limited efficacy with respect to the intensity and duration of sensory blockade that can be achieved. In some situations, use of local anesthesia with the maintenance of an awake patient also may be undesirable for the surgeon and impractical for the patient. Despite these shortcomings, local anesthetics are fundamentally ideal for use in facial plastic surgery.     

Allergy to local anesthetics

Suspected allergic reaction to local anesthetics is a frequently encountered problem. Although some reactions are proven to result from an allergic mechanism, many remain unexplained, raising various levels of risk depending on the type of hypersensitivity involved. Good clinical management of allergic reactions is now well standardized, allowing for proper identification of the causal agent in proven cases.     

Effects of topical anesthetics on tympanic membrane structure

Summary Topical application of a local anesthetic agent can induce adequate insensibility to pain, and therefore can avoid the use of general anesthesia or invasive infiltration techniques for myringotomy or the insertion of a tympanostomy tube. A comparative study was conducted on a guinea pig animal model to determine the effects of three agents on the structure of the tympanic membrane: 5% tetracaine base dissolved in dimethylsulfoxide (DMSO), pure DMSO, and Bonain's solution. Survival times ranged from 1 day to 3 months. Following removal from the animals, membranes were embedded in Spurr and cut in semithin sections. Signs of mild or severe external otitis were frequent; to avoid non-specific results, infected specimens were not evaluated. Bonain's solution caused loss of the epidermis and mucosal epithelium within 1 day of treatment. The connective tissue layers of the drum were severely hyperplastic after a survival time of 1 month. Tetracaine base in DMSO caused a loss of epithelium and mucosal cells in 3 days. Regeneration started within 7 days and a restitution to integrity was seen after 3 months in drums treated with tetracaine base or DMSO alone.     

Effects of topical anesthetics on tympanic membrane structure

Topical application of a local anesthetic agent can induce adequate insensibility to pain, and therefore can avoid the use of general anesthesia or invasive infiltration techniques for myringotomy or the insertion of a tympanostomy tube. A comparative study was conducted on a guinea pig animal model to determine the effects of three agents on the structure of the tympanic membrane: 5% tetracaine base dissolved in dimethylsulfoxide (DMSO), pure DMSO, and Bonain's solution. Survival times ranged from 1 day to 3 months. Following removal from the animals, membranes were embedded in Spurr and cut in semithin sections. Signs of mild or severe external otitis were frequent; to avoid non-specific results, infected specimens were not evaluated. Bonain's solution caused loss of the epidermis and mucosal epithelium within 1 day of treatment. The connective tissue layers of the drum were severely hyperplastic after a survival time of 1 month. Tetracaine base in DMSO caused a loss of epithelium and mucosal cells in 3 days. Regeneration started within 7 days and a restitution to integrity was seen after 3 months in drums treated with tetracaine base or DMSO alone.     

Late effects of local anesthetics on tympanic membrane structure

With the rat tympanic membrane used as a model, various topical anesthetics in current clinical use (phenol, Bonain's liquid, and Xylocaine spray) were tested. Structural changes were observed for up to five months from the time of anesthetic application. The most protracted changes affect the lamina propria, which exhibits a pronounced thickening. The extent of the changes, however, differs according to the agent used; for example, phenol applied to discrete areas exhibited the least widespread changes. In the tympanic portion of the lamina propria, the connective tissue was loosely packed with less regularly arranged collagen fibers, while a tightly packed fiber bundle existed on the meatal side. It is inferred that the submucosal connective tissue layer is the portion of the connective tissue layer where the remodeling and reconstruction of the fibrous layer occur.     

Topical anesthesia of the tympanic membrane using DMSO and local anesthetics

A solution of 10% cocaine hydrochloride plus 10% water in 80% dimethyl sulfoxide (DMSO) or 5% tetracaine base in pure DMSO was topically applied to the eardrum in 112 and 52 cases respectively. Both preparations induced well-tolerated analgesia suitable for myringotomy with or without insertion of a grommet in the office environment. DMSO-tetracaine induced analgesia within ten, DMSO-cocaine within 30 minutes. This method has distinct advantages as compared to iontophoretically induced analgesia or topical agents with a destructive mode of action.     

Local IgE production

Recent data from a number of groups have confirmed that IgE antibody may be produced, at least in part, locally within the nasal mucosa. Our data support the theory that B cell switching may also occur locally, although this remains to be confirmed. Local IgE may account for local disease expression in atopic subjects, although it is not clear which step is rate-limiting in this process. Our results highlight the importance of developing local strategies targeted against IgE for treatment of allergic diseases.     

喉颈联合手术经气管切开插管麻醉诱导药物的选择与应用

目的比较3种静脉麻醉药在喉颈联合手术经气管切开插管麻醉诱导中的效果.方法随机将108例SASⅠ～Ⅱ级择期全喉切除伴单侧或双侧颈淋巴清扫患者分为3组,A组羟丁酸钠诱导剂量为65.00±19.00mg/kg,B组依托咪酯诱导剂量为0.28±0.12 mg/kg,C组异丙酚诱导剂量为2.1±0.28 mg/kg.3组患者均在局麻气管切开手术开始后,予以咪唑安定0.1～0.2 mg/kg,芬氟合剂2～3ml,并以2%利多卡因经气管注入行表面麻醉,按3种药物不同的起效时间注入静脉,观察3组患者麻醉诱导前后,气管插管后的HR,MAP,RR和SpO2的变化.结果A组呼吸变慢18例,SpO2比诱导前降低明显,MAP升高,差异有显著性(P＜0.01).B组RR、HR、MAP与诱导前差异无显著性.C组入睡时间起效迅速,用药后MAP下降明显,与诱导前差异有高度显著性(P＜0.01).Spo2有下降趋势,但均在正常范围.结论依托米酯,异丙酚均可作为喉颈联合手术经气管切开插管麻醉诱导剂,但应掌握静注剂量与速度.     

Influence of volatile and intravenous anesthetics on the threshold of the acoustically evoked stapedius reflex

The influence of volatile and intravenous anesthetics on the threshold of the acoustically evoked stapedius reflex (SR) was studied prospectively in 45 patients undergoing elective ENT surgical procedures. After premedication with flunitrazepam the patients were randomly assigned to one of nine groups. Group I: 70% nitrous oxide (N₂O) in oxygen (O₂); Groups II–VII: induction of anesthesia with intravenous thiopental, followed by mask inhalation with 100% O₂ and 1.13% halothane (Group II), 2.52% enflurane (Group III) or 1.73% isoflurane (Group IV); or 70% N₂O in oxygen, and 0.44% halothane (Group V), 0.86% enflurane (Group VI) or 0.75% isoflurane (Group VII); Group VIII: intravenous midazolam and ketamine; and Group IX: intravenous midazolam and alfentanil. Tympanometry and ipsilateral and contralateral SR measurements were performed when the effects of the anesthetics had achieved a steady state. Flunitrazepam raised the SR threshold only slightly. Substances applied during inhalation anesthesia either markedly increased the threshold contralaterally more than ipsilaterally (thiopental, N₂O), or suppressed the reflex completely (thiopental, all volatile anesthetics with or without N₂O). Under intravenous anesthesia the reflex was always present. The midazolam–ketamine combination influenced the threshold bilaterally only slightly, while the midazolam–alfentanil combination led to a pronounced, contralaterally significant elevation of the threshold. Based on its minimal influence on the SR threshold, flunitrazepam is especially suitable for sedation and the midazolam–ketamine combination for anesthesia in audiological diagnostic procedures. Received: 14 December 1999 / Accepted: 13 March 2000