Chapter 6 Basic Concept of General Anesthesia Department of Anesthesiology Xiangya hospital Central South University

General anesthesia is an altered physiologic state characterized by reversible loss of consciousness, analgesia of the entire body, amnesia and some degree of muscle relaxation. Induction → Maintenance → Recovery Definition of General Anesthesia

1. Induction of General Anesthesia Definition 全麻诱导是指病人从清醒转为可以进行手术 操作的麻醉状态的过程。 There are some complications or risks in this stage, e.g. reduction of blood pressure, arrhythmia, myocardial ischemia.

Agent induction dose (mg/Kg) Diazepam0.2 Midazolam Thiopental3-5 Etomidate0.3 ketamine1-2 Propofol Fentanyl 5-6 μ g/kg Intravenous induction agents

Muscle Relaxants depolarizingnondepolarizingdose (mg/kg) Succinycholine 1-2 vecuronium atracurium pancuronium Rocuronium0.6-1

● Regurgitation and Vomitting ● Cardiovascular depression ● Respiratory depression ● Histamine release ● Pain on injection ● Hiccup and muscle movements

● young children ● myasthenia gravies ● upper airway obstruction, e.g. Epiglottitis ● lower airway obstruction with foreign body ● bronchopleural fistula or empyema ● no accessible veins

Initially, nitrous oxide 70% in oxygen is used and anesthesia is deepened by gradual introduction of increments of a volatile agent, e.g. Halothane 1-3%, Enflurane %, Isoflurane 1-2%.

● Spontaneous ventilation is to be maintained. ● the face mask is applied firmly as consciousness is lost and the airway is supported manually. ● Insertion of an oropharyngeal airway, a laryngeal mask airway or a tracheal tube may be considered when anesthesia has been established.

● Slow induction of anesthesia ● Airway obstruction, bronchospasm ● Laryngeal spasm, hiccups ● Environmental pollution

● Airway obstruction ● anticipant difficult intubation

● Maintaining spontaneous ventilation throughout the procedure ● Sufficient surface anesthesia

● Patient with the risk of regurgitation ● Patient with postural hypotension following anesthesia (e.g. paraplegia)

● intramuscular injection of ketamine ● take midazolam orally ● administration of fentanyl via mucosa

注意事项 保持呼吸道通畅 --- 首要任务 保持一定麻醉深度，减轻插管应激反应 静脉用药按 Kg 体重计算、维持循环稳定 诱导前，准备好麻醉机和插管用具，监测 生命体征 面罩加压给氧时， TV 不宜过大，避免气体 进入胃内 → 胃胀气、返流

⒉ Maintenance of general anesthesia 镇静 sedation 镇痛 analgesia 肌松 muscle relaxation

⒉ Maintenance of general anesthesia Inhalational agents Intravenous anesthetics Opioids Muscle relaxants

全麻维持与诱导紧密衔接 了解手术进程，麻醉深度与手术刺激相适应 做好呼吸管理，保持气道通畅，人工通气监 测 P ET CO 2 、 S P O 2 及血气分析 : 颅脑手术 P a CO 2 维持 30-35mmHg 冠心病病人 P a CO 2 不宜太低，以免冠脉痉挛 注意事项

■ 使用肌松监测仪指导肌松剂的使用 ■ 充分镇静、避免术中知晓 ■ 维持生命体征和内环境平稳，及时 处理术中失血性休克、过敏性休克、 心律失常等异常情况

⒊ Recovery Antagonizing residual neuromuscular blockade Extubation Airway supporting Recovery position is benefit to avoid airway obstruction

⒊ Recovery 严格掌握拔管指征，过早、过晚拔管均会 造成严重后果 自然苏醒，必要时使用催醒药 MACawake: 肺泡气内吸入麻醉药浓度降至 0.4MAC （ 0.5 或 0.58MAC ）时， 95% 病人 能按指令睁眼

4.Monitoring depth of anesthesia Stages of anesthesia

麻醉深度监测技术 食道下端肌肉收缩波形和振幅的测定 脑电双频谱指数（ Bispectral Index ， BIS ） 清醒 : 外科麻醉期 : 40 体感诱发电位 脑干听觉诱发电位