2010吸麻醉.ppt

第六章　吸入麻醉 Inhalation Anesthesia　 概念(concept) 麻醉药经呼吸道吸入，产生中枢神经系统抑制，使病人意识消失而不感到手术刺激导致的疼痛，称吸入麻醉。麻醉深浅与脑组织中的药物分压有关 Clinical evaluation of inhalational anesthetics 1、可控性 controllable 吸入麻醉药可控性优于静脉麻醉药；associated with blood/gas partition coefficient 麻醉药分压在两相中达到平衡时的麻醉药浓度比称为分配系数 麻醉药在血药内溶解度越低， 即血/气分配系数越小，可控性越好 2、麻醉强度 Anesthetic potency associated with oil/gas partition coefficient 油/气分配系数越高，麻醉强度越大，所需MAC也小 通常吸入麻醉药的血/气分配系数与油/气分配系数成反比，即麻醉强度越大，其可控性越差。 MAC（Minimal alveolar concentration）即肺泡最小有效浓度，指挥发性麻醉药和纯氧同时吸入时在肺泡内能达到50％的病人对手术刺激无体动反应的浓度 MAC is minimal alveolar concentration of an inhalational anesthetic at 1 atmosphere absolute that prevents movements of 50% of the population to a standard stimulus. 3. Depressant effects on Cardiovascular system Depression of myocardial contractility；Increased myocardial excitability Arrhythmias are common during halothane Increased circulating catecholamines Effects on respiratory Respiratory depression dose-dependent depression of ventilation Irritant to respiratory depression Relaxation of bronchial smooth muscle 5、对神经系统的影响 on ICP and EEG Dose-dependent depression of EEG activity, at moderate to high concentration (more than 3%), enflurane produces epileptiform paroxysmal spike activity Increase ICP, and this action of isoflurane is the lowest in all volatiles 6、对运动终板的影响 neuromuscular junction Skeletal muscle relaxation and potentiates non-depolarizing relaxants. Skeletal muscle relaxation of enflurane is the greatest in all inhalational anesthetic Hatholane relaxes uterine muscle and may cause postpartum hemorrhage 理想的吸入麻醉药应具备以下条件： 不燃、不爆。 室温下易挥发。 麻醉强度大。 血溶解度低，可控性好，诱导快，苏醒快。 体内代谢少；代谢产物无毒性，安全范围大。 不增加心肌应激性，能与肾上腺素合用。 使肌肉松弛。 能抑制过强的交感神经活动。 对呼吸道无刺激作用，有支气管扩张作用。 对心肌无明显抑制。 不致脑血管扩张。 无肝肾毒性。 Properties of the ideal inhalational anesthetic Pleasant odour, non-irritant to respiratory depression low blood/solubility—rapid induction and recover from anesthesi