合并呼吸系统疾病麻醉处理

合并呼吸系统疾病患者的 麻醉处理,天津医科大学总医院 王国林,目的,了解麻醉药对呼吸系统的影响 围手术期肺部并发症的诱发因素 肺部疾病患者术前准备的方法 减少术后肺部并发症的措施,全麻的影响,全麻对呼吸系统可产生多种影响 减少肺泡巨噬细胞的数量 增加肺泡毛细管的通透性 抑制肺泡表面活性物质的释放 增加NO合酶的活性 增强肺血管对-肾上腺素能受体激动剂的敏感性等 这些作用均可能促进PPCs的产生 全麻引起肺的机械性、结构性和功能性的改变，同样可能导致PPCs,全麻诱导后 患者的FRC下降并使肺下垂部位产生局灶性肺不张 在分流区或死腔样通气部位可产生V/Q失调 对膈肌运动有显著影响，使膈肌的腹侧和背侧产生近乎抑制的位移，这就可能会使上部肺区通气过度而下垂部位的肺区通气不足。 膈肌局部解剖和神经支配上的差异也会使其在全麻期间产生位置和移动上的异常,如果没有手术的影响，患者清醒后，呼吸系统能逐渐恢复到基础水平 麻醉及手术均可导致呼吸系统的显著变化，两者间的相互影响再加上肺部本身的潜在问题，可能是导致PPCs发生的原因,术前评估,PPCs通常发生于麻醉和手术患者，尤其是上腹部和胸部手术患者 PPCs的危险因素还包括吸烟、慢性呼吸系统疾病、急诊手术、麻醉时间超过180min及高龄等 非胸部手术的大手术患者PPCs的发病率约为20%30%,哮喘,支气管痉挛是麻醉中可能发生的最严重的呼吸系统并发症之一 哮喘患者发生PPCs的危险因素包括近期有哮喘症状、近期使用过抗哮喘药物或住院治疗、曾因哮喘而行气管插管等 非发作期的哮喘患者围手术期发生支气管痉挛的危险较低，即使发生通常也不会导致严重后果,有发生PPCs危险的哮喘患者应在手术2448h前进行激素治疗，因为类固醇激素对气道保护作用的起效时间较长 成人每天强的松的剂量通常为4060mg。不能口服的患者及手术当日的患者通常静注氢化可的松（100mg，q8h）。,若无支气管痉挛，术后可停用类固醇激素而无需逐渐减量 围手术期类固醇激素的短期使用对伤口的感染和愈合无明显影响,术前有哮鸣音的患者患者应使用2受体激动剂和皮质激素雾化吸入 茶碱类药物不是哮喘的一线用药，并可能具有明显的毒性 经治疗后症状改善的患者可接受手术,症状不改善的择期手术患者应延期手术 哮喘发作后气道高反应性仍可持续一到数周 因而哮喘症状的改善后仍有可能因各种刺激而诱发支气管痉挛,哮喘患者术中处理的目标是防止气道痉挛。应避免使用具有组胺释放作用的药物 吸入性麻醉药具有气道扩张作用，治疗气道痉挛的效果彼此间并无明显差异 异丙酚是治疗支气管痉挛的有效药物，在诱导过程中可减轻麻醉哮鸣音 一般认为应尽量选用局部麻醉，以避免气管插管。局部麻醉不会引起副交感神经占优势以及气道收缩,2激动剂可通过气管导管雾化吸入。联合应用利多卡因和2激动剂雾化剂可产生协同作用，抑制支气管收缩反应 喉罩对气道的刺激作用比气管导管轻，提示其可用于气道反应性高的患者,严重支气管痉挛患者的气道压升高，此时维持患者的氧合功能比排出CO2更重要 在此种情况下，应采用允许性高碳酸血症的处理方法，提高吸入氧浓度以保证适当的氧合，同时避免气道压过高，以防引起气压伤 气道压增高的患者，采用 ICU用呼吸机对改善患者的气体交换功能可能有帮助,COPD,患者必须戒烟，并应用抗生素治疗呼吸道感染 某些COPD患者还可能存在支气管痉挛 2激动剂雾化吸入、抗胆碱能药物及一个疗程的激素治疗有一定作用,COPD患者可能存在慢性呼吸肌疲劳,其病因常为营养不良、电解质紊乱和内分泌失调等，术前应加以纠正 如果患者还存在其他肺部疾病，术前也应予以治疗 呼吸肌功能锻炼可降低患者的死亡率,慢性低氧血症患者短期给氧具有一定效果，可减轻肺动脉高压、减少心衰的症状和体征、改善患者的精神状况,吸烟,术前短期戒烟（48小时）可使血中一氧化碳血红蛋白降至正常水平、解除尼古丁对心血管的作用、增强纤毛的运动 戒烟12周后患者的痰液量才降低，46周才可改善临床症状和肺功能 术前戒烟超过8周的患者PPCs发生率相对于未戒烟的患者大大降低,手术的影响,腹部手术（上腹部下腹部）和胸部手术患者术后闭合容量（VC）和FRC均下降 FRC下降会导致V/Q失调及低氧血症 腹腔镜手术患者FRC约下降50%，12周后才恢复正常,已有实验证实，膈神经功能异常所致的膈肌功能障碍可引起肺不张，而全麻期间刺激膈神经可减少肺不张 手术刺激本身也可增加气道张力和反应性 在气道反应性增高的情况下，气道刺激因素（如分泌物、感染等）可引起支气管痉挛，从而导致肺不张或肺炎,无论患者是否存在哮喘或COPD，支气管扩张剂的使用是术后呼吸系统治疗的重要措施之一,阻塞性睡眠呼吸暂停综合征（OSA）、睡眠呼吸异常与术后低氧血症,OSA以上呼吸道反复塌陷和呼吸暂停为特征的呼吸性疾病 上呼吸道肌肉张力的消失使本已狭小而松弛的上呼吸道变得更加狭窄，这在睡眠的快速动眼相（REM）表现更为明显 几乎所有的OSA患者都有打鼾史。OSA在男性、肥胖、老年人中的发病率日益增高，并同高血压、心律失常、充血性心力衰竭、冠心病及脑卒中等密切有关,术前鼾症也是术后发生窒息和低氧血症的危险因素之一,低浓度的挥发性麻醉药（0.1MAC）也会通过抑制外周化学感受器和CO2调节中枢，降低机体对低氧血症和高碳酸血症的反应性 呼吸的调控受下列因素影响：患者的觉醒状态、代谢因素（pHa,PaCO2,PaO2）、以及对低氧和高碳酸血症的反应性等 镇静浓度的挥发性麻醉药对上述通气反射的抑制作用大小取决与患者的觉醒状态及所使用的麻醉药,亚麻醉浓度的挥发性麻醉药抑制机体对低氧和高碳酸血症的反射，在术后患者低氧血症的出现和持续中可能起重要作用 由于低浓度的挥发性麻醉药术后可持续存在数小时，因而患者在离开苏醒室或PACU时仍可能存在对低氧和高碳酸血症反射的抑制,术前评估,名词： IC(吸气容量TV+IRV) -TV 500ml -IRV(补吸气):3000ml FRC(功能残气量)ERV+RV -ERV (补呼气)1000ML -RV 1500ML TLC(肺总容量)6000ML,CC(closing capacity闭合容量)为依赖部分肺的小气道开始关闭时的肺容量 CV（closing volume闭合容积）从气道开始关闭至最大呼气末的容量 CV=CC-RV,肺功能(PFTs),Step 1: Routine PFTs. If the patient meets the following criteria, no further workup is necessary:,If these criteria were met and the patient were to have pneumonectomy, he would be left with at least 1 liter of FEV1 in the residual lung.,Step 2: If the patient does not meet the above criteria on routine PFT, and if the FEV1 volume is less than 2 liter, we need to perform split lung function testing. Lungs with tumor may not be contributing to total FEV1 volume and thus removal of it may not significantly affect pulmonary function. On the other hand, in some patients the diseased lung is the best lung. The best and most current method of estimating split lung function is to perform quantitative V/Q scan. Perfusion scans correlate better with pulmonary function. One can calculate the FEV1 volume of left over lung by knowing percentage of perfusion to left and right lung.,For example:,The tumor is in the right lung. Following resection of the right lung, we can estimate 1.5 x .7 = 1.05 liters of the left lung to remain. The minimum acceptable predicted postoperative FEV1 is 800 ml. If the predicted postoperative FEV1 volume is less than 800 milliliters the patient is not a candidate for pneumonectomy.,Step 3:,If the patient has predicted post-operative FEV1 value is less than 800 ml, and the surgeon still feels that he has a respectable lesion with a good prognosis, the next evaluation would be to occlude the pulmonary artery and measure the pulmonary artery pressure at rest and with exercise. If the pulmonary artery pressure is elevated at rest or with exercise, the patient is not a candidate for pneumonectomy. The patient obviously has no capillary bed reserve and is not able to tolerate the loss of vascular bed. He will develop cor pulmonale and the expected 5 year survival will be less than 50%. This can also be done on the operating table by clamping the pulmonary artery and measuring PA pressures.,What about blood gases?,If the patient has CO2 retention and if it is due to an obstructive defect, the patient is not a candidate for any surgical resection. On the other hand, if the CO2 retention is due to causes other than obstruction, eg: central hypoventilation, it is not a contraindication for surgery. If the FEV1 volume is more than 1 liter, it is unlikely that the CO2 retention is due to obstructive defect. Hypoxemia is not a consideration. It is quite possible pO2 levels can improve following resection of lung with tumor.,What if we are only planning for lobectomy?,Estimate postoperative FEV1 with the assumption that the patient is going to have pneumonectomy(全肺). On the operating may encounter unexpected node requiring pneumonectomy. If preoperative PFT evaluation is not considered for pneumonectomy, the surgeon may be forced to close the chest without attempting a surgical resection. Each segment approximately contributes to 5% of pulmonary function and one can calculate the amount of FEV1 loss based on the anticipated number of segments that are going to be removed. Knowing this information, you can calculate post-op FEV1 volume for cases requiring limited resection.,How did we decide on 800 ml of FEV1 as the cut off point?,When the FEV1 is plotted against CO2 levels in patients with obstructive lung disease, CO2 retention is not seen until FEV1 levels drop below 800 ml. The expected 5 year survival of patients with CO2 retention is less than 50%. If the patient is not obstructed. Some old women will not even have a predicted FEV1 of 1.6 liters and can have perfectly normal lungs. These patients will be able to tolerate predicted post-op FEV1 values of less than 800 ml. Thus, the criteria of post-op FEV1 volume of 800 ml as the cut off point applies only to patients with obstructive lung disease.,What abou