Jöhr M, Gerber H
Institut für Anästhesie und Reanimation, Kantonsspital Luzern.
Schweiz Med Wochenschr. 1996 Sep 28;126(39):1649-53.
Sensitivity to neuromuscular blocking agents differs between individuals, and residual neuromuscular blockade is a common postoperative problem. Clinical signs such as head lift, hand grip, and inspiratory force are suitable means of showing residual blockade. However, an awake and cooperative patient is needed. Therefore, in clinical practice it is advantageous to use the responses evoked by a nerve stimulator.
In clinical anesthesia, the ulnar nerve is the most popular site. The response is evaluated by feeling the contractions of the adductor pollicis muscle. This muscle shows a slow onset of blockade and is highly sensitive to neuromuscular blocking agents. Therefore, the chance of overdosing the patient is decreased and during recovery additional safety is gained, as it can be safely assumed that at the time of normalization of the thumb twitches no residual blockade exists in the diaphragm or larynx. On the other hand, absent twitches of the adductor pollicis using train-of-four stimulation do not preclude intraoperative activity of more resistant muscles such as the diaphragm.
In clinical anesthesia, tactile evaluation of the muscle response is the usual method. Mechanomyography (Myograph) with a force transducer is used as the reference standard. This method, as well as the measurement of acceleration (Accelograph, TOF-Guard) and electromyography (Relaxograph) are mainly tools for teaching and research. Different patterns of nerve stimulation are used: during induction, single-twitch stimulation at 1Hz; during profound blockade, post-tetanic count stimulation (PTC); surgical blockade is evaluated using train-of-four stimulation (TOF); and recovery is followed by double-burst stimulation (DBS). Using simple train-of-four stimulation during recovery, a device is needed with a registering capacity to accurately determine a TOF-ratio > 0.7.
Relaxometry allows monitoring of neuromuscular function independently of the patient's cooperation, and should be standard. In the intensive care unit, relaxometry helps to minimize the risk of overdosing. However, muscular weakness can persist despite adequate drug dosage. Relaxometry is only part one of a concept. Intubating and operating conditions are highly dependent on the depth of anesthesia, and the risk of postoperative residual blockade can be minimized by using short or medium action drugs.
个体对神经肌肉阻滞剂的敏感性存在差异，术后残余神经肌肉阻滞是一个常见问题。抬头、握力和吸气力等临床体征是显示残余阻滞的合适方法。然而，这需要患者清醒且配合。因此，在临床实践中，使用神经刺激器诱发的反应是有利的。
在临床麻醉中，尺神经是最常用的刺激部位。通过感受拇内收肌的收缩来评估反应。该肌肉阻滞起效缓慢，对神经肌肉阻滞剂高度敏感。因此，减少了患者用药过量的可能性，并且在恢复过程中增加了安全性，因为可以合理地假设在拇指抽搐恢复正常时，膈肌或喉部不存在残余阻滞。另一方面，使用四个成串刺激时拇内收肌无抽搐并不排除术中如膈肌等更具耐受性的肌肉仍有活动。
在临床麻醉中，对肌肉反应进行触觉评估是常用方法。使用带有力传感器的机械肌电图（肌动图）作为参考标准。这种方法以及加速度测量（加速度图，TOF监护仪）和肌电图（松弛图）主要用于教学和研究。使用不同的神经刺激模式：诱导期间，采用1Hz的单刺激；深度阻滞期间，采用强直后计数刺激（PTC）；手术阻滞采用四个成串刺激（TOF）进行评估；恢复过程采用双短强直刺激（DBS）。在恢复过程中使用简单的四个成串刺激时，需要一种具有记录功能的设备，以准确测定TOF比值>0.7。
松弛测量法可独立于患者的配合情况监测神经肌肉功能，应成为标准方法。在重症监护病房，松弛测量法有助于将用药过量的风险降至最低。然而，尽管药物剂量合适，肌无力仍可能持续存在。松弛测量法只是整个概念的一部分。插管和手术条件高度依赖于麻醉深度，使用短效或中效药物可将术后残余阻滞的风险降至最低。
