Clinical Application of "Train of Four" Testing in the Intraoperative Monitoring Setting

The study examines the clinical application of TOF (train of four test) used by anesthesiologists and neurophysiologists during instrumented spine procedures, as well as certain associated parameters. 'Train of four' test is a test routinely used during the surgery, which is performed by stimulation of peripheral nerve with purpose to determine the degree of muscle relaxation by interpretation of muscle response. During spine surgery, it is helpful for the surgeon to have a patient's muscles as relaxed as possible with the least amount of tone, especially when exposing. Anesthesiologists achieve this level of relaxation by giving a neuromuscular blocking agent. If medication given to do this has not fully left their system by the time the surgeon needs to start putting in the screws and rods, then the intraoperative monitoring can not be adequately performed. If the muscles are too relaxed, then free run EMG and screw stimulation, two monitoring methods used, will not be analyzed correctly and the surgery may be adversely affected. This study compares the results of the 'train of four' test performed by neurophysiologists and anesthesiologists. Additionally, it looks at the differences, if any, in comparing stimulation of the foot nerve (tibial n.) or hand nerve (ulnar n.) Performing the TOF (train of four test) in the lower extremity can be relevant for many reasons. Train of four tests can show the presence of four twitches in the arms but the legs may not fully recovered from muscle relaxant given by anesthesia. Also, train of four test which uses subjective method of interpretation by anesthesiologists may present different results compared than objective quantitative method of train of four test interpretation. Ultimately, the goal of this study is to show the importance of 'TOF' testing in ensuring that any identifiable preventable intraoperative surgical complication is appropriately identified.