A Comparison of Accelerometric Monitoring by TOF Watch® SX and Electromyographic Monitoring by Tetragraph® for Recovery From Neuromuscular Blockade

Before the induction of general anesthesia both monitors will be placed in the same arm. After induction of general anesthesia and before neuromuscular blocking agent administration both devices will be consecutively calibrated and a baseline measurement will be obtained. During the surgical procedure the investigators will monitor neuromuscular function with one of the two devices. Then the investigators will switch the device used as a guide between subsequent patients. The protocol will start as soon as the leading device will register a train-of-four ratio (TOFr) ≥ 0.2. During the protocol a comparison between the two devices will be conducted as soon as the device used as a guide will display a TOFr ≥ 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1. For each of the TOFr reported, we will deliver two subsequent TOF stimulations with the guiding device followed by two TOF stimulations with the other monitor. Both the stimulations delivered by each device and the two consecutive stimulations delivered by different monitors will be conducted 20 sec from one another. Stimulations with the same device will be used to assess intraobserver variability for each methodology, while the second and the third measurements (consecutive stimulations with different devices) will be used to assess agreement between them. The protocol will end when the leading device will show a TOFr ≥ 1.0, or if, at the end of the surgical procedure, acceleromyographic TOFr will be > 0.9.