Electromyographic Assessment of Onset and Recovery of Neuromuscular Blockade

Residual neuromuscular blockade (weakness) is a common occurrence in the postanesthesia care unit when muscle relaxant drugs have been used in the operating room. The only method of reliably detecting the presence of neuromuscular blockade is through the use of quantitative neuromuscular monitors. These devices measure and quantify the degree of muscle weakness and display the results on a screen. When using train-of-four (TOF) nerve stimulation, the ratio of the fourth muscle contraction (twitch) to the first twitch will be displayed; when this ratio is 90% (or 0.9) or greater, full recovery of muscle strength is present, and the endotracheal tube can be removed. At the present time, there is only one commercially-available quantitative monitor available in the United States -the TOF-Watch. It is not used by many clinicians because it requires experience to obtain accurate results, is expensive, and is subject to interference by factors in the operating room. The aim of this investigation is to examine a new quantitative monitor (the T4-EMG (EMG = electromyography) that may not be subject to the same limitations as the TOF-Watch AMG (AMG = acceleromyography). In order to study the accuracy of this new device, the T4-EMG will be compared to the current "clinical gold standard", the TOF-Watch.