Subjective responses to train-of-four and double burst stimulation in awake patients

The present study was undertaken to determine whether the discomfort associated with the sequential bursts of stimuli comprising the two recommended forms of double burst stimulation (DBS) is comparable to that associated with the repetitive stimuli of train-of-four (TOF). Twenty-one unmedicated volunteers rated on a visual analog scale the discomfort associated with randomly applied DBS and TOF stimulations at 20, 30 and 50 mA. All participants were blinded to the mode of stimulation, as well as to the current intensity. At each amperage tested, TOF produced significantly less discomfort than either form of DBS (P less than 0.01). Stimulation at 50 mA produced median visual analog scale scores of 7.5, 7.0, and 5.0 for DBS3,2, DBS3,3, and TOF, respectively. At 30 mA the corresponding median visual analog scale scores were 4.5, 5.5, and 3.0, whereas at 20 mA the scores were 4.0, 4.5, and 2.0, respectively. Thus, DBS is more uncomfortable than TOF at each current tested; however, in light of reports of its higher sensitivity, DBS may be the preferred means of assessing neuromuscular function in the awake as well as the anesthetized patient when a force transducer and recorder are not readily available.