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

TOF test was performed by two routinely used devices, peripheral nerve stimulator and intraoperative neurophysiologic monitoring device. TOF monitoring of upper extremity included stimulation of ulnar nerve. Negative surface electrode was placed on the wrist in line with the smallest digit 1-2cm below skin crease and the positive 2-3cm proximal to the negative electrode. Active surface recording electrodes were placed on adductor pollicis muscle. TOF monitoring of lower extremity included stimulation of peripheral nerve, posterior tibial nerve. Surface stimulating electrodes were placed, negative over inferolateral aspect of medial malleolus, and positive electrode 2-3cm proximal to the negative electrode. Stimulation current was 20-30 mA for hand and 30-60mA foot TOF by a group of 0.2 millisecond pulses, spaced 500 millisecond apart, to deliver four contractions. Surface recording electrodes were used for measuring muscle response on foot, active electrode which was located on the Flexor hallucis brevis muscle and reference on the big toe. Intraoperative monitoring device was used, and software with TOF monitoring programe was installed. EMG response was calculated by the peak of amplitude (peak to peak amplitude) presented in quantitative value of online measurement. Interpretation was different, visual and subjective. Peripheral nerve stimulator was used for subjective TOF test. Output current was adjustable from 0 to 70 mA. Repeat stimulation of 4 pulses/0.2 milliseconds repeated every 500 milliseconds. Surface negative electrodes were placed over the course of ulnar nerve on the wrist, in line with the smallest digit, 1-2cm proximal from skin crease, and positive electrode 2-3 cm proximal. Response was followed on adductor pollicis muscle. All data were kept in electronic medical records and if data are not complete subjects were not included in the study. Results were compared between TOF methods on two different body sites, upper and lower extremity, by quantitative method and other comparison was made between subjective and quantitative method with TOF test located in both methods on the upper extremity.

Inclusion criteria

Subject undergoing spine fusion surgery when intraoperative neurophysiologic monitoring is included.

Exclusion criteria

Subjects with history of previous nerve injury or peripheral neuropathies when intraoperative neurophysiologic monitoring was precluded. Possible technical issues during surgery prior TOF test such as incorrect electrode placement, lead wire attachment, TOF device error or impossibility to correct it in acceptable time when TOF test can not be performed.