Clinical Application of "Train of Four" Testing in the Intraoperative Monitoring Setting
Condition: Neuromuscular Blockade; Muscle Relaxation
Study type: Observational [Patient Registry]

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Train of four test
Intervention type(s): Device
Intervention description(s): TOF test includes stimulation of peripheral nerve of upper extremity, ulnar nerve in this study. Two methods of interpretation are included, visual which uses anesthesiologist TOF device, and quantitative uses intraoperative neurophysiologic monitoring device, both devices are in routine clinical practice use. Different interpretation of muscle contractions are followed, by quantitative method and visual method. Visual evaluates number of twitches and determines the degree of neuromuclular block and percent of blocked acetylcholine receptors. Quantitative method record muscle contraction by using EMG, presents each twitch as amplitude, caluculate peak to peak value, and provide numerical value and difference for each twitch.
Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Probability Sample
Study population: 
        Subjects undergoing instrumented orthopedic surgical procedure which requires the use of
        neurophysiologic intraoperative monitoring modalities.
      
Keywords: Neuromuscular blockade; TOF test; Quantitative TOF method; Visual interpretation of TOF