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Train of Four

Train of Four is the test used to measure the degree of neuromuscular blockade. A peripheral nerve stimulator is used.

• Do a baseline measurement before paralytic agent is started to determine current necessary to obtain twitch.
• 20 mA may be enough for the patient.
• Complete and document until TOF to 2/4.
• Instructions
  1. Attach 2 electrodes along the course of the ulnar nerve. (Temporal may be used.)
  2. Connect the lead to the peripheral nerve stimulator by inserting the jacks into the Proximal (red) and Distal (black) output jacks. Connect the other end to the patient electrodes.
  3. Turn the stimulator on. Select the current necessary (usually 20) for that patient to twitch when the stimuli is applied.
  4. Press TOF once. It will deliver a train of four pulses where each is 0.5 seconds apart. Do NOT use the other buttons on the stimulator!
  5. Count the number of twitches the patient had out of four (0/4, 1/4, 2/4, 3/4, 4/4.) Adjust the medication as ordered. Goal is 1/4 to 2/4 twitches.