Longnecker's Anesthesiology > Part 4. Managing Anesthesia Care > Section A. Monitoring the Anesthesia Patient > Chapter 33. Monitoring and Managing Neuromuscular Blockade Richard M. Pino, MD, PhD, and Hassan H. Ali, MD

Techniques Used to Monitor Neuromuscular Blockade

"We have described the basic mechanisms controlling the contraction of a single muscle fiber. This knowledge must be extrapolated to the bedside analysis of the contraction of anatomically distinct muscles to assess the patient's degree of neuromuscular blockade.There are five patterns of stimulation.1. Single-twitch stimulus (Fig. 33–3) usually is given at a frequency of 0.1 Hz, that is, one stimulus every 10 seconds.⁶ The current is incrementally increased until a maximum twitch height is obtained. A current that is slightly greater than that used to achieve maximum twitch height is called the supramaximal stimulus. After an NMBD is administered, the decrements in twitch height are compared as percentages of the control twitch. This stimulus pattern is most often used to establish the basic pharmacodynamic properties of an NMBD. For example, the ED₉₅ is the dose at which the twitch height is depressed by 95% of maximal height. The primary shortcoming of a single-twitch stimulus is the requirement for a control response prior to the administration of the NMBD.

2. TOF stimulation (TOF; Fig. 33–4) is the most commonly used stimulus.^7,8 Each train consists of four stimuli at 2 Hz (four stimuli in 2 seconds) that are again repeated every 10–12 seconds. In the absence of neuromuscular blockade, the TOF will evoke four twitches of equal strength when the abducted thumb is palpated after stimulation of the..."