Effect of Tetanus on Neuromuscular Junction Monitor Performance in Pediatric Patients Undergoing Abdominal and / or Perineal Surgical Procedures With Using of Rocuronium

Effect of tetanus on neuromuscular junction monitor performance in pediatric patients undergoing abdominal and / or perineal surgical procedures with the use of rocuronium.

Routine monitoring of neuromuscular function during anesthesia offers some advantages. It helps promote proper relaxation according to each patient's individual sensitivity and reduces the possibility of postoperative residual block with its serious consequences, namely: reducing pulmonary forced vital capacity, decreased ability to increase ventilation during periods of hypoxia, increased risk of pulmonary aspiration due to lower strength of pharyngeal muscles. It can also reduce the waste of time caused by excessive paralysis. Furthermore, the interpretation of data from the monitor may indicate that pharmacological reversal of neuromuscular blockade is not required, with potential benefits over costs, as well as lower incidence of postoperative nausea and vomiting.

Acceleromyography was introduced for use in daily clinical practice in 1988 as a simple, reliable and easy to apply in the anesthetized patient monitor to assess muscle relaxation. The purpose of this neuromuscular junction (NMJ) monitor was replace mechanomyography, this modality that has greater complexity of assembling and using. The mechanomyography was considered long, the ideal objective neuromuscular monitoring. This measures the strength of isometric contraction of a muscle or digit (e.g. thumb) in response to nerve stimulation. Moreover, it requires an assembly that demands time and with strict rules for the positioning and application of non elastic preload on the thumb. This makes the method impractical for everyday use. Furthermore, monitors based on the method of mechanomyography are no longer commercially available. Acceleromyography gradually replaced mechanomyography as a method to monitor muscle relaxation in clinical practice and research.

Acceleromyography measures the acceleration (isotonic contraction) of a muscle or finger. The method is based on Newton's second law, which states that force is equal to the product of mass and acceleration. If the mass (e.g. thumb) is constant, the acceleration is directly proportional to the force. This means, in principle, it measures the unrestricted movement of the muscle in question.

Monitoring must present a stable response (baseline) for a period of 2 to 5 minutes before administration of neuromuscular blocker. The time required to reach this stable response depends on the duration of electrical stimulation and frequency in which electrical stimulation are applied. When using single mode stimulus at a frequency of 0.1 Hertz (Hz) or train-of-four (TOF) every 12 to 15 seconds, it may take 5 to 20 minutes to obtain a stable response. However, the stabilization period may be shortened by applying a short, high frequency stimulation (tetanic stimulation). Tetanic stimulation for 5 seconds can decrease the stabilization period of 2 to 5 minutes.