[Effects of precurarization on oxygen arterial saturation measure with pulse oximetry and neuromuscular function]

To study changes in arterial oxygen saturation (SpO2) measured by pulse oximetry, and the effect of neuromuscular function after precurarization with different nondepolarizing muscle relaxants.

One hundred twenty-four patients scheduled for elective surgery were randomly assigned to four groups according to the NDPMR received: d-tubocurarine 0.05 mg/kg, atracurium 0.05 mg/kg, vecuronium 0.01 mg/kg or pancuronium 0.015 mg/kg. We recorded SpO2 before precurarization and 4 minutes after administering the dose. We also recorded signs and symptoms of muscle weakness after the 4-minute period of precurarization.

We observed a statistically significant decrease in SpO2 4 minutes after starting precurarization in the groups receiving pancuronium, vecuronium and atracurium. These three groups were also significantly different from the d-tubocurarine group with regard to signs and symptoms of muscle weakness; the incidences of such symptoms were similar among the three groups, the only exception being the greater difficulty patients in the pancuronium group had in maintaining the Valsalva maneuver for 10 seconds. The lowest incidence of clinical signs of muscle weakness were in the d-tubocurarine group. We found a significant relation between decreased SpO2 caused by precurarization and the variables of inability to maintain the Valsalva maneuver for 10 seconds and to raise the head for more than 4 seconds.

SpO2 measured by pulse oximetry is an effective method for monitoring breathing function in the precurarized patient, as it detects early changes in arterial oxygen saturation related to respiratory muscle weakness. The agent d-tubocurarine is recommended for precurarization, because of its scarce effect on neuromuscular function at the dose used in this study.