priming principle and vecuronium: could it be a replacement for suxamethonium?

The effect of the priming principle on some pharmacodynamic parameters of vecuronium was studied. Sixty adult patients were divided into three equal groups; one received vecuronium in two divided doses, the second received a single bolus dose, and in the third group suxamethonium was used for comparison. The priming dose [0.01 mg.kg[-1]], interval [6.0 min] and the injection-intubation time of the main dose of vecuronium [one minute], were all fixed. The Datex Relaxograph was used for neuromuscular monitoring, while a scoring system was applied for assessment of intubating conditions. There was neither significant depression in T[1] activity and/or TOF ratio after priming, nor any clinical side effect. The intubation score improved with priming [a mean of 2.6 +/- 0.7] relative to non-primed patients [1.6 +/- 1.0], but it did not reach the score of suxamethonium [3.0 +/- 0.0]. There was a significant decrease in onset time of vecuronium from 4.2 +/- 1.6 min. in group II to 2.4 +/- 0.8 min. in group I. There was a tendency to increase in clinical duration and recovery rate with priming, but insignificantly. The improved intubation score with priming could not only be explained on the bases of T[1] and TOF ratio depression. The priming principle proved to be a useful technique in facilitating endotracheal intubation, but needs further study regarding its mechanism of action and possible routine use