Infusion of large particles of thiopental sodium during anesthesia induction.

STUDY OBJECTIVE

To determine the potential clinical significance of admixtures of thiopental sodium and acidic drugs, which are used during induction of general anesthesia and can cause the formation of particles of thiopental.

DESIGN

Using an infusion setup similar to that used for a rapid-sequence induction of general anesthesia, injection of either pancuronium bromide or vecuronium bromide caused formation of particles of thiopental that were measured using a particle analyzer. The effects of delaying the injection of the muscle relaxant on particle formation and the effects of plasma on particle dissolution were studied.

MEASUREMENTS AND MAIN RESULTS

The thiopental particles had a diameter of 17 to 39 microns, with a concentration of 15,000 to 20,000 particles/ml. Particle formation was prevented when a 30-second delay preceded administration of pancuronium or vecuronium following injection of thiopental. No particle formation was detected when succinylcholine was injected. Human plasma was far more effective than a crystalloid solution in dissolving thiopental particles.

CONCLUSIONS

It is unlikely that clinically significant particles of thiopental will remain intact upon entering the bloodstream. However, mixing thiopental with pancuronium or vecuronium has the potential of disrupting intravenous access due to occlusion with particles.