This study examined the stability of concentrated sodium nitroprusside infusions during administration by a motorized syringe‐pump system. Sodium nitroprusside and the free‐cyanide degradation product were determined in infusion samples collected over periods of up to 24 h. Measures which were taken to protect the delivery system from light, ensured satisfactory stability of the infusion for at least 12 h from the time of preparation.

The level of particulate contamination in a range of large volume injections has been measured using electrical resistance (Coulter) and light blockage (HIAC) techniques. Particle counts showed large variations between the two techniques and although a correlation could be shown for ionic solutions no such correlation could be found for sugar containing solutions. Shape factors alone cannot explain these discrepancies but other differences fundamental to the physics of the two measuring techniques play an important part. We conclude that results obtained using one technique cannot be correlated, theoretically or actually, with those obtained from the other technique.