Effect of preparation techniques on mixing of additives in intravenous fluids in nonrigid containers

It has been observed that the procedures of some hospitals do not require any mixing after drugs are added to intravenous bags. Previous studies have shown that mixing often is incomplete in the absence of specific mixing procedures. It has been asserted that mixing is effected by normal handling of bags, and that mixing is sufficient if drug is added to "bottom up" bags, which are then inverted. In this study the extent to which mixing occurred on addition of KCl solution or water to intravenous bags as a function of bag and needle position, additive, speed of addition, and bag handling procedure was determined. Also determined was the extent to which mixing occurred spontaneously. Most important, we determined the effect of incomplete mixing on the concentration of drug actually delivered from the bags. It was concluded that mixing is critically dependent on many factors, and that an effective technique to achieve complete mixing is essential to assure homogenous solutions. The most effective method of mixing solutions in plastic infusion bags is to grasp the bag by its two ends and rapidly invert it twice. This "double inversion" mixing technique, a maneuver requiring only 2 seconds, assures complete mixing of intravenous solutions.