Percent recovery of insulin from two different concentrations (3 U/250 mL and 45 U/250 mL) of regular insulin...

To compare the percent recovery of regular insulin prepared for administration as a continuous rate infusion (CRI) using 2 different concentrations, 3 and 45 U in 250 mL 0.9% saline.

In vitro experiment SETTING: Privately-owned emergency and referral teaching hospital.

None INTERVENTION: Commercial 250 mL 0.9% sodium chloride IV fluid bags were injected with either 3 U (solution bag A) or 45 U (solution bag B) of regular insulin. The insulin concentration was measured in each bag. A fluid administration and extension set were connected to each bag and 50 mL was drained through the IV tubing. The insulin concentration was then measured from samples post washout.

Comparison of the concentration of insulin injected into the bag and concentration of insulin in the bag showed that there was a 29.7 and 37.3% recovery of insulin from solution bag A and solution bag B, respectively. Comparison of the concentration of insulin injected into the bag and concentration of insulin in the post 50-mL washout samples showed that there was an 11.9 and 30.6% recovery of insulin from bags A and B, respectively.

Substantially more insulin was available after a 50-mL washout from solution bag B compared to solution bag A. Insulin binding to the IV bag and fluid administration set is likely the cause of this difference.

Patients receiving lower concentrations of insulin as a CRI, such as might be prescribed for cats and small dogs may require longer time for resolution of hyperglycemia and ketonemia.