RESUMO
INTRODUCTION: In total parenteral nutrition (TPN) solution, adsorbance of insulin to polyvinylchloride (PVC) surfaces of fluid containers and infusion-sets, decrease the amount of insulin that reaches the patients. OBJECTIVE: To clarify the biding sites of insulin and to propose a solution to overcome this problem. METHODS AND MATERIALS: To each of four 1000ml. PVC bottles of 5 percent dextrose solution, 300 microunit of insulin per each milliliter of dextrose solution were added. Each bottle was then connected to an infusion-set and the system made to run at an infusion rate of 100ml. per hour. One milliliter samples were then collected from both the PVC bottles and infusion-sets-terminal, separately, immediately at the starting point (time zero) and 15, 30, 45 and 60 minutes thereafter. The concentrations of insulin were checked using insulin kits. RESULTS: At the starting point (time zero) the mean of insulin concentrations among four PVC bottles was 213.79 microunit per each milliliter of 5 percent dextrose solution. No significant fluctuation was noted in the concentration of insulin in the PVC bottles through 60th minute period. However the concentration of insulin at infusion-set- terminal decreased significantly at the end of the same hour (p. value = 0.004). CONCLUSION: Our results demonstrate that the adsorbance of insulin takes place at the surfaces of infusion sets. It follows therefore that increase in the primary dosage of insulin added to PVC infusion solutions and the selection of a suitable infusion set (polyethylene) seem to be beneficial for overcoming this problem.
