Nitroglycerin delivery through a polyethylene-lined intravenous administration set

Adsorption and delivery of nitroglycerin through a new polyethylene-lined (PEL) i.v. administration set was compared with adsorption and delivery through an identical set composed of polyvinyl chloride (PVC) rather than PEL tubing. The new delivery system consisted of PEL tubing, a transparent PVC chamber, and a silastic segment for insertion in a peristaltic pump. Nitroglycerin was prepared in concentrations of 50, 125, and 200 micrograms/mL in 0.9% sodium chloride injection and run through both administration sets at flow rates of 12 and 60 mL/hr. Samples were obtained at 0, 0.5, 1, 2,4, and 8 hours from each of three sites: bottle, junction before silastic segment, and distal end of tubing. Nitroglycerin content was assayed using a modified high-performance liquid chromatography technique. A slight but significant average loss of nitroglycerin (2.3 +/- 9.3%) was observed at the distal end with the PEL set, whereas the PVC set showed a significant average nitroglycerin loss of 39.7 +/- 12.7% at the distal end. These differences were independent of infusion rate, nitroglycerin concentration, or time of sampling. Flow rate, concentration, and time had no significant effect on nitroglycerin adsorption with the PEL set, but all three had a significant effect on nitroglycerin adsorption with the PVC set. An unexpected finding was the approximately 14% loss of nitroglycerin from the admixture bottle over time. This phenomenon, which has been observed by other investigators, needs further investigation to determine its cause. It appears that a partially PVC-based administration set should provide consistent delivery of i.v. nitroglycerin to the patient.