Lipid uptake by silicone enteral access feeding devices

Deterioration of long-term enteral access devices remains a significant patient care and financial problem. Because it is known that lipids, particularly medium-chain triglycerides oil (MCT oil), can soften and break certain types of polymeric materials, the authors evaluated the effect of liquid enteral feeding formulas containing different amounts of MCT oil on silicone feeding tubes.

Commercially available and widely used gastrostomy silicone catheters of two sizes (20F and 15F) were sectioned in 5-cm-long samples and cleaned. Five groups of five pieces were immersed for 8 weeks in pure MCT oil and in four commercial formulas having similar protein, carbohydrate, and fat contents. These formulas were chosen because they contained similar percentages of fat (37% to 45%), although they contained differing amounts of MCT oil. Sodium azide 0.05% was added as a bactericide. Samples were maintained at 37 degrees C in an incubator-shaker. After incubation, specimens were rinsed, dried, and weighed. Selected samples were extracted with a chloroform-methanol solution (2:1). Super-critical fluid chromatography (SFC) and infrared (IR) spectroscopy were performed. A tensile tester was used to generate force-elongation curves for the remaining samples. A statistical analysis (ANOVA, alpha = .05) was conducted to compare data from test groups with results from 20 samples of control silicone material.

Data demonstrate that silicone is significantly affected by liquid formulas and pure MCT oil. SFC and IR findings indicated that fractions of MCT oil, corn oil, and canola oil were absorbed by the material. The most dramatic weight gain (3.7%) was observed for specimens immersed in pure MCT oil. An average increase (9.6%) of silicone compliance was measured along with oil migration in the tubing.

Lipid uptake contributes significantly to deterioration of the silicone tested, leading to device failure. Surface damage can create a potential nidus for microorganisms, particularly fungi. Lipid type and rate of administration should be taken into account when long-term enteral feedings are given. These data contribute to the understanding of the causes of the physico-chemical deterioration of long-term enteral feeding devices and provide helpful information for the design and manufacture of improved products.