Analysis of Failed Polyurethane Gastrostomy Devices and Comparison with Samples Incubated In Vitro

Abstract

Percutaneous endoscopic gastrostomy (PEG) devices provide a route for nourishment to those unable to swallow. The disintegration and discoloration of a type of polyurethane PEG device was evaluated. Five ex vivo samples were obtained and, where sufficient material remained, analyzed by nano-indentation, Dynamic Mechanical Analysis (DMA) and Scanning Electron Microscopy (SEM). The ex vivo samples showed discoloration, pitting and environmental stress cracking (ESC). A group of unused PEG devices were exposed to a gastric acid and pepsinogen formulation at 37°C for up to six weeks. An additional cohort was investigated for fungal colonization by incubating a group in Sabourard’s broth, and another group in Ensure Feed and Sabourard’s broth. Both groups were incubated with a Candida culture preparation at 37°C for up to six weeks. The samples incubated in Candida in broth only, or in Candida in feed and broth, hardened. In contrast, the samples incubated in the gastric acid formulation tended to soften. Samples that were incubated with Candida in feed and broth were discolored, more often than those exposed to Candida in broth only. Candida was shown to grow on all PEG samples exposed to it. Examination under SEM showed pit formation after exposure to Candida but no ESC was observed. In some, but not all, of the samples incubated in the gastric acid and pepsinogen formulation, ESC was seen. However, no discoloration took place in the samples incubated in the gastric acid and pepsinogen formulation. It is likely that the disintegration of the PEG devices in vivo is a multi-faceted problem, where the synergistic effects of acid, enzymes and micro-organisms all play a role in the detriment of the material.