Assessing the role of the biomaterial Aquavene in patient reactions to Landmark midline catheters.

Landmark midline catheters (Menlo Care, Inc., Palo Alto, CA) provide peripheral venous access for the infusion of medications or fluids. They are constructed of an inner layer of polyurethane and an outer layer of the biomaterial Aquavene, a blend of polyurethane and polyethylene oxide to which butylated hyroxyanisole (BHA), butylated hydroxytoluene (BHT), and triallyl-s-triazine trione (TTT) are added. Once inside the vein, the Aquavene material becomes hydrated and the catheter swells resulting in minimal trauma to the vein. It is well recognized that some patients experience reactions to catheterization. Recent reports of hypersensitivity-like reactions in some patients catheterized with Landmark catheters have prompted the manufacturer to reexamine biocompatibility data and clinical data to assess whether Aquavene was the source of the patient responses. None of the biocompatibility studies provided by Menlo Care in support of U.S. registration and marketing of Aquavene-based catheters demonstrated any tendency for Aquavene or material extracted from Aquavene to invoke an immunological or toxicological response. Examination of potential catheter residuals revealed that significant amounts of BHA and BHT were unlikely to be released from the catheters during expected use. The amounts of polyethylene oxide and TTT expected to be released during the first few minutes after catheter insertion (when most of the patient reactions were reported) are almost 92,500 and 270,000 times lower, respectively, than nontoxic animal exposures. These analyses do not support chemically mediated toxicity as an explanation for the adverse events experienced by some patients. A review of the postmarket surveillance data on Aquavene-based catheters revealed that the reported events were not consistent with a hypersensitivity (immunogenic) response to the biomaterial. The rare reported adverse events tend to occur quickly, most often after flushing of the catheter, and resolve quickly, even when the catheter remains in place. Determining the frequency and severity of adverse events reported in association with the use of Landmark catheters will ultimately require a controlled prospective study, preferably one with a concurrent control group using alternative products.