Mermel and colleagues [1] encountered two unexpected adverse events in 238 patients in whom Landmark catheters had been inserted, and they concluded that a toxin or allergen was responsible. In the accompanying editorial, Maki [2] interpreted these events as anaphylactoid reactions to elastomeric hydrogel.

As consultants to Menlo Care, the manufacturer of Landmark catheters, we reviewed all 140 adverse events reported to the company through early 1995, including those observed by Mermel and colleagues. The conclusions of Mermel and colleagues are unsubstantiated. Their two cases involved no urticaria, angioedema, bronchospasm, hypotension, or laryngeal edema. Symptoms resolved within 5 minutes. These clinical findings are inconsistent with anaphylactoid reactions or allergy.

As reported to Menlo Care, Mermel and coworkers' first patient had a torn bile duct with associated nausea and vomiting before catheter insertion. The second had endocarditis and was hospitalized under duress because of changes in mental status. The adverse event in the third patient was characterized by abdominal pain, dyspnea, and flushing, with no mention of syncope. Thus, alternative explanations such as vasovagal reactions [3], vascular responses [4], hyperventilation [5], and anxiety were clearly warranted.

Two adverse events within 2 weeks among 251 Landmark catheter insertions at one institution, when compared with an overall reported adverse event rate of 1/7000, raises more concern about that institution's procedure than about the chemical composition of the catheter, especially given that a peripheral catheter of the same material has an adverse event rate of only 1/190 000.

We also question the practice of assigning a P value when comparing prospective data on midline Landmark catheters with retrospectively analyzed data on unmonitored peripheral Teflon catheter insertions.

We agree with Dr. Maki that a randomized trial comparing midline catheters of different materials would be desirable. Given the low adverse reaction rate of 1/7000, such a study would be difficult. We strongly endorse postmarketing surveillance of medical devices for adverse effects, but premature condemnation of a product based on inaccurate clinical data and inappropriate analysis does not further the cause of optimal patient care.