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Norma Metheny is a professor of nursing at Saint Louis University, St Louis, Mo.
To purchase reprints, contact The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656. Phone, (800) 809-2273 or (949) 362-2050 (ext 532); fax, (949) 362-2049; e-mail, reprints{at}aacn.org.
A James Maloney, MD, and Norma Metheny, RN, PhD, reply: ______
Yes, there is controversy. This practice of adding blue dyes (usually FD&C Blue No. 1 food dye) to tint enteral feedings is common. In a 1999 survey of 281 US intensive care units, 86% of nurses reported using the blue dye method regularly.1 The rationale behind the method assumes that it is safe and effective (sensitive and specific) for detecting aspiration. The practice has never been reviewed or approved by the Food and Drug Administration. Like many hospital practices, the blue dye method was widely embraced based on assumptions and intuitive appeal, not based on results of clinical trials. Few studies were performed to test utility and safety. Nurses and clinicians noticed few downsides to dye use.
No study ever established the blue dye method as being sensitive. One prospective study of the method revealed a sensitivity for aspiration detection of only 15%.2 Other studies have provided similar conclusions.3,4 Furthermore, a recent animal model study showed that sensitivity of blue food dye as a marker for aspiration declined significantly following multiple aspiration events.5 Thus, the available evidence suggests that the blue dye method is not sensitive, which is one point of controversy as to why it is so widely used.
Safety is the second point of controversy. Assumptions of safety are based on the accepted non-absorbable, nontoxic properties of FD&C Blue No. 1, the most commonly used blue dye in American food. Although first reported in 1991, in the past 3 years 9 cases of FD&C Blue No. 1 absorption from enteral feedings have been published.6 A similar number of unpublished cases have been reported to the Food and Drug Administration. Many of these patients died within 1 to 2 days of developing green or blue discoloration of skin indicative of dye absorption. Whenever examined, FD&C Blue No. 1 could be found in tests of serum or urine, proving absorption occurred. All reported patients had bacterial sepsis or other illnesses known to increase gut permeability that promoted absorption of an otherwise nonabsorbable dye. In one case of a 1-year-old child, the serum and skin turned blue and the child developed a fever of 115°F, suggesting toxic uncoupling of mitochondrial respiration after dye absorption.7 Such mitochondrial toxicity occurs in test tube studies of isolated mitochondria exposed to similar levels of FD&C Blue No. 1, and may explain the high mortality observed with blue dye absorption cases.8 Thus, multiple case studies suggest that FD&C Blue No. 1 can be readily absorbed during critical illness and have toxic effects. Of note, the other dye used in this method, methylene blue, is readily absorbed and has potent inhibitory effects on nitric oxide pathways.
In summary, current evidence suggests that the blue dye method is not sensitive and is potentially harmful. Other less popular monitors of bedside aspiration in enterally fed patients such as testing of tracheal aspirates for glucose have not been proven to be sensitive or specific either.9 A multidisciplinary expert consensus committee on aspiration in enterally fed patients recently recommended abandoning the dye and glucose methods to detect aspiration.10 Prevention of aspiration in the enterally fed patient can be optimized by limiting gastric reflux through head-up patient positioning greater than 30°, by enhancement of gut transit through limiting opiates, by identifying excessively high gastric residual volumes, and by positioning the tube properly. Future bed side monitors are needed and will require testing in large clinical trials.
References
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