Preventing enteral tube feeding-associated aspiration: something no one should get blue in the face over.

In this issue of Nutrition in Clinical Practice, Maloney et al review the use of blue food dye for coloring enteral tube feeding and make a plea for the discontinuation of this practice. This popular technique has been used for nearly two decades to detect early evidence of pulmonary aspiration in an attempt to prevent the regurgitation of a large volume of enteral tube feeding from the gastrointestinal tract into the respiratory tree. To put this paper into context, I feel it is important to understand the pathophysiologic events that surround the development of aspiration pneumonia in patients receiving enteral tube feeding so that methods to prevent this complication can be appropriately applied. Nearly 50% of normal adults aspirate oropharyngeal secretions while they are sleeping. Lung injury generally does not occur because only a small volume is inhaled, most of these secretions are cleared by coughing and normal mucociliary function, and an intact immune system clears any bacteria that find their way into the lower respiratory tract. Aspiration pneumonia occurs when oropharyngeal material is not readily cleared from the lung or contains pathogenic microorganisms. Aspiration pneumonitis is the result of the inhalation of acidic gastric contents and particulate material that cause a chemical injury to the lung. Aspiration pneumonia usually occurs in elderly patients with dysphagia or gastric dysmotility, whereas aspiration pneumonitis occurs at any age in patients with a marked decrease in their sensorium. This latter group is most often composed of patients who receive general anesthesia or experience events that include drug overdose, seizure, and cerebrovascular accident. Hospitalized patients, especially those who are critically ill, are at the greatest risk for aspiration and aspiration pneumonia. There are several factors that contribute to this higher risk, including prolonged maintenance of a supine position, gastroparesis as a result of the underlying illness, and nasogastric intubation. Hospitalized patients are also more likely to develop aspiration pneumonia because the gastric contents may be colonized by pathogenic microorganisms when the pH of the stomach is increased by the use of histamine-2 receptor blocking agents, proton-pump inhibitors, and enteral tube feeding. Finally, the prevalence of aspiration associated with enteral tube feeding is approximately 5% with an incidence of 2.4 events per 1000 tube-feeding days. Fortunately for many of these patients, the event is not life-threatening, and enteral nutrition may be safely continued. Maloney et al focus their attention on FD&C Blue No. 1, the most commonly used coloring agent that is added to enteral feeding. They describe why FD&C Blue No. 1 rapidly gained acceptance over the last two decades as a means of detecting early aspiration, and the response by the manufacturers to develop supplies that make the addition of FD&C Blue No. 1 to enteral formula relatively easy. He summarized the rationale that has been used to justify the addition of coloring agents to enteral formula and the research that generally does not lend great support to the use of this technique in identifying clinically important aspiration. Two case reports are described where mortality is attributed to FD&C No. 1. This is followed by summaries of seven other cases reported in the medical literature where it is suggested that FD&C Blue No. 1 resulted in significant morbidity and mortality. The implication that FD&C Blue No. 1 was responsible for the injury experienced by these patients is substantiated by the demonstration that FD&C Blue No. 1 was present in the serum of three patients, a finding that should not have occurred with the use of a “nonabsorbable” dye. It is suggested that FD&C Blue No. 1 acts as a mitochondrial toxin and that an increase in gut permeability is necessary for this dye to be absorbed into the circulation in amounts that are sufficient to cause this problem. It is concluded that the addition of blue dye and specifically the use of FD&C Blue No. 1 should be abandoned as a means of monitoring enteral tube feeding tolerance Correspondence and reprint requests: Douglas L. Seidner, MD, Digestive Disease Center, The Cleveland Clinic Foundation, 9500 Euclid Ave, A30, Cleveland, OH 44195.