Dr. Colasanto and his associates are to be commended for skillfully and comprehensively reviewing the issues concerning the provision of nutritional support to patients undergoing radiation therapy. Their recommendations are well supported by review of scientific studies, and the article is written in such a way as to be accessible to those not fully versed in prescribing nutritional support. There remain a few points that deserve discussion.
When describing the effect of cancer on nutrition, the authors state that the tumor will compete with the host for nutrients. This explanation for the dysmetabolism of inflammatory disease has been discarded for the most part. Rather, it is the production and/ or stimulation of inflammatory mediators (which the authors go on to describe) that is responsible for the increased metabolic rate and alterations in protein and energy substrate metabolism.
The authors describe a study in which gastrostomy insertion was associated with less weight loss, whether prophylactic or in response to deleterious effects of treatment. A similar study showed that delayed gastrostomy insertion was associated with a significant increase in weight loss (8.5 kg) over prophylactic gastrostomy (3.1 kg) or an "acceptable amount" of weight loss (7 kg). This supports our practice of insisting that every patient undergoing combined chemotherapy and radiation therapy to the upper aerodigestive tract receive a feeding gastrostomy.
The authors include nasojejunal tubes in their list of "easy-to-place" devices. Where clinicians are inexperienced, or in the absence of special techniques, blind placement of nasojejunal tubes at the bedside is successful only 15% to 50% of the time. Success of placement improves in studies incorporating prokinetic medications. Success rates increase to 57%-78% with the use of specially shaped tubes, and to 88% using such techniques as stomach electrocardiographic monitoring.
Endoscopic placement of nasojejunostomy tubes is successful up to 90% of the time, but this negates the ease and relative lack of expense of bedside placement, and is highly dependent on operator skill and experience. Finally, the authors indicate that general anesthesia is required during laparoscopic placement of jejunostomies and gastrostomies. Safe and cost-effective surgical (including laparoscopic) placement of both jejunostomies and gastrostomies under local anesthesia has, in fact, been reported and is routine in many institutions.
Assessment of Nourishment
The authors refer to the use of serum proteins (albumin, prealbumin, transferrin) to assess the adequacy of nourishment. This concept is still taught to clinicians, despite a lack of data that intake and protein levels are independently related. The distinction between adequate nourishment and nutritional risk is subtle. Serum protein levels are important in the assessment of nutritional risk as they reflect the effect of disease on protein metabolism. The degree to which a patient may tolerate inadequate nourishment may then be derived. Starvation, however, does not cause hypoproteinemia unless it is coincident with systemic inflammation (catabolism). A lack of improvement in serum protein levels should be viewed as a sign of continued inflammation, rather than as an indication of inadequate nourishment.[7,8]
Use of Formulas
The authors describe formulas for use in patients with diabetes, pulmonary, and renal disease. For the most part, scientific evaluation of these products does not support their use. The most important determinant of CO2 production is total calories, not fat or carbohydrate content. The diabetic formulas have not been shown to improve glycemic control in acutely ill patients. Further, it is recommended that all acutely ill and perioperative patients receive supplemental protein. This includes patients with renal dysfunction, particularly those on dialysis. Most renal formulas are protein restricted.
Contraindications to Enteral Feeding
Finally, we would like to offer an alternative view to the portion of the authors statement that enteral feeding is "contraindicated in individuals with . . . severe pancreatitis [and] intractable vomiting." This is another situation in which clinical teaching is not supported by science. Multiple studies and clinical guidelines reflect the finding that enteral nutrition-particularly but not exclusively jejunal-may be safely and effectively provided to patients with the most severe pancreatitis, resulting in a reduction in the inflammatory response. Similarly, enteral nutrition may also be provided to those with continued vomiting.
Financial Disclosure:The authors have no significant financial interest or other relationship with the manufacturers of any products or providers of any service mentioned in this article.
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