Enteral nutrition for patients with renal failure in the ICU

Again, the available enteral supplements

One should not withhold protein from renal failure patients, hoping it will delay their progression to dialysis. Normal amounts of protein are appropriate. High-protein feeds should be commenced for patients on dialysis, with 2.0-2.5g/kg/day of protein. These people are constantly losing amino acids to CRRT. The rate of loss is about 10-15 grams per day. That actually is not that much (remember, even at a normal rate of replacement one ends up giving these people about 1g per kg, or 70-100g per day of protein). It appears that this hypersupplementation does not play havoc with their uraemia, which is what people were concerned about. Bellomo's group found these patients still ended up in a slightly negative nitrogen balance.

So, does Nepro actually benefit renal failure patients?

Nepro has the highest caloric concentration, and is therefore the liquid food of choice for people whose fluid balance you are obsessing over. I suppose those people would include ICU patients with renal failure. It also has the lowest protein content, presumably to reduce the urea load on the anephric organism.  This is bizarre. One would expect a nutritional supplement for the dialysis patient to have an excess of protein, given that we suck away their circulating amino acids with dialysis. In fact, the most recent evidence-based guidelines suggest that these people should receive a protein-rich diet, with 2.0-2.5 g per kg per day of protein. A 70kg patient would thus require 140-175g of protein per day while on dialysis. For protein-poor Nepro, which contains only 7g protein per 100ml, one's daily dose would be 2000-2500ml, at a rate of over 100ml/hr.

This seems insane. Wasn't the point of this to feed the patient something concentrated to reduce their daily fluid intake? Weren't we concerned with the fluid balance becoming positive? 2000ml of Nepro per day contributes 1400ml of pure water, is that too much?

Well. Close inspection reveals that Nepro is has the highest protein concentration of all the supplements. The next most protein-rich supplement in my table is Promote. However, it is twice as dilute as Nepro. The protein content is actually less, with only 6.4g protein per 100ml. The water content is actually greater. However, Nepro is usually given at a goal rate of 40ml/hr. This delivers 960ml per day, or 67.2g of protein and 672 ml of water. On the other hand, one's daily dose of Promote (at 60ml per hr, with a protein content of 6.3g per 100ml) ends up being 1440ml, which delivers 90.72g of protein (and only 1195ml of water) One must also ask the question whether fluid restriction matters at all in patients who are subjected to daily haemodiafiltration. Surely, the savvy intensivist can adjust their ultrafiltration goal rate to compensate for the extra fluid load from a protein-rich nutrient supplement.

In summary:

• There is no evidence that protein restriction benefits ICU patients with renal failure (in fact there is evidence that the reverse is true)
• Nepro at goal rate is inadequate to supply the recommended protein needs of a patient undergoing CVVHDF.
• The low fluid contribution is a positive influence only on haemodialysis outpatients.
• Therefore, one ought to feed their patients something like Promote while they are on CVVHDF.

Now, of course if you are OFF dialysis, or you are trying to keep the fluid balance negative, Nepro is a good choice. In addition to being low in water, it also contains the least sodium and potassium of all the tube foods. It does contain the least amount of phosphate, but - as a reader has pointed out - it is still quite high in phosphate, at 720mg per 1000ml. That might still exceed the daily excretory capabilities of somebody who is dependent on dialysis, particularly if it some sort of low-efficiency affair (eg. peritoneal dialysis). Some kind of phosphate binders and regular monitoring would still be required.