Oct07jc.html

 

University of Virginia Health System

Nutrition Support E-Journal Club

October 2007

 

Greetings,

Our October Journal club was held in conjunction with our Fall Nutrition Support Forum.   Our forums are ½ day events where nutrition support professionals from area facilities join us in an informal setting to share case studies and recent literature.  Our trainees for October hailed from Baltimore MD, Greenwood SC, Longmont CO, and Darby PA.  The journal article this month deals with the topic of protein in patients with acute kidney injury that are not yet dialyzed.

 

October Citation: 

  • Singer P.  High-dose amino acid infusion preserves diuresis and improves nitrogen balance in non-oliguric acute renal failure.  Wien Klin Wochenschr. 2007;119(7-8):218-222.

Summary: 

This was a prospective, randomized study of 14 critically ill patients with acute kidney injury (AKI) that required parenteral nutrition (PN).  All patients received 2000 non-protein calories (dextrose and lipid emulsion) and received either 75 gm protein (normal protein) or 150 gm protein (high protein).

The investigators monitored blood urea nitrogen (BUN), serum blood and urine creatinine, creatinine clearance, nitrogen balance, furosemide dose, fluid balance, and need for dialysis for 4 days.  Day 1 was considered baseline, with all patients receiving D5, then patients were monitored for 3 days of PN thereafter.

Inclusion and Exclusion Criteria were:

The study enrolled patients that met the following criteria: critically ill, receiving mechanical ventilation, required PN, had a creatinine clearance < 50mL/minute and furosemide-induced diuresis > 2000mL/24 hours.  Acute renal failure was defined as a 50% decrease in GFR, a doubling of serum creatinine or an increase in serum creatinine to 3.5mg/dl. There were no specific exclusion criteria listed (so presumably anyone not meeting inclusion criteria).

Major Results reported by authors:

The authors reported that the blood urea nitrogen increased significantly in the normal protein group, but did not increase significantly in the high-protein group. Creatinine clearance was unchanged in both groups.  High-protein patients did have a significantly more positive cumulative nitrogen balance ( -10.5 +/- 17 g/day vs. 9 +/- 8.3 g/day (p < 0.01), less positive fluid balance (2003 +/- 1336 mL vs. -2407 +/- 1990 mL) and lower furosemide requirement (1003 +/- 288 mg vs. 649 +/- 293 mg) (p < 0.05) { reported in order of low protein versus high protein, respectively}.  In the normal protein group, 2 out of 6 patients died and 1 received hemodialysis, while in the high protein group 3 out of 8 patients died and 2 received hemodialysis (not significantly different).

Author's Conclusions:

The investigators concluded that in non-oliguric ARF requiring large amounts of furosemide for conserved diuresis, high rates of amino acids infusion may not increase BUN more than a moderate dose, and may reduce furosemide requirements and improve nitrogen balance

Evaluation:

The most significant limitation to this study was the small number of patients that were enrolled, and the short time period (3 days) that patients were monitored.  It is certainly too small of a study to make any strong conclusions regarding need for dialysis, mortality or other outcomes.  However, in the absence of large studies that randomize patients with AKI to high and low protein, this study is a valuable contribution to our knowledge of the metabolic effects of feeding adequate protein to critically ill patients.  The results seem to support the current understanding of the effects of a protein restriction in the setting of AKI with critical illness - that reducing protein intake will not reduce BUN or creatinine, but will only lead to more muscle breakdown.

The BUN and serum creatinine had a numerical increase in both groups over the first 3 days of the study, which may reflect the natural progression of AKI, but it is notable that a significant increase in protein provision did NOT increase the magnitude of uremia.  In fact, only the normal protein group had a statistically significant increase in BUN and creatine.  The significant improvement in nitrogen balance in the high-protein group compared to the normal protein group suggests that patients were able to utilize increased protein, and that protein restriction in critical illness will lead to more muscle protein breakdown with no benefit to the level of uremia.

Our group noted that there was a trend for the high-protein group to have a numerically better creatinine clearance at the start of the study (normal protein 25.5 +/- 12.7 versus high-protein 33.1 +/- 12.2).  However, this difference was not statistically significant. The high protein group was significantly older (p < 0.05), but if anything, this would seem to favor the low-protein group.  The two groups were comparable in terms of severity of illness indices.  The other major limitation of this study that we discussed was the absence of any height, weight or BMI information on any of the patients.  Therefore, there was no way to assess the appropriateness of the calorie level or protein load for individual patients or to compare the two groups in terms of protein given per kilogram.

Our Take home message:

This study supports the theory that there is no benefit, and only potential disadvantages to providing reduced protein to critically ill patients with acute renal failure.  However, the very small study size, limited duration and lack of power to measure outcomes, limits the impact of this study.  A large randomized trial will be required before we will have "good evidence" to convince protein-phobic clinicians to provide adequate protein to critically ill patients.

Other News:

•1)     Check out the latest Practical Gastroenterology articles/info at:

http://www.uvadigestivehealth.org/ 
Scroll down to GI Nutrition to the pull down menu with links within the GI nutrition site and look for "Nutrition Articles in Practical Gastroenterology."  The October article is:

  • ¨ Krenitsky J, Makola D, Parrish CR. Pancreatitis Part II - Revenge of the Cyst: A Practical Guide to Jejunal Feeding. Practical Gastroenterology 2007;XXXI(10):54.

Joe Krenitsky MS, RD

Carol Parrish RD, MS

 

PS - Please feel free to forward this on to friends and colleagues.