November 2013 E-journal Club


We do not host a training program in November, but we all recently attended the annual meeting for the Virginia ASPEN chapter (VASPEN).  We had a nice time and heard some excellent speakers.

We first started posting summaries of our journal clubs to our website in November of 2003, so this posting marks the 10 year anniversary of our e-journal club.  I am grateful for the wisdom and insights of my co-workers, and wanted to say “Thank You” to everyone that has sent notes or asked questions and let us know that you appreciate our efforts.  Our November journal club article was about the influence of age on nitrogen balance in the ICU.

November Citation:

Dickerson RN, Maish GO 3rd, Croce MA, et al.  Influence of Aging on Nitrogen Accretion During Critical Illness.  JPEN J Parenter Enteral Nutr. 2013 Oct 11. [Epub ahead of print]


This was a retrospective observational study of adult trauma patients that received enteral and/or parenteral nutrition support and had a nitrogen balance study.  The goal was to evaluate how critically ill older patients respond to differences in protein intake compared with younger patients.  Patients were identified from the nutrition support service monitoring records, then categorized into those 60 years or older (older patient group) versus those from 18 to 59 years of age (younger patient group).

Older patients received a calorie goal of 1.3–1.4 times the Harris-Benedict equation and a protein intake of 1.5–2.5 g/kg/d. Younger patients were assigned 30–32 kcal/kg/d and 2–2.5 g/kg/d of protein.  Calorie and protein goals had been decided by the nutrition support service, and were not assigned as part of the study.

Enteral feedings were started at 25-30 mL/hr and advanced by 25-30 mL per day.  Gastric residual volumes (GRV) were checked every 6 hours, and feedings were stopped if GRV exceeded 200 mL.  Nitrogen balance studies were obtained within 5-14 days following hospital admission.

Inclusion and Exclusion Criteria:

Inclusion criteria:

Adult patients admitted to the trauma unit from June 2005 to June 2009, who had a 24-hour urine collection for nitrogen balance within 5–14 days after admission while receiving nutrition support.

Exclusion criteria:

Patients with acute kidney injury, chronic kidney disease, severe liver dysfunction, thermal injury, pregnancy, obese with hypocaloric feeding, corticosteroid or pentobarbital pharmacotherapy, patients who expired within 48 hours of ICU admission, EN or PN started before ICU admission and those allowed oral intake.

Major Results:

The data from 249 patients were extracted from a previous database that examined the protein catabolic response to traumatic injuries, with 54 patients identified as older and 195 as younger.  There were a total of 300 nitrogen balance studies in these 249 patients.  Only 11% of the older patients and 23% of the younger patients had a second nitrogen balance measurement.

Nutrition support was usually started within 1–4 days after hospital admission and nitrogen balance was checked within 4–7 days after initiation of nutrition support therapy for most patients.  Most patients received EN alone (85%) or EN together with PN (4%) – only 11% of the patients received PN alone.

When protein intake was segregated by 0.5 gm/kg increments, older patients did not appear to have an improvement in nitrogen balance until protein intake dose was increased. Younger patients experienced an improvement in nitrogen balance at the lower protein doses until a near plateau in NB was observed at the higher protein intakes.  Older patients had a numerically less negative nitrogen balance compared with younger patients, and this was significantly different when both groups were receiving just over 2 gm protein/kg.

Author’s Conclusions:

“Improvement in nitrogen accretion was blunted at lower protein intakes in critically ill, older patients compared with younger patients.”


This was an observational study where patients were not randomized into different protein intakes.  Patients were started at slow enteral feeding rates, and then advanced in a very conservative manner, so that it would take days to reach goal feeding.  Most patients had only a single nitrogen balance measurement early in their admission, likely before they reached goal feeding.  It appeared that only 8 (out of 54) older patients actually had a nitrogen balance measurement when they were receiving between 2-2.5 gm protein/kg.

Due to the very slow advancement of EN, patients would have only received a limited amount of calories and with limited protein intakes.  It is also likely that calorie provision was increased when patients were receiving full feeding with full protein.  Those few patients that had a second nitrogen balance measurement (N = 7) may have been more likely to be receiving full feedings with full protein provision, and the passage of time may have allowed decreased severity of illness with improvements in nitrogen balance.

There was no accounting of protein losses in wounds or drains in this study.

Our Take Home Message (s)

The observational design, small number of patients with a second nitrogen balance, and lack of control for calorie provision, or changes in disease severity over time limit any take home message from this study.


Other News on the UVAHS GI Nutrition Website: (

Upcoming Webinars 2013/2014:

  • Stay tuned for details on our upcoming webinars!s

Check out What’s New:

Latest Practical Gastroenterology article:

o    Groetch M. Food Allergies: Dietary Management.  Practical Gastroenterology 2013;XXXVII(11):46.


Joe Krenitsky MS, RD

Carol Rees Parrish MS, RD


PS – Please feel free to forward on to friends and colleagues.