Nutrition Support Traineeship
This month our journal club was part of our quarterly Nutrition Forum.
The Nutrition Forum invites dietitians within the region to share case presentations, clinical discussions, and journal reviews in a small, informal group setting.
The two articles reviewed were:
The study by Uehara is an older one, but I chose it because we had not reviewed it before, and I had recently seen it quoted in an article as “proof” that a patient’s calorie needs dramatically increase during the second week of their hospitalization.
This study was done by Graham Hill’s group – the group has published several other ‘oft quoted studies and are known for their hi-tech methods. In this study they measured just about every body compartment in 12 patients with sepsis, and 12 patients with trauma; they did indirect calorimetry 2X each day, and measured body weight, body water, body nitrogen, body fat, and body minerals on days 0, 5, 10 and 21 of the study. Trauma patients were on the vent for an average of 7 days, and septic patients were ventilated for 13 days. The authors reported average measured resting energy expenditure as 28 calories per Kg in the septic patients, and 32 calories/kg in the trauma patients.
The investigators also calculated a total energy expenditure (TEE) to take into account “activity” calories. They did this by adding up all of the stored fuel in the body that they measured (body fat, body protein, and body glycogen) and subtracting this from the recorded calories that were provided by tube feedings and or TPN.
The researchers reported that this total energy expenditure amounted to 47 calories/Kg in the septic patients, and 59 calories/Kg in the trauma patients.
This study relies on the accuracy of each method to measure stored fuel (body fat, body protein, and body glycogen) as well as (perhaps most importantly) the accuracy of how much nutrition was delivered with tube feeds and TPN. The potential for error is magnified because they added all of the fuels up, so the error in glycogen measurement is added to the error in protein and fat measurement as well. The patients would appear to be burning a large amount of calories if the patient did not actually receive or absorb all of the calories that were provided. Any calories spilled as glycosuria due to hyperglycemia would be counted as calories “burned” as well. There is no mention if the researches accounted for any “nutrients” that may have been provided from albumin infusion, blood products, or as D5 in intravenous medications.
Take home message:
The potential for error in the methods, and the fact that the calorie numbers are so far from what patients normally appear to require to maintain body mass would suggest that these numbers are suspect until there is some way to validate these findings.
There may be, in fact, some patients who do have a high calorie requirement due to work of breathing or physical activity after the initial phase of their critical illness has resolved. These patients should be considered on an individual basis, and in lieu of any reliable method of measuring “activity calories”, adjustments in calories provided will have to be estimated and clinical progress and weight trends monitored.
Rubinson L, Diette GB, Song X, Brower RG, Krishnan JA.
This was a prospective cohort study that enrolled all patients admitted to a medical ICU who were NPO > 96 hours. The primary outcome was the development of bloodstream infections during the study, and the patient’s percentage of calorie goals provided were monitored. Calorie goals were based on the American College of Chest Physicians (ACCP) guidelines of 25 calories/Kg (27.5 calories/Kg for SIRS) based on ideal body weight.
The authors reported that the overall mean calories provided were approx. 50% of the ACCP guidelines (49.4 +/- 29.3%). They also reported that those patients who received less than 25% of the ACCP goals had a significantly increased frequency of bloodstream infections. There was no significant difference in bloodstream infections between the groups that received 25-49%, 50-74%, or >75% of calorie goals. There was no significant difference in mean serum glucose between groups. There was no difference in the number of parenteral nutrition days between groups, however, the groups who received less calories had a greater percentage of calories provided via the parenteral route. The author’s conclusions were that patients who receive <25% of ACCP goals may be at increased risk of bloodstream infections.
This was not an intervention study, they only observed what happened to patients. Therefore, it has a similar potential for selection bias as a retrospective study; i.e. patients who are sicker are likely to receive less calories. In addition, the authors state that they did not prospectively decide the calorie groups until after the data was collected (post-hoc) - essentially they looked to see what cut-off point in calorie goals would be different in terms of infections, and then divided the groups.
The authors state that they did not monitor ventilator associated pneumonia, antibiotic use, or intravascular catheters.
Take home message:
This is an interesting observational study, but it would be inappropriate to state that it was the decreased calorie provision that caused the infections based on the results of this report (or that increased calorie provision protected against infection). There are just too many factors that they did not, or could not control for. This is just another example of why it is paramount that someone does an interventional study to determine how many calories are best for the “sick people”.
"There are those who seek knowledge for the sake of knowing, that is curiosity.
There are those who seek knowledge to be known by others, that is vanity.
There are those who seek knowledge in order to serve, that is love."
- Bernard of Clairvaux
We have not reconvened to discuss the adjusted body weight issue yet, but Joe has agreed to participate in a point-counterpoint on adjusted body weight at Nutrition Week 2005, so I imagine we will have more to report in the near future ! In other news, look for our article about the Nutrition Support Traineeship in the June issue of Support Line. We also have our new Traineeship web site up and running. We are still making some changes, but it is available at http://www.healthsystem.virginia.edudh/traineeship.html
Check it out and let us know what you think ! If anyone is interested in sending us thoughts on the program, we are thinking about adding a “comments page” from past trainees; we are also considering adding contact information for “references” from past trainees. Realize, this will ultimately be on our website and hence anyone accessing our website, may contact you. JJ
More websites to check out:
Clinical Nutrition Rounds: Web Address
PS – Please feel free to send this on to friends and colleagues.