University of Virginia Health System
Nutrition Support E-Journal Club
Summer passed too quickly again this year, and September, with it's blissfully cooler temperatures and a new group of dietetic interns, is here. We hosted another great group of trainees, who hailed from California, New York and Toronto Canada.
Alberda C, Gramlich L, Jones N, et al. The relationship between nutritional intake and clinical outcomes in critically ill patients: results of an international multicenter observational study. Intensive Care Med. 2009;35(10):1728-1737.
This was a prospective observational cohort study of nutrition intake and the outcomes of 2772 patients in 167 intensive care units (ICUs) across 37 countries. The investigators recorded the type and amount of enteral and/or parenteral nutrition received (including Propofol calories) as well as morning blood glucose for a maximum of 12 days or until death or discharge from the ICU. Information was recorded regarding admission category (surgery vs. medical), primary admission diagnosis, sex, age, weight, height, and APACHE II score. The investigators did not intervene in the determination of the nutrition prescription - the orders for the amount and type of nutrition provided to the patients were left to the judgment of the individual provider.
Patients were followed while in the hospital for a maximum of 60 days; data on ICU and hospital outcomes at the end of that period was reported. Nutritional adequacy was assessed by the amount of feeding received divided by the amount of feeding prescribed for the first 12 days.
The relationship between 60-day mortality as predicted by BMI, energy or protein, and the interaction between BMI and energy or protein in regards to 60-day mortality and ventilator-free days (VFD) was described. Predicted mortality was adjusted for known risk factors based on admission diagnosis and APACHE II score.
Inclusion and Exclusion Criteria were:
Inclusion criteria were critically ill adults that were mechanically ventilated within 48h of admission requiring ICU care >72h.
Exclusion criteria included patients that did not meet the inclusion criteria, as well as those missing information for BMI, caloric intake, or 60-day mortality status.
Major Results reported by authors:
The researchers reported that 69.0% of the patients received only enteral nutrition (EN), 8.0% received only parenteral nutrition (PN), 17.6% received EN plus PN, and 5.4% received no EN or PN.
Patients received a mean intake of 1,034 kcal/day (range 0-2780) and 47.1 g protein/day (range 0-178.3). Overall, patients received 59.2% of the energy and 56% of protein prescribed. Patients in the BMI < 20 group received greater nutrition per kg than patients with higher BMIs. Average morning blood glucose levels ranged from 7.3 to 8.0 mmol/l (131 to 144 mg/dl) and were significantly different across groups.
The provision of higher calories was associated with a significant overall reduction in mortality; the adjusted odds ratio (OR) for 60-day mortality for every 1000 kcal/day provided was 0.76 [95% confidence intervals (CI) 0.61- 0.95, p = 0.014]. This relationship varied across the BMI groups in which the odds ratio of mortality per 1000 kcal received per day was consistent with a large mortality reduction at the extremes of BMI and no association with mortality in the groups with a BMI of 25-35. Similar beneficial trends were reported with protein; an additional 30 g protein was associated with an adjusted OR of 0.84 (95% CI: 0.74-0.96, p = 0.008). The improved survival in those that received increased protein was primarily observed in patients with a BMI < 25 and > 35.
In regards to ventilator-free days (VFD), after adjustment for risk factors an increase of 1000 kcal/day was associated with a increase of 3.5 (95% CI 1.2-5.9, p = 0.003) VFD. After adjusting for covariates, greater amounts of protein were not significantly associated with VFD.
The authors concluded that greater intakes of energy and protein were associated with better clinical outcomes in critically ill patients, particularly if their BMI is < 25 or >35.
A positive aspect of this study includes the fact that it enrolled large numbers of subjects from multiple critical care units. The primary limitation of this study, which the authors describe in the discussion section, is that cause and effect conclusions about calorie and protein provision cannot be made from observational studies. There is no way to control for all of the factors that can impact the outcome of patients in the ICU setting in an observational study. The association between nutrition provision and outcome may simply reflect that patients with compromised medical status (i.e., sicker patients) may have experienced more interruptions in their nutrition support.
Another limitation to this study that we discussed is that nutritional status prior to admission was not included. The indicator of nutrition status for this study was BMI, which is not a valid sole indicator of nutrition status. It is possible that some lean patients may have stable nutrition status, while those with normal or elevated BMI can have poor oral intake and weight loss, and thus severely compromised nutrition status on admission. Therefore there was not a true, valid control for existing nutrition status on hospital admission. The authors also mention that the protein intake of the obese patients was "very low" and that few obese patients received supplemental protein. This may help explain why any calorie deficit in the obese group might influence outcome. The authors actually term this inadequate protein provision a form of "iatrogenic malnutrition."
Our Take Home message:
This study adds to the body of observational studies that demonstrate an association between nutrition provision and outcome. However, due to the observational nature of these studies, it would not be appropriate to make cause-and-effect statements about failure to meet nutrition goals on outcome. There is a need for randomized studies to investigate the amount of calories and protein that would most favorably affect outcome of critically ill patients.
- Check out the full schedule of webinar programs at:
- October 27: Pediatric Parenteral Nutrition--Ana Abad-Jorge, MS, RD, CNSC
- November 17: Nutrition Support in Renal Failure--Joe Krenitsky, MS, RD
- December 8: Enteral Nutrition--Carol Parrish, MS, RD
See the latest Practical Gastroenterology articles:
- August 2009: Lacy BE, Loew B. Diagnosis, Treatment and Nutritional Management of Chronic Intestinal Pseudo-Obstruction. Practical Gastroenterology 2009;XXXIII(8):9.
- September 2009: Turza K, Krenitsky J, Sawyer RG. Enteral Feeding and Vasopressors-Guidelines for Clinicians. Practical Gastroenterology 2009;XXXIII(9):11.
Joe Krenitsky MS, RD
Carol Rees Parrish MS, RD
PS - Please feel free to forward this on to friends and colleagues.