Greetings,
Although summer is winding down, and school is back in session, it feels like we have just recently started having real “Virginia summer” temperatures. Perhaps it is only my perception, but of late, it feels like the summer zooms-by faster than ever! What ever happened to feeling so bored by summer’s end, that even school starting back was acceptable?
This month, our journal club article returned to the topic of nutrition adequacy in the adult ICU – and the effects of strategies to enhance the delivery of enteral nutrition (EN). See our April-May and June e-journal entries for some recent discussions on the same topic.
August Citation:
Peake SL, Davies AR, Deane AM, et al. Use of a concentrated enteral nutrition solution to increase calorie delivery to critically ill patients: a randomized, double-blind, clinical trial. Am J Clin Nutr. 2014 Jul 2;100(2):616-625. [Epub ahead of print]
Summary:
This was a multi-center, randomized, double-blind study of 112 adult mixed ICU patients that require mechanical ventilation. The goal was to determine if the use of concentrated EN (1.5 kcals/mL) formulas allowed the delivery of increased calories in the first 10 ICU days, compared to a 1.0 kcal/mL formula. The feedings were provided in identical 1 liter bags and the formulas had similar protein content (primary difference between formulas was fat and CHO content). The goal rates for all feedings were based on a rate of 1 mL/kg of ideal weight up to a maximum of 100 mL/hr, with a plan to achieve goal rate within 48 hours after starting.
The primary outcome of the study was calorie delivery from enteral nutrition. Secondary outcomes included calories delivered from all sources, calories/kg ideal weight, ICU and hospital LOS, ventilator-free days, and ICU, hospital, 28- and 90-day mortality.
Inclusion and Exclusion Criteria:
Inclusion criteria:
Adult patients who required mechanical ventilation expected to receive EN > 2 days.
Exclusion criteria:
Patient who had previously received EN or PN during their ICU stay, those who could not receive the study goal rate, such as a requirement for fluid restriction, or if there was a requirement for a specific enteral nutrition solution (determined by the treating clinician).
Major Results:
There were 415 patients assessed, and 112 patients randomized. Only 1 patient withdrew from the study (1.5 kcal/mL group) and 1 patient was lost to follow-up by day 90 (1.0 kcal/mL group). The mean age was 56.4 ± 1.4 years, with an APACHE II score of 23 ± 9.0, with 71% medical and 14% emergency surgical diagnosis. There were no significant differences in baseline characteristics between the 2 groups.
The average daily volume of study enteral nutrition delivered in the 2 groups was similar (1221 mL in the 1.5 kcal group, compared with 1259 mL in the 1.0 kcal group). There were 364 feeding days in the 1.5 kcal group, with goal rate achieved on 37% of the days, compared with 311 feeding days and goal rate achieved for 44% of the days in the 1.0 kcal group.
The use of a 1.5-kcal EN formula resulted in a significantly greater (46% more) daily calorie delivery: 1832 kcals (95% CI: 1681-1984) compared with 1259 kcal (95% CI:1143-1374 kcal) in the 1.0 kcal formula; (P < 0.001). The 1.5 kcal group received an average of 27.3 +/- 7.4 kcals/kg/day compared with 19.0 ± 6.0 kcal/kg/day in the 1.0 kcal group (P < 0.001).
Supplemental parenteral nutrition was administered to 4 patients during the study (2 from each group). There were no differences between groups in the number of patients with increased gastric residual volumes, the use of promotility medications, laxatives or diarrhea. The group that received the 1.5 kcal formula had a trend to higher peak blood glucose over the 10-d study period (1.5 kcal/mL; 12.4 ± 3.9 mmol/L compared with 1.0 kcal/mL; 12.0 ± 3.9 mmol/L; P = 0.056), but the number of patients who required insulin on, or after day 1, was not different between groups.
Mortality at 90 days was 11 patients (20%) in the 1.5-kcal group and 20 patients (37%) in the 1.0-kcal/mL group (P = 0.057). The absolute risk reduction in mortality for the 1.5-kcal group compared with the 1.0-kcal
group was 17% (95% CI: 0.6-33). Survival time from randomization to day 90 tended to be longer in patients who received the 1.5-kcal formula (P = 0.057). ICU, hospital, and 28-d mortality were not different between the 2 treatment groups. The number of mechanical ventilation free
days to day 28, ICU, and hospital length of stay and destination after hospital discharge were not different between groups.
Author’s Conclusions:
The substitution of a 1.5-kcal/mL EN in place of a standard 1.0-kcal/mL EN formula resulted in an increase in calorie delivery and was associated with a trend to improved survival.
These data support the conduct of a large, multicenter, randomized, double-blind trial to determine whether the delivery of more calories by using a concentrated enteral nutrition solution can result in improved survival and functional outcomes for critically ill patients.
Evaluation:
This was a well conducted study, strengthened by successful efforts to blind investigators and caregivers to the EN formula provided to the patients. It is also one of the few studies that did not provide more calories and protein to the “increased calorie” group. The authors note in the discussion section that one consideration when evaluating this study is that patients in both groups received modest levels of protein (1gm/kg ideal weight) – which is at least 50% less than we would provide to our ICU patients. Perhaps providing increased calories is less critical when full protein is provided. It will require further studies before the full effect of different calorie/protein intakes and timing in critically ill patients will be adequately understood.
The authors also point out that 112 patients is much too small to make any conclusions about mortality in a heterogeneous group of ICU patients, but does support the need for a much larger study that can fully examine mortality issues. Unlike other studies that attempted to acutely increase the rate of feeding day to day, this study does not suggest any negative effects of starting the average patient with a somewhat higher initial goal.
We did have one minor issue with this study, that does not affect our take-home message, but we just can let it go unsaid: Figure 2 includes the calculation of the “calories provided by the study enteral solution minus the gastric residual volume”. We have seen this type of calculation mentioned before in other studies and would like to see any mention of it stricken from the scientific record, because it is based on the totally bogus1 notion that gastric residuals are completely composed of only tube feeding, and the stomach does not have substantial endogenous secretions that needs to be accounted for. There is evidence that gastric residuals may be measured when there is active gastric emptying of the feeding formula, and the residual measured may be composed of substantial amounts of endogenous gastric secretions2.
Our Take Home Message (s)
- Use of 1.5 kcal/mL EN formulas in adult ICU patients appear to allow increased calorie delivery without increased GI symptoms, compared to the use of 1.0 kcal/mL formulas.
- A much larger study will need to be completed before we will be able to fully appreciate any possible effects on increased calorie delivery in the ICU on patient outcomes.
- Current evidence does support the need to investigate the effects of increased nutrition provision in the ICU on patient outcomes.
Reference:
1) Logan, T. Bill and Ted’s Excellent Adventure. 1989, Orion Pictures.
2) Chang WK, McClave SA, Lee MS, Chao YC. Monitoring bolus nasogastric tube feeding by the Brix value determination and residual volume measurement of gastric contents. JPEN J Parenter Enteral Nutr. 2004 Mar-Apr;28(2):105-12.
Other News on the UVAHS GI Nutrition Website: (www.ginutrition.virginia.edu):
Upcoming Webinars 2014:
–October 7: Nutrition Support in Gastroparesis
–November 18: Feeding the Critically Ill Adult Patient
–December 16: Issues in Long Term Enteral Nutrition
Check out What’s New:
–“Nutrition Support Blog”
–“ Resources for the Nutrition Support Clinician”
Latest Practical Gastroenterology article
–DiBaise J, Parrish CR Part 1: Short Bowel Syndrome in Adults–Physiological Alterations and Clinical Consequences. Practical Gastroenterology 2014;XXXVIII(8):30.
Joe Krenitsky MS, RD
Carol Rees Parrish MS, RD
PS – Please feel free to forward on to friends and colleagues.