May 2016 E-Journal Club

Greetings,

We hosted clinicians from Buena Park, CA; Jackson, CA; Charlotte, NC; and San José, Costa Rica during our May traineeship.  Charlottesville was unseasonably cool and wet for May, but at least our trainees did get a view of the mountains on Monday.

Our journal club in May focused on the difference between continuous and bolus EN in terms of the effect on glycemic control and variability and tube feeding provision in critically ill adults.

May Citation:

Evans DC, Forbes R, Jones C, et al. Continuous versus bolus tube feeds: Does the modality affect glycemic variability, tube feeding volume, caloric intake, or insulin utilization? Int J Crit Illn Inj Sci. 2016 Jan-Mar;6(1):9-15.

Summary: 

This was a single-center, randomized, unblinded study comparing continuous with bolus feeding in 50 adult surgical and neurologic ICU patients who received a PEG tube.  The primary study objective was to compare the effect of different EN regimens on glucose variability and insulin utilization. Secondary outcomes included the incidence of hypoglycemic episodes (glucose ≤ 75 mg/dl), EN volume received, calorie intake, and time to ≥ 80% of nutrition goal.  Additional data collected included EN formulas used, patient demographics, Acute Physiology and Chronic Health Evaluation (APACHE) II scores, Simplified Acute Physiology Score (SAPS) II, and the Glasgow coma scale (GCS).

The ICU protocol was sliding scale insulin every 6 hours for blood glucose values >120 mg/dL. A continuous insulin infusion could be initiated for two consecutive glucose measurements >200 mg/dL (or at the discretion of an intensivist). Ultimately, glucose measurements were obtained over a range between every 1-8 hours, and then all glucose measurements were divided into 12 hour periods.  Glucose variability was calculated by recording the first, last, lowest and highest glucose measurement for each time period, then determining serial differences between the maximum and the minimum value for each standardized time period.

Glucose measurements for the bolus-fed group were recorded before each feeding was infused.

Inclusion and Exclusion Criteria:

Inclusion criteria:

Admission to the ICU, age ≥18 years and ≤89 years, PEG placement during ICU admission and attainment of informed consent.

Exclusion criteria:

Pregnancy, prisoner status or contraindication to PEG placement.

Major Results:

Fifty patients were enrolled in the study and no patients died during the study period (up to 18 days post-PEG). There were no meaningful imbalances between study groups and the mean BMI was 30.6 ±8.

After the initial 12-hour time period, there were no significant differences in the primary outcome of glucose variability between the groups during the next 34 study periods, and no statistical differences in insulin use between the two groups. There were no significant differences in the secondary outcomes of median time to ≥ 80% goal nutrition, TF interruptions, and incidence of hypoglycemia. Tube feeding volume and calorie intake were not significantly different between groups, with the exception of mean feeding volume that was higher for the bolus group during the first 12-hour period.

Glucose variability decreased over time, such that the variability during the first time period was significantly greater than during the last time period (P < 0.05). In contrast, insulin use significantly increased towards the mid-point of the data analysis period (17th time period) and then decreased toward the final recorded period (34th time period, P < 0.05).

Author’s Conclusions:

The choice of continuous or bolus EN does not affect glucose variability, insulin utilization, median time to ≥80% goal nutrition or incidence of hypoglycemia. Providers should not feel limited to either type of feeding modality related to concerns for glucose variability or insulin usage and should consider other factors such as resource utilization, ease of administration, or institution/unit and patient-specific considerations.

Evaluation:

This study piqued our interest, in part because there are so few controlled studies comparing continuous with bolus feeding in ICU patients.  One aspect of this study that was immediately evident was the fact that only ICU patients that were receiving a PEG placement were enrolled.  Percutaneous feeding tubes are generally only placed in patients who must remain on EN for longer periods of time, so these study results are not necessarily applicable to ICU patients during the initial part of their admission.

Additionally, there was no mention of how long these patients were hospitalized or in the ICU before the PEG was placed, and if the length of stay before PEG was different between groups.  Insulin resistance due to illness or injury, insulin doses, issues with tube feeding intolerance and interruptions in feeding (all of which can influence glucose variability) tend to be much greater during the early part of the admission.  These patients very likely had been receiving EN for some time prior to PEG placement, so it is not surprising that both groups rapidly progressed to goal feeding, with less likelihood of hypoglycemia.  Interestingly, glucose variability and insulin needs continued to decline near the end of the study, which highlights the fact that glucose variability is much less during the later parts of an ICU stay.  Only 6 patients of the bolus group and 4 of the continuous group had a history of diabetes, so these study results also may not apply to patients with high baseline insulin resistance/requirements or brittle diabetes.

An important limitation that our group thought limited the impact of this study was the fact that the bolus group often had the glucose checked prior to the feeding, which would lead to an underestimation of the bolus group’s actual peak glucose measurements.  Essentially the groups were not treated equally because one group had their glucose checked while fed, and the other group had at least some of their glucose measurements while feedings were held.

Other considerations for this study were that there was no mention of how many patients were evaluated, compared to have many were enrolled.  There was also no mention of how the patients were randomized and if there was concealed allocation into groups. The number of patients in the study was based on detecting a 25% difference in glucose variability and insulin use, and was likely inadequate to detect smaller differences, and certainly did not have adequate numbers of patients to study patient outcomes.

Our Take Home Message(s)

1. ICU patients who receive PEG tubes may have similar glucose variability, insulin requirements and nutrition delivery with either continuous or bolus feeding schedules.
2. There is a need for larger studies that compare patient outcomes during continuous, cyclic and bolus feeding during ICU admissions.

Other News on the UVAHS GI Nutrition Website: (www.ginutrition.virginia.edu):

Having trouble seeing any of the resources on our page?  Retype www.GInutrition.virginia.edu into your browser to reach our newly updated page

Upcoming Webinars 2016:

Thursday, June 23 at 1:00 PM (ET) :  Micronutrient Deficiencies after Gastric Bypass Surgery

Fall webinars to include Small Bowel Bacterial Overgrowth (September), Fluid Management in the ICU (December) and more!  Stay Tuned!

Also, one of our colleagues has asked us to share the following information:  

There is interest in developing a Ketogenic Diet Therapies DPG (Dietetics Practice Group) at the Academy of Nutrition and Dietetics and your support is needed!  If you would like more information on this group, the benefits, or how to show your interest and support, please contact Lisa Shkoda at:  LS7JU@hscmail.mcc.virginia.edu.   Feel free to share this with your colleagues, as well!

 

Joe Krenitsky MS, RDN

 

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