February 2013 e-journal Club

February e-journal Club

Greetings,

February weather in C’ville has been more volatile than usual, with some days downright balmy, then dropping to near zero (Fo) in the Blue Ridge during a Winter backpacking trip the next week.  Work has been more consistent than the weather, although the fates somehow know to provide more consults when your peers are away at a Clinical Nutrition Week, or if you are trying to get out of town on a Friday!  Our February journal club was on one of our favorite topics – the “art and science” of checking residuals in the ICU.

February Citation:

Reignier J, Mercier E, Le Gouge A, et al. Effect of not monitoring residual gastric volume on risk of ventilator-associated pneumonia in adults receiving mechanical ventilation and early enteral feeding: a randomized controlled trial.  JAMA. 2013;309(3):249-56.

Summary: 

This study was a randomized, multicenter, non-inferiority trial in 449 mechanically ventilated patients comparing routine gastric residual volume (GRV) monitoring (250mL cut-off) versus not checking GRV at all during enteral nutrition (EN).  Patients were from medical and medical-surgical ICU’s with ultimately more than 90% of the patient’s admitted with a medical diagnosis.  EN was provided via a 14-Fr NG with continuous feeding of 20-25 kcals/kg/day for the first 7 days and then 25-30 kcals/kg thereafter.  Feedings were started at the goal flow rate within 36 hours of being intubated.  The study was not blinded, although the committee that diagnosed VAP was blinded to group allocation.

The primary outcome of the study was the proportion of patients with at least 1 episode of ventilator associated pneumonia (VAP).  There were a host of secondary study outcomes including the cumulative incidence and total number of VAP episodes, microorganisms causing VAP, emesis, EN intolerance, prokinetic treatment, diarrhea, SOFA score variations, albumin and C-reactive protein (CRP), ICU acquired infections, proportion of patients meeting calorie targets, cumulative calorie deficit, duration of mechanical ventilation, ICU and hospital lengths of stay, and ICU, 28, & 90 day mortality rates. 

Inclusion and Exclusion Criteria were:

Inclusion criteria:

Patients over 18 years admitted to 9 ICUs between May 2010 and March 2011, expected to require > 48 hours of mechanical ventilation, and started on EN via a nasogastric tube < 36 hours after intubation.

Exclusion criteria:

Abdominal surgery within the past month, Hx esophageal, duodenal, pancreatic, or gastric surgery, bleeding from esophagus, stomach, or bowel, contraindications to prokinetics, EN via a jejunostomy or gastrostomy, pregnancy, treatment-limiting directives, current inclusion in another trial of VAP prevention or EN tolerance.

Major Results:

Data from this study was analyzed in two ways – via a “modified intention to treat” (excluded data from the 3 patients that withdrew consent), and per-protocol (excluding 7 control and 19 intervention patients who did not complete full protocol).

In the primary outcome (proportion with at least 1 episode VAP) there was no significant difference between the two groups (modified ITT as well as the per-protocol populations).  In the modified ITT analysis there was 16.7% in the intervention group and 15.8% in the control group who had at least 1 VAP episode (difference, 0.9%; 90% CI, −4.8% to 6.7%)  In the secondary outcomes:

·         There was no significant difference in cumulative VAP, total VAP or microorganisms identified between the two groups.

·         Significantly more vomiting episodes were reported in the intervention group than in the control group (90 versus 60 episodes, P=.003; per-protocol P=.002).

·         Proportion of patients meeting the group specific definition of EN intolerance was higher in the control group, resulting in more prokinetic use.

·         Calorie target was achieved in a higher proportion of patients in the intervention group than in those in the control group P .001; per-protocol P .001. 

·         Consequently, patients in the intervention group had a lower cumulative calorie deficit from day 0 - 7 compared with patients in the control group.

·         Incidence of other secondary outcomes were not significantly different between groups.

Author’s Conclusions:

1)   A protocol of enteral nutrition management without GRV monitoring is not inferior to a similar protocol including GRV monitoring in terms of protection against VAP.

2)   GRV monitoring leads to unnecessary interruptions of enteral nutrition delivery with subsequent inadequate feeding and should be removed from the standard care of critically ill patients receiving invasive mechanical ventilation and early enteral nutrition.

Evaluation:

This study has the strengths of being randomized with blinded allocation into groups and blinded VAP diagnosis.  Additionally, it was a multicenter design with a relatively large N (for VAP as an outcome) with patients from a variety of hospital types, although primarily a medical population.  One unavoidable limitation is that it is not feasible to use a double-blind design for a study of his type, and the authors address the issues related to a nonblinded study in the discussion section.  The 10% non-inferiority boundary was relatively broad, however, the actual difference in VAP between the two groups was very similar.  The number of patients in this study was too small to reliably detect modest changes in outcomes such as mortality.

Although the no-residuals group received more nutrition, the difference in the median cumulative 7-day nutrition deficit between the two groups was very modest – about 200 calories in a week.  Obviously, some individual patients may be underfed much more than the group median.  In addition, facilities that use a smaller diameter feeding tube than 14-french may see a larger impact on nutrition delivery, because checking GRV leads to increased occlusion of small bore feeding tubes (1).

One aspect of this study that will likely lead to some ongoing discussion was the fact that emesis occurred significantly more often when GRV were not checked.  The incidence of VAP did not seem to be affected by the occurrence of emesis, which is consistent with the 2010 REGANE study (2) which compared 200 with a 500 mL residual cut-off.  Of course, there is no way to know if it was the GRV checks that resulted in less vomiting, or that GRV checks resulted in greater use of prokinetic medications, or just the act of periodically interrupting feedings and providing less enteral formula that was responsible.  However, in selected unintubated patients that are critically ill, who are unable to protect their airway or complain of nausea, the data suggest that a more conservative initial monitoring or feeding advancement strategy should be considered.

Our Take Home Message (s)

1.   Checking gastric residuals decreases the amount of nutrition provided to critically ill intubated patients, without any measurable improvement in patient outcome.

2.   Checking and “treating” gastric residuals in critically ill patients that receive early feedings started at goal flow rate results in less episodes of vomiting, but no differences in VAP incidence.

Reference

  1. Powell KS, Marcuard SP et al.  Aspirating gastric residuals causes occlusion of small-bore feeding tubes.  JPEN 1993 May-Jun;17(3):243-246.
  2. Montejo JC, Miñambres E, Bordejé L, et al  Gastric residual volume during enteral nutrition in ICU patients: the REGANE study.  Intensive Care Med. 2010;36(8):1386-93.

 

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

 

Upcoming Webinars 2012/2013:

--March 26th:  Building Collaboration Between Nutrition and Physical Therapy to Improve Patient Outcomes

--April 16th:  Nutrition Support for the Adult CF Patient

--May 14th :  The Role of Fiber in Nutrition Support

--June 18th:  Food Allergies in the Pediatric Patient

Check out What’s New:

--“Nutrition Support Blog”  

--“ Resources for the Nutrition Support Clinician

Latest Practical Gastroenterology article:

--Rogers, C. Nutritional Management of the Adult with Cystic Fibrosis – Part I.  Practical Gastroenterology 2013;XXXVII(1):10.  

--Rogers, C. Nutritional Management of the Adult with Cystic Fibrosis – Part II.  Practical Gastroenterology 2013;XXXVII(2):13.  

 

Joe Krenitsky MS, RD

Carol Rees Parrish MS, RD

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