University of Virginia Nutrition
We are unable to deny that summer is ending now that school has restarted, and we have just completed our September traineeship week. Dietitians from Virginia Beach and Warrenton , VA and High Point , NC attended, and we had a great time, including a visit to a wonderful Thai restaurant for our night out. Our article this month is from JPEN, and the subject is one of our Favorites…..Residuals !
- Metheny, NA. Effect of Feeding-Tube Properties on Residual Volume Measurements in Tube-Fed Patients. J Parenter Enteral Nutr 2005;29(3):192-197.
Study Question (s):
- Does feeding tube size and port configuration affect the ability to measure gastric residual volume (GRV). Do you need to measure residuals while feeding into the small bowel. Gastric pH measurements via small and large bore tubes were also compared.
- Study was completed in 5 intensive care units in a large teaching hospital in patients receiving continuous feedings through a nasally or orally inserted tube where there was radiographic confirmation of tube site.
- 62 patients received continuous gastric feedings via a small-diameter tube (10 Fr)* while a large-diameter gastric sump tube (14 or 18 Fr) was concurrently present – total of 645 attempts to check GRV.
- 75 patients received small-bowel tube feedings via a small-diameter tube (10 Fr)* while a large-diameter gastric sump tube (14 or 18 Fr) was concurrently present - total of 890 attempts to check residuals.
- Both groups received continuous feedings at rates ranging between 10 and 70 mL per hour (mean = 42 mL/hr).
- Residuals were checked from both tubes at 4-hour intervals from 8 AM until 12 AM for a maximum of 3 days.
- The researchers discuss the gastric residual volume levels “variably considered to be excessive” as 50-200 mL.
- GRV obtained from the large-diameter sump tubes were approximately 1.2–1.7 times greater than those obtained from the 10-Fr tubes, i.e.; a reading of 150 mL from a 10-Fr tube could be estimated as equivalent to 225 mL (150 mL x 1.5) from a 14-Fr or 18-Fr sump tube.
- Gastric pH was higher when measured from small bore tubes than from the large bore tubes (6.3 +/- 0.6 vs 5.6 +/- 0.9, p < 0.001)
- The mean residual volume obtained from the small-bowel tubes was 4.6 mL (range, 0–105 mL). Ninety percent of small bowel aspirates were <12 mL. The highest small-bowel residual volume (105 mL) was obtained from a tube positioned in the duodenal bulb of a patient diagnosed with ileus.
- GRVs decreased over time, likely because of the effect of adaptation to feedings; however, this finding did not affect the results because our aim was to compare simultaneous readings from the 2 types of gastric tubes.
- Five percent of patients fed into the small bowel had a gastric residual > 150 mL.
Authors Conclusions :
- According to the above findings, it is concluded that small-diameter tubes may substantially underestimate GRVs; therefore, clinicians should take into account the type of feeding tube used when evaluating the significance of a specific GRV. The results described above may be helpful in estimating actual GRVs when small-diameter tubes are being used. It is also concluded that a small percentage of patients receiving postpyloric feedings will have substantial GRVs. Thus, GRV monitoring may be needed during small-bowel feedings when other risk factors for aspiration are present.
- One limitation to this study is that information was not collected in a “blinded” fashion - the study nurse knew what type of tube they were checking residuals from, and knew the results of the first residual check, and this knowledge may have affected the collection of subsequent residuals.
- It is also noted that residuals were always checked from the small bore tube first- it is possible that the act of withdrawing and then re-instilling residual fluids may prompt increased secretion of endogenous gastric juices, resulting in an increased residual on the second attempt.
- It is unknown if the results apply to other sizes or types of small bore feeding tubes.
- The study discussion of “excessive” gastric residuals (50-200 mL) can be considered within the safe and expected range for gastric residuals of critically ill patients – there is no evidence that GRV within this range leads to increased morbidity.
- The only small bowel residuals that appeared significantly elevated were measured from the duodenal bulb in a patient with ileus – there was no clinically significant information obtained from 889 attempts at checking small bowel residuals. Considering that checking residuals can increase the chance of tube clogging, it would seem that there should be a demonstration of clear benefit before recommending an intervention with a possible negative (tube clogging) outcome.
Take home message:
- The Myth that it is not possible to check residuals from a small bore feeding tube appears to be “busted” by this study.
- The possibility that different feeding tubes may result in different residual measurements should be considered when comparing studies of residual measurements.
- It is unclear whether differences in residual measurements from different size tubes need to be considered in the clinical setting; there is no clinical outcome data presented in this study.
- There does not appear to be a need to check residuals from small bowel placed feeding tubes.
- Avoid feeding (or at least not in the duodenal bulb) in patients with an ileus.
- There is inadequate data to know what level of residuals may negatively affect clinical outcome; much of the study data to date was collected with small bore feeding tubes.
- We disagree with the portion of the major conclusion of the study that states, “and therefore, clinicians should take into account the type of tube when evaluating the significance of a specific GRV”….remembering that GRV is a practice without evidence to support its use in the first place. Many facilities already have “cut-offs” for gastric residual volumes that are excessively conservative and limit enteral feedings infused into patients – we would advise NOT multiplying results from small bore tubes by 1.2-1.7 – it would put more patients “over the top” of what might be considered an elevated GRV in their particular institution and result in withholding of even MORE enteral nutrition than currently takes place.
“Theory helps us to bear our ignorance of facts”
- George Santayana
1.) Check out the latest Practical Gastroenterology articles available at:
To Access the GI Nutrition Page at UVAHS, go to:
Scroll down to GI Nutrition on the far left column and click on link
Then scroll down to box with links within the nutrition site
Nutrition Articles in Practical Gastroenterology is in the left column.
- Plonk WM. To PEG or Not to PEG. Practical Gastroenterology 2005;XXIX(7):16.
- Krenitsky J. To PEG or Not to PEG – Another Perspective. [Editorial]. Practical Gastroenterology 2005;XXIX(7):32.
- Parrish CR, Yoshida C. Nutrition Intervention for the Patient with Gastroparesis: An Update. Practical Gastroenterology 2005;XXIX(8):29.
- Parrish CR. The Clinician's Guide to Short Bowel Syndrome. Practical Gastroenterology 2005;XXIX(9):67.
2. A good reference website - everything from weather to insults from Shakespeare's work.
Joe Krenitsky MS, RD
Carol Parrish RD, MS
PS – Please feel free to forward this on to friends and colleagues.