Residual volume measurement should be retained in enteral feeding protocols.

I n a study reported in this issue, O’Meara and colleagues provide evidence that underfeeding via the enteral route is a serious problem in critically ill patients. Although other researchers have reported similar findings, these researchers provide an opportunity to consider where changes could have been made to alleviate the problem. In their observational study, O’Meara and colleagues found that it took a mean (SD) of 18 (26.9) hours for bedside nurses to insert feeding tubes into the small bowel. This is an area of practice that can be improved. Following a reasonably short training period, a group of critical care nurses were able to insert 339 small-bowel feeding tubes in a time-efficient manner (mean, 22 min; range, 5-180 min). Therefore, in intensive care settings where postpyloric feedings are commonly used, it behooves each unit to train several nurses in this technique to prevent lengthy delays in starting feedings. Another preventable reason for feeding interruptions is tube clogging. It is unclear how often clogging occurred in the study, because the authors include this complication in a category with other small-bore feeding tube issues; however, it apparently occurred relatively often. There is evidence that regular flushing can prevent tube clogging. In a study of 135 critically ill patients, researchers were able to maintain tube patency during more than 1800 residual volume checks merely by flushing the tube with 30 mL of water or isotonic saline following each 4-hour measurement. Approximately 13% of the feeding interruptions reported by O’Meara et al were due to “increased residual volumes” from either feeding tubes in the small bowel or large-bore tubes in the stomach. It is disappointing that the authors did not provide definitions of “increased residual volumes” in the small bowel and gastric sites. Instead, individual caregivers seem to have arbitrarily chosen values to decide when feedings should be stopped. Some feedings may have been stopped for residual volumes that presented no risk. Again, this is an area of practice that can be improved. Implementation of a residual volume protocol can eliminate unnecessary feeding interruptions. Such a protocol is predicated on the number of high residual volumes encountered in a specific patient. A single gastric residual volume of 200 mL or more is considered less significant than 2 or more gastric residual volumes in this range. Unfortunately, rather than reporting the number of increased residual volumes in individual patients, the authors described the frequency of increased residual volumes according to the total number of observations in the 59 patients. Although specific information about residual volumes was sparse, the investigators reported volumes of 200 mL or more in 22 instances from large-bore orogastric tubes and in 5 instances from small-bore feeding tubes assumed to be positioned in the small bowel. Whereas it is not unusual to find residual volumes of 200 mL or more in the stomach, it is highly unusual to find volumes of this magnitude in the small bowel. Several studies conducted in critically ill patients found that residual volumes from the small bowel were usually less than 10 mL. A few of the small-bowel feeding tubes in the study by O’Meara and colleagues may have dislocated upward into the stomach during the 10day study period. If so, this could account for the unusually high residual volumes from these tubes. About the Author Norma A. Metheny is Professor and Dorothy A. Votsmier Endowed Chair in Nursing at Saint Louis University, St. Louis, Missouri.