Gastric residual volumes in critical illness: what do they really mean?

The practice of measuring gastric residual volumes (GRVs) has become a routine part of enteral feeding protocols in the critical care setting. However, little scientific evidence indicates that their use improves patient outcomes. The use of GRVs is more of a tradition, which unfortunately guides the delivery of enteral nutrition (EN). The practice of GRVs is predicated on several flawed assumptions. Using GRVs in hospitalized patients assumes that the practice is well standardized, that GRVs reliably and accurately measure gastric contents, and that they sufficiently distinguish normal from abnormal emptying. The practice also assumes that GRVs are easy to interpret, that a tight correlation exists between GRVs and aspiration, and that continuing EN after a high value for GRV is obtained leads to pneumonia and adverse patient outcomes. And finally, clinicians assume that GRVs are an inexpensive "poor man's test" for determining tolerance of EN. This article reviews studies showing the fallacies of these assumptions. Although clinicians are unlikely to stop using GRVs, interpretation of these must be modified so as not to interrupt the delivery of EN. Using a protocol that directs appropriate responses to elevated GRVs should promote the delivery of EN and improve patient outcome.