Gastric Residual Volumes in the Adult Intensive Care Patient: a Systematic Review

Background: Enteral nutrition is one method of delivering nutrition to intubated patients. There are several issues that prevent optimal delivery of the prescribed enteral nutrition goal rates. The measurement of the patient's gastric residual volume (GRV) may demonstrate tolerability, or intolerability, of enteral nutrition. Identifying a safe GRV, at which to accept and continue enteral nutrition delivery, is essential to ensure the delivery of enteral nutrition adequately achieves the nutritional requirements of patients, and to mitigate the risks associated with the delivery of enteral nutrition. Objectives: This systematic review sought to answer the research question: what is the maximum GRV to accept in order to continue the delivery of enteral nutrition in the Intensive Care Unit (ICU) adult patient? This is specifically related to the primary outcome measures indicative of accepting a specified GRV that is too high or too low. Accepting a GRV that is too high would put the patient at risk of vomiting, regurgitation, aspiration of gastric contents and potentially aspiration pneumonia. Conversely, accepting a GRV that is too low would put the patient at risk of not achieving caloric needs, potentially placing the patient at risk of malnutrition and increased morbidity. Search methods: Databases searched included: CCTR, CLCMR, CLTA, CLEED, OVID MEDLINE (R) (Ovid SP), EMBASE, CINAHL Plus with Full Text (EBSCO host via helicon), AMED, Ovid Nursing Full Text plus, CDSR, ACP Journal Club, DARE, Proquest via helicon (advanced search), Pubmed via helicon (limits "all adult", "humans", "abstract", "title"), all EBM reviews, and the reference lists of articles. Selection criteria: The types of studies eligible for inclusion were published randomised controlled trials, case controlled studies, cohort studies and observational studies. Interventions considered were a comparison of two or more GRV measures. The participants eligible were adult ICU or critical care patients receiving enteral nutrition. The primary outcome measures for study inclusion were caloric requirement met, and specified potential adverse events including vomiting, regurgitation, or aspiration. Data collection and analysis: Data was extracted using a data extraction tool created by the researcher. Risk of bias was assessed by the author using two risk of bias assessment tools. Main results: Three studies met the inclusion criteria for the systematic review (McClave et al., 2005; Metheny, Schallom, Oliver, & Clouse, 2008; Pinilla, Samphire, Arnold, Liu, & Thiessen, 2001). Each of these studies contained methodological risks of bias and limitations related to their study designs. McClave et al.'s study was a prospective study (n = 40), Metheny et al.'s study was a prospective descriptive study (n = 206), and Pinilla et al.'s study was a randomised controlled trial (n = 80). No one study, or a combination of studies, provided conclusive evidence to support the use of one particular GRV over another. Author's conclusion: No recommendation for a definitive GRV was made in this systematic review due to the lack of strong evidentiary support for one GRV over another. There remain opportunities for enhancing practice through developing a consistent, multidisciplinary approach to managing GRVs. There are future research opportunities related to improving the management of GRVs in the enterally fed ICU patient, and achieving optimal volumes of nutrition delivered.