Use of a sensitive multi-sugar test for measuring segmental intestinal permeability in critically ill mechanically ventilated adults: a pilot study

Background Increased intestinal permeability (IP) is associated with sepsis in the Intensive Care Unit (ICU). This study aimed to pilot a sensitive multi‐sugar test to measure IP in critically ill patients in the non‐fasted state. Methods Critically ill mechanically ventilated adults were recruited from two ICUs in Australia. Measurements were completed within three days of admission using a multi‐sugar test measuring gastroduodenal (sucrose recovery), small bowel (lactulose‐rhamnose [L‐R] and lactulose‐mannitol [L‐M] ratios) and whole gut permeability (sucralose‐erythritol [S‐E] ratio) in 24‐hour urine samples. Urinary sugar concentrations were compared at baseline and post‐sugar ingestion, and IP sugar recoveries and ratios were explored in relation to known confounders including renal function. Results Twenty‐one critically ill patients (12 males, median 57 years) participated. Group median concentrations of all sugars were higher following sugar administration; however, sucrose and mannitol increases were not statistically significant. Within individual patients, sucrose and mannitol concentrations were higher in baseline than post‐sugar ingestion in nine (43%) and four (19%) patients, respectively. Patients with impaired (n = 9) versus normal (n = 12) renal function had a higher L‐R ratio (median 0.130 versus 0.047,p = 0.003), a lower rhamnose recovery (median 15 versus 24%,p = 0.007) and no difference in lactulose recovery (median 2.5 versus 2.4%,p = 0.508). Conclusion Small bowel and whole gut permeability measurements are possible to complete in the non‐fasted state, while gastroduodenal permeability could not be measured reliably. For small bowel IP measurements, the L‐R ratio is preferred over the L‐M ratio. Alterations in renal function may reduce the reliability of the multi‐sugar IP test, warranting further exploration.