The gut in critical illness: evidence from human studies.

Data from a large number of published human studies support the hypothesis that the gastrointestinal tract of the critically ill patient is an important factor in ICU morbidity and mortality. Changes in proximal gut flora in the critically ill patient predict nosocomial infection with the same organism, while gut-directed therapeutic measures clearly reduce rates of nosocomial infection and may have an impact on mortality Modulation of the systemic inflammatory response through gut derived measures has been no more successful than modulation of that response through more conventional systemic forms of mediator-directed therapy. But if the gastrointestinal tract is an important factor in nosocomial ICU-acquired infection, the bigger unanswered question is, to what extent does infection per se alter outcome in critical illness? Current articulations of the gut hypothesis challenge long-held and probably outmoded views of host-microbial interactions. The challenge to replace them is no less compelling and no less treacherous than it was in the era of Metchnikoff, Lane, or their ancient forebears.