Probiotics, Critical Illness, and Methodologic Bias

Abstract

It has been proposed that probiotics can favorably influence the course of critically ill patients. To address this question, a limited systematic review was undertaken (MEDLINE search for articles published in English) to identify randomized, controlled trials that compared a group of critically ill patients taking probiotics with a group that did not. Ten such trials, mostly with high risks of methodologic bias, were identified. When the data were combined, the probiotics did not appear to influence mortality or duration of hospitalization. However, the recipients of the probiotics had fewer infectious episodes (absolute risk difference-21%). This effect was seen particularly in trials employing one combination of probiotic agents (Pediococcus pentosaceus, Leuconostoc mesenteroides, Lactobacillus paracasei, Lactobacillus plantarum). Unfortunately, this effect may be overly optimistic, as methodologic shortcomings could have introduced biases into the trials. Three trials of patients with severe acute pancreatitis were not included in this primary analysis because not all of the patients were in the intensive care unit. The largest of these, and the one with the lowest risk of bias, demonstrated that probiotics increased mortality, in part because of the precipitation of ischemic bowel disease (in patients who were also receiving postpyloric enteral nutrition infusions). Probiotics also appeared to reduce the incidence of antibiotic-associated diarrhea in hospitalized patients, although these trials did not specifically focus only on those who were critically ill. In summary, it is not clear that probiotics are beneficial (and they may even be harmful) in the critically ill patient group.