August 2010 Issue
Promising Potential — Science Uncovers Benefits, and Some Risks, of Probiotics in Critical Care
By Megan Tempest, RD, LDN
Vol. 12 No. 8 P. 10
What comes to mind when you read the word “probiotics”? To many of us, the term has come to be synonymous with healthy. Yet the utility of probiotics to improve the health of individuals who are critically ill is not so straightforward. Critical-care patients are extremely vulnerable to dramatic alterations in gut barrier function and at high risk of infection. The efficacy of probiotics in reducing these risks is a significant area of interest among clinicians and researchers. Although probiotics show great promise, thus far the literature regarding their use in critical care has communicated contradictory evidence. Several studies suggest the therapeutic ability of probiotics to reduce infection and minimize gastrointestinal side effects of antibiotic therapy. However, the results of other studies showing potential harm from the use of probiotics implore clinicians to use caution when providing them to patients who are critically ill.
The World Health Organization and the Food and Agriculture Organization of the United Nations define probiotics, commonly known as “friendly bacteria,” as “live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host.” Their usefulness in the critical-care setting revolves around their potential ability to prevent bacterial proliferation and translocation, thereby protecting this vulnerable patient population from infection and further distress as well as their ability to restore normal gut function in the face of prolonged illness and antibiotic treatment.
Strains and Species
There are countless species and strains of probiotic bacteria, the health benefits of which are believed to vary widely. It’s probably sufficient to know that most bacteria come from one of two groups: Lactobacillus or Bifidobacterium. Within these two groups are different species, and within those species there are different strains. Some probiotics, such as Saccharomyces boulardii, are actually yeasts. Research has shown beneficial effects of Saccharomyces boulardii on reducing the incidence and duration of diarrhea in critically ill, tube-fed patients.1 One study found that a different probiotic, Lactobacillus plantarum 299, significantly decreased the rate of postoperative infection in patients who had received a liver transplant.2
But a study concluding that a probiotic “cocktail,” which contained six different strains, did not lower the risk of infectious complications in patients with acute pancreatitis and was associated with increased mortality and bowel ischemia raised concern about using probiotics in vulnerable critical-care patients.3
What’s New in the Literature
A study published in the March issue of the Journal of Critical Care Medicine examined the potential benefits of probiotics in preventing ventilator-associated pneumonia in patients who were critically ill. A meta-analysis of randomized controlled trials found that administering probiotics was beneficial in reducing the incidence of ventilator-associated pneumonia, the length of hospital stay, and the colonization of the respiratory tract with the bacteria Pseudomonas aeruginosa, a frequent culprit of bacterial infection in hospitalized patients. The researchers observed no benefits in probiotics’ ability to reduce mortality rate, the duration of mechanical ventilation, or the incidence of diarrhea.
Results of a pilot study by Australian researchers provide support for using probiotics to alleviate diarrhea in patients who are critically ill. Published in the May issue of the American Journal of Critical Care, the researchers analyzed the decreased frequency of liquid stool in enterally fed critically ill patients when given VSL #3, a multispecies probiotic containing live freeze-dried lactic acid bacteria and eight different probiotic strains. Patients requiring enteral nutrition support for an average of eight days were given VSL #3 or a placebo, and their stooling was subsequently monitored for up to 12 days. Results showed that the patients receiving VSL #3 had a significantly reduced frequency of liquid stools.
According to Christy Stavros, RD, LDN, a critical-care dietitian at the University of Chicago Medical Center, the benefits of VSL #3 have been observed in patients and, thus, physicians commonly prescribe the probiotic. “At our institution, we have used VSL #3 to treat pouchitis and to alleviate diarrhea in patients with inflammatory bowel disease and seen positive results.”
The use of Lactobacillus plantarum to prevent gastrointestinal side effects related to antibiotic treatment was the focus of a study published in the February issue of the Journal of Clinical Gastroenterology. The risk of developing loose or watery stools was found to be significantly lower among the subjects receiving the probiotic. However, there was no observed reduction in the incidence of Clostridium difficile, a diarrhea-inducing toxin that commonly afflicts critically ill hospitalized patients.
Urging caution with the use of probiotics in certain patients, a study published in the November 2009 issue of the Journal of Annals of Surgery found them contraindicated in patients with organ failure. The study was initiated to examine the influence of probiotics on intestinal barrier dysfunction, bacterial translocation, and clinical outcome in patients with predicted severe acute pancreatitis. The development of bacteremia, infected necrosis, organ failure, and mortality were all associated with intestinal barrier dysfunction early in the course of acute pancreatitis. Treatment with the combination of probiotic strains overall reduced bacterial translocation among the subjects; however, it was found to increase bacterial translocation and enterocyte damage in the patients who developed organ failure.
Finally, a systemic review of the literature supporting the safety of probiotic use in patients receiving enteral or parenteral nutrition support was published in the March issue of the American Journal of Clinical Nutrition. Researchers found 20 case reports of adverse events in 32 patients, all of which were attributed to infections related to Lactobacillus rhamnosus GG or Saccharomyces boulardii. The risk factor was related to central venous catheter infections and disorders associated with increased bacterial translocation. However, the overall findings suggest that probiotics have been safely used in patients receiving nutritional support, while some specific strains may increase risk of complications in specific patient populations.
More Research Is Necessary
The current evidence makes a strong case for continued research into the benefits of probiotics in critical care. For now, due to limited data on the effects of various probiotic strains and limitations of the available research, no established recommendations have been made for the safe use of probiotics in the critical-care setting.
Stavros weighs in on this issue: “Due to the highly compromised condition of our critical-care patients, along with the absence of established guidelines or protocols for their use, we generally do not provide probiotics in our intensive care.”
However, she continues, “Given the promising results of several studies and the potential for probiotics to lessen diarrhea and prevent infection in the critically ill patient, further research is needed to determine which specific strains are most beneficial, as well as appropriate dosage and duration of treatment.”
— Megan Tempest, RD, LDN, is a clinical dietitian at the University of Chicago Medical Center.
1. Bleichner G, Blehaut H, Mentec H, Moyse D. Saccharomyces boulardii prevents diarrhea in critically ill tube-fed patients. A multicenter, randomized, double-blind placebo-controlled trial. Intensive Care Med. 1997;23(5):517-523.
2. Rayes N, Seehofer D, Theruvath T, et al. Supply of pre- and probiotics reduces bacterial infection rates after liver transplantation — a randomized, double-blind trial. Am J Transplant. 2005;5(1):125-130.
3. Besselink M, van Santvoort HC, Buskens E, et al. Probiotic prophylaxis in predicted severe acute pancreatitis: A randomized, double-blind, placebo-controlled trial. Lancet. 2008;371(9613):651-659.