SSI Prevention Bundle in Cardiac, Hip, and Knee Surgery - A Home Run

...and I'm being modest...

As I mentioned yesterday, it's really hard to write a post when you've already written the accompanying editorial. Today, I have a taller task - posting on a study led by two close colleagues (and favorite people), Marin Schweizer and Loreen Herwaldt. (COI alert) Fortunately, JAMA Associate Editor, Preeti Malani, has done the heavy lifting with her excellent editorial.

In today's JAMA, Schweizer and colleagues reported the results of an AHRQ-funded trial examining the benefits of an SSI prevention bundle in orthopedic and cardiac surgery. The bundle was outlined in a meta-analysis they published in BMJ two years ago and included preoperative nasal screening for MRSA/MSSA, mupirocin BID and daily CHG baths for 5 days if screen positive and vancomycin added to perioperative prophylaxis if MRSA positive. The quasi-experimental intervention study took place in 20 US hospitals across 9 states with 39 months of pre-intervention SSI rates and 21 months of rates collected during the intervention period.

Overall, the results are impressive (i.e. not modest). First, there was a 42% reduction in SSIs after the intervention was implemented (see Figure, below), despite modest bundle adherence (39% full adherence, 44% partial adherence).

The key finding for me relates to the number of months where there were ZERO SSIs across all 20 hospitals. Looking at the Figure above, you can see that "the number of months without any complex S aureus SSIs increased from 2 of 39 months (5.1%) to 8 of 22 months (36.4%; P = .006 by Fisher exact test)." Seven times as many zero-months in all 20 hospitals. That's not a modest finding. ;)

Key points from the editorial:

"inclusion of patients undergoing emergency or urgent operations, a population recognized as at high risk for SSI, improves the generalizability of the findings."

"the primary study outcome was limited to complex S aureus SSIs, eliminating much of the subjectivity of infection surveillance. Even though surveillance practices varied among participating hospitals, complicated S aureus SSIs are not clinically subtle and can be identified easily by any surveillance system."

and given the modest adherence to the bundle, "Moving forward, efforts to promote and maintain adherence to prevention protocols will remain important"

"The study’s setting is among its limitations. All 20 study sites were from a single health care system with a well-established quality improvement infrastructure - certain factors in this health care system may differ from other clinical settings, including a below-average baseline infection rate. It remains unclear what challenges and barriers may present as this bundle is implemented at other institutions. Further studies in different settings will offer additional guidance."

and my favorite quote:"Although getting to zero is unlikely to be achievable, efforts that move closer to this elusive goal hold tremendous value for clinicians, hospitals, payers, and, most importantly, patients."

My final thoughts:
This is a wonderful study that took many years of planning, hard work and tremendous collaborators, including HCA and Ed Septimus. Congrats to all involved. Not every study is a grand slam, but we'll take a home run for infection prevention.

E. coli 0157:H7 and hypertension, renal and cardiac disease

Text-size doesn't correlate with population size

Another not exactly HAI prevention post, but as Mike just told us, we don't have much evidence in ID, so anything can be exciting, no?  This report out of BMJ tells of a May 2000 E. coli O157:H7 and Campylobacter outbreak that arose in the Walkerton, Ontario municipal water system after heavy rainfall drove livestock faecal matter into water supply. The outbreak resulted in 2300 cases of GI illness, at least 27 cases of haemolytic-uraemic syndrome, and seven deaths.  Amazingly, the government created a Walkerton Health Study to monitor individuals for the possible long-term consequences associated with the infection.  After 4-years, there was a 28% increase in hypertension associated with the exposure.  The BMJ report tells of the impact out to 2008.

Overall, people who had acute gastroenteritis were 1.3 times more likely to develop hypertension, 3.4 times more likely to develop both structural and functional renal impairment, and 2.1 times more likely to report a physician-diagnosed cardiac disease. The authors do an excellent job discussing the potential limitations of the study including recall bias and confounding. They also explain away the impact of Campylobacter coinfection by saying that the infectious dose of 0157:H7 is 10 bacteria, while it is 500 for Campylobacter, so people were unlikely to have avoided 0157:H7 exposure.

This is a very unique study.  Most studies that have assessed infections as risk factors for chronic diseases were case-control studies that identified patients with specific outcomes and looked back for certain risk factors.  You would imagine that recall bias would play a much larger role in remembering certain distant and unremarkable exposures like GI illness in a case-control study. With this cohort study, exposures and outcomes were well characterized and measured.  I wonder what this study's impact will be in ascertaining the causes of hypertension, renal and cardiac disease in the general population?  Their recommendation that patients who are post-exposure from E coli 0157:H7 should be carefully monitored for hypertension and renal disease seems prudent.


Clark WF et al. BMJ Nov. 17, 2010 (open access)