A surgical site infection enhancement bundle?

A new paper in the Archives of Surgery evaluated the implementation of a surgical site infection (SSI) prevention bundle for colon surgery (see free text of the paper here). The bundle contained the following components:

• Omission of mechanical bowel preparation
• Preoperative and intraoperative patient warming
• Increased concentration of inspired oxygen during and immediately after the surgical procedure
• Limiting intraoperative intravenous fluid volumes
• Use of wound barriers to protect the surgical wound from contamination during the procedure 

Each component of the bundle was supported by 1 or more randomized trials demonstrating reduction in SSIs. About 200 patients were randomized to receive either the bundle or standard care. SSIs were determined by IPs using CDC case definitions. The study was terminated after a planned interim analysis revealed a <1% chance of showing a positive effect of the bundle were the study to continue to the accrual goal.

The overall rate of infection was 35%. In the control group, 24% of patients developed an SSI vs. 45% in the intervention group (p .003). In multivariate analysis, the bundle was shown to an independent predictor for SSI (RR 2.49, CI95 1.36-4.56).

I was struck by the very high rate of infection in this study, so I looked at CDC's most recent surveillance report, which shows that the mean pooled infection rates for colon surgery depending on risk category ranges from 3.99% to 9.47%. The authors postulate that their case ascertainment may be greater since the study was performed at a VA hospital where outpatient follow-up of patients is much easier to track. However, even in light of that, the rate still seems quite high. But on the other hand, unless there is something very unique about these patients or the care provided at this hospital, you might think that an effective prevention bundle would have even more impact in a setting with exceedingly high infection rates. This raises more concern that the bundle was not just ineffective but actually increased the risk of post-operative infection.

This paper is another example of how immature implementation science remains. I think the authors of this paper are correct to conclude that bundles of evidence-based interventions need to be formally tested before there is wide spread implementation.

Gentamicin-collagen what?

Am I the only hospital epidemiologist who had absolutely no idea these things existed? Now I’m glad I ignored them for so long, because they don’t seem to work worth a damn, according to studies recently published in JAMA and NEJM. They might even be harmful!

Laziest possible post about the new CMS rule

I am on vacation. Last week I biked across Iowa with 9,999 other people (see photo below), and I’m now in Michigan, recovering from my bike ride across Iowa. So I haven’t done much deep thinking about the new CMS rule related to healthcare associated infections. From what I understand, participation in the Medicare program (at least receipt of full payment) will soon require surveillance and reporting (through NHSN) of CLABSI (beginning in 2011; ICU only) and SSI (beginning in 2012). The rates will eventually be reported via the hospital compare website. This doesn’t mean a lot to hospitals that already perform CLABSI and SSI surveillance, unless they don’t currently report through NHSN, in which case they’ll have to get enrolled.

We’ve already blogged about pitfalls in public reporting, and about problems with the NHSN definitions, validation, etc. So I really don’t have anything new to say about this rule. I refer all interested readers to a six-part series at Safe Healthcare (only 2 posts so far, 4 to come) on the new rule.

Should we just skip SCIP?

There is a new paper and editorial on SCIP (Surgical Care Improvement Project) in this week's JAMA. SCIP is a Medicare project to improve compliance with practices that have been shown to reduce surgical site infections. These metrics include correct antimicrobial selection and timing, and appropriate hair removal. In this study the authors correlate compliance with SCIP metrics to surgical site infection rates, and the conclusion is that SCIP compliance doesn't correlate with reduction in SSIs. However, in my opinion, there's a huge problem with this study. The outcome data on SSIs were obtained using administrative data (ICD-9 codes), which are notoriously inaccurate. Kurt Stevenson showed that the positive predictive value of ICD-9 codes when compared to NHSN surveillance methods for 8 different categories of surgical site infections was as low as 14% and only as high as 51%. Thus, I don't think this study should sway our opinion about SCIP one way or the other. Since nearly all hospitals collect SCIP data and some states mandate NHSN SSI surveillance, the data should be available to replicate the study with better outcomes data. And if that shows similar findings, SCIP should be put to pasture.

Obesity and surgical site infections

Abstracts being presented at a national GI meeting this week demonstrate the impact of obesity on surgical complications. One study found that patients with a waist circumference of 45 inches or more were three times more likely to develop a surgical site infection after rectal cancer surgery. The authors of another study demonstrate increased surgical complications in obese patients and go on to criticize pay-for-performance programs that reward surgeons for better outcomes given that a patient's obesity is out of the surgeon's control. Moreover, they claim that since obesity is more common among minority patients, these policies may have adverse unintended consequences that result in discrimination.

Rhinoceroses and Total Hip Arthroplasty

Distinctions are very important. I was just visiting Ohio last week and had the chance to visit the Columbus Zoo. It's a pretty cool place if you like zoos. I enjoyed reading about various animals and learned that the Black Rhino is endangered, while the White Rhino is not. Thus, it would make sense to spend your conservation money, if you have some, on Black Rhinos first, since time is running out. In infection control, we ought to do the same thing, but in reverse; spending our limited resources on preventing more common infections first. Also, with the rise of public reporting and other methods of interhospital comparison, efforts must be made to place hospitals on a level playing field. There is a nice study that highlights these two issues in the May ICHE by Surbhi Leekha and colleagues at the Mayo Clinic in Rochester, MN.

They examined at a 5-year cohort (2002-2006) of all total hip arthroplasties (primary and revision) and looked to see who developed SSI, using CDC definitions. After controlling for age, gender and NNIS index, patients who had a revision total hip arthroplasty had twice the odds of SSI compared to primary surgery (OR=2.2, 95% CI 1.3-3.7). The difference was even more stark when outcomes were restricted to deep or organ space SSI with revisional surgery associated with four times the odds of SSI (OR 3.9, 95% CI, 2-7.9). One note, they didn't appear to control for duration of surgery as a confounder, even though it was associated with both revisions and SSI. I think this is correct. They were not completing a risk-factor study, but were interested in outcomes.

The usual caveats apply to these types of studies including a single center study and a relatively unique single center at that. However, this is an important study and if these findings hold up at other institutions, which they most certainly will, this suggests that the case-mix of revision and primary hip arthroplasty must be taken into account when SSI rates are reported and hospitals compared. Perhaps an easier solution, as the authors suggest, is to treat them as two different animals, if you will, and report them separately. Also, if one wanted to target specific infections or high-risk procedures, these results suggest targeting revision surgeries over primary ones.

Note: Surbhi is joining the group at my old Maryland stomping grounds and I know everyone is excited for her to arrive.