Do we really need surgical masks and caps in the operating room?

Prior to one’s first surgical rotation in medical school, each student is required to attend training with the staff that oversees OR operations. That training includes what protective equipment to wear, how to scrub, and how to maintain sterility. Many, many students have had experiences during third year where they’ve been yelled at by OR staff for nearly contaminating some of the equipment. And in some cases, for actually doing so. But it’s all for good reason - ensuring the patient’s safety and protection.

One component of those protective measures is appropriate attire, including a sterile gown, sterile gloves, a face mask, and a cap on the head (the mask and cap are non-sterile). The goal of all of these items is to minimize the chance of any infection. I’ve seen attendings not involved in a case standing at the OR door to just speak to another attending, ten or more feet from the patient and barely holding a mask over their mouth. And occasionally, I’ve seen them not holding a mask over their face at all. How could they do that, when it’s common sense that we all breath out bacteria and other contaminants?

Well it turns out, as can be the case, common sense isn’t exactly correct. I recently heard a trusted attending say that there has yet to be a single study demonstrating that masks and caps are effective at reducing surgical site infections (SSI).

What? How in the world is that even possible? If we didn’t wear caps or masks in the OR, there wouldn’t be any difference in infection rates?? So I decided to do a little research on the topic.

The first study I found looked at whether or not non-scrubbed operating personnel being masked made any difference in the rate of SSI. After looking at over eight-hundred patients, which were split into two groups where in half of the cases all of the non-scrubbed OR staff wore masks and in the other half they did not, they found no difference in the rates of SSI between the groups.

A Cochrane review in 2002, which involved a total of 1453 patients, even hypothesized that in some cases surgical masks may contribute to SSI. Their ultimate conclusion was also that it is unclear if wearing a mask “results in any harm or benefit to the patient undergoing clean surgery.”

Another study, “Disposable surgical face masks: a systematic review,” published in 2005, also identified ways that masks might contribute to surgical site contamination. The conclusion of their systematic review was that, “it is unclear whether wearing surgical face masks results in any harm or benefit to the patient undergoing clean surgery.” (And no, that’s not a typo on my part, the conclusions of both studies were worded almost identically.)

“Reducing Surgical Site Infections: A Review,” by Drs. Reichman and Greenberg, reviewed a number of studies and concluded that:

Several other practices, such as the standard use of “scrub suits,” surgical caps, and shoe covers have never been definitively demonstrated to reduce rates of surgical infection, although SSI outbreaks have been traced to hair or scalp organisms (regardless of whether a cap was worn), and increased foot traffic through the operating room has been demonstrated to increase ambient microbial levels and ensuing infection risk.

So stay out of the OR, but once you’re in, it doesn’t matter whether you wear a mask or a cap. It is interesting that they note “SSI outbreaks have been traced to hair or scalp organisms (regardless of whether a cap was worn).” It could suggest that the caps we wear don’t do anything to reduce infection. Maybe we need better caps, or caps that cover more of the head. We could wear those bubble helmets that astronauts wore in the 1960s.

Or we need to use the caps that we do have better.

One of the most referenced studies was authored by Tunevall, entitled “Postoperative wound infections and surgical face masks: a controlled study.” Tunevall referenced a study in which a 50% decrease in SSI was seen after omitting face masks, and then proceeded to conduct the single largest study to date, including 3,088 patients. In half of the procedures, all operating room staff wore masks; in the other half, they did not. The result? They found no difference in the rate of infection between the two groups, and concluded that while masks might protect the OR staff from infection from the patient, the masks did not prove to protect the patient undergoing surgery by a “healthy operating team.” The healthy part is a subtle but important distinction.

Interestingly enough, the only intense defense of using masks all the time was published in The Operating Theatre Journal, and written by the Director of Clinical and Scientific Documentation from Kimberly-Clark Health Care, a leading manufacturer of surgical masks and attire. I’m not suggesting that his article was misleading, but more that they have a vested interest in ensuring we keep using masks all the time, and their defense is likely to focus on research that supports that motive.

So what does this all mean? Should we stop spending money on caps and masks, since we can’t even prove they do anything? Well, no, that’s not the only interpretation of the data. An alternative view is that the masks we’re using don’t do a good enough job at trapping infectious organisms. Maybe the material they’re made from is insufficient at filtering the air. Maybe they don’t provide complete enough coverage of the face to filter what we breathe. Maybe we should only be wearing sterile masks. Maybe we’re not wearing them properly. Or, of course, maybe the chances of getting an infection transmitted via the air is very small for the typical patient, and very high for the very sick patient who is more likely to pick up an infection from anywhere. Perhaps, it’s just very, very, very hard to get an infection from somebody breathing around a wound, except under specific circumstances.

We clearly don’t have enough evidence to answer those questions either way. Of course, nobody in their right mind would endorse halting the use of masks and caps in the OR - especially since none of these studies demonstrates a clear, consistent harm to the patient by doing so. But it does raise the question of, if what we’re currently doing isn’t making things any better than doing nothing, why is that and how can we improve?