Backed by the latest research that paints CHG as the ideal pre-surgical skin prep, many facilities have adopted chlorhexidine gluconate as their standard prepping choice. Fair enough. But know that nothing in the literature warns against the continued use of iodine-based products. In fact, there are compelling reasons to keep it on hand.

While CHG and povidone-iodine both provide broad-spectrum antimicrobial activity, they have very different properties. The preps aren't interchangeable, and to apply one without regard for the effect it has in terms of SSI prevention, or for its potential adverse effects, can prove a big mistake.

• CHG. Once applied, CHG starts working fairly quickly. Its primary benefit is its long-lasting residual effect. Some areas of a patient's anatomy, however, are off-limits. It shouldn't be used near the eyes or ears due to the potential risk of irritation or damage to the cornea or inner ear. Caution is also advised in the vicinity of mucous membranes. Also, CHG is not recommended for use on neonatal patients.
• Iodine. Like CHG, povidone-iodine has an intermediately fast microbial kill, though it tends to take slightly longer to dry. Its residual effect is limited by the fact that its antiseptic effect can be inactivated through contact with blood or bodily fluids, tissue proteins or other organic matter. While it can be used on mucous membranes, including in eye surgery, you must exercise caution due to its potential skin irritation or toxicity.

Leading the charge for CHG
Quickly scan the recent literature on surgical skin antisepsis and you'll come away thinking that CHG outperforms other skin prepping solutions. Study after study shows CHG's impact in lowering microbial counts and reducing the risk that incisions will result in surgical site infections. But prepping isn't a one-size-fits-all process. Even in the face of this mounting evidence, there's still a time and place for iodine-based preps.

A clinical study published in the Jan. 7, 2010, issue of the New England Journal of Medicine generated many discussions among infection control experts by suggesting that CHG was significantly superior to povidone-iodine.

For the multi-center study, led by Rabih Darouiche, MD, of the Baylor College of Medicine in Houston, 409 patients were pre-operatively prepped with a 2% CHG, 70% isopropyl alcohol product and 440 were prepped with an aqueous solution of 10% povidone-iodine. They were tracked for SSIs for 30 days following surgery. By the end of the 30 days, the povidone-iodine group had exhibited an infection rate of 16.1% and the CHG group 9.5%.

The NEJM study followed 2 other notable reports that appeared in the Journal of Bone and Joint Surgery's American edition. In an August 2009 study, orthopedic surgeons at Chicago's Northwestern University prepped 150 shoulder patients with either 2% CHG and 70% isopropyl alcohol, 0.7% iodophor and 74% isopropyl alcohol or a 0.75% povidone-iodine scrub and a 1% iodine paint. In a May 2005 study, University of California San Diego orthopedic surgeons prepped 125 foot and ankle patients with 0.7% iodine and 74% isopropyl alcohol, 3% chloroxylenol or 2% CHG and 70% isopropyl alcohol. In both cases, the CHG-alcohol combination topped the disinfecting results.

What's more, an evidence review of infection prevention practices published in the July 2007 JBJS noted that "current literature strongly suggests that chlorhexidine gluconate is superior to povidone-iodine for preoperative antisepsis for patients."

While the Centers for Disease Control and Prevention and the Association of periOperative Registered Nurses don't recommend one type of skin prep over another, such advice may be on the way. The CDC, which hasn't revised its surgical site infection prevention guideline since 1999, is planning to issue updates keyed to specific procedures, beginning with joint replacement. In addition, AORN, in conjunction with the Association for Professionals in Infection Control and Epidemiology, expects to release a guide to eliminating SSIs in orthopedic surgery by year's end.

Did iodine get a fair shake?
CHG's antimicrobial persistence certainly seems to tip the scales in its direction, but the CHG product used in the NEJM study that caused such a splash included alcohol, and its effects were compared to those of plain povidone-iodine, not an iodine-alcohol combination. Since the addition of alcohol to either CHG or iodine creates a superior skin prepping agent, a critical reader might feel the study didn't "compare apples to apples."

As a prep, alcohol has a rapid microbial kill but little residual activity to speak of, which is what makes it such a valuable complement to longer-effect preps. It should not be used on mucous membranes, it can cause corneal and nerve damage, it is a flammable substance and it can dry the skin, so caution must be exercised when it is used alone or in a combination prep.

Always an alternative
The location of the surgical site is a major consideration when choosing the proper prep for a procedure, as are the primary pathogens and SSI risks you might encounter there. Patients may also have allergies or tissue sensitivities to certain substances. For any given case, an alternative to the standard prep may be necessary, so there's always a reason to have more than one skin prep on hand.

The primary infection risk in orthopedic cases is skin flora, Gram-positive bacteria against which CHG is highly effective, so it makes sense that the American Academy of Orthopaedic Surgeons has recommended the use of CHG preps. On the other hand, the main pathogens in abdominal surgery are often Gram-negative bacteria from bowel flora. Skin preps may not have as strong an effect here. A study published in the October 2009 issue of Infection Control and Hospital Epidemiology suggests that an iodine-alcohol prep may be superior to a CHG-alcohol product among general surgery patients.

In the study, a research team at the University of Virginia Health System compared the effects of 3 preps — a povidone-iodine scrub-and-paint combination plus an application of isopropyl alcohol between the steps; 2% CHG and 70% isopropyl alcohol; and iodine povacrylex in isopropyl alcohol — by using each in turn as the preferred method for 6 months of consecutive general surgeries. The patients undergoing these 3,209 operations were tracked for 30 days following surgery. Researchers calculated the SSI rate for iodine povacrylex at 3.9%, for povidone-iodine at 6.4% and for CHG at 7.1%.

Another reason why general surgeons might prefer iodine to CHG for their procedures is the practical issue of visibility. CHG-and-alcohol preps used to be colorless. Some are now marketed with a tint, but even with this added color they're nowhere near as dramatic as iodine, and some surgeons preparing for abdominal cases have complained of difficulties visualizing where the prep ends. The color of a prep doesn't affect its antiseptic effectiveness, but a user who can't easily see where it is effective may consider this a huge disadvantage.

While economy shouldn't influence your infection prevention decisions, CHG preps tend to cost several times more per volume than comparatively low-cost iodine formulations. If you're considering consolidating your preps in accordance with recent studies' findings, look at the big picture. If your SSI rate is low, there may be no reason to give up iodine for CHG in every case. Rather, consider dual preps — CHG and alcohol or iodine and alcohol — to be the product combination that provides increased effectiveness.